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What keeps a bike upright?



 
 
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  #21  
Old January 6th 19, 04:34 PM posted to rec.bicycles.tech
Sir Ridesalot
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Posts: 4,045
Default What keeps a bike upright?

On Sunday, January 6, 2019 at 11:01:48 AM UTC-5, Frank Krygowski wrote:
On 1/6/2019 9:40 AM, wrote:

I cannot see how you couldn't ride a rear steering bike as easily as a front steering bike remembering that you do not turn the wheel much and that would be a handicap since you couldn't determine how much you were turning the rear wheel by sight.


If you did some reading on the "rear wheel steering" attempts people
have made for decades, and the very limited success they've had, you
might change your mind.

If rear wheel steering were easy, almost every recumbent would use it
because of the simpler and more compact drive train.

--
- Frank Krygowski


Just wondering if rear wheel steering would be easier if it was the FIRST method of riding a bicycle a person learned? That is like the almost unsteerable bike I linked to above, is it the learned behaviour of riding a normal steering bicycle that makes it so hard to ride a rear steering bicycle? Would a person who has never ridden a bicycle find a rear steering one so difficult?

Cheers
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  #22  
Old January 6th 19, 04:40 PM posted to rec.bicycles.tech
AMuzi
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Posts: 10,167
Default What keeps a bike upright?

On 1/5/2019 5:05 PM, John B. Slocomb wrote:
On Sat, 5 Jan 2019 10:29:06 -0800 (PST), wrote:

On Friday, January 4, 2019 at 3:41:22 PM UTC-8, John B. Slocomb wrote:
On Fri, 4 Jan 2019 10:43:12 -0800 (PST), Sir Ridesalot
wrote:

On Friday, January 4, 2019 at 12:28:54 PM UTC-5, Frank Krygowski wrote:
On 1/4/2019 11:37 AM,
wrote:
https://www.nature.com/news/the-bicy...matics-1.20281

Of course this isn't for John or Frank who could fall down if they were sitting on the ground.

You're just reading that now??

--
- Frank Krygowski

Seems to me that the guy has made a few basic false assumptions.
Any bicycle I've ever seen with the front fork in it's proper position
soon falls over after being pushed without a rider on it. I also think
that the gyroscopic force of rotating bicycle wheels keeping the
bicycle upright is miniscule unless the wheels are turning at very
high revolutions. I once saw a video on You Tube of a normal bike
with the front fork reversed, and without a rider, that went quite a
distance when pushed before toppling over.

I think too that making a bicycle stable enough to be riderless might end up being extremely difficult to ride. Look at how even small changes in frame/trail geometry on a road bike creates quite different handling characteristics.

Cheers

There has been a lot of research into what makes a bike stable. One
paper I read described a bike that was built with a front fork that
allowed the trail to be adjusted from a negative number to a rather
large positive number and yes "trail" has a great effect on the (would
one say) the longitudinal stability of a bike - how easily the fork
turns, and during the same experiment it was "discovered" that BB
height, vertical location of center of gravity, also effected this
same stability. Bikes have also been built with counter rotating
wheels which counter act the gyroscopic effect of the spinning wheels.

My own guess is that bicycles require stability in at least two planes
and so far no one seems to have built a bicycle that is completely
stable.

cheers,

John B.


All you have to do is look at a Penny Farthing which had totally different geometry but not only was ridable but they raced them. That gives you some idea of just how odd a bicycle really is.


Ridable? A bloke rode one across the U.S. in 1884.... and today people
brag when they ride down a gravel road.

There was a discussion here about riding wheelers some time ago and
Frank, I believe, described riding one and apparently they are easier
to balance then the more modern bicycles.



They are indeed. The taller the wheel the easier to control.
But as has been noted the geometry is unlike modern chain
driven safety bicycles.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


  #23  
Old January 6th 19, 07:12 PM posted to rec.bicycles.tech
Ralph Barone[_4_]
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Posts: 319
Default What keeps a bike upright?

Sir Ridesalot wrote:
On Sunday, January 6, 2019 at 11:01:48 AM UTC-5, Frank Krygowski wrote:
On 1/6/2019 9:40 AM, wrote:

I cannot see how you couldn't ride a rear steering bike as easily as a
front steering bike remembering that you do not turn the wheel much and
that would be a handicap since you couldn't determine how much you were
turning the rear wheel by sight.


If you did some reading on the "rear wheel steering" attempts people
have made for decades, and the very limited success they've had, you
might change your mind.

If rear wheel steering were easy, almost every recumbent would use it
because of the simpler and more compact drive train.

--
- Frank Krygowski


Just wondering if rear wheel steering would be easier if it was the FIRST
method of riding a bicycle a person learned? That is like the almost
unsteerable bike I linked to above, is it the learned behaviour of riding
a normal steering bicycle that makes it so hard to ride a rear steering
bicycle? Would a person who has never ridden a bicycle find a rear
steering one so difficult?

