Reference

J MBS

Publications

NATL INST. OF STAND & TECH

AlllDb

MBSIR 82-255U

evaluation of Chain Saw Kickback

Motion Using an Optoelectronic

Measurement System

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Manufacturing Engineering

Mechanical Production Metrology Division

Washington, DC 20234

August 1 932

Report to Consumer Product Safety Commission

-QC Bethesda, MD 20016

100

, Ubo

92-2559

I9o2

NBSIR 82-2559

l m. • EVALUATION OF CHAIN SAW KICKBACK

MOTION USING AN OPTOELECTRONIC

MEASUREMENT SYSTEM

*5 BURKA I STANDARD!

USRABY

SEP 2 3 1982

05

Donald Robinson and Charles Federman

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Manufacturing Engineering

Mechanical Production Metrology Division

Washington, DC 20234

August 1 982

Report to Consumer Product Safety Commission

Bethesda, MD 20016

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Table of Contents

1. Introduction

2. Kickback Test Arrangement

3. Optoelectronic Measuring System

4. Experimental Program

4.1. Selection of Test Saws

4.2. Kickback Test Conditions

4.3. Volunteer Test Operators

5. Determination of Test Saw Rotational Displacements

6. Principal Test Results

6.1. Kickback Energy during Hand-Held Tests

6.2. Comparison of Saw Motion with Energy Measured in

Kickback Machine

6.3. Evaluation of Low Kickback Energy Chain

6.4. Evaluation of Handle Spacing Effect on Saw Motion

7. Discussion

8. Acknowledgments

9. References

Appendix A. Development of Test Protocol

Appendix B. Human Factors, Recommendations, and Rationale for

Testing Chain Saw Kickback with Volunteer Operators

Appendix C. Computer Analysis of Recorded Data

1. Introduction

Background

In 1978, the Consumer Product Safety Commission (CPSC) accepted a proposal from the Chain Saw Manufacturers' Association (CSMA) to develop a voluntary performance standard to address the kickback hazard for chain saws. The

process included participation by CPSC, the National Bureau of Standards

(NBS), consumers, and industry in the development of kickback testing equipment and procedures, study of operator/saw interactions, and analysis of injury data. A kickback test machine (KBM) was adapted so that test procedures

could be developed for assessing the kickback energy potential of chain saws.

A report describing the exploratory chain saw kickback research at NBS in the

joint effort with CPSC and the chain saw industry is given in Reference [1].

In 1980 the CPSC decided to initiate the in-house development of a mandatory standard to address chain saw kickback. Part of that effort involved relating known chain saw energy levels generated during kickback in the KBM to

the final angle that a saw might travel when held in the hands of a chain saw

operator. The present report describes the experimental program developed at

NBS to determine the relationship between kickback energy and chain saw motion

during hand-held kickbacks for selected samples of consumer-type chain saws

and volunteer test subjects. The measurement system employed in this research

included a computer-controlled optoelectronic system for measuring the displacements of selected points on the test saws, test fixture, and the right

arm motion of selected test subjects during simulated kickbacks. Included in

the report is a description of the test equipment and procedures, the experimental design, and analyses of the measured displacement data for chain saws

having known values of kickback energy.

1
2. Kickback Test Arrangement

In order to establish the relationship of energy during a simulated kickback to the kickback angle of a saw in the hands of a chain saw user, it was

necessary to develop a suitable test fixture and outline the procedures before

making the appropriate measurements. A KBM had been developed and shown in

prior investigations by both NBS and the chain saw industry to simulate

kickback conditions in a reproducible manner for determining the energy associated with chain saw kickback motion. 1 Thus, the procedures successfully implemented for the KBM formed the basis for developing a test fixture for handheld tests of simulated kickbacks in the present investigation.

Kickback is initiated in the KBM by accelerating a carriage, holding a

"wood" (i.e., medium density fiberboard) specimen, into contact with the moving saw chain on the upper quadrant of the saw guidebar nose. The method

selected to accelerate the carriage, control its approach speed, and adjust

the specimen contact angle for the hand-held tests was the same as that used

in the KBM [1]. Figure 1 shows the fixture and test arrangement for the kickback experimental program.

In the hand-held kickback investigations, volunteer test subjects were

required to hold an operating test saw in a simulated bucking mode of operation. (This procedure will be discussed in a later section.) During preliminary kickback tests, it was found necessary to constrain the rearward carriage motion as the kickback was initiated in order to adequately transfer the

carriage momentum to the test saw via the wood-saw interaction. The test carriage momentum in the KBM is efficiently transferred to the test saw since the

^The Round Robin I kickback tests which demonstrated the interlaboratory

reproducibility are discussed [1].

2
3

Figure

1.

Test

Arrangement

for

Kickback

Experimental

Program
saw can only rotate about its center of gravity during kickback; i.e., the saw

is constrained so that no lateral motion is permitted. Similar constraint of

a test saw’s initial motion during the hand-held kickback simulation of a

bucking operation was considered, but was judged to be overly restrictive. The

use of a pawl and rack mechanism in the test fixture to constrain the carriage's initial rearward motion was found to effectively transfer the carriage

momentum to the saw without unrealistically constraining the test saw.

The initial horizontal position of a test saw in the KBM was controlled

in a manner which prevented downward motion of the guidebar during a kickback

test. For the hand-held test arrangement, the chain saw motion was similarly

controlled by using a lightweight shield surrounding the flat portion of the

guidebar as shown in figure 1. (Another purpose of the shield was to protect

the test subjects^). This procedure served both to simulate a bucking mode of

operation, wherein a log is cut by the chain on the straight portion of the

guidebar, and to control the initial horizontal position of the guidebar to

insure that the wood-saw contact angle was properly maintained.

The horizontal alignment of the guidebar shield, which rested on a wooden

block, was monitored by the principal investigator during each kickback test.

Immediately prior to the release of the test carriage to initiate a kickback,

a technician would signal the test subject to adjust the saw alignment if

necessary to insure that the guidebar was properly aligned in a vertical

plane. The initial guidebar alignment in the vertical and horizontal planes

was necessary in order to reproduce the same initial conditions as achieved

during kickback tests in the Kickback Test Machine.

full discussion of the various safety precautions, which included a barrier

to prevent excessive rotational saw motion is given in Appendix A.

4
3. Optoelectronic Measuring System

An optoelectronic tracking system was used to measure x and y coordinates

in real time at preselected locations on a test saw, the test fixture, and on

several of the volunteer operators during the kickback experimental program.

Small light-emitting diodes (LED's) were attached to each test saw near the

guidebar nose, the center of gravity, the rear handle, and at three other

positions of interest on the test fixture or on the right arm of an operator.

Figure 1 shows the typical test arrangement; for several tests, the diodes on

the wood carriage were placed on the wrist and elbow of the operator.

The main component of the computer-controlled optoelectronic system is a

specially-developed infrared camera having an analogue photodetector with four

electrodes. When the infrared light from an LED is focused on the detector

surface through the camera lens system, the generated photocurrent is divided

among the four electrodes. The current is used to obtain two signals which

are linearly related to the x and y coordinates of the LED. The resolution of

the system digital output is specified as 1 part in 1024 (i.e., 10 bits).

For the kickback experimental program, the detector was used to measure

the position of six LED's.^ This was achieved by turning the LED's on and off

at a rate of 312 Hz. Thus, the time was 0.0032 sec. interval between successive tracking cycles measured during a kickback. The image field was scanned

so that the x and y coordinates for each LED point location could be digitized

and stored in a mini-computer memory for data reduction and analysis. The

displacement data were visually observed on a video terminal following the

first kickback test for each saw in order to check that the recording

2 The Selspot optoelectronic system was used in this investigation.

Note: Commercial instruments and products are identified in this report in

order to specify adequately the experimental procedure. In no case does such

identification imply recommendation or endorsement by the National Bureau of

Standards, nor does it imply that the equipment identified is necessarily the

best available for the purpose.

OJ A maximum of 30 LED's can be tracked in one cycle.

5
system was properly triggered. Coordinate-time data were stored on floppy

disks, and a hard copy was subsequently printed to enable the kickback motion

to be analyzed as described in other sections of this report.

4. Experimental Program

4.1. Selection of Test Saws

The CPSC provided 34 consumer-type chain saws from which to select saws

for the experimental program. From this population of currently-manufactured

saws, 5 gasoline and 2 electric chain saws were selected. Preliminary selection of the test saws was based only on the total kickback energy determined

by CPSC with the Kickback Test Machine. Since some of the saws in this group

were found to have relatively little kickback motion when held by each of several operators, a second group of saws was chosen taking into account the polar moment of inertia of the saw in addition to its kickback energy characteristics. The final selection took into account additional design features

which provided somewhat greater diversity among the test saws. The general

characteristics of the saws selected for the kickback experimental program are

listed in table 1.

4.2. Kickback Test Conditions

During the preliminary hand-held kickback tests to select the test saws

for the experimental program, the saws were tested at conditions where the

total energy obtained in the KBM was found to be maximum. After the test saws

were selected, it was found that somewhat larger kickback motion would result

if the saws, when held by an operator, were tested at conditions where the

rotational energy obtained in the KBM was at a maximum.

A list of the kickback test parameters which were used for the chain saws

in the experimental program is given in table 2. The maximum values for rotational energy as determined in the KBM are also noted in this table.

6
Table 1. Characteristics of chain saws in hand-held kickback

experimental program

Chain Weight

Saw'

1, N (lbf)

Guidebar

Length2 cm (in) Chain Type

Total

Polar Inertia Energy 3 p m-N-sec joule

( in-lbf-sec 2

) ( in-lbf

)

G1 (1.6) 2.270 (10.10) 30.48 (12) Low Profile 0.0617 (0.546) 12.6 (112)

G2 (2.0) 2.172 (9.66) 30.48 (12) Low Profile 0.0651 (0.576) 13.6 (120)

G3 (2.1) 2.934 (13.05) 35.56 (14) Low Profile 0.0942 (0.834) 10.7 (95)

G4 (2.6) 2.967 (13.20) 40.64 (16) Standard 0.1321 (1.169) 36.3 (321)

G5 (3.6) 3.992 (17.76) 40.64 (16) Standard 0.1527 (1.351) 51.8 (458)

E6 (2.25) 2.423 (10.78) 35.56 (14) Low Energy 0.0584 (0.517) 9.6 (85)

E7 (2.0) 2.774(12.34) 35.56 (14) Top Sharp 0.0817 (0.723) 11.9 (105)

'•For gasoline-powered saws, designated by "G," the number in parentheses

represents the engine cubic-inch displacement. For electric-powered saws,

designated by "E," the number in parentheses represents the engine horsepower

capacity.

p All the guidebars were equipped with a sprocket nose, and each of the latter were

symmetric except for Saw E7.

q The kickback energy was measured in the Kickback Test Machine at those conditions

producing the maximum value of rotational energy. The same test conditions were

used in the hand-held kickback program and are given in table 2.

7
Table 2. Test parameters for the hand-held kickback experimental program 1

Test Saw

o Rotational Energy

joule (in-lbf)

Contact Angle

(deg)

Engine Speed

(rpm)

Approach Speed

(in/ sec)

G1 9.5 (84) 20 10,000 30

G2 11.1 (98) 15 11,000 35

G3 9.7 (86) 15 11,000 35

G4 32.5 (288) 15 9,500 25

G5 46.7 (413) 10 11,500 30

E6 8.6 (76) 20 7,200 20

E7 8.7 (67) 10 7,200 35

^The warm-up, clutch-burn or torque, and chain-tension procedures for the

hand-held saws were the same as the test procedures developed for use with the

Kickback Test Machine. The test saws and chains were broken in by the CPSC prior

to conducting the hand-held experimental program.

Determined by CPSC using the Kickback Test Machine.

8
4.3. Volunteer Test Operators

A total of 9 male and 2 female volunteers served as test operators in the

hand-held kickback program. Selection of the volunteer subjects and other human

factors aspects of the experimental design for the program were developed under

the guidance of a research psychologist. Detailed information concerning the latter topics, including the test subject profiles, are given in Appendix B.

Prior to testing, the principal investigator orally gave each subject the

following instructions, which had been prepared by a research psychologist:

"It is very important that you understand the following instructions:

What we want you to do is to pretend that you are cutting a log.

Let the chain saw rest on the wooden block and pretend it is cutting

its way through it. Do not lean into or push down on the saw. When you

get the saw in the correct position, just hold it steady. Do you have

any questions?"

Prior to the tests for each saw, the principal investigator demonstrated a

kickback for that particular saw. The safety bar height was then adjusted so that

the subject could not see when the wood carriage was released to initiate the

kickback motion. The subject was given an opportunity to experience several

kickbacks as part of the indoctrination before the kickback motion was measured

for five consecutive tests for each saw.

5. Determination of Test Saw Rotational Displacements

For most of the kickback tests, the LED's, whose coordinates were measured in

real time during a kickback, were placed on both the test saw and the test fixture. Three diodes were always located on the test saw: a) on the guidebar

shield near the nose tip of the guidebar, b) near the saw center of gravity, and

c) near the rear handle of the saw. Usually, three diodes were also located on

the test fixture, one at a fixed reference position at the base of the carriage

rails and two on the clamp of the moving carriage.

9
The primary purpose of the reference diode at the base of the carriage rails

was to ensure that the camera set up of the measuring system was the same for the

various tests, since the instrumentation was frequently disassembled after a test

and reassembled for succeeding tests. ^ The purpose of the diodes mounted on the

carriage clamp was to check the angle of the wood specimen and to monitor the carriage motion during the kickback. Since the contact angle and carriage speed were

accurately measured with other equipment, the coordinate data at these positions

were additional indicators that these parameters were correctly adjusted. For

several of the kickback tests, the diodes were removed from the carriage clamp and

placed on the wrist and elbow of the test subject. The coordinate data for these

positions were then used to plot the motion of the right-arm wrist and elbow for

several of the larger male test subjects. This information was used in an evaluation of the motion produced in the Human Factors Apparatus (HFA), the data for

which will be presented in a separate report [2].

