Re: From the sublime to the ridiculous

On 6/14/2024 12:42 PM, Jeff Liebermann wrote:

On Fri, 14 Jun 2024 14:44:10 -0000 (UTC), db
<dieterhansbritz@gmail.com> wrote:
 

On Thu, 13 Jun 2024 16:05:22 -0500, AMuzi wrote:
>

French, of course:
https://www.guinnessworldrecords.com/news/2024/6/record-breaking-25-

foot-tall-rideable-bike-built-by-two-friends-770016
>
I'm glad he had a safety line

 I wonder if the new record would have been accepted if he had used a
balancing pole, as is common in tightrope walking:
<https://www.google.com/search?q=tightrope+balancing+pole+bicycle&tbm=isch>
 "Why Do Tightrope Walkers Carry A Pole/Bar During Their Performance?"
<https://www.scienceabc.com/eyeopeners/why-tightrope-walkers-carry-a-polebar-during-their-performance.html>

The moment of inertia explanation is correct. The idea of lowering one's center of gravity is wrong, as in "... anything with a lower center of gravity (closer to the ground) is typically more stable than something with a high center of gravity. That’s one of the reasons why sports/racing cars have such low ground clearance."
Road racing cars have lower CGs to reduce body roll (which can have a bad effect on suspension geometry) and to minimize the unloading of the inside wheels, with resulting detriments to lateral traction and control. And anyway, when trying to get around a corner fast, you want nimbleness, not stability.
But when balancing a tightrope walker or a bicyclist on a fore-aft axis, lower CG is a detriment, not a benefit. Lower CG reduces moment of inertia about that forward axis. Any imbalance will tend to cause a faster angular acceleration to the side. The lower CG would become a benefit only if the CG of pole+walker were below the tightrope, making the system stable due to gravity. There are toys and novelty items that use that trick.
In the world of bicycles, antique high wheelers or penny farthings are amazingly easy to balance at slow speeds. Recumbents are far trickier to balance than standard bikes. And 12" rulers are trickier to balance than yardsticks.
--
- Frank Krygowski