SMALL SUBJECT

LARGE SUBJECT

Figure 3. Body Conformity of the Cords With Large
and Small Subjects in a Kneeling Posture

12


Use the following scale to indicate your
appropriate number after each question.

4.

5.

6.

5 - Standard cord much more

Standard cord somewhat more
Standard and coil cord are the same
Coil cord somewhat more

4
3
2
1 - Coil cord much more

Which cord was more uncomfortable?

Which cord interfered more with
your movement or work?

Which cord, when snagged, made your
helmet loose or fall off?

Which cord, when snagged, resulted
in amore forceful jerk to the neck?

Which cord allowed you to stop
crawling before a snag jerked

your neck?

With which cord did you feel safer?

Which cord would you recommend?

response;
1 2 3
1 2 3
1 2 3
1 2 3
1 2 3
I 2 3
1 2 3

Figure 2. Questionnaire used after completion
of the pull test experiment.

circle the

45
45
45
465
45
45
4 5


Figure 6. View from Front Door Down Locomotion Path.

16


30272-101

REPORT DOCUMENTATION |. REPORT WO. 2 3. Recipienta Accession Ne.
PAGE

‘© Title and Sobtitie Tismea Dae

Experiments on Personal Equipment For Low 31 January 1980
Seam Coal Miners: IV. Incorporating Coiled Cord ©
Into Cap Lamp Battery Cords

nacre Tyler Blake, Ph,D;Mark Sanders ,PH.D, ;aregor & Performing Organization Rept. Ne
Krohn; Baniel fick: Kent Ve kmer, Barry Beith 10-3054-4
3. Performing Orgenizeion Fame end AGGrs Ta. Proeet/Tash7wart Unit fa

CANYON” RESEARCH GROUP, INC.
741 Lakefield Road, Suite B

TH, CantrectiG) or Grent(G) Ne,

Westlake Village, CA 91361 ° 30387213

TE. Sponsoring Organitation Nome and AdSTanE 15. Tyee of Revert © Period Covered
U.S. Bureau of Mines; Bruceton Research Center

4800 Forbes Avenue Te.

Pittsburgh, PA 15213

1S Supplementary Notes

Te Abeirecs tami EO wares
This report describes a study designed to evaluate a pro-

posed modification in the cap lamp battery cord intented to reduce the
incidence of snagging and catching of the cord. A three phase evaluation
as performed comparing a prototype with the standard, currently available
cord. First, a "pull test" equipment was run. The second evaluation was a
body conformity study. The third evaluation involved subjects performing
fommon tasks in a low seam coal mine simulator. °
The results of these evaluations clearly demonstrated significant
Safety advantages of incorporating coiled cord into the design of the cap
cord. The coil cord presented less of a snagging hazard, allowed the
earer.more time to respond to a snag, and transmitted lower levels of
force to the helmet when snagged.

The research team recommended that cap lamp cords be commercially
developed which incorporate coiled cord at the battery and helmet.

17, Document Analyala 8, Descriptors

Cap lamp cord
Hazard Analysis

B. Identifiers /Open-Ended Terms

Mine Safety Task Performance
Personal Equipment Human Factors
Underground Coal Mining Ergonomics
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Unclassified
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c. Shoveling

d. Timbering

Figure Illustrations of Each Simulator Task (Continued)


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The ideal cord design must be durable, strong, and electrically
safe. The present cords appear to be excellent on all three of these
criteria. In addition, however, the cord should conform as closely to
the body as possible to minimize catching hazards and interference with
work. The cord should also be designed to fit the Sth to 95th
Percentile miner comfortably and allow for variation in the manner in
which it is worn (e.g. right or left side, under the arm or down the

back).

One potential design concept which might meet these requirements
would be the incorporation of coiled sections (like the cord on a
telephone) in the cap lamp cord. Coiled cord is made in several gauges
and is as strong, durable, and electrically safe as the current cord
being used. In addition, it is flexible and should conform closer to
the miner's body. The cord will also stretch to accommodate the entire
miner population. Further, in the event that a cord is caught, the
stretching action of the cord should give the miner additional time to
take corrective action before the full impact is delivered to the

helmet.

1.3. Experiments

A prototype cord was constructed incorporating coiled sections into
it. A three phase evaluation was performed comparing the prototype with
the standard, currently available, cord. The evaluation focused on the
human factors aspects of the design rather than the durability or
electrical properties of the cord. First, a “pull test" experiment was
rune The cords were snagged while the subject crawled along a
predetermined route. The subjects reaction time (time to stop) and the
maximum force delivered to the helmet were measured. It was
hypothesized that less force would be transmitted to the helmet with the
coiled cord because of its stretch characteristics.