The coordinate-time data for the diodes mounted on the test saws were analyzed in this investigation. Primary emphasis was placed on evaluation of the saw

rotation, because of the severity of kickback injuries associated with such displacements [3].

Criteria and Method for Assessing the Kickback Angle . The method for assessing the kickback angle for this preliminary analysis was chosen on the basis of

the CPSC evaluation of the apparent angle of rotation from in-depth investigation

reports (IDIR's) of chain-saw accidents. This angle is measured as though a saw

rotates about a point in line with the top of the guidebar at point a on that line

(line A) where it is intersected by another line (line B) perpendicular to it and

^The instrumentation was required for another research activity which ran concurrently with the kickback experimental program.

10
touching the rearmost part of the rear handle (see figure 2). Another line is then

drawn from this point to the point of chain contact with the operator (line C) , as

shown. The angle from line A lying along the top of the guidebar to line C about

point a was measured in the IDIR's as the apparent angle of rotation. This approach was developed by the CPSC as a measure of the difference between the position of the saw just prior to kickback and the location of the body part injured.

This criterion for assessing the apparent kickback angle implies that the

operator’s right hand continues to grip the saw’s rear handle for the duration of

the kickback. There was no method for evaluating this assumption prior to conducting the experimental program. Other postulated methods for assessing the

kickback angle depended similarly on assumptions which could not be evaluated

prior to conducting the experimental program.

In the analysis of the saw LED (diode) coordinate data to compute the derived

angle of rotation (DAR), a correction was made so that the rear handle diode position was adjusted to lie along line B in figure 2. A second correction was made

to account for the fact that the diode at the end of the guidebar was, in general,

not aligned with the rear handle diode. Although other modifications to the recorded data were omitted for this preliminary analysis, an estimate was made of

their influence on the kickback angles. These second-order corrections will be

discussed in a later section of this report. It should be noted that the

operator's control of the saw for the CPSC kickback angle criterion, based upon

IDIR's, was confirmed during the experimental program: the test subjects maintained right-hand grip of the rear handle throughout the kickback for all the

tests

The derived angle of rotation (DAR) was determined from the digitized coordinate data as follows:

li
POINT

OF

CONTACT

WITH

BODY

Figure

2.

CPSC

Determination

of

Aona-t-erit-
DAR = DARX + DAR2 ,

where DAR-^ is the angle through which the guidebar rotates above a horizontal line

passing through the rearmost part of the rear handle, i.e. , (^QjY^q) as shown in

figure 3. Since the diode located at the end of the guidebar, having coordinates

^

3

^

3 ), was generally not located on this horizontal line when the saw was held

as the kickback was initiated, the term DAR2 was added to DAR]^ to incorporate the

angular travel of this diode before it reached the horizontal. The complete equation is:

DAR = tan- 1 [(Y 3 -Y50 )/(X50-X3

)] + tan" 1

[ (Y50-Y30 ) / (X50-X30 )

]

where (X2 q,Y3 q) are the diode coordinates at the end of the guidebar at initiation

of kickback (time t = 0 ); the sign conventions for the displacement measuring sys4

tern are shown in figure 3.

Before the derived angle of rotation could be computed, it was first necessary to determine when the test saw was contacted by the wood specimen. The best

indication was vertical motion recorded from the diode placed near the tip of the

saw guidebar. Contact with the wood occurred just prior to the first indication

of guidebar vertical motion. Thus, the displacements measured for the diode positions one measurement sample (0.003 sec) prior to the latter motion were taken to

define the initial diode coordinates as contact was made. The coordinate data

were printed out in units of the optoelectronic measurement system, which were

subsequently used to estimate the derived angles of rotation for an initial analysis.

Since the diode located near the rear handle of each test saw was not precisely in the desired reference position, a correction was made to the initial

coordinates for this diode to compute the kickback angles as shown in figure 3.

13
CD

>-

14

Figure

3.

Diode

Coordinates

and

Sign

Convention

for

Computing

DAR
Similar corrections to the other diode positions on the guidebar, the saw, and at

its center of gravity, were estimated to have a minor influence on the computed

angle of rotation about the rear handle. These corrections and other second-order

factors were investigated by computer analyses of the displacement data for Test

Subjects CDS and NB which are given in Appendix C.

A summary of the computed DAR (derived angle of rotation), for each of the

hand-held kickback tests, is given in tables 3 through 9.1 In addition to the values for DAR, the average DAR for each data set (5 tests) is given, along with the

standard deviation and coefficient of variation. Following the same convention

used in analyses of KBM kickback data, the coefficient of variation is defined as

the standard deviation divided by the average value for each data set.

1 There were 11 test subjects who participated in the Test Series 1 kickback tests;

replicate tests for 7 of these subjects were conducted during Test Series 2.

Additional information pertaining to the subject treatment and other human factors

considerations is presented in Apendix B.

15
Table 3. Computed values of kickback derived angle of rotation (DAR) for Saw G1

Test

Series

1

2

DAR for Replicate Tests, deg Coefficient

Test

Subject 1 2 3 4 5 AverageDAR, deg

Standard

Deviation

of

Variation

CS 5R 1 3R 7R 1R 6R 4.4 2.41 0.55

CK 7R 19R 16R 1 IF 7F 12.0 5.38 0.45

CR 25R 24R 7R 10R 15R 16.2 8. 10 0.50

CN 16F 15F 10F 13F 10F 12.8 2.77 0.22

CJ 9R 21R hr 18F 13F 14.4 4.97 0.34

CD 16F 13F 17F 11R 8R 13.0 3.67 0.28

CMJ 19F 16F 15F 19R 15R 16.8 2.05 0.12

CA 44R 2 2 2 29F — —

NB 14R 16R 12R 10R HR 12.6 2.41 0.19

CDS 26F 27F 30F 2 26F 27.2 1.89 0.07

CHD 43F 18F 19F 16F 13F 21.8 12.07 0.55

CDS 24F 29F 17F 27F 20F 23.4 4.93 0.21

CR 22F 15F 35F 25F 18F 23.0 7.71 0.34

CJ 27F 35F 25F 39F 27F 30.6 6.07 0.20

CHD 26R 28R 23R 24R 25R 25.2 1.92 0.08

CN 1 IF 10F 14F 15F 10F 12.0 2.34 0.20

NB 17R 21R 13R 18R 16R 17.0 2.92 0.17

CD 41R 23R 25R 34R 2 30.7 8.34 0.27

Average coefficient of variation for 17 tests was 0.28.

^Right-hand on rear (R) or front (F) throttle trigger.

^Malfunction of recording system occurred during the test which interrupted the

data transfer to the computer memory.

16
Table 4. Computed values of kickback derived angle of rotation (DAR) for Saw G2

DAR for Replicate Tests, deg Coefficient

Test

Series

Test

Subject 1 2 3 4 5 Average

DAR, deg

Standard

Deviation

of

Variation

1 CS 19 26 35 20 26 25.2 6.38 0.25

CK 18 19 14 18 19 17.6 2.07 0. 12

CR 15 14 19 16 14 15.6 2.07 0. 13

CN 19 14 29 16 17 19.0 5.87 0.31

CJ 23 17 16 19 21 19.2 2.86 0.15

CD 15 14 1 10 14 13.2 2.22 0.17

CMJ 37 16 29 12 26 24.0 10.07 0.42

CA 19 14 23 20 22 19.6 3.51 0.18

NB 11 15 14 15 13 13.6 1.67 0.12

CDS 37 21 27 30 25 28.0 6.00 0.21

CHD 17 27 22 23 20 21.8 3.70 0.17

2 CDS 32 30 34 19 29 28.8 5.80 0.20

CR 16 18 13 17 10 14.8 3.27 0.22

CJ 17 14 14 12 16 14.6 1.95 0.13

CHD 30 27 24 27 20 25.6 3.78 0. 15

CN 15 14 18 10 15 14.4 2.88 0.20

NB 25 15 28 17 15 20.0 6.08 0.30

CD 17 22 14 16 14 16.6 3.29 0.20

Average: coefficient of variation for 18 tests was 0.20.

^Malfunction of recording system occurred during the test, which interrupted data

transfer to the computer memory.

17
Table 5. Computed values of kickback derived angle of rotation (DAR) for Saw G3

Test

Series

1

2

DAR for Replicate Tests, deg

Test

Subject 1 2 3 4 5

CS 22 10 17 28 24

CK 14 14 17 13 13

CR 10 14 14 16 18

CN 10 13 12 12 14

CJ 14 7 15 13 11

CD 18 16 16 22 23

CMJ 18 14 30 24 20

CA 11 14 16 14 21

NB 12 8 11 14 11

CDS 20 17 23 31 32

CHD 23 21 26 22 20

CDS 32 41 26 27 26

CR 18 17 15 17 15

CJ 16 15 14 14 14

CHD 20 25 22 24 25

CN 11 18 18 21 20

NB 21 23 16 18 12

CD 16 17 23 22 22

Coefficient

Average

DAR, deg

Standard

Deviation

of

Variation

20.2 6.94 0.34

14.2 1.64 0.12

14.4 2.97 0.21

12.2 1.48 0.12

12.0 3.16 0.26

19.0 3.32 0.17

21.2 6.10 0.29

15.2 3.70 0.24

11.2 2.17 0.19

24.6 6.65 0.27

22.4 2.30 0.10

30.4 6.43 0.21

16.4 1.34 0.08

14.6 0.89 0.06

23.2 2.17 0.09

17.6 3.91 0.22

18.0 4.30 0.24

20.0 3.24 0.16

Average coefficient of variation for 18 tests was 0.19.

18
Table 6. Computed values of kickback derived angle of rotation (DAR) for Saw G4

DAR for Replicate Tests, deg

Test

Series

Coefficient

Test

ub ject 1 2 3 4 5

Average

DAR., deg

Standard

Deviation

of

Variat

CS 39 34 31 24 26 30.8 6.06 0.20

CK 15 14 14 18 15 15.2 1.64 0.11

CR 41 40 30 34 44 37.8 5.67 0.15

CN 35 41 33 29 41 35.8 5.22 0. 14

CJ 32 24 23 24 30 26.6 4.10 0. 15

CD 25 18 26 30 34 26.6 5.98 0.22

CMJ 48 28 32 34 28 34.0 8.25 0.24

CA 36 36 36 24 41 34.6 6.31 0.18

NB 39 37 44 41 31 38.4 4.88 0. 13

CDS 52 1 49 36 36 51

44.8 8.10 0.18

CHD 39 32 40 33 36 36.0 3.54 0.10

CDS 50 1 52 1 30 35 43 42.0 9.46 0.22

CR 28 46 38 26 48 1 37.2 10.06 0.27

CJ 31 35 33 31 32 32.4 1.67 0.05

CHD 41 38 45 47 33 40.8 5.58 0. 14

CN 41 38 34 38 32 36.6 3.58 0.10

NB 48 46 34 41 35 40.8 6.30 0.15

CD 2 24 34 20 25 25.8 5.91 0.23

Average coefficient of variation for 18 tests was 0.16.

*-Saw struck safety bar.

^-Malfunction of recording system occurred during the test, which interrupted the

data transfer to the computer memory.

19
Table 7. Computed values of kickback derived angle of rotation (DAR) for Saw G5

Test

Series

1

2

DAR for Replicate Tests, deg

Test

Subject 1 2 3 4 5

CS 8 16 13 10 19

CK 25 25 25 23 12

CR 33 36 38 34 37

CN 46 47 45 38 34

CJ 32 27 18 20 24

CD 15 16 37 9 16

CMJ 23 13 16 22 15

CA 37 30 25 25 29

NB 21 5ll 43 35 22

CDS 47 32 5ll 49 1 48

CHD 42 26 29 41 30

CDS 49 1 49 1 5ll 52 1 47

CR 41 42 34 32 28

CJ 32 37 35 47 36

CHD 41 42 49 42 37

CN 39 45 36 28 25

NB 53 57 32 45 28

CD 18 33 14 22 24

Coefficient

Average

DAR, deg

Standard

Deviation

of

Variation

13.2 4.44 0.34

22.0 5.66 0.26

35.6 2.07 0.06

42.0 5.70 0. 14

24.2 5.58 0.23

18.6 10.69 0.57

17.8 4.44 0.25

29.2 4.92 0. 17

34.4 13.07 0.38

45.4 7.64 0.17

33.6 7.37 0.22

49.6 1.95 0.04

35.4 5.98 0. 17

37.4 5.68 0.15

42.2 4.32 0.10

34.6 8.14 0.24

43.0 12.71 0.30

22.2 7.16 0.32

Average coefficient of variation for 18 tests was 0.23.

1 Saw struck safety bar.

20
Table 8. Computed values of kickback derived angle of rotation (DAR) for Saw E6

DAR for Replicate Tests, deg Coefficient

Test

Series

Test

Subject 1 2 3 4 5 AverageDAR, deg

Standard

Deviation

of

Variation

1 CS 7 12 9 13 12 10.6 2.52 0.24

CK 5 2 3 4 4 3.6 1.14 0.32

CR 10 8 7 8 9 8.4 1.14 0. 14

CN 6 7 14 10 11 9.6 3.21 0.33

CJ 6 13 12 13 11 11.0 2.92 0.26

CD 22 16 18 14 23 18.6 3.85 0.21

CMJ 17 27 26 29 17 23.2 5.76 0.25

CA 18 26 16 16 27 20.6 5.46 0.26

NB 9 10 10 8 13 10.0 1.87 0.19

CDS 21 22 26 26 22 23.4 2.41 0.10

CHD 9 7 7 18 17 11.6 5.46 0.47

2 CDS 17 16 19 16 18 17.2 1.30 0.08

CR 15 8 9 10 10 10.4 2.70 0.26

CJ 13 14 13 13 11 12.8 1.10 0.08

CHD 23 18 22 16 14 18.6 3.85 0.21

CN 9 10 10 7 12 9.6 1.82 0.19

NB 16 18 15 19 11 15.8 3.11 0.20

CD 12 15 16 20 12 15.0 3.32 0.22

Average coefficient of variation for 18 tests was 0.22.

