View Full Version : Summary: Crank/Pedals for Force/Power Measurements

Shane Kimber Best
04-05-1996, 09:47 AM
Below is a very large summary of the responses I received to the
following questions. Thanks to everyone for the advice and
large list of references and resources.


Shane K. Best

On Wed, 3 Apr 1996, Shane K. Best wrote:

I have a question regarding bicycle pedals and/or cranks that can be used
to measure forces exerted by the rider and/or power output. If such a
device exists, I would appreciate advice in regards to where such an
instrument can be purchased. Also, can the data retrieved be stored
and somehow downloaded to a computer?

************************ Summary of Replies *********************


Our lab has developed several 2D and 3D pedal dynamometers to
measure pedal forces and moments. We have built dynamometers for other
labs but I don't think you will find them readily available
commercially. We have built them primarily for lab use with the data
acquisition performed with a PC. But we have recently built a mountain
bike (SPD) dynamometer designed to be used outdoors with a portable data
acquisition system.
The advantage of using a pedal dynamometer rather than
instrumenting the crank arm is the information you have regarding the
pedal forces. You can still compute crank torque and thus power but you
also have the pedal forces available for more complex analyses.
I hope this helps. Let me know if you have any other questions.


__________________________________________________ _____________________
Richard R. Neptune
Biomechanics Research Laboratory
University of California, Davis
Davis, CA 95616
Tel: (916) 752-2235
Email: rrneptune@ucdavis.edu


The device you want is SRM. It's made in Germany and costs about $4000. It
does everything you want and is very accurate. Contanct SRM Training System
by phone 49-2463-3156 or fax 49-2463-3090.

Good luck,

Jim Martin

/ Jim Martin /
/ University of Texas at Austin /
/ j.martin@mail.utexas.edu /
/ 512-495-9339 /


I don't know the name but I have heard of a "new" system that measures
power and force per crankarm. I read about it in VeloNews - try looking
there or contacting the publisher.

good luck,


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%
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% Dan A. Johnson (d-johns1@students.uiuc.edu %
% Rehabilitation Engineering %
% Univ. of Illinois %
% 309 E. John St. (217) 328-6777 %
% Champaign, Il. %
% 61820 - 5679 %
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I came across a paper written by G. Alvarez. I haven't read it so I
don't know if it will help you or not.

Title: A new bicycle pedal design for on-road measurements of cycling forces
Sourc: Journal of Applied Biomechanics Feb. 96 v.12 is.1 pp. 130-142

Hope this will help you out!

Brad Capstick


We have been pondering on a similar problem here in the Memphis
campus. The best we could get was a dynamometer-equipped exercise machine
which also gave the power output. You may cantact Faunne Anderson at
(901) 448-6535. She had been dealing with the problem since I left off.

-Debarag Banerjee


get in touch with Hartwig Distler (mad@mpik-tueb.mpg.de).
He is using a device like the one you described in a VR-setup.

Dietrich Opitz

MPI fuer biologische Kybernetik
Spemannstr. 38
72076 Tuebingen

Tel: ++49(7071) 601 606
FAX: ++49(7071) 601 575
e-mail: dio@mpik-tueb.mpg.de


Try looking for papers by Maury Hull (usually listed as ML Hull) at UC
Davis. You may also try contacting him directly at (916) 752-6220.


*****************LIFE_IS_NOT_A_REHEARSAL********** *******

Joel M. Bach, Ph.D.

UC SanFrancisco Ergonomics Program
1301 S. 46th St Bldg. 112
Richmond, CA 94804

Phone:(510)231-9448 Fax:(510)231-9500


*****************Another_Friend_of_Ishmael******** *********


I took a part in such an experiment at NASA one summer, but we had to
instrument the bicycle ourselves with load cells and develop the
software with Labview to collect the data. You should contact Dr.
Fernando Figueroa at the University of New Brunswick who developed the
system. He may be willing to send you copies of his reports and
papers. His e-mail address is figueroa@unb.ca.