The second evaluation was a body conformity experiment. A 5th and
95th percentile subject wore the cords and assumed standard work
postures. The cords were photographed to ascertain if the cords
conformed differently to the subjects’ bodies.

The third evaluation experiment involved subjects performing common
manual tasks in a low seam coal mine simulator. Task completion time
and subjective evaluations were obtained. The Purpose of this was to
determine if the experimental cord interferred in any unexpected way

with work performance.

After a description of the prototype cord, each of the evaluations
will be discussed separately.


tugging at the helmet. There was, however, a clear preference among all
four subjects for the coiled cord and they clearly felt safer Yerom
catching) wearing the coiled cord.

In summary, no major objections to the coiled cord were found and a
consistent trend indicated that it may be found preferable to the
standard cord in subjective evaluation.

5.4. Discussion of Simulator Evaluation

This mini-evaluation of the coiled cord in the simulator confirmed
the hypothesis that there would be no negative impact on task completion
times. Although the simulator does simulate salient low seam mine
features, it is probably not as hazardous (in terms of catching and
snagging of cords) as is a real mine. It is possible, therefore, that
in the real mine situation, any reduction in snagging by using the
coiled cord could translate into reduced task times.

22


SECTION
1.0.

2.0.
3.0.

4.0.
5.0.

6.0.

7.0.

* TABLE OF CONTENTS

PAGE
INTRODUCTION. ©... . eee rrr i]
1.1. Purpose. 2... ee ee ee ee ee 1
1.2. Background. 2... eee ee 1
1.3. Experiments ............0.-...0002 2
DEVELOPMENT OF COILED CORD. ..............0., 3
PULL TEST EVALUATION. 2... .. ee ee le 5
3.1. Purpose... . eee ee 5
3.2, Method... . eee ee Ll! 5
3.3. Results... . ee et ell 8
3.4. Discussion of Experiment I... ......2.,2,/,22 9
BODY CONFORMITY EVALUATION. ........,.....044.- WW
SIMULATOR EVALUATION. ©... ee ee ee 14
5.1. Purpose... ...... eee tee ee ee eee 14
5.2, Method... . ee lll 4
5.3. Results... . 2... et tll! 20
5.4. Discussion of Simulator Evaluation. ......2.2..~. 22
CONCLUSIONS AND RECOMMENDATIONS. ............... 23
6.1. Discussion... . 2... ee ee ee 23
6.2. Conclusions... . 2... .....00002..0220. 23
6.3. Recommendations... ............,20020~ 23
6.4. Synopsis... 2... ee ee eee lll 24
REFERENCES ©. 2... ee ee ee eee eee eee 25


FORWARD

This report was prepared by Canyon Research Group, Inc., 741 Lakefield
Road, Suite B, Westlake Village, California 91361 under U.S. Bureau-of Mines
Contract Number J0387213. It was administered under the technical direction
of Bruceton Safety Research Center with Mr. James Peay acting as Technical
Project Officer. Mr. John Minko (Bruceton Safety Research Center) supplied
constructive comments on the Draft Report. Ms. Debbie Mariner was the
Contract Administrator for the Bureau of Mines. This report is @ summary of
the work recently completed as a part of this contract during the period
1 January 1979 to J September 1979. This report was submitted as a draft
by the authors on 15 September 1979.


4.0. BODY CONFORMITY EVALUATION

The pull test evaluation clearly indicated that when the cord is
snagged, the coiled cord gives the subject more time to respond thus
allowing the subject to stop at a lower force level than with the
standard cord. Beside this safety: feature, it was also postulated that
the coiled cord would conform more closely to the body than the standard
cord and thus would be less likely to snag in the first place. This was
tested by photographing an anthropometrically large and an
anthropometrically small subject wearing: the coiled and standard cords
in various work postures.

In virtually every comparison, the coiled cord conformed more
closely to the body than did the standard cord. Figure 3, for example,
shows the large and small subjects in a kneeling posture wearing the
coiled and standard cord. The large subject is not sitting as is the
small subject, but the important upper torso is erect in both sets of
pictures. As expected, the difference between the cords jis most
striking with the small subject. The kneeling posture places the cord
in the same position as would be found if the subjects were standing
erect.

Figure 4 shows the large and small subject in a crawling posture.
The differences between the cords are less apparent, but none the less,
noticable.

The coiled section at the battery pack allows the cord to.assume
just about any angle as it leaves the battery instead of projecting
straight out and away from the battery as is the case with the standard
cord.

, From a safety standpoint, therefore, the coiled cord creates a
smaller catching and snagging hazard than the standard cord.