21
Table 9. Computed values of kickback derived angle of rotation (DAR) for Saw E7

DAR for Replicate Tests, deg Coefficient

Test

Series

Test

Subject 1 2 3 4 5 Average

DAR, deg

Standard

Deviation

of

Variation

1 CS 9 21 20 10 25 17.0 7.11 0.42

CK 10 13 35 9 10 15.4 11.06 0.72

CR 8 8 8 10 12 9.2 1.79 0. 19

CN 13 10 11 10 15 11.8 2.17 0.18

CJ 12 11 15 10 8 11.2 2.59 0.23

CD 21 18 14 15 14 16.4 3.05 0.18

CMJ 25 12 16 16 14 16.6 4.98 0.30

CA 27 42 27 1 1 32.0 8.66 0.27

NB 18 32 24 8 10 18.4 9.94 0.54

CDS 14 14 18 13 31 18.0 7.52 0.42

CHD 15 9 16 14 13 13.4 2.70 0.20

2 CDS 11 20 21 11 17 16.0 4.80 0.30

CR 7 12 10 12 7 9.6 2.51 0.26

CJ 12 12 16 9 15 12.8 2.77 0.22

CHD 27 23 17 19 18 20.8 4.15 0.20

CN 9 7 12 20 9 11.4 5.13 0.45

NB 6 8 10 14 10 9.6 2.97 0.31

CD 21 28 14 31 42 27.2 10.57 0.39

Average coefficient of variation for 18 tests was 0.32.

^Malf unction of recording system occurred during the test which interrupted data

transfer to the computer memory.

22
6. Principal Test Results

6.1. Kickback Energy During Hand-Held Tests

One of the principal objectives in the experimental program was to relate the

kickback angle through which a chain saw might travel when held by an operator to

the kickback energy determined for the saw in the Kickback Test Machine (KBM).

Since the test conditions during the hand-held kickbacks were based on KBM energy

data, it was desirable to determine as well as possible the kinetic energy achieved

during the hand-held kickback tests. It should be emphasized that the accuracy of

conclusions drawn from kinematic studies of motion depends heavily upon the accuracy of the displacement measurements which are the precursors for calculation of

such quantities as the energy [4].

An initial attempt, using high-speed photography, was made to estimate the

kickback energy for a hand-held saw based on evaluating the saw displacements for a

kickback filmed at a speed of 300 frames per second. This estimate did not compare

well with the energy determined for that saw during a simulated kickback in the KBM

under the same test conditions. The major sources of inaccuracy were the

relatively slow frame speed and the difficulty in visually analyzing the data from

film. It was also recognized that the very small displacements associated with the

initial kickback motion of the test saw center of gravity made the estimation of

lateral and vertical energy components difficult without sophisticated measurement

and analysis of the saw powerhead motion. Although a better estimate of the

rotational energy component for a test saw was achieved by filming a kickback at a

speed of 500 frames per second, the estimation of the other energy components was

not greatly enhanced. As noted by other investigators, attempts to calculate

velocities (required to determine the energy) by differentiation of displacements

have been plagued by amplification of the noise inherent in even apparently smooth

displacement data [4].

23
The use of an optoelectronic system for measuring the kickback motion in the

present experimental program permitted a more reliable estimate to be made for the

rotational energy for some kickback tests. The source of error due to visual analysis of film is eliminated, but the noise associated with very small displacements

of the saw powerhead was not greatly improved. The standard sampling rate of 312

Hz for the optoelectronic measuring system was sufficient to enable good estimates

to be made for saw rotational velocities, at least for the test saws having large

kickback motion when held by relaxed test subjects. Attempts made to increase the

standard sampling rate were unsuccessful due to the inability to multiplex the number of LED positions required.

The estimates of rotational energy for each of the test saws and the rotational energy obtained with the KBM for the saws at the same test conditions are

given in table 10. The values in this table were computed for test conditions

where the duration of the kickback per degree of rotation indicated that the test

subject was relatively relaxed. 5 In this regard, it is evident that a large amount

of energy can be absorbed if the saw motion deviates from a planar path

(planar motion is ensured in the KBM by constraint of a test saw). Thus, the estimates of rotational energy are in best agreement with the known energy values when

the test subject does not impose constraints on the rotational motion of the saw

that differ substantially from those in the KBM.

^Typical values for this index found by a major saw manufacturer were in the range

of 0.002 to 0.005 sec per degree.

24
Table 10. Estimated rotational kickback energy for saws during hand-held tests.

Rotational Energy Estimated Rotational

Determined in KBM Energy in Hand-Held Tests ^ Test Saw joule ( in-lbf

)

joule ( in-lbf)

G1 9.5 (84) 6.8 (60)

G2 11.1 (98) 8.4 (74)

G3 9.7 (86) 8.4 (74)

G4 32.5 (288) 27.0 (239)

G5 46.7 (413) 42.1 (373)

E6 8.6 (76) 7.6 (67)

E7 7.6 (67) 7.2 (64)

*- Energy estimated from Iw2 /2 where I is the measured polar moment of inertia

about the saw c.g. and oo is the maximum rotational velocity determined from

optoelectronic displacement data. The velocity was estimated during the initial

kickback motion (while the chain was in contact with the wood specimen) and only

the inertia due to the saw was considered.

25
6.2 Comparison of Saw Motion with Energy Measured in Kickback Machine

In order to compare the chain saw rotational motion measured during the handheld kickback tests with the energy measured for the test saws in the kickback

machine, it is useful to average the computed kickback angles. The average and

maximum values for the derived angle of rotation (DAR) for each test subject and

saw are presented in tables 11 and 12 for the first 11 kickback tests (Test Series

1) and the last 7 tests (Test Series 2), respectively. A tabulation of the composite mean and maximum DAR values for Test Series 1 and 2 is given in table 13.

Comparison of the Series 1 and 2 data in the latter table indicates there was

probably some effect from subjects learning on saw kickback, particularly for saws

Gl, G4 and G5. The total kickback energy and rotational components of energy for

the test saws determined using the kickback machine are given in the last column of

the table.

26
Table 11. Summary of average and maximum values of derived angle of rotation (DAR)

for kickback test series 1.

DAR, deg

Test Subject Kickback Angle G1 G2 G3 G4 G5 E6 E7

CS Average 4 25 20 31 13 11 17

CS Maximum 7 35 28 39 19 13 25

CK Average 12 18 14 15 22 4 15

CK Maximum 19 19 17 18 25 5 35

CR Average 16 16 14 38 36 8 9

CR Maximum 25 19 18 44 38 10 12

CN Average 13 19 12 36 42 10 12

CN Maximum 16 29 14 41 47 14 15

CJ Average 14 19 12 27 24 11 11

CJ Maximum 21 23 15 32 32 13 15

CD Average 13 13 19 27 19 19 16

CD Maximum 17 15 23 34 37 23 21

CMJ Average 17 24 21 34 18 23 17

CMJ Maximum 19 37 30 48 23 29 25

CA Average 1 20 15 35 29 21 32

CA Maximum 44 23 21 41 37 27 42

NB Average 13 14 11 38 34 10 18

NB Maximum 16 15 14 44 51 13 32

CDS Average 27 28 25 45 45 23 18

CDS Maximum 30 37 32 52 51 26 31

CHD Average 22 22 22 36 34 12 13

CHD Maximum 43 27 26 40 42 18 16

Insufficient data to compute average DAR.

27
Table 12. Summary of average and maximum values of derived angle of rotation (DAR)

for kickback test series 2.

DAR, deg

Test Subject Kickback Angle G1 G2 G3 G4 G5 E6 E7

CDS Average 23 29 30 42 50 17 16

CDS Maximum 29 34 41 52 52 19 21

CR Average 23 15 16 37 35 10 10

CR Maximum 35 18 18 48 42 15 12

CJ Average 31 15 15 32 37 13 13

CJ Maximum 39 17 16 35 47 14 16

CHD Average 25 26 23 41 42 19 21

CHD Maximum 28 30 25 47 49 23 27

CN Average 12 14 18 37 35 10 11

CN Maximum 15 18 21 41 45 12 20

NB Average 17 20 18 41 43 16 10

NB Maximum 21 28 23 48 57 19 14

CD Average 31 17 20 26 22 15 27

CD Maximum 41 22 23 34 33 20 42

28
Table 13. Comparison of average and maximum values of derived angles of rotation

for Kickback Test Series 1, Series 2, and combined test series with

energy determined in Kickback Machine (KBM)l.

Test Series

1 Test Series

2

Combined

Test Series

Test

Saw

Avg.

DAR

(deg)

Max.

DAR

(deg)

Avg.

DAR

(deg)

Max.

DAR

(deg)

Avg.

DAR

(deg)

Max.

DAR2 (deg)

Total

joule

Energy

(in-lbf

)

Rotational

Energy

joule (in-lbf)

G1 15 23 23 30 18 26 12.6 (112) 9.5 (84)

G2 20 25 19 24 20 25 13.6 (120) 11.1 (98)

G3 17 22 20 24 18 22 10.7 (95) 9.7 (86)

G4 33 39 36 44 34 41 36.3 (321) 32.5 (288)

G5 29 36 38 46 32 40 51.8 (458) 46.7 (413)

E6 14 17 14 17 14 17 9.6 (85) 8.6 (76)

E7 16 24 15 22 16 23 11.9 (105) 7.6 (67)

Avg.

Coef. of

Variation 0 .25 0 .20 0 .23

^For Test Series 1 and 2, the DAR values are averages for 11 and 7 test subjects,

respectively. For the combined test series, the DAR values are for 18 subjects (11

test subjects with replicate tests for 7 of these during Series 2).

2 The maximum DAR values denote the mean of the largest derived angles of rotation

for the respective test series.

6.3 Evaluation of Low Kickback Energy Chain

At the request of the CPSC, an extra set of hand-held kickback tests were conducted for three test subjects to evaluate a specially designed saw chain. In the

last few years, several chain manufacturers have developed saw chains designed to

reduce the kickback energy potential for some types of consumer chain saws. A

series of kickback tests had been performed during earlier tests with the KBM in

which one of these "low energy" chains was compared with a standard-type chain for

test saw G5 [ 1 ]

29
A similar set of hand-held kickback tests were conducted using the low energy

chain as well as the original equipment chain for saw G5. Since these two chains

were identical to the chain used in the evaluation of kickback energy determined

with the KBM, it was possible to compare the reduction in kickback for the low

energy 'chain in terms of kickback derived angle of rotation as well as in terms of

kickback energy. The results of kickback tests in the KBM and during the hand-held

tests for the two chain designs are summarized in table 14.

Table 14. Comparison of kickback tests using original equipment (0)

and low energy (L) chain for Saw G5.

Kickback Test

Average

Chain 0

DAR, deg

Chain L

Total

joule

Chain 0

Energy

(in-lbf

)

Chain L

Reduction

Kickback,

percent

in

1

Hand-held (Subject CDS) 50 11 - - 78

(Subject CR) 35 5 - - 86

(Subject CJ) 37 7 - - 81

Kickback Machine

\

- 53.0 (469) 14.9 (132) 72

"^Percent Reduction in Kickback = Kickback for Chain 0 - Kickback for Chain L Y 100

Kickback for Chain 0

30
6.4. Evaluation of Handle Spacing Effect on Saw Motion

Test Saw G1 was unique among the saws used in the hand-held kickback program

in that it had two throttle trigger locations on the rear handle. The forwardmost

trigger was located approximately 5 cm (2 in) from the saw front handle, and the

rearmost trigger was located 16 cm (6.5 in) from the front handle, measured along a

line parallel to the flat portion of the guidebar. Due to this trigger arrangement, it was possible to investigate the influence of handle spacing on the motion

of Saw G1 during the hand-held kickback tests.

To facilitate an unbiased determination of the handle spacing effect, the replicate tests for Saw G1 were arranged so that some test subjects gripped only the

front throttle trigger, some gripped only the rear trigger, and some subjects

alternated the trigger they gripped for the replicate tests. 6 a summary of the

derived angles of rotation for the Test Series 1 and 2 for Saw Gl, using the two

right-hand grip positions, are given in table 15. The throttle trigger gripped for

each kickback test is noted in the table by the symbols F (forward throttle) and R

(rear throttle). The average DAR when the subject gripped the rear throttle trigger was 17.6 deg; when the subject gripped the front throttle trigger, the average

DAR was 19.5 deg. Although the differences in the average DAR for the two righthand grip positions is not large, it is in the direction which was expected since

the operator’s hands are closer together when the front trigger is gripped.

£ The random match for the replicate tests was provided by the CPSC and is discussed

in Appendix B.

31
Table 15. Derived angles of rotation for kickback tests with Saw G1

for two rear handle grip positions.

Derived Angle of Rotation, deg

Test Subject Test 1 Test 2 Test 3 Test 4 Test 5

CS 5(R) 3(R) 7 (R) 1(R) 6(R)

CK 7 (R) 19(R) 16(R) 11(F) 7(F)

CR 25(R) 24(R) 7 (R) 1 0 ( R

)

15(R)

CN 16(F) 15(F) 10(F) 13(F) 10(F)

CJ 9(R) 21(R) 11(R) 18(F) 13(F)

CD 16(F) 13(F) 17(F) 11(R) 8(R)

CMJ 19(F) 16(F) 15(F) 19(R) 15(R)

CA 44(R) 1 1 1 29(F)

NB 14(R) 16(R) 12(R) 10(R) 11(R)

CDS 26(F) 27(F) 30(F) 1 26(F)

CRD 43(F) 18(F) 19(F) 16(F) 13(F)

CDS 24(F) 29(F) 17(F) 27(F) 20(F)

CR 22(F) 15(F) 35(R) 25(R) 18(R)

CJ 27(F) 35(F) 25(F) 39(F) 27(F)

CHD 26(R) 28(R) 23(R) 24(R) 25(R)

CN 9(F) 10(F) 14(F) 15(F) 10(F)

NB 1 7 (R) 21 (R) 13(R) 18(R) 16(R)

CD 41 (R) 23(R) 25(R) 34(R) 1

(F) - Subject gripped front throttle trigger.