Cheers


I believe that there's a positive feedback mechanism to rear wheel steering
that makes it more "twitchy". When cars were playing around with four
wheel steering in the 80s/90s, I seem to recall they were using in phase
rear wheel steering at low speeds for tighter turning circles, but
anti-phase rear wheel steering at high speeds for stability.

  #24  
Old January 7th 19, 03:42 AM posted to rec.bicycles.tech
news18
external usenet poster
 
Posts: 307
Default What keeps a bike upright?

On Sun, 06 Jan 2019 06:40:57 -0800, sltom992 wrote:


As part of the driving test you are required to be able to back a
vehicle up. Particularly as part of a Class B license exam. And it is
quite easy to do since you look into mirrors and hence everything is
shown in reverse.


It is a skill that a lot of people forget very quickly. Try looking after
the loading/unloading bay of a live steamers meet where it is vey common
to carry their loco in a trailer. Trailer aside, It is the same with any
"facility' that requires people to reverse in.

I cannot see how you couldn't ride a rear steering bike as easily as a
front steering bike remembering that you do not turn the wheel much and
that would be a handicap since you couldn't determine how much you were
turning the rear wheel by sight.


Re-reasd the article you posted where he talks about how to front steer
and then think how many people can safely adapt their skills to rear
steer.

  #25  
Old January 8th 19, 12:19 AM posted to rec.bicycles.tech
Mark J.
external usenet poster
 
Posts: 537
Default What keeps a bike upright?

On 1/5/2019 7:26 PM, Sir Ridesalot wrote:
On Saturday, January 5, 2019 at 4:49:17 PM UTC-5, Frank Krygowski wrote:
On 1/5/2019 1:29 PM, wrote:
On Friday, January 4, 2019 at 3:41:22 PM UTC-8, John B. Slocomb wrote:
On Fri, 4 Jan 2019 10:43:12 -0800 (PST), Sir Ridesalot
wrote:

On Friday, January 4, 2019 at 12:28:54 PM UTC-5, Frank Krygowski wrote:
On 1/4/2019 11:37 AM,
wrote:
https://www.nature.com/news/the-bicy...matics-1.20281

Of course this isn't for John or Frank who could fall down if they were sitting on the ground.

You're just reading that now??

--
- Frank Krygowski

Seems to me that the guy has made a few basic false assumptions.
Any bicycle I've ever seen with the front fork in it's proper position
soon falls over after being pushed without a rider on it. I also think
that the gyroscopic force of rotating bicycle wheels keeping the
bicycle upright is miniscule unless the wheels are turning at very
high revolutions. I once saw a video on You Tube of a normal bike
with the front fork reversed, and without a rider, that went quite a
distance when pushed before toppling over.

I think too that making a bicycle stable enough to be riderless might end up being extremely difficult to ride. Look at how even small changes in frame/trail geometry on a road bike creates quite different handling characteristics.

Cheers

There has been a lot of research into what makes a bike stable. One
paper I read described a bike that was built with a front fork that
allowed the trail to be adjusted from a negative number to a rather
large positive number and yes "trail" has a great effect on the (would
one say) the longitudinal stability of a bike - how easily the fork
turns, and during the same experiment it was "discovered" that BB
height, vertical location of center of gravity, also effected this
same stability. Bikes have also been built with counter rotating
wheels which counter act the gyroscopic effect of the spinning wheels.

My own guess is that bicycles require stability in at least two planes
and so far no one seems to have built a bicycle that is completely
stable.

cheers,

John B.

All you have to do is look at a Penny Farthing which had totally different geometry but not only was ridable but they raced them. That gives you some idea of just how odd a bicycle really is.


It's actually hard to build a bicycle that is not rideable. There's a
somewhat well-known but quirky physics paper out there documenting a
physicists quest to build an unrideable bike. As I recall, he tried
several weird front end geometries, including doing away with trail
entirely. He mounted a second front wheel next to the original and just
above contact with the ground, which he rotated in the opposite
direction to cancel any gyroscopic effects. As I recall, he could ride
anything he built.

But back in the early and most experimental days of modern recumbents
(probably the 1970s) I read about a guy who tried to build a
rear-steering recumbent, based on the idea that it would simplify a
front wheel drive train. IIRC, that was almost impossible to ride.

The variety of current bikes is pretty amazing - long and short
wheelbase recumbents, small wheel folding bikes, kids bikes with
questionable geometries, tandems, box bikes, tall bikes, long-tail cargo
bikes. People ride them all. Handling on some can be a bit quirky,
especially at first, but people adapt.

And that's one of the main things about human beings: We're very adaptable.


--
- Frank Krygowski


Even this bicycle became ridable after months of practice by the adult. The child learned much quicker. I found it quite interesting.

https://www.youtube.com/watch?v=MFzDaBzBlL0

Cheers


Wow. Just wow. Video definitely worth watching, especially for those
of us in (or formerly in) the teaching biz.

I have never seen this video before, and yet feel like I've witnessed
this transition in hundreds of students. Topics of cognition,
meta-cognition, and "neuroplasticity."

Mark J.
 




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