11


1.0 INTRODUCTION

1.1. Purpose

This report is one of a series produced under Bureau of Mines
Contract J0387213 entitled, “Use of Personal Equipment in Low Coal."
The objective of the project is to determine optimal personal equipment
design for use in low coal, based on ergonomic, biomechanic, and safety
considerations.

The purpose of the study described in this report was to evaluate a
modification in the design of cap lamp battery cords to reduce the
potential and consequences of snagging the cap lamp cord on protrusions,
Machine controls, etc.

1.2. Background

During Phase I of this contract, an extensive review of the
literature pertaining to personal equipment design was prepared
(Sanders, Beith, and Blake, 1978). The following background material
was taken, in part, from that report. Additional information can be
found in the Phase I literature review.

The current cap lamp system (light, cord and battery) has remained
virtually unchanged since it was first introduced. There are only two
manufacturers of MSHA approved systems and both are almost identical.
The cap. lamp cord presently used is .3125 inches (.79 cm) in diameter
and is 4 feet (19 cm) in length. It is rigidly attached to the battery
and the lamp. The cord contains two 18 gauge insulated wires inside a
shielded rubber coating. This design makes the cord somewhat stiff.

Site visits and interviews with miners revealed two problems with
current cap lamp cords. First, the cords come in only one size but the
miners do not. The important body dimension for assessing cord length
is sitting height (i.e. the verticle distance from the seat to the top
of the head). In the general population (Stoudt, Damon, and McFarland
1965), the range for sitting height of the 5th to 95th percentile is
approximately 5 inches (12.7 cm). Thus, the cord can be too short for
the tallest miners, and will tend to pull their helmets back. It can be
too long for the shortest miners, and thus result in an excess of cord
flopping about.

The second problem with cap lamp cords is that they present a
distinct catching hazard. The cords tend to bow out away from the body
on all but the tallest miners. This loop of cord can, and does, catch
on machine controls, moving equipment and protruding hazards. The
result is that the miner's head is jerked back and often his helmet is
pulled off. Machines are accidently activated, and occasionally the
miner can even be dragged into moving machine parts or pulled along
behind moving equipment, both with potentially severe consequences.


The mine simulator was constructed around four manual tasks
commonly performed by low seam coal miners. These tasks were selected
because they require the greatest range of body positions, are the most
physically demanding tasks, and represent the worst case situations with
respect to personal equipment usage. These tasks were: timbering,
shoveling, cart pushing and locomotion. Figure 8 a,b,c, and d show a
representative picture of each task. .

Cart pushing. A 70 Ib (31.75 kg) cart, simulating a fire boss's
shot cart or a small face drill was used for this task. One trial
consisted of alternatively pushing the cart ten. times down two 5 ft.
(1.52 m) pathways. A digital counter kept track of the repetition and
was activated when the cart touched the switch at the end of the
pathways.

Removing and replacing the cart in the far corner of the simulator
started and stopped a timer. .

Locomotion. Subjects crawled 350 ft. (106.75 m) around a
circumscribed 50 ft. (15.25 m) route in the Simulator. The subject
activated a timer when starting and stopped the timer at the end of the
trial.

Shoveling. As shown in Figure 5 two bins, containing large gravel
were positioned side by side. To the. left, were two empty bins. A
trial consisted of the subject lowering the bin door, starting the timer
and shoveling the contents of one bin into the empty bin. After
emptying the bin, the timer was stopped. “The second bin was used for
the second trial.

Timbering. A trial consisted of the subject putting up and taking
nine timbers. The roof and floor fixtures were installed to hold the
timbers so that each subject would set the timbers in exactly the same
place. A small simulated wedge was placed above each timber and hit
twice with a rubber mallet. The timer was started when the timbers were
removed from the storage area and stopped when all timbers and materials
were returned.

5.2.3. Procedure

A repeated measures design was used with each subject completing
two "cycles" on each task: one cycle using the standard cap lamp cord
and one using the experimental coil cord. The order was counterbalanced
across subjects.

One cycle consisted of a subject performing two trials on each
task. The two trials of a task were. performed consecutively before
moving onto the next task. Thirty (30) seconds separated each trial of
a task.


Open File Veport 34(s) -82

EXPERIMENTS ON PERSONAL EQUIPMENT
FOR LOW SEAM COAL MINERS: IV.
INCORPORATING COILED CORD INTO
CAP LAMP BATTERY CORDS

Prepared for:
United States Department of the Interior
Bureau of Mines

By:

Tyler Biake, Ph.D.; Mark Sanders, 7h.d.;
Gregory Krohn; Daniel Wick;
Kent Volkmer; Barry Beith

CANYON RESEARCH GROUP, INC.
747. Lakefield Read, Suite B
Westlake Village, CA 91361

>
a
rm,
tb
e

i Report, Ne. 4

Contract Ne. J0387213
Study of the Use of Persenal Equipment in Low Coal

31 danuary 1986


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2.0. DEVELOPMENT OF COILED CORD

Cap lamp systems must meet requirements set forth in CFR 30:19.0.
The only specific standard set forth for the cord is a durability test
defined as follows:

Ten cords, assembled with the cord armor
and outlet of the lamp with which it is
to be used, are slatted at least 100,000
times through an arc of 50 degrees at
approximately 90 slattings per minute.

