NBSIR 75-913

Structural Test Procedures for

Bicycles

Donald E. Marlowe

Engineering Mechanics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

October 1975

Final

Prepared for Office of Consumer Product Safety

Center for Consumer Product Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

NBSIR 75-913

STRUCTURAL TEST PROCEDURES FOR

BICYCLES

Donald E. Marlowe

Engineering Mechanics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

October 1975

Final

Prepared for Office of Consumer Product Safety

Center for Consumer Product Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

U.S. DEPARTMENT OF COMMERCE, Rogers C.B. Morton, Secretary

James A. Baker, III. Urtder Secretary

Dr. Betsy Ancker-Johnson. Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Director

TABLE OF CONTENTS

page

1. SCOPE 1

1.1 Test Purpose 1

2. TEST EQUIPMENT 2

2.1 Load-Deflection Recorder 2

2.2 Loading Frame 2

3. TEST PROCEDURE 3

3.1 Test Flow 3

3.2 Drive Chain Test (1512.8) 3

3.2.1 Test Equipment 3

3.2.2 Procedure 3

3.3 Handlebar Stem to Fork Clamp (1512.18 (h)(1)) 3

3.3.1 Test Equipment 3

3.3.2 Test Procedure .3

3.4 Handlebar Strength (1512.18 (h)(2)) 4

3.4.1 Test Equipment 4

3.4.2 Test Procedure 4

3.5 Handlebar Stem Test (1512.18 (g)) 4

3.5.1 Test Equipment 4

3.5.2 Test Procedure 4

3.6 Seat Clamp Tests (1512.18 (1)) 5

3.6.1 Test Equipment 5

3.6.2 Test Procedure 5

3.7 Rear Hub Retention Test (1512.12 (a)(1) 5

3.7.1 Test Equipment 5

3.7.2 Test Procedure 5

3.8 Rim Test (1512.18 (j)) 5

3.8.1 Test Equipment 5

3.8.2 Test Procedure 5

3.9 Frame Test (1512.18 (k)(2)) 6

3.9.1 Test Equipment 6

3.9.2 Test Procedure 6

3.10 Fork Test (1512.18 (k)(l)) 6

3.10.1 Test Equipment 6

3.11.2 Test Procedure 7

4. RESULTS 7

5. DISCUSSION 7

6. CONCLUSIONS 8
Table of Contents (Con't.) page

7 . REFERENCES 8

APPENDIX A A-1

APPENDIX B B-1
STRUCTURAL TEST PROCEDURES

FOR BICYCLES

Donald E. Marlowe

Tests for several structural performance criteria

have been included in a mandatory regulation on bicycle safety which has been proposed by the Consumer

Product Safety Commission. The apparatus and procedures

developed to conduct these tests and results from

15 representative bicycles are described. Several

of the bicycles tested failed to meet the requirements for the seat and handlebar stem friction clamp

strength.

Key Words: Bicycle, consumer safety, regulations,

safety, structural testing.

1 . SCOPE

Accident reports received by the Consumer Product Safety Commission

(CPSC) list many injuries to children as a result of accidents involving

bicycles. Many of these injuries result from failure of the structural

components of the bicycle during normal use. As a result, the CPSC has

included a set of structural performance criteria in the proposed mandate

regulations [ij on bicycle safety. This report describes the apparatus

and procedures developed at the National Bureau of Standards for the

performance of tests to measure the structural properties of bicycles

in accordance with the mandatory regulation and its proposed amendments.

1.1 Test Purpose

The purpose of the tests described here is to verify the technical

feasibility of the tests as proposed in the regulation and to exercise

the test apparatus which was designed at NBS for CPSC.

The tests included in the program and the paragraphs of the regulation to which they refer are as follows:

1) Drive chain strength (1512.8)

2) Handlebar strength (1512.18 (h))

3) Seat clamp strength (1512.18 (1))

4) Handlebar stem strength (1512.18 (g))

5) Frame strength (1512.18 (k)(2))

6) Fork strength (1512.18 (k)(l))

7) Rear hub retention strength, and (1512.12 (a)(1))

8) Wheel rim strength (1512.18 (j))
2. TEST EQUIPMENT

The equipment used for these tests included a universal testing

machine with a 11100 N (2500 Ibf) range which complied with the calibration requirements of ASTM E-4 [2j, spring force gages with capacities

of 450 N (100 Ibf) and 900 N (200 Ibf), a loading frame equipped with

a load cell, def lectometer and an X-Y plotter, and several specialized

test jigs which will be described in conjunction with particular tests

in later sections of this report.