Beth Todd

Dr. Beth A. Todd
Assistant Professor
Engineering Science and Mechanics
Box 870278
University of Alabama
Tuscaloosa, AL 35487-0278
fax: (205)348-7240


You may want to contact the following professor at the Univrsity
of Illinois:

name: klein richard e
phone: (217) 333-3299
address: 354 meb, MC 244
: 1206 w green
: urbana, il 61801
department: mechanical & industrl eng
title: assoc prof of mech eng
email to: r-klein@uiuc.edu (r-klein@ux1.cso.uiuc.edu)



Try contacting Bob Gregor at Georgia Tech. He not only uses them
regularly, but he has designed different versions for measuring forces.
His e-mail address is:
bob.gregor@oip.gatech.edu (Bob Gregor)

good luck,
__________________________________________________ _________________
Dan Ferris
UC Berkeley Biomechanics Laboratory
103 Harmon
Berkeley, CA 94720

(510) 642-8662


You are asking for a device that sounds simple but is complicated.
Measuring the power output of a cyclist easy, measuring pedal forces will
require some very special components.

I would suggest a strain gage array on the pedal crank. The power for
these strain gages depends on how the data will be transmitted. One can
either employ some type of sliding contacts that will allow electrical
current from circuits on the spinning crank power supply and data
aquisition equipment that is not spinning, i.e. on the frame.
Alternately, one could develope a completely telemeterized unit in which
the strain gage output is communicated to data aquisition equipment
without wires. Such systems have been used in implantable orthopedic
devices to track in vivo loads. One recent reference on the subject is:

Rohlman et. al. Telemeterized Load Measurement Using Instrumented Spinal
Internal Fixators in a Patient with Degenerative Instability, SPINE 20
(24) pp 2683-2689.

My intuition tells me that these systems are veeerrryyy expensive. The
sliding contact idea seems feasible, though you would need output from at
least 6 gages. That is 12 leads plus two power supplies that need to be
communicated accross the contacts.

I have no experience with these devices, just thought I would pass along
some ideas.

Hans Hoffman, MS
Yale School of Medicine

Dear Shane,

Regarding force pedals, please refer to the following publications;

1. Broker JP, Gregor R. A dual piezoelectric element force pedal for kinetic
analysis of cycling. International Journal of Sport Biomechanics 6: 394-403,

2. Gregor RJ, Broker JP, Ryan MM. The biomechanics of cycling. Exercise and
Sport Sciences Reviews. Vol. 19, pp. 127-169, 1991.

3. Gregor RJ, Wheeler JB. Biomechanical factors associated with shoe/pedal
interfaces: implications for injury. Sports Medicine 17 (2): 117-131, 1994.

4. Wheeler JB, Gregor RJ, Broker JP. A dual piezoelectric bicycle pedal with
multiple shoe/pedal interface compatibility. International Journal of Sports
Biomechanics 8: 251-258, 1992.

5. Wheeler JB, Gregor RJ, Broker JP. The effect of clipless float design on
shoe/pedal interface kinetics and overuse knee injuries during cycling.
Journal of Applied Biomechanics 11: 119-141, 1995.

Also, the latest issue of Cycling Science featured an article on the US
Olympic Cycling movement and discussed the use of these pedals. Regarding
the force pedals mentioned in these publications; two pairs and a single
pedal were made by the group at UCLA (Gregor, Wheeler, Broker et al.) and
now one pair is at the US Olympic Training Center (see contact person below)
and one pair is at Georgia Tech under the direction of Robert J. Gregor,
Ph.D. The single pedal made was formerly at U. Maryland but I think (?) is
now at UMass with Graham Caldwell, Ph.D.

Regarding a crank power device;

You may want to consider the SRM device. A starting point would be to
contact Jeffrey P. Broker, Ph.D. sport biomechanist at the US Olympic
Training Center in Colorado Springs and inquire about the SRM (also your
contact at the USOTC regarding the force pedals). You may have seen or
heard of this device in some bicycle publications, scientific journals, etc.
but Dr. Broker has been intimately involved with the SRM's introduction to
North America (I believe it is German manufactured) and has experience using
it with the Olympic cyclists on the track, in the windtunnel, and on the
road. You may recall that in the past Greg Lemond and others used this
device to train and monitor some race performances. Anyway, I think its what
you are looking for and rather than list all the specs and possibilities
here, contact:

Jeffrey P. Broker, Ph.D.
US Olympic Training Center
Sport Science & Technology Division
One Olympic Plaza
Colorado Springs, CO 80909