Several manufacturers of coiled cord indicated that commercially
available coiled cord should be able to pass this durability test. In
fact, manufacturers indicated that technology exists which could produce
a smaller diameter, lighter weight straight cord than that currently
used with cap lamps without sacrificing strength or durability.

Several prototype configurations involving coiled cord were
informally tested and evaluated. It quickly became apparent that the
entire cord could not be coiled. -This would greatly increase the weight
of the cord, it would add height to the helmet where the cord runs over
the top to the lamp, and it was uncomfortable to wear’ under the arm.
Further, very little coiled cord is required to allow for anthropometric
differences in miners. Most commercially available coiled cord will
stretch to four times its resting (coiled) length. Therefore, it was
decided to: keep the coiled sections to a minimum. This would also
reduce the cost of production. The logical step was to combine small
sections of coiled cord with standard straight cord. The question then
became where to place the sections of coiled cord. Observations of test
subjects performing simulated manual tasks revealed that the cord bulges
out principally at the battery pack, and to a lesser extent at the base
of the helmet. Therefore, these two sites were selected for placement
of small sections of coiled cord. .

After discussions with manufacturers and informal testing of cord
samples, the coiled cord selected for use was a 22 gauge two wire cable
manufactured by Belden. The 22 guage coiled cord is smaller in diameter
(.1875 in; .48 cm) than the standard 18 gauge cord (.3125 in; .79 cm)
but can still handle the power requirements of the cap lamp.

Figure 1 illustrates the prototype cord configuration. A straight
piece of cord extends over the cap lamp to the base of the helmet, where
it becomes coiled for seven complete turns before straightening again.
dust before entering the battery it is again coiled 21 complete turns
and enters the battery directly. The coiled cord has an elasticity
ratio.of 4 to 1. This means that the 5.75 in (14.6 cm) length of coiled
cord used could be stretched to a maximum length of 23 in (58.5 cm).
This, then, is the coiled cord configuration that was used in the three
evaluation experiments.


6.4. Synopsis

This report describes a study designed to evaluate a proposed
modification in the cap lamp battery cord intented to reduce the
incidence of snagging and catching of the cord. A three phase
evaluation was performed comparing a prototype with the standard,
currently available, cord. First, a “pull test" experiment was run.
The second evaluation was.a body conformity study. The third evaluation
involved subjects performing common tasks in a low seam coal mine
simulator.

The results of these evaluations clearly demonstrated significant
safety advantages of incorporating coiled cord into the design of the
cap lamp cord. The coil cord presented Jess of a snagging hazard,
allowed the wearer more time to respond to a snag, and transmitted lower
levels of force to the helmet when snagged.

The research team recommended that cap lamp cords be commercially
developed which incorporate coiled cord at the battery and helmet.

7.0 REFERENCES

Sanders, M.; Beith, B.; and Blake, T. Use of Personal Equipment in Low
Coal: A review of the Personal. Equipment Literature (J0378213)
Pittsburgh: Bureau of Mines, 1978.

Sandler, J. Critical valves for A. British Journal of Psychology
1965, 46, 225-226.

Stoudt, He, Damon, A., and.McFarland, R. Weight, Height, and Selected
Body Dimensions of Adults. DHEW Publication No. (HRA). 76-1074.
Rockville, Maryland: Health Resources Administration, 1965.

Weiner, B. Statistical Principles in Experimental Design. New York:
Mc Graw HilT Book Company, [97T.

24


6.0. CONCLUSIONS AND RECOMMENDATIONS

6.1. Discussion

The results: from the three evaluations were very consistent. The
coiled cord appears to have a significant safety advantage over the
standard cord. In addition, it can accommodate both large and small
wearers equally well.

The particular design of coiled and straight cord used in these
evaluations is probably not the optimal design. More than likely, less
coiled cord could be used at the battery and at the helmet and still
achieve the same results. (It was beyond the scope of the current
contract to further modify and reevaluate other variations on the basic
design tested.)

The coiled cord used in the test was hung on a wall to determine
the amount of "stretching out” which would develop over time from the
weight of the cord itself. After five months, there was virtually no
additional stretching than had already occurred during the various
evaluation tests.