2,1 Load-Deflection Recorder

This instrumentation was used for all tests which were conducted

in the loading frame. The complete package includes an X-Y plotter,

control box, load cell, and deflection transducer.

Operation: For operation and maintenance of the recorder, see the instruction

manual [3 J provided with the recorder.

Load Channel: An electrical signal proportional to load is provided

for recording on the Y-axis of the recorder. Load is sensed with 2200

N (500-lbf) capacity load cell. The load scale is adjusted to 220 N/cm

of record (50 Ibf /in of record) when the recorder multiplier switch

is set at 1 mV/in and the push to calibrate button results in a deflection

of 22.4 cm (8.80 in).

Deflection Channel: An electrical signal proportional to deflection

is provided for recording on the X-axis of the recorder. Deflection

is sensed with a displacement transducer having a maximum range of 10 cm (4 in). The deflection scale is adjusted to 0.25 cm per cm (0.25

in per in) of record when the recorder multiplier switch is set at 100

mV/in and the push-to-cal ibrate button results in a pen deflection

of 19.2 cm (7.55 in).

Schematic: A schematic of the control box circuit, which includes the

load and displacement transducers, is shown in Figure 1.

2.2 Loading Frame

A loading frame, designed to supplement the use of a testing machine, was used in several of these tests. Its use will be illustrated for

several tests in later sections of this report. The loading frame provides

attachment points for the bicycle parts and the loading actuator employed.

The actuator used was a double acting hydraulic cylinder and power supply.

Drawings of this load frame are provided in Appendix A.

/

2
3. TEST PROCEDURE

3.1 Test Flow

Special attention must be given to the order in which tests are performed if a single bicycle is to be used for all the tests. If care

is not taken, the loading and subsequent destruction of bicycle parts

not under test may occur which will invalidate tests to be performed

later in the program. One possible order for these tests is shown in

Figure 2. It should be noted that no component tests can be conducted

until all braking tests, probe tests, reflector tests and road tests

have been completed.

3,2 Drive Chain Test (1512.8)

3.2.1 Test Equipment

The apparatus used for these tests is shown in Figure 3. The fixtures are mounted as shown in a universal testing machine having a loading

range of 11100 N (2500 Ibf) capacity. The detailed drawings of the test

fixtures are given in Appendix A.

3.2.2 Procedure

The chain grips (Figure 4) were suspended in the testing machine

using the testing machine pull rods. The drive chain was removed from

the bicycle and installed in the grips. This was done by inserting the

chain onto the sprocket wheel such that the test section of the chain

was on the axis of the testing machine and the chain was wrapped around

the sprocket until the last link rested in the tooth adjacent to the

hole through the sprocket. A light gage wire was then inserted through

the hole and wrapped around the chain or inserted through the hole in

the last chain link (Figure 4). After placing the fly mesh screen around

the specimen to contain all broken chain pieces, load was applied until

chain failure (1512.8).

3.3 Handlebar Stem to Fork Clamp (1512.18 (h)(1))

3.3.1 Test Equipment

The apparatus used to conduct this test is shown in Figure 5. It

includes a load bar clamped to the handlebar and a spring force gage

attached to the load bar a measured distance from the stem clamp axis.

3.3.2 Test Procedure

The front fork was restrained from rotating by clamping it against

a stationary object. The load bar was clamped to the handlebar. The

3
distance from the stem axis to the loading point on the Loading bar was measured. A gradually increasing load was applied through the force

gage until a torque on the clamp of 47.2 N-m (35 ft-lb) was reached

or the stem began to turn in the fork (1512.18(h)(1)),

3.4 Handlebar Strength (1512.18 (h)(2))

3.4.1 Test Equipment

The apparatus used to conduct this test is shown in Figure 6. It

includes a fixture to hold the handlebar stem in the testing machine,

and a loading jig to apply loads to the ends of the handlebar. The test was conducted in a testing machine for convenience only and could have

been done with the stem inserted in the bicycle. The detailed drawings

of these test fixtures are given in Appendix A.