Phone (719) 578-4588
Fax (719) 632-5194
email jpbiomch@ix.netcom.com

Good luck. You will probably receive a response directly from Jeff Broker


Jeff Wheeler

Jeffrey B. Wheeler, M.S.
Biomechanics Research & Consulting, Inc.
840 Apollo Street, Suite 218
El Segundo, CA 90245

Telephone: (310) 615-3112
Facsimile: (310) 615-3038
emial: brccal@ix.netcom.com


There is a guy in Holland who produces (or did produce) such a device.
The cranks have sensors on them that are picked up by a handlebar
mounted device that has a display that gives the rider on the
spot info as well as storing the data to be downloaded to a pc
at the end of the ride/race/training session.

I saw the info in them 2 years ago in VeloNews. The article
expose'd how Greg Lemond was using it to get himself into
shape for that year.

Not much has been heard of them since.

The units are quite expensive... $5300 then... which included
the inventor personally installing the equipment.

If interested I can see if I can find the back issue. It
would take a bit though and no promise that I would be able
to find it.



I am doing research here at UC Davis using a six-load-component pedal
dynamometer to measure forces and moments at the pedal. It was here long
before I arrived, but it was made by Shimano Industrial Corporation of
Osaka, Japan. (Model PD-001) Please reference papers by ML Hull from the
early 1980's for more information. Hope this helps.

Shawn Sobelman, PE


I got this from a bicycle mailing list. I thought you might be interested
in contacting Utopian Designs, which produces a data acquisition network
called StressNet. I know they have used it for measuring the stress in
things like handlebars, so I'm pretty sure they could come up with something
for you. It can even be used in a wireless setup, so you can do road tests
(they have used it for OFF-road tests of mountain bikes) It produces digital
data in a spreadsheet compatible format.

Contact info:

Utopian Designs
4077 Ebony Terrace
Victoria, BC V8N 3Z2

Tel: (604) 477-4839
FAX: (604) 477-1487

email: utopian@islandnet.com


I recall seeing such a setup at the USOC traning center in Colorado
Springs a few years ago. I think they had to build it themselves. You
might contact Dr. Sarah Smith, the biomechanist there. She may be able
to answer your question.


************************************************** ***************
Leonard G. Caillouet 57840 Homestead Drive
Graduate Student Plaquemine, Louisiana 70764
Department of Kinesiology
Louisiana State University
Baton Rouge, Louisiana e-mail: lcaillo@unix1.sncc.lsu.edu

"The world may not end in catastrophe. There are at least two
other possibilities, paperwork and nostalgia." -Frank Zappa
************************************************** ***************


Check out the leatest Journal of Applied Biomechanics Winter 1996.

Gene Jameson
Sport Science and Technology
United States Olympic Committee


I don't know of any commercially available pedal instrumentation, but
here are a few references you might find useful:

ML Hull and RR Davis,
Measurement of pedal loading in bicycling: I. instrumentation.
J Biomech, (1981) V14(12):843-856

J Newmiller, ML Hull and FE Zajac,
A mechanically decoupled two force component bicycle pedal dynamometer.
J Biomech (1988), V21(5): 375-386

JP Broker and RJ Gregor,
A dual piezoelectric element force pedal for kinetic analysis of
cycling (1990) International Journal of Sports Biomechanics


$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$$$$$$$
Danielle Toutoungi,
Oxford Orthopaedic Engineering Centre,
University of Oxford.
tel: ++ (0)1865 227684
fax: ++ (0)1865 742348 email: danielle.toutoungi@eng.ox.ac.uk

"Time flies like an arrow, Fruit flies like a banana" - Anon.
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I have an article in front of me in Cycling Weekly (UK mag) from July 1 '95
(the Tour Special issue).
It's about "SRM Power Cranks".

It say's "German developed SRM Power Crank System" in the article. And that
Gewiss (the road race team) use them in early season training.
Cycling Weekly's phone number is +44 171 261 5588

CW quote an email address: snowdons@cix.compulink.co.uk
BUT it's down as "race round-up", but you could try enquiring..

It says "..signals are transmitted to the handlebar-mounted mini-computer,
which then calculates power output... which can be printed out in graph
form for analysis".
Doesn't say how exactly.

Hope this gives you something to go on.