6.2. Conclusions

The results from the pull test, comformity, and simulator
evaluations clearly demonstrate significant safety advantages of
incorporating coiled cord into the design of the cap lamp cord.

The coiled cord, compared to the standard cord,

1. Presents less of a snagging hazard;

2. Allows the wearer more time to respond to a snag; and

3. Transmits lower levels of force to the helmet when snagged.
6.3. Recommendations

It is the strong recommendation of the research team that cap lamp
cords be commercially developed which incorporate coiled cord at the
battery and helmet. These cords should be fully tested to meet MSHA
requirements and field tested at several mines. The cost of switching
from a straight cord to a coiled cord would be minimal but the potential
safety benefit would be large. In addition, conversations with miners
revealed a strong willingness to try such a cord with a belief that it
might well prove superior to their current cord. User acceptance may,
therefore, not be a major problem.

23


TABLE

FIGURE

1.

2.

LIST OF TABLES

QUESTIONNAIRE RESULTS FROM PULL TEST EXPERIMENT. . . . - + + +

LIST OF FIGURES

Illustration of Prototype Cap Lamp Cord Used Showing
Sections of Straight and Coiled Cord... - - +e eee eres

Questionnaire Used After Completion of the Pull Test Experiment .

Bady Conformity of the Cords with Large and Small Subjects in

a Kneeling Posture . «6. eee ee ee ry
Body Conformity of the Cords with Large and Smal] Subjects
in a Crawling Posture... 2 +--+ ese eee
Schematic Top View of Simulator... . +--+ +

View from Front Door Down Locomotion Path . .

Simulated Rock Plate Floor Hazard. ...- -
a. Cart Pushing -* + ect ccc
b. Locomotion Se ee eee
c. Shoveling we ee ee
d. Timbering es

Mean Task Completion Times (Seconds) for Each of the Simulated

Tasks While Wearing the Coiled and Standard Cords

Vi

PAGE
10

PAGE


5.0 SIMULATOR EVALUATION

5.1. Purpose

The pull test and body conformity evaluations clearly demonstrated
the hazard reduction potential of the coiled cord design. The purpose
of this simulator evaluation was to assess whether the coiled cord
created any interference while the miner performed typical manual tasks
in a low seam mine environment. A small number of subjects was used in
this evaluation as it was not anticipated that any interference effects
would be obseved. If anything, the closer contour of the coiled cord
might actually present less interference than the standard cord.

5.2. Method

5.2.1. Subjects

Four male subjects were used in this experiment. Two subjects were
selected from the 1 to 15th percentile in height and weight for the
general population. The other two subjects were selected from the
85-99th percentile. Subjects ranged in height from 64 to 75 inches
(163-190 cm) and in weight from 135 to 190 Ibs (61-86 kg). All subjects
had, previous to this experiment, worked in the simulator a minimum of
five hours. Subjects were paid for their participation.

5.2.2. Simulator and Experimental Tasks

A simulator, designed to recreate ‘the essential features of a low
seam coal mine was constructed for this. project. The general
configuration of the simulator is shown in Figure 5. It consisted of an
8 x 36 ft. (2.44 x 11.0 m) main tunnel and three separate 6 x 8 ft.
(1.83 x.2.44 m) alcove areas. The simulator was constructed of plywood
with stucco covered walls. This provided a highly irregular and
realistic surface. The entire simulator was painted flat black with
dark gray modelling.

The roof consisted of interchangeable, irregular panels which
varied in height # 6 inches (¥ .15 m). The roof was adjustable to
either a 36 in. (.92 m) or 42 in. (1.06 m) average height. For this
experiment, the roof was set at 36 in. (.92 m). The roof also contained
simulated roof bolts, cross beam timbers and rock outcroppings. The
location of the roof hazards are shown in Figure 5 and some can be seen
in Figure 6. The floor was irregular with bumps, dips, inclines, and
“rock plates" (see Figure 7). Ten wooden posts, 6 in. (.15 m) in
diameter, were fixed in various locations to simulate temporary roof
timbers.

No light penetrated the simulator. Ventilation was achieved by
fans and air conditioning. Temperature was maintained at 65-75°F
(18-24°C). Observation portals allowed visual access to the simulator
for the experimenter.

14


During the first trial of each cycle, the subject wore the cap lamp
cord under their arm. That is, the cord coming off the back of the
helmet ran over the shoulder across the breast pocket and under the arm
to the battery pack. During the second trial, the cord was worn
straight down the back. .