3.4.2 Test Procedure

The stem was removed from the bicycle, inserted in the holding

fixture and the stem clamp tightened. Adjustments were made to the fixture

to level the portions of the handlebar near the ends where load would

be applied. The fixture was placed in a testing machine. The loading

yoke was placed on the handlebar ends and load slowly applied by the

machine until a load of 445 N (100 Ibf ) was reached, or an energy of

22.6 J (200 in-lb) was absorbed in handlebar bending, or the handlebar

slipped in the clamp (1512.18(h)(2)).

3.5 Handlebar Stem Test (1512.18 (g))

3.5.1 Test Equipment

This test was performed in a testing machine which complies with

the requirements of ASTM designation E4-72. The apparatus used for this

test is shown in Figure 7. This test fixture fulfills the requirements

of paragraph 1512.18 (g)(1) and Figure 2 of the proposed regulation.

A detailed drawing of this fixture is given in Appendix A.

3.5.2 Test Procedure

The handlebar was removed from the stem and a solid bar inserted

in the stem in its place. The handlebar clamp was retightened. The stem

was placed in the stem loading fixture at its minimum insertion mark

and the stem bolt tightened. For stems which did not have a minimum

1 insertion mark, the diameter of the stem was measured and the stem was inserted into the fixture to a depth of 2.5 diameters. Gradually increasing

loads were applied in the testing machine through the loading yoke in

a direction as shown in Figure 2 of the regulation until a load of 2000

N (450 Ibf) was reached (1512.18(g)(1)). The load was removed. The

stem was removed from the fixture and checked visually for cracks.

4
3.6 Seat Clamp Tests (1512.18 (1))

3.6.1 Test Equipment

For this test a 900 N (200 Ibf) spring force gage was used as shown

in Figure 8.

3.6.2 Test Procedure

With the bicycle frame restrained from movement by clamping its

frame to the frame of a testing machine, 668 N (150 Ibf) was applied

downward, 25 mm (1 in) from the seat front and then 25 mm (1 in) from

the seat back so as to test the seat clamps in pitch. A load of 222

N (50 Ibf) was then applied horizontally at these same distances from

the seat front and back so as to test the seat clamps in yaw (1512.18(1 )(1 )).

3.7 Rear Hub Retention Test (1512.12 (a)(1)

3.7.1 Test Equipment

The equipment needed for this test is shown in Figure 9. This equipment included a hydraulic ram and load cell for applying and measuring

the load, the connectors needed to grip the bicycle frame and rear axle,

and a reaction frame.

3.7.2 Test Procedure

For this test, the front wheel was removed from the bicycle. The

test fixtures for holding the frame and axle were attached to the bicycle

(Figure 10). The fixtures were attached to the reaction frame and hydraulic

ram such that the applied load was in the direction of the axle adjustment

slot in the frame. Force was gradually applied to the axle-frame coupling

until 1780 N (400 Ibf) had been reached or until the axle moved in the

frame

3.8 Rim Test (1512.18 (j))

3.8.1 Test Equipment

The test apparatus used in this test is shown in Figure 11. This

equipment included the masks for each tire size, a hydraulic ram to

apply the load, a load cell and indicator to measure the load, a coupling for each bicycle axle, and a reaction frame. The mask rested on

the frame and supported the rim through the tire around its entire circumference. A coupling which fitted the threads of the axle and a chain

(Figure 12) was used to connect the loading ram to the wheel.

5
3.8.2 Test Procedure

Wheel rims were tested in accordance with paragraph 1512.18 (j)

of the regulation. If both wheels of the bicycle were symmetric about

the plane of the tire, only one was to be tested. If, however, the wheel

hub was offset, as occurred when a multiple drive sprocket was used

on the rear axle both wheels were tested. For the wheel with the offset,

load was applied in the direction of the offset.

After the wheel to be tested was removed from the bicycle, the

tire was inflated to the pressure recommended by its manufacturer. The

axle coupling was installed, and the wheel was placed on the mask in

the reaction frame with the mask supporting only the tire. The chain

was attached to the loading ram and the axle coupling. A gradually increasing

load was applied to 2000 N (450 Ibf ). This load was held for 30 seconds

and removed. The wheel was then reinstalled on the bicycle according

to the manufacturers instructions and tested for alinement in accordance

with paragraph 1512.11 of the regulation.