(R) - Subject gripped rear throttle trigger.

1 Malfunction of recording system occurred during test.

32
7. Discussion

| The preceding sections of this report describe the experimental program developed to determine the relationship between kickback energy and chain saw motion

during hand-held kickbacks for selected samples of consumer-type chain saws and

volunteer test subjects. The parameter selected to characterize the saw motion was

the derived or apparent angle of rotation as defined from in-depth investigation

analyses of chain saw accidents by the CPSC. For each of the test subjects, significant differences were found in both average and maximum angles of rotation

among the sample of saws which they held during simulated kickback.

A computer-controlled optoelectronic system employed for measuring the displacements in real time, at selected locations on the test saws, was required to

determine the saw positions throughout a simulated kickback. The computer analyses

of the large amount of displacement-time data required to define the path of a

chain saw during kickback demonstrated several advantages of this measurement system compared to high-speed cinematography. Visual analyses for the latter are both

time-consuming and suceptible to human error. ^ The analyses of digitized data with

a computer obviate the need for visual procedures to define the saw position over

small time increments which characterize a kickback event. Furthermore, since the

coordinate-time data are measured in digital form, additional kinematic parameters

are easily computed. An example of this feature is given in Appendix C, in which

the chain saw rotations for two test subjects were computed using three different

reference systems. Such analyses permit a more thorough assessment to be made of

the potential hazards to a chain saw operator in the absence of quantitative kickback data in a "field" situation.

^Reference [5] provides an additional critique of film techniques to collect

kinematic data.

33
A coefficient of variation for the computed angles of kickback rotation, i.e.,

the standard deviation divided by the mean value for five replicate tests, was

chosen as an index of the test variability. For Test Series 1 and 2, the overall

coefficient of variation for all test subjects and saws was 0.25 and 0.20, respectively. This result is comparable to the same measure of repeatability characteristic of the kickback data obtained with the KBM, particularly when the orders of

magnitude for the rotation angle and the kickback energy are compared [1].

Analyses of the hand-held kickback data clearly indicate that the test arrangement and procedures for the experimental program resulted in saw motion data

which were both repeatable and discriminating. Thus, it is possible to compare the

derived angles of rotation with the energy data, which is required for CPSC injury

reduction studies [3]. The large reduction in the derived angle of rotation for

Saw G5 when equipped with a low kickback energy chain, compared to the original

equipment chain, tends to confirm the known reduction in kickback energy for the

same saw and chain combinations when evaluated in the KBM using the corresponding

test parameters. In a special investigation for Saw G1 it was found that the effect of handle spacing on the saw kickback motion was not large, but indicated that

larger handle spacing tended to reduce the angle of rotation as would be expected

based on consideration of mechanical principles.

Procedures for the simulation of hand-held kickbacks other than those used in

this investigation might have achieved larger chain saw motion, but also might have

posed greater risks to the volunteer operators and/or introduced greater test variability. In this regard, it should be noted that, during kickback tests for three

operators who held either of two saws, the shielded guidebar struck the safety bar

which limited the saw rotation—in some cases, with considerable impact force.

'•The safety precautions developed for the experimental program were designed

specifically for this type of contingency (see Appendix A).

34
Thus, the average and peak angles of rotation for these tests, which are noted in

the report, represent conservative values. It can be expected that the additional

test saw inertia due to use of the guidebar shields would also tend to reduce the

saw motion compared to that encountered in a "field" situation during a kickback

event

8. Acknowledgments

The assistance of Messrs. J. Huckeba and H. Kratz in conducting the experimental program and construction of the test apparatus, respectively-, is gratefully

acknowledged. Dr. A. Dainis and Mr. D. Brenner provided valuable assistance in the

operation of the optoelectronic measurement equipment and interfacing of the latter

with a high-speed computer. Mr. H. Lucas of the Consumer Product Safety Commission

provided useful information throughout the experimental program; Ms. V. Brown and

Ms. L. Santelli of the CPSC provided valuable assistance in the human factors and

data analysis aspects of the program, respectively. Dr. H. P. Van Cott, BioTechnology, Inc., served as a human factors consultant; his recommendations for the

experimental design are summarized in Appendix B.

35
9. References

1. Robinson, D.C. Assessment of the kickback energy potential for chain saws.

Wat. Bur. Stand. (U.S.) NBSIR 81-2193, 1981 January. 49 p.

2. Robinson, D. C. ; Huckeba, J. A. Evaluation of a human factors robotic

device for simulation of chain saw kickback. Nat. Bur. Stand. (U.S.) NBSIR

(in preparation).

3. Newman, R. Overview of chain saw related injuries. Consumer Product Safety

Commission Epidemiology Report; 1981 August.

4. Pezzack, J. C. , et al. An assessment of derivative determining techniques used

for motion analysis, J. Biomechanics, 10, (5/6); 1977.

5. Engin, A. E. On the biomechanics of major articulating human joints, in

Progress in biomechanics, N. Akkas , (ed.). NATO Advanced Study Institutes

Series E: Applied Science (32); 1979.

36
Appendix A. Development of Test Protocol

Test Stand Arrangement

In order to develop the test protocol for conducting hand-held chain saw

kickback tests, it was first necessary to fabricate a test stand to assist in

controlling specific test parameters and test-subject variability. Since the

hand-held kickback data were required to establish the relationship between

the energy determined when using the Kickback Test Machine (KBM) and kickback

angle, the test stand was arranged to simulate a kickback in the same manner

as for the KBM [1].

For the hand-held tests, a volunteer operator held an operating chain saw

so that the guidebar was aligned in a horizontal position. Detailed procedures required to accomplish this in a safe manner are described later. The

method for initiating a kickback during hand-held tests was identical to the

procedure developed for the KBM; i.e., a fiberboard test specimen, clamped to

a carriage assembly, was brought into contact with the moving chain at the upper quadrant of the test saw guidebar nose. The principal change in the handheld test arrangement was the necessity for covering the straight portion of

the guidebar with a shield to protect the saw operator. The shields were made

as light in weight as possible to minimize their inertia. The carriage horizontal motion was controlled by a pair of horizontal rails to which the carriage was attached by four low-friction linear bearings. The carriage, which

weighed 6.08 kg (13.401bm), was accelerated by a weight falling inside a vertically mounted tube; the carriage assembly is shown in figure A. 1

37
38

Figure

A.l.

Test

Fixture

Carriage

Assembly
Protocol for Initiation of Chain Saw Kickback

In the Kickback Test Machine, a kickback is initiated by guiding a low

friction carriage, holding a fiberboard specimen, along a guiderail into the

upper nose quadrant of a clamped chain saw. The guidebar of the test saw is

aligned in a horizontal position and the saw is free to rotate about its center of gravity following contact of the wood specimen with the guidebar. The

carriage design features in this arrangement include: 1) acceleration of the

carriage by means of a falling weight to achieve the desired approach speed,

after which the weight is bottomed to permit the carriage to maintain the desired speed just prior to contact of the wood specimen with the saw guidebar;

2) an adjustable clamping assembly to permit the wood specimen angle to be adjusted relative to the initial horizontal position of the test saw guidebar;

and 3) provision for the addition of weights so that the carriage weight can

be adjusted (the latter is a requirement in the test protocol for the KBM)

In the test arrangement for the hand-held kickbacks, all of the principal

features of the KBM carriage were reproduced in order to enable the results of

the hand-held kickbacks to be correlated with data obtained with the KBM without introducing additional test carriage variables. In lieu of the instrumentation for the KBM, a photocell device was used to record the approach velocity of the carriage, which is an important test parameter.

Rationale for Kickback Initiation Procedure

The procedure for initiating kickback in the KBM requires that the wood

test specimen be guided at a preselected constant velocity into the upper nose

quadrant of a motionless chain saw. The saw is positioned so its guidebar is

horizontal and precautions are taken in the test procedures for the KBM to

closely control: 1) the initial horizontal position of the saw, 2) the contact angle, and 3) the approach velocity of the wood specimen. Initiation of

39
a kickback during hand-held tests was achieved in the same manner so as to

permit close control of the latter test parameters, which fundamentally influence the experimental initial and boundary conditions.

Furthermore, it was found from exploratory hand-held tests in which kickback was initiated by moving a saw guidebar toward a fixed wood specimen that

the approach speed and initial saw position are more difficult to control if

the saw guidebar is not supported. Alternatively, if a saw was supported on a

level device which in turn is guided at a preset speed into a fixed wood specimen, then the time-dependent operator forces required to keep the moving saw

in the proper alignment introduced other sources of test variability.

Additional Test Procedures

In addition to the procedures associated with the kickback initiation,

several other test procedures were required due to the use of volunteer chain

saw operators. As has been indicated, the kickback initiation procedure used

in the experimental program required that a test subject assume a passive

mode. This mode simulated a bucking operation, with the guidebar partially

supported as if a chain saw were cutting through a horizontally positioned

limb. Based on data from the CPSC accident investigations, a guidebar support

length of approximately 18 cm (7 in) was chosen. The test saw guidebar was

held in a horizontal position by resting the guidebar safety shield on a

wooden block. The thumb of the operator’s left hand was hooked below the saw

front handle, and the operator stood so that his/her body was to the side of

the cutting plane (plane of chain rotation passing through the saw guidebar).

For the additional safety of the operator, a wood barrier was placed in front

of the operator to prevent excessive rotational saw motion. The primary consideration with regard to upper torso position was the comfort of the test

subject.

40
The rear handle of a chain saw typically has incorporarated into it the

throttle control trigger. This trigger is usually a lever or switch activated

by the operator’s right index finger as his/her right hand grips the rear

handle. It was necessary that all the test subjects keep a firm grip on the

rear handle of the test saws. The requirement for squeezing the throttle control trigger to control the preset engine speed for a gasoline saw or activate

an electric-powered saw tended to insure that the rear handle was properly

gripped.

When the operator held the front handle of a test saw there were two

specific requirements: 1) the fingers of the left hand were wrapped around

the handle such that the handle diameter was kept in the webbing between the

subject's thumb and index finger, and 2) the left hand was positioned on the

handle such that it was approximately adjacent to the top end of the handle;

i.e., the end of the handle closest to the cutting plane of the guidebar. The

first of these requirements insured that the operator had the saw under control, whereas the second requirement was intended to minimize out-of-plane

kickback motion of the test saw.

The test subjects were allowed to experience low energy kickbacks after

the gripping and stance modes were explained and demonstrated by the principal

investigator. For both the safety of the operators and the uniformity of the

test results, the initial subject body position and method of gripping the

test saws was maintained throughout the experimental program. Detailed discussions of the various human factors aspects of the program are given in Appendix B.

41
Appendix B. Human Factors Recommendations and Rationale for Testing Chain Saw

Kickback with Volunteer Operators.

Introduction

The Consumer Product Safety Commission (CPSC) funded the National Bureau

of Standards (NBS) to develop and implement a test protocol and test procedures in order to obtain kickback data on chain saws operated by volunteer

operators. NBS obtained the services of Bio Technology, Inc., to provide

human factors recommendations for the test. This appendix presents Bio Technology’s human factors recommendations and rationales for the kickback experimental program.

Purpose

In support of chain saw standard development, NBS performed a study to

measure the magnitude and relative difference in the kickback of different

chain saws operated by individuals under conditions simulating consumer chain

saw use. The objective of the study was not to measure human performance but

rather to measure kickback performance of saw-person combinations.

Representatives and Realism

Insofar as possible the test protocol and procedures approximated the

conditions of real-world saw use but in an environment that protected volunteer subjects from injury and that permited adequate experimental control to

be exercised in taking kickback measurements. This required some compromise

between safety and the generality of results to real-world saw use.

42
Subject Characteristics

Ideally, subjects to be employed in the test should be statistically representative of the population of chain saw users. However, the user population characteristics were not known so the subpopulation of injured saw users

as defined by the National Electronic Injury Surveillance System (NEISS) data

were used to identify subject characteristics. Subject variables judged to be

of importance in subject selection included: sex, age, weight, height, handedness (if this appears as a discriminating variable in the NEISS data) and

chain saw use. Other subject variables, such as socio-economic status or educational achievement were not judged to be important variables in determining

saw-user behavior.

Sample Size and Selection

Volunteers from NBS and the Consumer Product Safety Commission were used

with full recognition that volunteers drawn from either organization may have

special knowledge or attitudes on risk and safety which would limit the generality of findings to the injured population at large. The subject profiles

are attached to the end of this appendix (table B-2).

Subject Safety Vs. Realism

To the maximum extent possible, the conditions (modified to insure subject safety) of saw use in the test were representative of the conditions of

real-world use. All subjects were required to wear hearing protectors to guard

against the possibility of hearing loss, though such loss was not likely in

the brief periods of exposure to the testing situation.

The test saws were held by subjects in a test arrangement that did not

interfere with saw operation or attenuate saw kickback. Subjects were

43
protected from facial injury by a transparent barrier, rather than a helmet,

which did not restrict the size of the visual field or encumber subject movement. A shield covering the flat portion of the guidebar was employed to protect against injury to the limbs and torso without constraining the subject

and without requiring an unnatural stance or grip of the saw during saw use. A

floor covering was employed in order to reduce the possibility of slips and

falls. Ambient lighting in the test environment was adequate for subjects to

see and operate the saw and test samples.

The test environment was free from extraneous noise and distractions that

would interfere with or stress subject performance or degrade oral communication between subjects and test personnel.