Fifteen (15) minutes was alloted to finish the two trials of each
task; unused time was rest. This amounted to approximately five (5)
minutes rest between each task. A ten (10) minute rest was given at the
beginning of each cycle. At the end of the experiment, the subject was
questioned concerning the two cords on comfort and interference while
performing each of the tasks in the simulator. In addition, the
following six overall questions were asked:

1. Which cord did you reposition or readjust more?

2. Which cord caught on your belt, battery, or your self-rescuer
more?

3. After being repositioned, which cord shifted out of position
more quickly? :

4. Which cord tugged or pulled more at the back of your helmet
when you twisted or turned?

5. Which cord would you feel was safer?
6. Which cord would you recommend?
5.3. Results

5.3.1. Task Completion Time

Figure 9 presents the mean task completion times for each task
while wearing each of the cords. The differences between cords, with
the small sample size used were not statistically reliable for any task.
Further, the direction of the differences were not consistent. On two
tasks performance was faster with the coiled cord, and on two tasks
performance was faster with the standard cord.

Even with this small sample size, it is safe to assume that the
coiled cord does not adversely effect task completion time on the tasks
simulated in this experiment. Thus, any safety or comfort advantage
which the coiled cord might possess should not be offset by any expected
degradation in performance. .

5.3.2. Interview Results

The results of the interview indicated that the subjects detected
no difference between the cords in terms of comfort or interference on
any of the tasks. The overall questions also showed no differences
between cords in terms of repositioning, catching, reshifting, and

20


DISTRIBUTION/AFPROVAL. OF MINERALS. RESEARCH CONTRACT RETORT

Title: Experiments on Personal Equipment for Low Seam Minéts: IV. Incorporating

: Coiled Cord into Cap Lamp Battery Cords
Report Date: January 31, 1980 Type of Report (Final/Interim): Phase II Report
Value/Impact of Results: Results of testing the cord in a simulated low coal seam
environment revealed that when compared against a standard cord, the coiled cord
presents less of a snagging hazard: allows the wearer more time to respond to a snag
and transmits lower levels of “force to the helmet when snagged

Users/Audience: Industry, Academia. and Manufacturers

Contractor Name: Canyon Research Group, Inc.

Contract Number: J0387213 Total Contract Funding: $290,488
nS

TPO: James M. Peay Element Manager: George Manthey

Has contractor filed a Patent Form DI 1217? Yes | No_ x

If yes, attach Solicitor's approval to make public,

Press Release Recommendation: ‘Yes Noa >
Recommended for Open File: Yes x No |RASHINGTON OFFICE oe
Recommended for NTIS: Yes x No
IDate Rec'd T.T.5/5/81_[-311K
IOFR #: 39(5)-82 |
. . [NTIS |
If no, explain: : . l# of pages: 28 |
| Price: : |
| |
Distribution: (Check or fill in es appropriate.)
" DOI Library (2_each) OSH Library (1 each)

10 BOM. Research Centers x
4 Field Operation. Centers
DOE, Carbondale, IL x’ SDDRXXMARY MEF XXAKXERK NO DOE, Pittsburgh, PA x :
MSHA, Arlington, VA x

National Mine H & S$ Academy, Beckley, WV Xx

State Geologists in:
Other:

If not recommended for distribution, state why.

Concurrences:

Element Manager Chee, Che, zi Date a/o/52
Branch Chief Ay Gl Sy De Oa Date 2 /jo/Bz
Program Director | Ly A®ee oe” Veliwronet lL. Date 277757
Deputy Director  —~ 7 Date :

Ya [/
Approval: f ;
Chief, OPI |: D bite Date Sih ft

ATTACHMENT CHECKLIST

Summary of Results AXW Ssmmary and Evaluation of Final Report £xxt H



3.2.4 Procedure

Warm up trials. Subjects were asked to locomote over the track
while counting backwards by two's from a number provided by the
experimenters. The counting served to distract the subjects from their
cap lamp cords. They were instructed to follow the track and to move at
a comfortable consistent “moderately quick" pace. Subjects were asked
to adopt a comfortable head posture, and to maintain that position as
closely as possible during the experimental trials. It was suggested
that they note the point where their cap lamp beam shined on the track,
and that they try to keep the beam at roughly the same distance ahead of
them as they crawled. The experimenter recorded the time required to
complete each trial. When the subject's time did not vary moré than 2
seconds for three runs, the actual data collection trials were begun.
All but one subject achieved consistency on the first three trials. The
other subject required four trials.

‘

Data Trials. Before each data trial, the subjects were asked to
close their eyes and face away from the track while the experimenter
walked down the entire length of the track and installed a metal clip at
a pre-determined point on the rope. The clip could be placed at any one
of 20 positions on the rope. (or not at all in the case of a “false”
trial). The position of the clip on any trial was provided by a
predetermined random order. When the subjects crawled, they pulled the
metal ring along the rope. When the ring struck the clip it stopped and
pulled the cap lamp cord, thus simulating a snag. The subject was
instructed to stop the instant he realized his cord was snagged. A
piece of foam rubber was attached to the side of the metal clip to
muffle the sound of the ring hitting the clip.

