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From: Frank Krygowski <frkrygow@sbcglobal.net>
Newsgroups: rec.bicycles.tech
Subject: Re: Extensive article on Rivendell and Grant Petersen
Date: Tue, 24 Sep 2024 22:05:09 -0400
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On 9/24/2024 3:17 PM, Catrike Ryder wrote:
> On Tue, 24 Sep 2024 14:14:41 -0400, Frank Krygowski
> <frkrygow@sbcglobal.net> wrote:
> 
>> You might do well to read some of the archives of this group. There have
>> always been people posting opinions that were factually wrong, and there
>> have always been people pointing out those mistakes. As I've noted
>> earlier, having mistakes pointed out is a necessary part of the process
>> of education.
> 
> That's fine of the person being corrected understands that the
> corrector is qualified to do so and is truly interested in making
> things better. In my opinion, you fall far short of both those
> standards.

Your opinion on that matter is worthless. You don't have anywhere near 
the background needed to judge technical proficiency. Professional 
Engineering licensing boards of two different states have disagreed with 
you, not to mention those conferring my engineering degrees and those 
institutions for whom I've worked.

>> There are many examples of ideas that were posted frequently, and noted
>> as wrong. Most of them seldom pop up any more - and not only, I think,
>> just because there are fewer posts. I think people actually learned things.
>>
>> Examples of mistaken claims? Chains wear by stretching the metal. Old
>> frames get "soft." Increasing spoke tension makes a wheel more rigid.
>> Tying and soldering spokes makes a wheel stronger. Headsets fail by true
>> brinelling due to impact loads. Hanging a bike by the front wheel makes
>> the spokes stretch... and many more.
>>
>> BTW, what was that stopping distance from 20 mph again?  ;-)
> 
> 20 MPH would be maybe 9/10 feet if I didn't concern myself with
> slamming the chain rings into the ground or doing a face plant on the
> ground in front of the bike. 30 MPH would be a little further. Two
> front brakes work better than one, especially when the rider's weight
> is already more over the front wheels before he applies the brakes.

Right, good one. There is no way you can stop your tricycle in 10 feet 
from 20 miles per hour. That would require a deceleration of 43 ft/s^2 
or 1.34 times the acceleration of gravity. IOW you'd need tires with a 
static coefficient of friction at least 1.34, plus absolutely perfect 
application of both brakes so that both wheels were at the absolute 
limit of traction but not skidding. And you'd have to be in a "nose 
wheelie" all the while, with your rear tire up in the air so every bit 
of your weight was on the front wheels. It's essentially impossible.

For 9 feet, your acceleration would have to be nearly 48 ft/s^2, and 
besides absolutely perfect braking reflexes, you'd need tires with a 
static coefficient of friction at least 1.48.

And 30 mph would be _much_ farther, not "a little." The velocity term 
gets squared in the relevant calculation, much as it does when 
calculating kinetic energy.

I'm sure you don't know what a lot of that means. But what you're 
claiming is practically impossible. Feel free to prove me wrong by doing 
what you claim and posting video evidence.


-- 
- Frank Krygowski