3.9 Frame Test (1512.18 (k)(2))

3.9.1 Test Equipment

The equipment needed for this test is shown in Figure 13, It includes

a reaction frame, load cell and def lectometer for measuring load and

deflection, the X-Y plotter, and a hydraulic ram for applying the load.

3.9.2 Test Procedure

After the wheels were removed from the bicycle, the rear fender

brackets were removed. The frame was inserted in the reaction frame

as shown in Figures 13 and 14. Shown in Figure 14a is the positioning

of the def lectometer to measure frame deformations. As the load was applied using the hydraulic ram, a plot of load versus deflection was made. Load was gradually applied until a force of 890 N (200 Ibf) was reached or 39.5 J (350 in-lb) of energy was absorbed in frame deflection,

whichever resulted in the greater force (1512.18(k)(2)). After the load

had been released, the frame was removed from the test fixture and the

front wheel reinstalled on the bicycle and checks were made to determine

if the steering of the bicycle had been affected.

3.10 Fork Test (1512,18 (k)(l))

3.10.1 Test Equipment

The equipment needed for this test is shown in Figure 15. This

fixture complies with the requirements of paragraph 1512.18 (k)(l)(i)

and Figure 1 of the proposed regulation. Also required for this test

6
is a testing machine, a deflectometer and the X-Y plotter. A drawing

of the apparatus used in the test is given in Appendix A.

3.10.2 Test Procedure

After the results of the frame test had been evaluated, the fork was removed from the bicycle and all bearings, hardened shoulders and

any cable fittings were removed. A hardened steel roller wheel was installed

at the axle attachment point (Figure 15). The fork was placed in the

fixture with the fork yoke hard against the V block. The def lectometer

was adjusted to measure fork deflection. The X-Y plotter was connected

to the load readout of the testing machine and to the def lectometer

and the spans adjusted to a convenient value. Gradually increasing loads

were applied through the roller wheel until a deflection of 64 mm (2.5

in) was reached. The area under the force deflection curve was computed

to find the energy absorbed. The Regulation required that a minimum

of 39.5 J (350 in-lbf) of energy shall be absorbed in bending of the

fork (1512.18(k)(l)).

4. RESULTS

All tests were conducted in a normal laboratory environment at

room temperature. It is estimated that the errors did not exceed 1 percent for load measurement and 0,05 inches for deflection. Fifteen bicycles

were tested to evaluate the regulation and the test equipment. These

bicycles are described in Table 1. The results of the structural tests

performed during this evaluation are given in Table 2. Typical loaddeflection autographic recordings, from which the energy of deformation

for the forks and frames are calculated, are shown in Figure 16 and

17.

Because no spare forks were submitted with these bicycles, the

frame test (1512.18 (k)(2)) was performed before the fork test. The

regulation provides that a second fork, identical to that tested in

the fork test be installed in the bicycle for this test but that provision was not possible for these tests. Accordingly the fork, which

was supplied on the bicycle at the time of purchase and which may have

been deformed by the frame test, was tested.

5. DISCUSSION

As can be seen from Table 2, 11 of the 15 bicycles tested failed

to pass one or more of the clamp tests. These clamps were tested in

the "as received" condition, or as "assembled" in our laboratory before

the bicycle was ridden during the braking system tests. No attempt was made to retighten and retest a clamp which had failed.

7
The apparatus and the procedures used for these tests are not unique.

Several alternate ways of applying the necessary forces to the bicycle

components could have been devised. One of the purposes of these tests was to exercise the test apparatus which was assembled at NBS for CPSC.

This was done with only a few minor modifications to the test apparatus.

The procedures used and the order in which the tests were performed

were developed during this program.

6. CONCLUSIONS

The structural tests proposed in the mandatory regulation have

been performed on 15 bicycles which represent many of the types and

sizes which are currently available in the marketplace.

The greatest number of "failures" occurred during the testing of

friction clamps such as are used in seats and handlebar stems. However

the bicycles had been tested for brake performance before these tests

and the clamps were adequately tight.

The testing of the bicycle forks in accordance with the regulation

requires that a new fork, nominally identical to that provided with the

bicycle, be the test object. Many of the sources of bicycles, such as department stores, large drug stores, hardware retail stores, etc., may

be unable to supply the part at the time the bicycle is procured for

testing. Some consideration should be given to the meaning of a test

performed on an already damaged fork.