The experimenter started a silent stop watch when the ring hit the
clip and stopped the timer when the subject stopped crawling. A large
piece of foam rubber was placed on the back of the subject and the cord
rested on the pad. This prevented the subject from sensing the tactile
cue of the cord lifting off their back when the cord was snagged. The
subjects also wore overalls, helmet, battery pack and cap lamp,
self-rescue device and knee pads.


trials, thus allowing much of the random fluctuation to average out.
Second, there is no reason to believe that the experimenter's reaction
time would be systematically different when the subject wore the
different cords. Therefore, the .372 m sec difference probably
indicated a true difference in reaction time to snags with the two
cords.

3.3.3. Questionnaire Results

Table 1 contains the means and standard deviations for each
question on the questionnaire. The mean of each item was tested using
the parametric, "t" test (Winer, 1971) to determine if it was reliably
different from 3.0 ("Standard and coil cord are the same"). The results
of these “t" tests are also contained in Table 1. The results showed
that, on the average, ‘subjects felt that the standard cord was more
uncomfortable, interfered more with their movement, was more likely to
make their helmet loose or come off when snagged, and resulted in a more
forceful jerk to the neck than the coiled cord. Further, they felt
safer wearing the coiled cord and would recommend it much more than the
standard cord. These results are in keeping with the peak force data.
Item 5 was the only item not to show any significant opinion toward
either cord. The authors believe that it is because the question is
ambiguous with respect to the force of the jerk. In essence, the
subjects only stopped when they felt a jerk so the question has no
answer.

3.4. Discussion of Experiment I

The results clearly show that the coiled cord delivers considerably
less force to the helmet than the standard cord under the conditions
simulated. Further, subjects were slower to respond to a snag while
wearing the coiled cord. This is logical when the following is
realized. First, subjects have a threshold force below which they can
not perceive a snag. Second, the force to the helmet builds up more
slowly in the case of the coiled cord due to its inherent elasticity.
Third, there is a certain reaction time between the sensing of the snag
and the cessation of crawling. In the case of the standard cord, the
force is sensed; but it builds up so quickly that by the time the
subject stops, he has endured considerable more force. In fact, the
subjects' heads often snapped back from the force of the snag while
wearing the standard cord. With the coiled cord, on the other hand, the
force is sensed and, because of the slow build up of force, only a
relatively small increase in force has resulted before the subject stops
crawling.

There are, then, obvious safety advantages to wearing a coiled
cord, as opposed to a standard cord, if it is snagged while the miner is
moving. The miner's head is not jerked back and there is more time to
take corrective action and free the cord.


me, re

United States Department of the Iriterior
BUREAU OF MINES

PITTSBURGH, RESEARCH CENTER
COCHRANS MILL ROAD
POST OFFICE BOX 18070

PIETSBURGH, PENNSYLVANIA 15236

June 25, 1982
Memorandum .

To: Librarian: .
Department of the Interior Library (2)
Office of Surface Mining Library
Albany Facility Library
Avondale Facility Library
Boulder City Engineering Laboratory
Denver Facility Library
Pittsburgh Facility Library
Reno Facility. Library
Rolla Facility Library
Salt Lake City Facility Library
Spokane Facility Library
Tuscaloosa Facility Library
Twin Cities Facility Library
National Mine Health & Safety Academy, Beckley, West Virginia
Mine Safety and. Health Administration Library, Arlington, Virginia
Technical Information Specialist, PRC
DOE, Carbondale, IL —- DOE, Pittsburgh, PA
Fron: Research Director, PRC .

Subject: - Mistribition of Report EXPERIMENTS ON PERSONAL EQUIPMENT FOR
LOW SEAM MINERS: IV. © R. COILED CORD INTO CAP LAMP

BATTERY CORDS

“@ are enclosing copy/copies of the firal resort froa Canyon Research

Group, Inc. ( 20387213 : 1/31/80 _).
Contractor Contract flo. Report Sate :

A copy of the memorandum to the Chief, Office Of Public Information,

épproving Open File Placement is attached. The Cpen File Report number

is: OFRe 39(5)-82 .
enw reas
dohn t. Murphy
Pase

arch Director; PRC
“rclosures ;

ce: Div. of Technical Reparts, W.0.
Technical Project Of ficer--JMPeay


a. Cart Pushing

b. Locomotion

Figure 8. Illustrations of Each Simulator Task.

18


DISCLAIMER

The views and conclusions contained

in this document are those of the
authors and should not be interpreted .
as necessarily representing the
official policies or recommendations
of the Interior Department's Bureau

of Mines or of the U.S. Government.