Subject Treatment

Prior to testing (at least one day in advance) all test subjects were

given and required to read and understand saw safety guidelines provided by

the CPSC. Subject release forms required subjects to attest to having read

the CPSC safety guidelines prior to testing.

Prior to testing, each subject completed a questionnaire requesting information on the subject's sex, age, height, weight, and previous saw use experience. Other variables, such as corrected vision or occupation, were included in the questionnaire, but these variables are unlikely to be important

sources of variance in subject performance.

All subjects were given the same oral instructions prior to testing.

Standardization was insured by having the same test supervisor read the instructions to all the subjects. Instructions described what the subject was

to do and how it was to be done. It was neither necessary nor desirable that

the subject be informed of the purpose of the study since such knowledge might

bias performance.

44
All saws were tested by each subject. In order to account for the effects of subject learning (i.e., experience) on saw kickback, the order in

which saws were presented was randomized across and within subjects as shown

in table B-l. Over half of the subjects tested were retested to determine if

there were any differences between the first and second trial of saw use.

Subject Tension/Relaxation

Since the subject-saw combination is a mechanical linkage having unknown

stiffness and damping characteristics, some estimate of the degree of tension

or relaxation of the subject is desirable. Although myographic measures of

muscle tension or other physiological measures could have been taken, their

correlation with a subject's state of relaxation or tension is known not to be

high. A somewhat better measure is self-perceived tension/relaxation. Each

subject was asked to estimate his/her degree of relaxation or tension on a

scale from 1 (very relaxed) to 5 (very tense) after each measurement trial.

While this is a less than perfect tension measure, data from such ratings may

partially account for between-sub ject differences in saw kickback.

^These ratings were recorded and evaluated by the CPSC for the kickback experimental program. The evaluation forms were analyzed by the CPSC Division of

Human Factors.

45
Table B-1. Chain saw hand-held test random match of subjects and saws.

Saw G1 Trigger Match^

Subject Saw Order-*-

Test

Series

Trigger

Used

Times Rear

Trigger

was Used

First

Trigger

Used

1 6, 1,3, 2, 4, 5,

1 Rear 5 Rear

2 6, 7, 5, 4, 1,2,

3

Both 3 Rear

3 6,4, 1 ,3, 5, 2,

Rear 5 Rear

4 6, 4, 5, 2, 7, 3,1 Front 0 Front

5 6, 4, 5, 2, 1,3,

Both 3 Rear

6 6, 7, 3, 4, 1,2,5 Both 2 Front

7 6, 5, 7, 1,2, 4,

3

Both 2 Front

8 6, 4, 2, 3, 5, 1,7 Both 2 Rear

9 6, 4, 3, 5, 7, 1,2 Rear 5 Rear

10 6,3,1 ,5, 7, 2,

Front 0 Front

11 6, 1,7, 5, 2, 4,

3

Front 0 Front

10 6, 2, 5, 3, 1,7,

2 Front 0 Front

3 6, 3, 1,4, 2, 5,

Front 0 Front

5 6,5, 3, 2, 7,1,4 Rear 5 Rear

1

6, 4, 1,5, 7, 3,

Both 3 Front

4 6, 7, 2, 5, 4, 1,3 Rear 5 Rear

9 6, 4, 1,7, 5, 2,

3

Front 0 Front

6 6, 5, 7, 1,4, 2,

3

Rear 5 Rear

^Random matches were provided by the Consumer Product Safety Commission. Saw

E6 was presented first to each subject for training purposes, since it was a saw having relatively small kickback characteristics based on prior tests with

the Kickback Test Machine.

^Saw G1 was the only test saw having two throttle triggers, both located on the rear handle.

46
Test Subject Evaluation

The following evaluation sheet was prepared by the CPSC as another means

of subject evaluation to supplement the measurements of saw kickback motion.

TEST SUBJECT EVALUATION SHEET

Names Date

Instructions: After completion of each trial, please indicate, by circling one number on

the sccle of from I to 5 that value which best describes your state of muscle relaxation during that trial. 12 3 4-5 - -

Very Relaxed Very Tense

47
Table B-2. Test subject profiles

Subject Sex

Age

(years)

Height

(in)

Weight

(lbs) Handed

Chain ; Use

CR M 55 65 154 R Yes

CHD M 40 71 176 R Yes

NB M 44 59 160 R Yes

CN F 54 63 128 R Yes

CJ M 43 65 158 R Yes

CD M 33 69 184 R Yes

CMJ M 31 76 197 R Yes

CDS F 25 65 112 R No

CA M 43 67 198 R Yes

CK M 33 67 174 L No

CS M 42 75 286 R Yes

48
Appendix C. Computer Analysis of Recorded Data.

A high-speed computer was utilized to perform necessary corrections and

transformations of the digitized saw displacement data recorded by the optoelectronic measurement system. This analysis included corrections for lens

curvature of the recording camera and for the desired diode positions to facilitate interpretation of the saw motion relative to the body of a chain saw

operator. Transformations of the data to a coordinate system at the saw center of gravity when the kickback was initiated (time = 0), and conversion of

the displacements from the measurement system units to inches were also performed.

Furthermore, it was required that the saw rotational motion during a

kickback be defined relative to three saw references: 1) the moving center of

gravity of the saw, 2) a fixed reference at the rearmost position of the saw

as the kickback was initiated (CPSC definition of the derived rotation angle),

and 3) a fixed reference at the rear handle throttle trigger at the kickback

initiation (CSMA definition of the derived rotation angle). The equations for

these corrections and transformations of the recorded data are given in the

following sections of this appendix.

Correction for Recording Camera Lens Curvature

A program was written for calculating the change in the diode coordinates, due to distortion in Selspot camera system, using a look-up table. The

program corrects for the discrepancies between the known calibration points in

the object space and the optically produced position of these points.

A grid of 1024 by 1024 coordinate components used by the Selspot electronics (a direct result of a 10-bit word address) is divided up into 289 xcomponents and 289 y-components which are each represented by a 17 by 17

49
matrix or look-up table. For the program printed at the end of this appendix,

the x and y look-up tables are given in tenths of millimeters. Conversion

from millimeters to inches is performed after an interpolation process is completed.

Under controlled laboratory conditions, the true grid (1600 mm by 1600

mm) was measured by the Selspot System, as shown in figure C-l. Subsequently,

corrected look-up tables were generated to account for the change in coordinates due to lens distortions. By incorporating these corrected look-up

tables, a simple interpolation routine was then used to find the corrected

coordinates from those recorded by the Selspot System during the kickback

tests. One critical factor that had to be taken into account in the above

analysis was the camera-to-ob ject distance. This factor was entered as a constant related to the camera-to-grid distance used in the initial calibration

of the Selspot System.

Conversion of Diode Positions and Computation of CPSC Kickback Angles

Throughout the experimental program, the positions of the saw tip, center

of gravity, and rear handle were defined by the coordinates (X3,Y3), (X4,Y4),

and (X5,Y5), respectively. In general, the diodes were placed adjacent to,

but not exactly at the desired saw positions. The parameters used to relate

the test coordinates and these desired positions for the diodes at the saw

tip, center of gravity, and rear handle were (A1,A2), (C1,C2), and (R1,R2),

respectively, when the saw was in its original position at the inception of

kickback, i.e., at time t = 0. Table C-l summarizes the saw parameters required for these computations. At the time chosen as t = 0, the following

constants define the saw initial position:

50
Figure C.l. Arrangement of Optoelectronic Camera and Calibration Grid

(instrumented bar moved to various elevations)

51
VO = Y3 (C.l)

HO = X3 (C.2)

YO = Y4 (C. 3)

XO = X4 (C.4)

At the inception of kickback (t = 0), let

SI = X5 + R1 ( C. 5)

S2 = Y5 + R2 (C.6)

Ql = XO + Cl ( C. 7

)

Q2 = YO + C2 ( C. 8)

The rotation of the saw about its center of gravity is then defined as

A = tan-1

[ (Y3-Y4)/ (X3-X4) ] - tan-1

[ (V0-Y0)/ (H0-X0) ] (C.9)

where A is an angle in degrees for all times during the kickback event.

Table C-l. Saw paremeters used to correct diode test coordinates

to desired positions.

Rear

Test Tip Correction (in) C.G. Correction (in) Handle correction (in)

Saw A1 A2 Cl C2 R1 R2

G1 - 1.00 - 0.44 0 0 - 2.12 + 0.69

G2 - 1.31 + 1.06 + 0.06 0 - 1.56 - 1.31

G3 - 1.31 + 0.88 - 0.38 + 0.88 - 2.62 + 0.50

G4 - 0.75 + 1.12 0.0 - 0.75 - 2.56 + 1.62

G5 - 1.69 4- 0.34 + 0.16 + 0.06 + 0. 12 - 0.03

E6 - 1.25 0 + 0.62 + 0.50 - 2.44 - 0.12

E7 - 1.75 + 0.81 + 0. 19 + 0.19 — 0.50 + 0.19

52
The corrected positions for the diode positions at the saw tip, center of

gravity, and rear handle are defined as (Tl, T2), (Gl, G2), and (HI, H2),

respectively, and are computed as follows:

Tl = X3 + A1 cos A — A2 sin A (C.10)

T2 = Y3 + A1 sin A + A2 cos A (C. 11)

Gl = X4 + Cl cos A - C2 sin A ( C. 12)

G2 = Y4 + Cl sin A + C2 cos A ( C. 13)

HI = X5 + R1 cos A - R2 sin A (C. 14)

H2 = Y5 + R1 sin A + R2 cos A ( C. 15)

The derived angle of rotation (DAR) relative to a fixed position at the

rear of the saw is computed as follows:

D = tan-1

[ (T2-S2)/ (Tl-Sl ) ] - tan" 1

[ (V0+A2-S2)/ (H0+A1-S1 ) ] (C.16)

where D is the angle in degrees for all times during the kickback (CPSC definition of DAR).

To convert the displacement data to the coordinate system whose origin is

at the saw center of gravity as it moves, the following transformations are

used:

Tl = Tl - Ql ( C. 17)

T2 = T2 - Q2 ( C. 18)

Gl = Gl - Ql (C. 19)

G2 = G2 - Q2 (C.20)

HI = HI - Ql ( C. 21

)

H2 = H2 - Q2 (C.22)

53
where (T1,T2), (G1,G2), and (H1,H2) define the (X,Y) coordinates at the saw

tip, center of gravity, and rear handle, respectively, for all times during

the kickback.

Computation of CSMA Derived Angle of Rotation

In order to compute the derived angle of rotation in terms of the CSMA

reference system, it is necessary to use additional saw parameters. These

parameters define the (X,Y) coordinates of the rear handle throttle trigger at

the kickback initiation and locate the guidebar tip coordinates somewhat differently than for the CPSC reference system. The parameters (L3,L4) and

(A3,A4) define the trigger and tip coordinates, respectively, and are summarized for the various test saws in table C-2.

Saw parameters used to compute CSMA derived angle of rotation.

Saw Dimensions (in)

Test Saw L3 L4 A3 A4

Gl + 6.06 1 + 2.44 1 - 1.12 - 0.93

G2 + 4.06 + 3.00 - 1.06 - 0.93

G3 + 3.75 + 2.31 - 0.87 - 0.94

G4 + 9.00 + 1.25 - 1.13 - 1.12

G5 + 8.69 + 0.62 - 1.13 - 1.07

E6 0

2 0 0 0

E7 + 6.06 + 0.94 - 0.75 - 0.69

1 Dimensions for L3 and L4 were based on measurements at the rear trigger

location for test saw Gl.

2 Saw dimensions not measured for test saw E6. Values of zero were used to

implement running of the computer program.

54
Using the definitions for Tl, T2, A, Ql, and Q2, as defined in eqs.

(C.7) through (C.ll), the following expressions are computed at each time:

T3 = Tl + A3 cos A - A4 sin A - Ql (C.23)

T4 = T2 + A3 sin A + A4 cos A - Q2 (C.24)

The CSMA derived angle of rotation (DAR) relative to a fixed position at the

throttle trigger is computed as follows:

B = tan-1

[ ( T4-L4 ) / ( T3-L3 ) ] (C.25)

where B is the DAR in degrees for all times during the kickback.

Computer Analysis

Equations for the corrections and the transformations which have been

discussed were programmed for a mini-computer to analyze the recorded kickback

displacement data; the software for this analysis is given at the end of the

appendix. Examples of the corrected values for the CPSC and CSMA derived

angles of rotation for Test Subjects CDS and NB are given in tables C-3 and

C-4, respectively.

Corrections due to distortion in the recording camera system were found

to change the computed angles of rotation by approximately one degree or less,

based on comparison of corrected and uncorrected displacement data. Corrections due to the diode positions generally modified the computed angles of rotation by two degrees or less.

In order to facilitate the interpretation of the saw rotational motion

during the kickback tests, the maximum rotation angles about the saw center of

gravity were determined for Test Subjects CDS and NB and are presented in

tables C-5 and C-6, respectively. The time intervals from the first contact

of the saw and wood specimen to the point of maximum rotation about the moving

55
saw center of gravity are also shown; these values were less than or equal to

the times required for the saws to reach the maximum values for the derived

angles of rotation shown in tables C-5 and C-6. A sample of the computer

analysis is given following table C-6.

56
Table 03. Corrected values of kickback derived angles of rotation (DAR)

for subject CDS.

Test

Saw

(DAR)cpgc for Replicate Tests

[(DAR)csMA for Replicate Tests

(deg)

(deg)

]

Average

DAR, deg

Std.

Dev.

Coef. of

Variation

Gl 26.6 28.4 31.0 1 26.7 28.2 2.06 0.07

[22.3] [24.7] [27.6] 1 [22.5]

G2 40.8 23.8 30.4 32.8 28.5 31.3 6.27 0.20

[42.4] [20.2] [28.3] [32.3] [26.9]

G3 22.1 18.5 24.5 31.2 33.6 26.0 6.29 0.24

[18.9] [14.6] [26.3] [30.3] [33.8]

G4 54.

