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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: Suspension losses
Date: Sat, 4 Jan 2025 12:35:20 -0600
Organization: Yellow Jersey, Ltd.
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On 1/4/2025 12:02 PM, Frank Krygowski wrote:
> On 1/3/2025 11:46 PM, Jeff Liebermann wrote:
>> On Thu, 2 Jan 2025 12:17:22 -0500, Frank Krygowski
>> <frkrygow@sbcglobal.net> wrote:
>>
>>>>> A pair of series RLC circuits (one for the road-tire 
>>>>> interface
>>>>> and a second for the suspension-rider interface) would 
>>>>> be a good
>>>>> start. I'm not skilled enough to do the calculations, 
>>>>> but others
>>>>> on this group likely are.
>>>
>>> I _may_ have been able to do such calculations 50 years 
>>> ago, but I'm not
>>> sure. I certainly can't do them now.
>>
>> Actually, the analogy between a mechanical system and RLC 
>> (resistance,
>> inductance and cazapitance) calculations are fairly 
>> simple.  For
>> example:
>>
>> "Mechanical-electrical analogies"
>> <https://en.wikipedia.org/wiki/ 
>> Mechanical%E2%80%93electrical_analogies>
>>
>> "Electrical Analogies of Mechanical Systems"
>> <https://www.tutorialspoint.com/control_systems/ 
>> control_systems_electrical_analogies_mechanical.htm>
>>
>> "RLC circuit: Analogy with mechanical systems."  (From 
>> Brazil)
>> <https://proceedings.sbmac.org.br/sbmac/article/ 
>> download/134486/3384/0>
> 
> I'm pretty familiar with the RLC analogy to mechanical 
> vibrations.
> 
> Actually, I remember sitting in a Vibrations class taught by 
> my least favorite professor on the day he brought in a 
> large, demonstration-sized Analog Computer (Remember those?) 
> to model something we had been calculating. To the amusement 
> of the students, he was not able to get the thing to work 
> properly.
> 
>>
>>>>> The hardest part is apt to be finding
>>>>> an equivalent circuit for the rider, who isn't a rigid 
>>>>> mass but
>>>>> rather a dissipative blob....8-)
>>
>> If you're going to build a computer simulation, there are 
>> cut-n-paste
>> mechanical models of various human bodies available.
>>
>> "A mechanical model to determine the influence of masses 
>> and mass
>> distribution on the impact force during running"
>> <https://pubmed.ncbi.nlm.nih.gov/10653036/>
>> "Simple spring-damper-mass models have been widely used to 
>> simulate
>> human locomotion. However, most previous models have not 
>> accounted for
>> the effect of non-rigid masses (wobbling masses) on impact 
>> forces."
>>
>> Ok, a running model is not going to work well on a 
>> bicycle.  So, look
>> around for something that's a better fit.  I'll admit that 
>> I've never
>> done anything like this, but I can see how it might be 
>> possible to
>> model a wobbling blob on a bicycle.
>>
>> Also, modeling is NOT the hardest part of the problem.  In 
>> my never
>> humble opinion, the most difficult part is dealing with 
>> the large
>> number of significant figured necessary to maintain 
>> accuracy.  I human
>> or bicycle model might work accurate to maybe 1/10th of a 
>> watt, while
>> the power produced by a road bump powered energy 
>> harvesting system
>> might be on the order of fractions of a milliwatt.  This 
>> forces the
>> human model to be accurate well beyond reasonable limits.
> 
> My idea wasn't to model a human body for computation 
> purposes, although others are probably interested in doing 
> that. I'm thinking more of coming up with a physical device, 
> perhaps for weighting a tire during a rolling drum test, so 
> the test would more accurately reflect behavior of tires 
> when ridden by a human pedaling a bicycle. Maybe 75 pounds 
> of raw meat?
> 
> 

Analog computer?
Like the fluid logic plate in an automatic transmission?

https://www.carid.com/acdelco/gm-original-equipment-automatic-transmission-valve-body.html-- 

Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971