7. REFERENCES

1. Requirements for Bicycles, Part 1512, Federal Register, Vol. 39,

No. 137, July 16, 1974, as amended; Federal Register, Vol. 40, No.

4, January 7, 1975, as amended; Federal Register, Vol. 40, No. 116,

June 16, 1975.

2. Standard Methods of Verification of Testing Machines, ASTM E4-72,

American Society for Testing and Materials, Philadelphia, Pennsylvania.

3. Instruction Manual, Series 2000 Omnigraphia X-Y Recorder, Houston

Instrument Co., Bellaire, Texas.

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s

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01

0>

l-i O

w

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ac a.

«-» X

Hi- ^ J =

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(U
HANDBRAKE DRIVE HANDLEBAR

TESTS CHAIN STEM TO

STRENGTH FORK CLAMP

TORQUE

HANDLEBAR

STRENGTH

HANDLEBAR

STEM

STRENGTH

SEAT CLAMPS

IN PITCH

AND YAW

REAR HUB

RETENTION

STRENGTH

RIM

TEST

FRAME

TEST

FORK

TEST

Figure 2 - Flow Diagram for Bicycle Performance Tests
Figure 4 - Drive Chain Test Loading Fixture
Figure 6 - Handlebar Strength Test Fixture
Figure 7 - Stem Test Fixture
Figure 8 - Seat Clamp Test
Figure 9 - Rear Hub Retention Test

Figure 10 - Rear Hub Retention Test - Close-up of Axle Attachment
Figure 12 - Rim Test Fixture - Close-up of Axle Coupling
gure 13 - Frame Test Fixture
Figure 14a - Frame Test Fixture - Close-up of Front Attachment

Figure 14b - Frame Test Fixture - Closeup of Rear Attachment
Figure 15 Fork Test Fixture



Appendix A

Test Fixtures for

Structural Tests on Bicycles

Detailed drawings for the fixtures used for the tests

described in this report are given in Figures A-1 to A-18.

2 ^e^^^f^e i^
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2




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I

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I
Appendix B

Test Fixtures for

Structural Tests on Bicycles

The operation manuals for equipment purchased to

uct the structural tests on bicycles include:

Dynamod Power Products Corp. (Power Supply)

American Design Components (Load Cell)

NBS Load Cell Calibrations - Ormond Cell No. 1196

Houston Instrument Co., Series 2000 XY Recorder

Research Inc. Displacement Transducer, Model 7101-4

Enerpac, Hydraulic Pump, Model PER 1541
NBS IUA (RKv

U.5. DEPT. Or COMM. BIBLIOGRAPHIC DATA

SHEET

1. in:iU.l( ATION (M< Ki;P()KT NO. NBSIR 75-913

2. Gov't Acctssujn

No.

4. Ti l (.!•: \,ND SLiHTil I.

Structural Test Procedures for Bicycles

7. AU THOKrSI

D. E. Marlowe

9. PHRl ORMINC ORGANIZATION NAME AND ADDRKSS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Same as No. 9

3. Kcc ipic nt '.s Alllssioo No.

5. Publication IVitc October 1975

6. Performing Org.inization Code

8. Performin; <'fj ,,|,. Report No. NBSIR 75-913

10. Proicct/Task/Work Unit No.

11. C~ontrart/Gf am No.

13. Type ol Report & Period

r.ovcic.i Final

14. Sponsorin^^ Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual surrmary of most significant information, fl document includes u significant

bibliography or literature survey, mention it here.)

Tests for several structural performance criteria have been included

in a mandatory regulation on bicycle safety which has been proposed by

Consumer Product Safety Commission. The apparatus and procedures developed

to conduct these tests and results from 15 representative bicycles are described. Several of the bicycles tested failed to meet the requirements for

the seat and handlebar stem friction clamp strength.

17. KE^' UORDS (six to twelve entries; alphabetical order; capitalize only the Inst letter ol the first key word urie.ss a proper name; separated by semicolons)

Bicycle; consumer safety; regulations; safety; structural testing.

18. AVAILABILITY

^ Unlimited

d^J For Official Distribution. Do Not Release to NTIS

1_ ! Order From Sup. of Doc, U.S. Government Printing Office Uashineton. D.C. 20t02. SD Cat. No. CI3

7X Order From N.Mional Technical Information Service (NTIS)

Springfield. Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

21. NO. OF PAGES

47

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

$ 4.00

USCOMM.OC 29042-P74