2 51.1 37.7 38.7 53.5 47.1 8.20 0.17

[54.5] [51.7] [38.4] [39.1] [54.8]

G5 49.9 32.9 52.

9

2 51.2 48.9 47.1 8. 10 0.17

[51.2] [33.6] [53.8] [52.4] [49.0]

E7 15.7 15.2 19.9 14.0 32.9 19.5 7.79 0.40

[14.3] [13.6] [18.7] [12.4] [34.5]

Gl 1 27.7 16.6 26.2 19.3 22.4 5.35 0.24

1 [21.9] [ 9.2] [20.3] [12.8]

G2 34.5 33.2 1 26.0 36.4 32.5 4.54 0. 14

[33.5] [31.1] 1 [19.3] [34.7]

G3 33.3 42.9 27.9 28.6 27.5 32.0 6.50 0.20

[32.4] [46.9] [26.7] [27.3] [26.1]

G4 53.

2 54.

6

2 31.2 36.8 44.8 44.1 10.14 0.23

[53.7] [54.5] [30.3] [36.0] [44.2]

G5 50.

3

2 50.

5

2 53.

0

2 53.

5

2 47.4 50.9 2.45 0.05

[50.7] [52.1] [53.9] [54.4] [47.9]

E7 12.6 21.8 22.2 12.4 18.0 17.4 4.76 0.27

[10.2] [21.7] [21.2] [ 9.6] [15.8]

^-Malfunction of recording system occurred during the test, interrupting data

transfer to computer memory.

2 Saw struck safety bar.

NOTE: for test saw Gl, (DAR)^^ was based on the rear trigger location.

57
Table C-4. Corrected values of kickback derived angles of rotation (DAR)

for subject NB.

Test Test (DAR)(gpgc for Replicate Tests (deg) Average Std. Coef. of

Ser. Saw [(DAR)^g^ for Replicate Tests (deg)] DAR, deg Dev. Variation

Gl 13.15.5 11.5 9.5 11.3 12.2 2.25 0.18

[ 8.2] [ 8.4] [ 9.0] [ 8.6] [ 9.1]

G2 12.8 17.2 15.5 16.6 15.4 15.5 1.69 0.11

[ 6.6] [12.2] [ 9.5] [10.4] [ 8.9]

G3 11.4 9.12.15.3 12.0 12.0 2.22 0.18

[ 4.9] [ 9.5] [ 5.9] [10.3] [ 5.8]

G4 41.

0

2 39.3 46.0 43.1 32.7 40.4 4.99 0.12

[40.6] [39.1] [45.4] [42.7] [31.7]

G5 22.4 51.

9

2 43.2 36.0 22.7 35.2 12.88 0.36

[21.6] [51.4] [42.3] [35.2] [21.6]

E7 19.7 33.4 25.4 9.8 11.4 19.9 9.83 0.49

[18.1] [34.8] [24.8] [ 5.8] [ 8.4]

Gl 15.5 20.9 12.9 1 15.9 16.3 3.34 0.20

5.9 [13.8] [ 5.1] 1

[ 7.6]

G2 26.4 16.6 32.0 18.9 17.0 22.2 6.76 0.30

[19.9] [10.9] [28.5] [11.6] [ 9.2]

G3 22.2 24.7 17.5 18.4 13.3 19.2 4.40 0.23

[18.5] [22.6] [12.2] [13.5] [ 7.2]

G4 50.3 47.6 35.6 43.3 36.6 42.7 6.51 0. 15

[49.8] [46.8] [34.3] [42.4] [35.3]

G5 52.8 58.8 33.2 45.2 28.9 43.8 12.67 0.29

[53.9] [60.5] [33.0] [46.2] [28.9]

E7 7.0 9.

10.3 14.8 10.4 10.3 2.85 0.28

[ 4.2] [ 6.8] [ 8.2] [12.7] [ 8.2]

^Malfunction of recording system occurred during the test, interrupting data

transfer to computer memory.

2 Saw struck safety bar.

NOTE: for test saw Gl, (DAR) cgHA was based on the rear trigger location.

58
Table 05. Maximum angles of kickback rotation about saw center of gravity

for subject CDS.

Average

Test Test Maximum Rotation about Saw C.G. , deg Duration,

Series Saw (Duration from Saw-Wood Contact, sec) sec.

G1 23.2 25.4

(0.413) (0.446)

G2 38.3 26.7

(0.099) (0.086)

G3 26.4 24.3

(0.080) (0.080)

G4 47.0 44.2

(0.231) (0.196)

G5 50.3 36.2

(0.099) (0.096)

E7 18.4 17.5

(0.064) (0.067)

G1 1 22.0

1 (0.423)

G2 35.6 33.3

(0.096) (0.096)

G3 30.4 38.7

(0.093) (0.115)

G4 49.8 52.8

(0.147) (0.125)

G5 52.1 53.4

(0.112) (0.106)

E7 14.7 26.0

(0.064) (0.096)

^•Malfunction of recording system.

29.2

(0.401)

1

1 27.8

(0.433) 0.423

33.0

(0.093)

37.3

(0.086)

32.7

(0.086) 0.090

29.4

(0.093)

28.0

(0.086)

36.8

(0.093) 0.086

38.0

(0.109)

39.5

(0.112)

48.8

(0.218) 0.173

59.9

(0.090)

57.6

(0.099)

46.9

(0.102) 0.097

21.9

(0.093)

19.3

(0.080)

29.9

(0.096) 0.080

20.3

(0.118)

26.1

(0.125)

20.6

(0.458) 0.281

1

1 22.9

(0.071)

28.2

(0.080) 0.086

32.8

(0.096)

32.1

(0.093)

27.2

(0.096) 0.099

31.2

(0.093)

35.5

(0.109)

38.6

(0.471) 0.189

60.4

(0.093)

59.7

(0.090)

43.1

(0.106) 0.101

25.6

(0.090)

15.5

(0.077)

20.9

(0.077) 0.081

59
Table C-6. Maximum angles of kickback rotation about saw center of gravity

for subject NB.

Test

Saw

Maximum Rotation about

(Duration from Saw-Wood

Saw C.G.

,

Contact

deg

sec)

Average

Duration,

sec

G1 13.3 13.9 11.1 8.0 10.7

( 0 . 676 ) ( 0 . 609 ) (0.452) (0.401) (0.494) 0.526

G2 14.4 19.2 17.4 17.7 16.5

(0.054) (0.067) (0.051) (0.067) (0.054) 0.059

G3 14.

12.9 15.0 19.5 10.7

(0,061) (0.064) (0.054) (0.067) (0.056) 0.062

G4 37.8 39.1 41.4 40.2 33.3

(0. 154) (0.115) (0.160) (0.151) (0.099) 0.136

G5 24.7 47.7 39.0 36.3 25.2

(0.083) (0.118) (0.090) (0.090) (0.083) 0.093

E7 16.9 25.7 22.4 11.9 14.0

(0.497) (0.510) (0.436) (0.048) (0.054) 0.309

G1 11.5 16.8 11.2 1 12.4

(0.474) (0.381) (0.064) 1 (0.401) 0.330

G2 18.8 19.0 19.4 16.6 12.9

(0.070) (0.074) (0.086) (0.080) (0.074) 0.077

G3 25.4 30.1 19.8 20.6 15.6

(0.077) (0.090) (0.077) (0.083) (0.064) 0.078

G4 44.5 38.9 31.2 38.0 34.4

(0.189) (0.336) (0.138) (0.144) (0.112) 0.184

G3 43.8 43.4 29.9 34.1 32.4

(0.106) (0.586) (0.099) (0.426) (0.090) 0.261

E7 10.

13.0 14.3 13.2 13.5

(0.058) (0.067) (0.070) (0.061) (0.061) 0.063

^Malfunction of recording system.

60
l ip Tip CG CG RH RH CG CAR DAR

Time X Y X

V

\ Y Y An s CPSC IND

( msec

)

< in ) ( in ) ( in ) ( in ) ( in ) ( in) ( dSd ) ( ded ) ( ded )

o o o o 17,343 0,067 0,000 0,000 11,505 1,867 0,000 0,000 3,701

3 , 205 17,284 0,059 0,000 0,001 11,504 1 ,748 0,41? 0,243 3 * 4 2 4 6,410 17,334 0,307 0,057 0,055 11,611 1 , 630 1,055 0,739 2,870

9,615 17,207 0,313 0,114 0 , 050 11,771 1,393 2,745 1,734 1,737

12,821 17,019 1,561 0,283 0,159 11,875 0,978 4,855 3,221 0 , 063

1 o , 0 A 6 16,758 n / r,n 0,453 0,264 12,034 0 , 336 8,23? 5,49? 2,50?

19,231 16,369 4,067 0,621 0,367 12,234 0,381 12,509 8,347 5 , 726

22,436 15,919 w' T 7 0,844 0,471 12,330 0,971 16,385 11,026 8,746

25,641 15,465 6,592 0,956 0,633 12,316 1,620 20,177 13,772 11,827

28 , 846 14,395 7 ,795 1,067 0 , 7 9 6 12,252 2,035 23,905 16,490 14, 37 6

32,051 14,274 C , 86/ 1,232 0,959 12,240 2,566 27,246 19,023 17,716

55 , 256 13,656 n n e- r. 7 , COO 1,398 1,124 12,175 2,979 30,347 21 * 455 20 , 424

38,462 13,091 10,842 1,562 1,289 12,056 3,452 33,332 23,883 23,111

41 , 667 12,479 11,702 1,783 1 * 455 12,101 3,746 35,931 26 * 133 25,594

44 , 872 11,814 12,443 1,947 1,622 11,931 4,100 38,411 28,232 27,920

48,077 11,144 13,284 2,111 1,733 11,972 4,27? 41,168 30,587 30,506

c.i 1 0 ~r vJ X 4 10,485 13,995 2,331 1,956 11,800 4,516 43,445 32,713 32,323

54,487 9,888 14 ,643 2,495 2,133 11,795 4,577 45,411 34,681 34 , 960

57,692 9,285 15,347 2 r 6 6 0 2,410 11,623 4,813 47,520 36 , 792 37,228

60,397 3,745 15,988 2,824 2,638 11,511 4,816 49,32? 38 , 7 25 39,234

64,103 8 , 1 32 16,515 2,989 2 , 866« 11,397 4,936 51,013 40 , 523 41,210

67 , 308 7,605 17,047 3 ,098 3 » 036 11,339 4 9d3 52,861 42,296 43,092

70,513 7,005 17,578 3,262 -7 o / cr G * 11,232 4,940 et i c: r> n* joo 44,162 45 , 063

73,718 O , -J / IS, 102 3 , 4 3 3 3,495 11,171 4,942 crcr r*n t xJ vJ r O Z 4 45,834 46 , 7v0

76,923 6,036 18,455 3,701 UtOi)/ 11,169 4 , 942 tr r. n / GO * OZO 47,202 48,215

80,128 5,637 18,920 3,865 3*898 11,112 4,944 cr “7 r. -j G/ * 7 A i 48,637 49,723

85 , 333 5,158 19,331 4,028 4,072 11,166 4,827 59*201 50,180 51,269

86 , 539 4,754 19,622 4,243 4,306 11,059 4,712 59,804 51,355 52,463

89,744 4,639 19 , 849 4,368 4 , 4 S3 11,227 4,478 59*899 51,917 53,000

92,949 i CT / 4 * xj G O 20,071 A E7 o ST * xj G •J 4,773 11,286 4,302 59,602 52,450 53,487

96,154 4,480 20*184 4,580 4- * 896 11,454 4 067 59,594 52,723 53,745

99,359 4,548 20,345 4,692 5,074 11,514 3,833 59,077 52 , 853 53,314

102 , 564 4,568 20,393 4,359 5,252 11,633 3,598 53,346 52,892 53,806

105,769 4,702 20,438 4,971 5,431 11,795 3,421 57,447 52,723 53,576

61

Tie Tip CG CG RH RH CG DAR DAR

Time X Y X Y X Y A ns CF'SC INB

( msec

)

( in ) ( in ) ( in ) ( in ) ( in ) ( i n ) ( ties

)

( ties ) ( ties )

0 * 000 17*423 0*127 0.000 0*000 11*274 1*85? 0*000 0*000 3*816

3*205 17*365 0*001 0*056 0*001 11*327 1*741 0 * 4 1

9

0*243 3*541

6*410 17*414 0*246 0*057 0*055 11*435 1*622 1*04? 0*741 2*93?

9*615 17*296 0*555 0*169 0*110 11*433 1*503 1*883 1*347 2*313

12*821 17*224 1*061 0*225 0*105 11*593 1.265 3*553 2*355 1,177

1 6 026 17*090 1*749 0*338 0.156 11*752 0*903 5.645 3*737 0*372

19*231 16*777 2*683 0*562 0*263 11,854 0*432 n -7 / n O ¥ JOO 5*642 2*503

22*436 16*512 3*742 0*730 0*370 12.064 0*044 11*495 7 + 836 4*953

25*641 16*076 4*798 0*897 0*534 12*161 0*576 14*527 10*093 7 + 46?

28*846 15*693 5*744 1*008 0*641 12*207 0*990 17*413 12*157 9*773

32*051 15*362 6*745 1*119 0 * 806 12*253 1*288 20*244 14*354 12*206

35*256 14*863 t cr i/ *>J&0 1*175 0*972 12*191 1*642 22*760 16*275 14*345

38*462 14*483 8*442 1*341 1*138 12*233 1*93? 25*199 18,297 16*571

41*667 14*048 9*187 1*506 1*305 12,230 2*234 27.294 20*100 18*556

44*872 13*558 9*868 1*672 1*472 12*27? 2*413 29*286 21*337 20*471

48*077 13*183 10*542 1*837 1,641 12*273 2,650 31*074 23,506 22*23?