Reference to specific brands, equip-
ment, or trade names in this report
is made to facilitate understanding
does not imply endorsement by the
Bureau of Mines.

6-332
(December 1961)

etter 15213 .


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21


3.0, PULL TEST EVALUATION

3.1. Purpose

The current cord is, of course, not elastic. As such, any time the
cord is snagged the full force is transmitted to the helmet almost
immediately. The coiled cord, on the other hand, will stretch and
should provide a gradual build up of force at the helmet when snagged.
This gradual buildup could allow the wearer to respond before the full
force of the snag is transmitted to the helmet.

This: experiment was designed to test this hypothesis. Subjects
crawled along a route at a constant speed. At random locations, the
cord was snagged and both maximum force on the cord and subject's
reaction time to stop were measured.

3.2. Method

3.2.1 Subjects

Eight male subjects were used. The subjects represented the
extremes (1-15th and 85-99th percentile) of the general population in
height and weight. Subjects ranged in height from 64 to 75 inches
(163-190 cm) and in wieght from 135 to 190 lbs (61-86 kg). Subjects were
paid to participate.

3.2.2. Pull Test Apparatus

The route followed by the subjects was a straight path 18 ft (5.5
m) long. A dashed white line ran the entire length of the path. This
helped the subjects stay on the path and maintain a consistent pace.

The force measuring equipment, a rope 22 ft (6.7 m) in length, was
attached, adjacent to the track, on the wall 4 ft (1.2 m) off the floor.
The rope was stretched and held taut by a spring and stationary hook at
one end, and a memory torque wrench secured at the other end. When the
rope was pulled, the peak force would be recorded on the torque wrench.
(The reading on the torque wrench (in in - Ibs) would later be converted
to force (Ibs) using a standard engineering formula).

A metal ring was placed so as to slide along the rope. A length of
fishing line was attached to the ring and tied to the cap lamp cord of
the subject. The line was attached to the cord 13 in. (33 cm) above the
battery pack. This corresponds closely to the apex of a typical loop
formed by any excess cord.

A curtain blocked the subject's view of the rope. This prevented
him from seeing where the snag would occur.

3.2.3. Questionnaire

At the completion of the experimental section each subject
completed the questionnaire shown in Figure 2.


Each subject ran 18 trials with each cord. The order in which the
cords were worn was counterbalanced across subjects. Six of the 18
trials were "false" trials in which no snag occured. The false trials
served two purposes. First, they prevented the subjects from
anticipating snags as they. approached the end of the track. Second,
they provided an opportunity for the experimenter to record the time
required for the subject to crawl the length of the track. The
experimenter could then determine if the subjects were maintaining a
consistent pace and if not, could advise the subject to speed up or slow
down. Subjects maintained remarkably consistency paces (+ 1.5 sec. per
run) and seldom had to be coached.

3.3. Results

It is important to establish that the subjects were crawling at the
same speed when wearing the two cords. A difference in crawling time
might result in different forces being transmitted to the helmet when
the cord was snagged. The time required to locomote the length of the
track was recorded on the six false trials in which no snag occurred.
These six locomotion times for each subject were averaged for each cord.
The average across all subjects was 7.76 seconds while wearing the
standard cord, and 7.78 seconds while wearing the coiled cord. Any
differences in force or reaction time found between the cords cannot be
due to two-one hundreds of a second difference in locomotion time.

3.3.1. Peak Force

Sandler's A statistic (Sandler, 1955) was used to compare
performance with the coiled and standard cords. Sandler's A is derived
directly from the “t" test, but is computationally simpler. The results
of an analysis using the A test will be the same as the “t" test for
related measures.

The peak forces recorded on the twelve trials in which a snag
occurred were averaged for each subject, for each cord. The mean peak
force for all eight subjects when wearing the standard cord was 7.81 lbs
(34.7 N) compared to only 4.52 Ibs (20.1 N) when wearing the coiled
cord. This difference is statistically significant (Sandler's A = .188,
p<.01). Thus the force delivered to the helmet when wearing the coiled
cord was averaged only 58% of the force typically delivered when wearing
the standard cord.

3.3.2. Reaction Time

The mean reaction time (time from snag to detection) while wearing
the standard cord was 622 msec, compared to 994 msec while wearing the
coiled cord. This difference is statistically significant (Sandler's A
= .160, p<.01). Thus, the subjects were slower to react to the snag
when wearing the coiled cord.

Although there was some error introduced into the reaction time
measure because the experimenter started and stopped the timer, it is
believed that it would not bias the results for two reasons. First the
reaction time scores used for each subject were an average of twelve

8