Can anyone refer me to studies of Stopping Distances of Bicycles? 2

[Wolfdog]

I remember reading somehwere that a modern bicycle is unique among vehicles in that it can stop within either (I am not sure which) its own length or its wheelbase. However, so can a car if its velocity is low enough!

I am seeking any studies of bicycles' stopping distances at various speeds.

Thanks in advance if you can help.

 

[Nigel]

I think a fairly good answer can be generated by the application of simple physics.

Nigel Waterhouse & Associates
Aeronautical Consulting Engineers

Transport Canada and F.A.A approval & certification of fixed and rotor wing aircraft alterations: Structures, Systems, Powerplants and electrical. FAA PMA, TC PDA.
n_a_waterhouse@hotmail.com

 

[Wolfdog]

Thanks Nigel, but strict physical analysis, if it is to include reaction time, variations in rider size and mass, wheel diameter, etc., can become extremely complex. I was seeking an existing study.

Wolfdog

Wolf / "Wolfdog"

 

[Nigel]

The following is the Federal Requirment for bicycle stopping distance with a hand brake. It is in 16 CFR 1512.5. Hope it helps.

(1) Stopping distance. A bicycle
equipped with only handbrakes shall be
tested for stopping distance by a rider
of at least 68.1 kg (150 lb) weight in accordance
with the performance test,
§ 1512.18(d)(2) (v) and (vi), and shall have
a stopping distance of no greater than
4.57 m (15 ft) from the actual test speed
as determined by the equivalent
ground speed specified in
§ 1512.18(d)(2)(vi).

Nigel Waterhouse & Associates
Aeronautical Consulting Engineers

Transport Canada and F.A.A approval & certification of fixed and rotor wing aircraft alterations: Structures, Systems, Powerplants and electrical. FAA PMA, TC PDA.
n_a_waterhouse@hotmail.com

 

[ACtrafficengr]

What is the test speed?

 

[ACtrafficengr]

See the AASHTO Guide for the Development of Bicycle facilities.

They use a stopping sight distance formula of

S = V^2/(254(f+G) +V/1.4

S = meters
V = km/h
F - 0.25

 

[ACtrafficengr]

That should be

S = meters
V = km/h
F = 0.25
G = Grade

PS: NYSDOT uses 20 mph for a bicycle design speed. Higher speeds should be used on downhill sections.

 

[grippy]

Wolfdog, I think that Nigel has supplied you with all that it's possible to supply. i.e. "requirments" re braking performance.

A study of actual stopping distances and performance would be next to useless because of the huge number of variables to do with frame design, front suspension, actual brake employed, tyre type, surface... in fact the list goes on way too far to list here.

 

[ACtrafficengr]

Grippy, if the brake can supply enough torque to lock the wheel, it comes down to normal force on the tire and coefficient of friction. Granted, at high speeds locked-wheel braking may not be likely, or even desirable.

For rigid frame bikes, frame design will matter little. Suspension design would have a much bigger effect, since it will affect weight transfer from the back tire to the front tire.

For road or path design purposes, we can eliminate many of these variables, since we're interested in the poor end of the performance spectrum. That's where the AASHTO equation listed above comes in.

------------------------------------------
"Come to think of it, there are already a million monkeys typing on a million typewriters, and the Usenet is NOTHING like Shakespeare.

Blair Houghton

 

[grippy]

ACtrafficengr, not wishing to hijack Wolfdog's thread (but I do think he's got about all he's likely to get to be honest), I understand the need for the AASHTO... there has to be SOME standard, but there really are so many variables. I agree (for instance) that a full suspension bike will transfer weight in a different way to a rigid frame, but the variables of suspension compression and dampening then come into play PLUS the fact that many bikes are front suspension only... giving us yet again a totally different set of variables. But having said that I should point out that the huge differences in design of full rigid bike frames nowadays makes it impossible to accept that all rigid frames will, in essence, produce similar braking effects. There are frames out there that bias both their own weight and that of the rider in MANY different positions, to which you have to then add in the uncalcuable variables of individual componentry set-up.

All of which I really point out to justify my very first statement to Wolfdog. Sorry if I took this too far off-topic.

Cheers

Jon Weaving

http://www.gripsport.com.au