51*282 12*701 11*213 O 1*0 JL- * 11a. 1*809 12*378 2,712 32*835 25*273 24*212

54*487 12*326 11*384 *)^ n 1*977 12*313 2 * 889 34*633 26*974 26*055

57 * 692 11*900 12*493 2 * 3o8 2*146 12*423 2*892 36 * 345 28*60? 27*322

60*897 11*430 12*970 2*553 2,374 12*366 3*010 37*531 30 * 036 2? * 364

6 ‘r. 1 0 O 11*067 13 * 336 2*71? 2*602* 12*418 2,954 33*901 31*594 31*018

67 * 308 10*644 14*090 2*829 2*771 12*414 3*073 40 + 464 33*122 32*65?

70*513 10*237 14*614 2*939 3*053 12*413 3*016 41*573 34*567 34*130

73*713 9.932 15*024 3*105 3*230 12*357 3*017 42*563 35*790 35*475

76*923 9*637 15*430 3*216 3*460 12*410 2*960 43*392 36*941 36 673

80*128 9*395 15*391 3*382 3*631 12*464 2*903 44*253 33+131 37*906

83 * 333 9.053 16*235 3*603 3*862 12*463 2,845 44*787 39*229 39+044

86*539 8*818 16*530 3*769 4 038 12*572 2*72? 45*336 40*139 40*023

89*744 3*591 16*864 3*881 4*332 12*628 2*612 45*572 41*025 40 * 876

92*949 8*355 17*264 4*047 4*567 12 *738 2*378 46*113 42*086 41*94?

96*154 8*127 17*548 4*214 4*802 12*793 2*31? 46 * 363 42+921 42+792

99*359 7*839 17*895 4*270 5*036 12*903 2*085 47*03? 43+333 43*774

102*564 7*716 13*178 4*437 5*212 12*904 2*027 47*296 44*634 44*525

105*769 7*493 1 8 * 404 4 604 5*443 13*06? 1*851 47*402 45 * 353 45+251

108*974 7*375 13*687 4 * 660 5*632 13*125 1*675 47*655 46+021 45*904

112*179 7.265 13*910 4*772 5*913 13.127 1*500 47,622 46 > 566 46*432

115*385 7*154 19*133 4*940 6*095 13*237 1*382 47*592 47*107 46*955

118*590 7 *040 19*414 5*052 6*331 13*348 1*207 47*69? 47,747 47*576

121*795 6*933 19*635 5*165 6*567 13*351 1*031 47*525 43*186 47+985

125.000 6*936 19*800 5*277 6*744 13*517 0*796 47*353 48*532 43*307

128*205 6*773 19*911 5*334 6*979 13*573 0*67? 47*325 48*967 48+741

131*410 6.777 20*130 5*447 7*216 13*634 0*503 47*014 4? » 305 49*039

134*615 6*775 20*297 5*448 7*392 13*742 0*211 46*996 49*571 49*233

137*821 6*722 20*463 5*560 7*570 13*744 0*094 46*834 49*911 49+601

141*026 6*669 20*628 5*672 7*745 13*909 0*024 4 o * 6 7 7 50,250 49*916

144*231 6*671 20*738 5*673 7*91? 13*965 0*200 46*523 50,413 50*060

147*436 6*559 20*905 cr 7 r, sr vJ / OJ 8*092 14*021 0*435 46*50? 50*343 50*473

150*641 6*557 21 073 5,785 8*266 14.075 0*494 46+500 51*093 50*713

153*846 6.617 21*180 5*736 8*440 14*136 0*730 46*208 51,161 50*748

157*051 6*675 21*343 5*842 3*61 j 14*137 0*847 45*923 51*303 50 360

160*256 6*619 21*455 5*898 8*731 14*18? 1*082 45*915 51*560 51+103

163*462 6*618 21*567 5*844 8*904 14*244 1*200 45*893 51.724 51,254

166*667 6*620 21,676 5*899 9*021 14*408

62

1*435 45*753 51+330 51*391

10 REN

20 REN

30 REN

40 REN

50 REN

60 REN

70 REN

BO REN

90 CALL

100 DIN

110 DIN

120 DIN

130 DIN

%%%%% % $ % ;f %%%%%%% % %t%t % % % %% %%%

% % %£%%%% % % t % % % % % % %%% % %

#** Program? CHAIN %%%

% %tt% % % % % % % % %%%%%% t %%%% %% tt%%

% %%%% % % % * % %%%%% t %%%%%%% % %%%%

t

XI ( 17 7 1 7 )

Y 1 ( 17 1 17 ) X 3( 300 ) ? Y3( 300 ) ? X4( 300 ) , Y4( 300 ) ? X5( 300 ) ? Y5( 300 } A$( SO ) ? b$>: 10 )?C$< SO > D$( 20 )?L$( 20 ) jQ$( 10)

140 DIN R$( 4 )? S3\ 4 )?T3( 6 ) 150 DIN 20 ) 160 DIN D( 20

)

170 REN

180 REN % %

190 REN * Sub-program to generate lookup table of correction factors* t

200 REM * t

210 REN %%%%%%*%%%%%*%%%%*%%%%%*%%%%%%%%%*%%%%%%%%%%%*%%*%%%%%%*%%%%%.%*

220 PRINT "" 230 PRINT " <7>

240 PRINT "Wait ! ! ! The computer is now generating a lookup"

50

420

430

440

450

460

470

480

490

500

510

520

PRINT "table of correction factors*"

PRINT " <7>"

PRINT "" FOR 1=1 TO 17

FOR J=1 TO 17

READ XKIjJ)

NEXT J NEXT I FOR K=1 TO 17

FOR L=1 TO 17

READ Y 1 < K ? L ) NEXT L NEXT K REN

REN

PRINT "" PRINT H " PRINT "<7>"

PRINT "Type the name of the data file to be read?"

L INPUT G$

IF 0$="" THEN GOTO 3150

PRINT "<1 17- PRINT " <11X77* <11 >" j R$

PRINT "" PRINT "" PRINT "Type the first line number to be analyzed?"

INPUT Z1

PRINT -<11>

530 PRINT

540 PRINT

550 PRINT

560 PRINT

i 570 INPUT

580 PRINT

590 PRINT

600 PRINT

<1 1X7X1 1>" *Z1

"Type the last line number to be analyzed*"

12

"<11>

" <1 1X7X1 1>" j Z2

63

610 PRINT

620 IF Z2=Z1 THEN GOTO 3150

630 IF Z2<21 THEN GOTO 3150

640 T$=fi$( 1 ?2 ) 650 rem 660 REM % %

670 REM * Reading in measured constants for LED correction ecus lions, %

6o0 REM %

690 REM %%%%%1(X%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

700 READ A 1 » A2 ? C 1 ? C2 ? R 1 ? R2 ? L3 ? L4 ? A3 ? A4

710 IF T'5="G1" THEN GOTO 830

720 HEAD Al 7 A2 ? C 1 ? C2 ? R 1 ? R2 ? L3 ? L4 ? A3 ? A4

730 IF T$="G2" THEN GOTO 830

740 READ A 1 j A2 ? C 1 ? C2 ? R 1 ? R2 ? L3 ? L4 ? A3 ? A4

750 IF T$="G3" THEN GOTO 830

760 READ Al j A2

j

Cl * C2? El ? R2 ? L3 ? L4 ? A3 ? A4

770 IF T$="G4‘‘ THEN GOTO 830

780 READ Al ? A2 ? C 1 ? C2 ? Rj R2 ? L3 ? L4 j A3 ? A4

790 IF T$="G5" THEN GOTO 830

800 READ Al 7 A2 7 C 1 ? C2 ? R7 R2 7 L3 ? L4 7 A3 ? A4

810 IF T?="E6" THEN GOTO 830

820 READ Al ? A2 7 C 1 ? C2 7 R 1 ? R2 7 L3 ? L4 ? A3 7 A4

830 L$="AC "+Q$4 H

7 7F1"

840 CALL 4 ?L$

8 5 0 R EM %%%%%%% $ %%%% % %%%%%%%%% t*****

%

* % % * *% *** * % % % %%%%%% * % %

360 REM *

* * 870 REM % Sub-program to read in data file from disk? and * 880 REM * to correct for addition of "128" to ASCII value * 890 REM * of last digit in each data column* * 900 REM £ * 910 rem nntunmnnnnnnutnnntuntunntnnu

920 PRINT

930 PRINT "<7>"

940 PRINT "Wait ! I ! The computer is now reading in the data"

950 PRINT "file from the floppy disk*"

960 PRINT "" 970 PRINT "<7>"

980 FOR 1=1 TO Z2

990 L INPUT ON ( 7 )A$

1000 FOR N=6 TO 11

1010 A=N#5

1020 B$=A$'A?A)

1030 CALL 37 7 B$ 7 V

1040 V=V-123

1050 CALL 367

V

7 B$

1060 B=A-4

1070 C=A-1

1080 V$=A$(B7C)+B$

1090 IK N )=VAL< 0$ ) 1100 NEXT N 1110 X3( I )=D( 6 ) 1120 Y3( I )=B< 7 ) 1130 X4( I )=D( 8

)

1140 Y4( I )=IR 9)

1150 X5( I )=D( 10)

1160 Y5( I )=D( 11 ) 1170 NEXT I 1180 REM ************************************************************

1190 REM * * 1200 REM * Sub-program to correct for Seispot lens distortions? end * 64

1210

1220

1230

1240

1250

1260

1270

1280

1290

1300

1310

1320

REM % conversion from Selspot units to inches %

REM % %

R E M * t % % %%

4 1 1 %t % t%%1 1 % % % % % 1% % t% % %

t

f % t % 1 1 %% % % 1 1 %%%% % * t% %%%t% % t % %

PRINT "" PRINT "<7>"

PRINT “Us it !

1

I The computer is now correct ins for Selspot"

PRINT "lens distortions? end converting from Selspot units to"

PRINT "inches,"

PRINT "" PRINT " <7>

FOR W=Z1 TO Z2

1330 IF 2=1 THEN X=1023-X3( W ) 1340 IF Z=1 THEN Y=Y3( id

)

1350 IF Z=2 THEN X=1023-X4C Id

)

1360 IF Z=2 THEN Y=Y4( Id

)

1370 IF Z=3 THEN X=1023-X5( U ) 1380 IF Z=3 THEN Y=Y5(W>

1390 M=INT( X/64 )f

1400 N=INT( Y/64 )f 1 1410 F‘=( X/64 )-M+l

1420 Q=( Y/64 )--Nf 1 1430 R=X1( N?M )+P*(XK N?H+i )-Xl< N?M )

)

1440 S=P*:( Xl( Nil ?Mf 1 )~X1( N+l ?M )

)

1450 X=R+G*( X 1 < N+1?M )+S-R

)

1460 R=Y1( N?M )+F'*( Yl( N?MF1 >-Yl( N?M )

)

1470 Y-R+Q*( Y 1 ( N+l ?M )+P*< Yl( N+l ?M+1 )-Yl( N+l ?H ) >-R ) 1480 REM

1490 REM "C* is the conversion factor from tenths of millimeters

1500 REM to inches*

1510 C=l/( 10*25*4 ) 1520 REM

1530 REM "D" is the factor for adjusting the diet ence from the

1540 REM camera to the dr id? from the initial calibration

1550 REM distance? of 125 inches? to the actual test condition*

1560 REM

1570 0=125/154

1 580

1590

1600

1610

1620

1630

1640

1 6o0

1660

1670

1680

1690

1700

1710

1720

1730

1740

1750

IF X<0 THEN X=0

IF Y<0 THEN Y=0

X=C*D*X

Y=C*D*Y

IF Z=1 THEN

IF Z=1 THEN

IF Z=2 THEN

IF Z=2 THEN

IF Z=3 THEN

X3( Id )=ABS< X-53 ) Y3( Id )=Y

X4( Id )=ABS( X-53)

Y4( U )=Y

X5( Id )=AB3( X-53 ) IF Z=3 THEN Y5( Id )=Y

NEXT Z NEXT Id REM JK**#**##*##########*#*##*#*##***######*#**# #** ###*##***#

REM % %

REM % Sub-program to print out corrected and scaled data file* %

REM * t

REM %%%%%%%*%%%%%%%%%%%%%*%%%%%%%%%%%%%%*%%%%%%%%%%%%%%%%%%%%%%%

F'RIN T

i n ii 1760 PRINT "<7>"

1770 PRINT "Wait I ! ! The computer will now print out the corrected"

1780 PRINT "and scaled data file*"

1790 PRINT "" 1800 PRINT " <7>

65

1310 RtM At the time chosen as t-~0? the following constants are sett

1820 V0=Y3(Z1)

1830 H0=X3( Z1 ) 1840 Y0=Y4( 21 ) 1850 X0=X4( Zl ) 1860 S1=X5( Z1 HR!

1870 S2=Y5( Z1 )rR2

1880 01=X4( Z1 HCl

1890 Q2=Y4<Z1)+C2

1900 PRINT ON (2)" "+Q$

1910 PRINT ON ( 2

)"

1920 PRINT ON (2)" 11 1930 C$=" Tie Tip- CG CG RH RH

1940 B$=" CG BAR BAR"

1950 C$=C$+D$

1960 PRINT ON ( 2 >C*

1970 C$=" Time X Y X Y X Y 1980 B$=" And CPSC IND"

1990 C$=C$tD$

2000 PRINT ON < 2 )C$

2010 0 $=""

2020 B$="

2030 C$=" ( msec ) (in) ( in ) (in) ( in ) ( in ) ( in ) ( ti" 2040 B*="ed) ( dee

)

(ded)"

2050 C$=C$tD$

2060 PRINT ON ( 2 )C$

2070 PRINT ON (2)""

2080 REM Computation and conversion of LED positions to

2090 REM desired locations*

2100 FOR U=Z1 TO Z2

2110 A3=ATN< ( Y3( U )-Y4< 0 ) )/( X3( U 5-X4( U ) )

)

2120 A9=ATN< ( VO-YO )/( BO-XO )

)

2130 A=A8-A9

2140 T 1=X3( U HA1*C0S< A >-A2*SIN( A ) 2150 T2=Y3( U HA1*SIN< A HA2*C0S< A ) 2160 G1=X4( U )+Cl*COS( A )-C2*SIN> A ) 2170 G2=Y 4( U )+Cl*SIN< A >+C2#C0S( A ) 2180 H1=X5( U )+Rl*COS< A >-R2*SIN( A ) 2190 H2=Y5( U )+Rl*SIN( A HR2#C0S( A ) 2200 B8=ATN< ( T2-S2 )/( Tl-Sl )

)

2210 D9=ATN( ( V0+A2-S2 )/< H0+A1-S1 )

)

2220 D-B8-B?

2230 T i=T 1-Q1

2240 T2=T2-Q2

2250 G1=G1-Q1

2260 G2=G2-Q2

2270 H1=H1-Q1

2280 H2=H2-G2

2290 T3=T1+A3*C0S( A )-A4*SIN( A ) 2300 T4=T2+A3*SIN< A )+A4*C0S( A ) 2310 B=ATN( ( T4-L4 )/( T3-L3 )

)

2320 A=A*( 180/3. 14159)

2330 B=B*< 180/3.14159)

2340 B=B*( 180/3*14159 ) 2350 T=( U-Zl )#< 1000/312

)

2360 PRINT USING "066.000" f T,Tl ,T2»G1 jG2»H1 »H2»A»B»B

2370 PRINT ON (2) USING "600.600" iT»T1»T2»G1»G2»H1»H2*AiB7B

2380 NEXT U 2390 REN %%%%*%%%%%%%%%%%%**%*%*%%*%*%%%%%*%%%*%%%%%%*&%

2400 REM % ft 66

2400

2410

2420

2430

2440

2450

2460

2470

2480

2490

2500

2510

2520

2530

2540

2550

2560

2570

2580

2590

2600

2610

2620

2630

2640

2650

2660

2670

2680

2690

2700

2710

2720

2730

2740

2750

2760

2770

2780

2790

2800

2810

2820

2830

2840

2850

2860

2870

2880

2890

2900

2910

2920

2930

2940

2950

2960

2970

2980

2990

REM % % REM % Lens correction date for the x --coordinates* t REM * * R EM % % % 4 * * # #

%% * %% % % % % *% % %%%* 11% %* %

4 % t% % % t%t %

t

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

REM

REM

REM

REM

REM

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

DATA

-674 ? 437 ? 1545? 2647 ? 3744 ? 4833 » 591

? 7000 » 8087 ? 9 1 85 ? 1 0273 ? 1 1 343

12429 ? 13541 ? 14609 ? 15641 ? 16636 ?-721 ? 414 ? 1533 ? 2635 ? 3718?4808

5899

6990 ? 8031 ? 9 164 ? 1 0249 ? 1 1 338? 12422 ? 1 3499 ? 1 4579 ? 1 5660 ? 1 6743 ? -749

395 ? 1 5 17 ? 26 1 3 ? 3692 ? 4783 ? 5882 ? 6977 ? 8070 ? 9 1 47 ? 10232? 11 332 ? 1 24 1

5

13474 ? 14562 ? i5672 ? 16805 ? -758 » 379 ? 1497 ? 2594 ? 3666 ? 4758 ? 5863 ? 6960

8055 ? 9133 ? 1 0220 ? 1 1 325 ? 1 2409 ? 13464 ? 1 4556 ? 15675 ? 1 6823 ? -737 ? 370

1470 ? 2561 ? 3640 ? 4735 ? 584 1 ?6939 ? 8033 ? 9125 ? 10218 ? 11315? 12403

13478

1 4 5 6 8 ? 1 5 6 6 B ? 1 6 7 7 9 ? - 7 3 6 ? 3 5 5 ? 1 4 4 5 ? 2 5 3 3 ? 3 6 1 4 ? 4 7 1 0 ? 5 8 1 8 ? 6 9 1 8 ? 8 0 1

911 1 ? 10209 ? 1 .1311 ? 12402? 13480 ? 14568 ? 15663 ? 16764 ? -752 ? 334 ? 1421

2506 ? 3533 7 4683? 5789 ? 6892 ?7994 ? 9092 ? 10195 ? 1131 1 ? 12405 ? 13474

14561 ? 15659 ? 16768 ? -763 ? 320 ? 1 405 ? 2489 ? 3573 ? 4668 ? 5775 ? 6880 ? 7984

9083 ? 10186 ? 11304 ? 12399 ? 13467 ? 14554 ? 15653 ? 16764 ? -772 ? 31 1 ? 1 396

2431 ? 3565? 4662? 5771 ? 6877 f 7982 ? 9079 ? 10180 ? 11293 ? 12387 ? 13456

14545 ?15646 ? 16759 ? -787 ? 300? 1388 ? 2474 ? 3557 ? 4655 ? 5769 ? 6873 ? 7972

9067? 10167? 11280? 12374? 13444 ? 14531 ? 15630 716739? -7 96? 294? 1333

2470 ? 3552 ? 4650 ? 5765 ? 6867 ? 7964 ? 9057 ? 1 0 1 54 ? 11263 ? 1 2356 ? 1 3428

1 4517 ? 15617 ? 16730 ? -788 1 296 ? 1 331 ? 2466 ? 3549 ? 4646 ? 5756 ? 6859 ? 7959

905 1 ? 1 0143 ? 1 1240 ? 1 2330 ? 1 3407 ? 1 4502 ? 1 56 1 0 ? 1673 1

? -81 9 ? 285 ? 1 382

2472 ? 3549? 4643 ? 5749 7 6849 7 7949 ? 9033 ? 101 28 ? 1 1223 ? 12312? 13385

14482 ? 15599 ? 16737 ? -891 ? 263,? 1389 ? 2433 ? 3553? 4639 ? 5740 ? 6335 ? 7931

9015 ? 10105? 1 121 1 ? 12299 ? 13355 ? 14453 ? 15588 ? 16762 ? -893 ? 256 ? 1 381

2482 ? 3552? 4640 ? 5739 ? 6833 ?7929 ?901 1 ? 10099 ? 1 1199 ? 12283 ? 13353

14447 ? 1 5566 ? 1 67 1 3 ? -852 ? 259 ? 1 364 ? 2462 ? 3550 ? 4645 ? 5743 ? 684 1 ? 7938

9020 ? 10103 ? 1 1 189 ? 12277 ? 13372 » 14457 ? 1 5536 ? 16610 ? -770 ? 271 ? 1339

2429 ? 3547 ? 4652 ? 5753 ? 6356 ? 7957 ? 9040 ? 1 01 1 8 ? 1 1 ISO ? 1 2268 ? 134 1

14484 ? 1549? ? 16453

% t

% Lens correction dais for the Y-coordinstes* * * * mmmmmmmmmmmmm********

-1035 ? -1137 ? -1188 ? -1192 ?-1137 ?-l 115 ? -1103 7-1091 ? -1071 ? -1041

-101 3 ? -981 ? -97 0 ? -992 f -976 ? -933 ? -859 ? 56 ? -9 ? -44 ? -48 ? - 17 7 -2 7 5 ? 23

48 ? 69 ? S3 ? 105 ? 119 ? 123? 137 ? 146 ? 155? 1163? 1122? 1097 ? 1091 ? 1108

1118 ? 1126? 1145? 1171 ? 1186 ? 1199

2300 ? 2261 ? 2233 ? 2230 ? 2240 ? 2243

2332 ? 2361 ? 2364 ? 2347 ? 2309*3460

3407 ? 3421 ? 3437 ? 3448 ? 3451 *3456

4522 ? 4510? 4524 ? 4533 ? 4543 ? 4552

460 1 ? 4 607 ? 46 1 4 ? 57 56 ? 57 1 4 ? 5683

5724 ? 5731 ? 5734 ? 573? ? 5748 ? 5754

6854 7 63o7 ? 6361 ? 6864 ? 6863 ? 6873

6907 ? 8033 » 302? ? 8027 ? 8025 ? 8024

8020 ? 8023 ? 8033 ? 8041 ? 8048 ? 8054

9202 ? 9202 ? 9200 ? 91 96? 9189 ? 9173

10351 ? 10373? 10380 ? 10367 ? 10361

10313 ? 1031 1 ? 10330 ? 10342 ? 10351

1 15 1 5 ? 1 1 503 ? 1 1 49 1 ? 1 147 7 ? 1 1 462

11467711477711486712541 ? 12611

12597 ? 12579 ? 12577 ? 12572 ? 1255?

13673? 13731 ? 13763 ? 13772 ? 13751

13691 ? 13667? 13655? 13651 ? 13666

14878 ? 14845 > 14830 ? 14322 ? 1480?

14744 ? 14756? 14778 ? 148.12 ? 15759

1206 ? 1219 ? 1246? 1251 ? 1240 ? 1211

2256 ? 2273 ? 2296 » 2309 ? 2319 ? 2320

3406 ? 3372 ? 3361 ? 3375 ? 3334 ? 3395

3467 ? 3471 7 3471 ? 3467 ? 4611 ? 4555

4560 ? 4575 ? 4585 ? 4587 *4591 ? 4596

5678 ? 5683 ? 5695? 5702 ? 5708 ? 57 15

5753 ? 576 1*6396 ? 687 1*6855 ? 6843

6876 ? 6377 * 6332 .* 6391 ? 6898 ? 6903

3023 ? 8021 ? 8022 ? 8023 ? 3023* 8023

9 1 8 1 .* 9 1 9? ? 920? ? 92 1 1 * 9204 ? 9202

9172 ? 9189 .* 9200* 9203 *9212 ? 10313

10359 ? 10354 ? 10348 ? 10343 ? 10334

10357 .* 11421 ? 11484 ? 11522 ? 11535

11458711453711443711443*11456

12652 ? 12665 ? 12642 ? 12628 ? 12614

12557? 12565 ? 12576 ? 12593 *12616

13733 ? 13727 ? 13714 ? 1369? ? 1369?

13701 ? 13757 ? 14739 *14822? 14867

14793 ? 14792? 14783? 14753 ? 14741

15890 ? 15962 ? 15978 ? 15924 *15904

67

3000 DATA 15902? 15888? 15369 ? 15866 ? 15855 ? 15823 ? 15815? 15338 ? 15342? 15333

3010 DATA 15809 ? 16736 ? 16937 ? 17047 ? 17072? 16990 ? 16963? 16967 ? 16951 ? 16927

3020 DATA 16921 ? 16909 ? 16877 ? 16876 ? 16931 ? 16924 ? 16867 ? 16753

3030 rem mmmmmmmmtmmmmmmmmm

3040 REM * %

3050 REM % Measured constants for LED Correction Eaustions* %

3060 REM %

' %

3070 REM %%%%%%%%%%%%%%%%%%%t%im%%tX%%%%%%t%%%%%%%%%t%%%%%%%%

3080 DATA -1 ? - * 44 ? 0 ? 0

? -2 * 1 2 ? * 69 ? 6 06 ? 2 44 ? - 1 12 ? - . 93

3090 DATA -1 . 31 ? 1 *06? 6E-1 ? 0

? -1 * 56 ?-i . 31 ? 4 * 06 ? 3

? -1 *06 ? - , 93

3100 DATA -i*31? *83?- *38? *88? -2* 62? *5? 3 *75? 2 *31?- *87?- *94

3110 DATA - *75? 1 * 12? 0

? - *75? -2 *56 ? 1 *62? 9 ? 1 * 25 ? -1 . 13 ?-l * 12

3 120 DATA -1 * 69 ? * 34 ? * 1 6 ? * 6E- 1 ? * 1 2 ? - 3E- 1 ? 8 * 6 9 ? * 62 ? - 1 * 1 3

? - 1 * 07

•i 1 30 DA i A -1 * 25 7 0 ? * 62 ? * 5 ? ~2 44 ? - * 12 ? 0 7 0 ? 0 ? 0

3140 DATA -l*75?*81?*19?*19?-»5? » 19 ? 6 * 06 ? * 94 ? - * 75 ? — * 69

3150 CALL 3

3160 END

68

NBS-114A (rev. 2 *80 ) U.S. DEPT. OF COMM.

4.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR 2 REPORT NO.

NBSIR 82-2559 I TITLE AND SUBTITLE

. Performing Organ. Report No. 3. Publication Date August 1982

Evaluation of Chain Saw Kickback Motion

using an Optoelectronic Measurement System

5. AUTHOR(S)

Donald Robinson and Charles Federman

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

10.

SUPPLEMENTARY NOTES

[ ] Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

In 1980 the Consumer Product Safety Commission initiated the in-house development of a mandatory standard to address chain saw kickback. Part of that effort involved relating

known chain saw energy levels generated during kickback to the final angle that a saw might travel when held in the hands of a chain saw operator. The present report describes the experimental program developed at NBS to determine the relationship between

kickback energy and chain saw motion during hand-held kickbacks for selected samples of

consumer- type chain saws and volunteer test subjects. The measurement system employed

in this research included a computer- controlled optoelectronic system for measuring the

displacements of selected points on the test saws and test fixture during simulated

kickbacks. Included in the report is a description of the test equipment and procedures,

the experimental design, and analyses of the measured displacement data for chain saws having known values of kickback energy.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

chain saw kickback motion; displacement measurements; kickback energy; optoelectronic

measurement system; simulated kickback motion; volunteer test subjects.

13. AVAILABILITY 14. NO. OF

PRINTED PAGES

IX 1 Unlimited

1 | For Official Distribution. Do Not Release to NTIS 63

H Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402. 15. Price

|Xj Order From National Technical Information Service (NTIS), Springfield, VA. 22161 $9.00

USCOMM-DC 6043-P80