Full size folding bicycles for camping -- Good or Bad?

"GaryO" @ . wrote in message
news
On Wed, 27 May 2009 12:49:08 -0500, AZ Nomad

Have you seen this one? It's no skateboard!
http://www.militarybikes.com/products.html

...gary

Not to mention the price is very reasonable. I almost ordered one! KM
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"Neon John" wrote in message
...
On Thu, 28 May 2009 03:13:58 -0400, Neon John wrote:

On Wed, 27 May 2009 20:56:26 -0500,
(Robert Bonomi) wrote:

Actually you're wrong on all accounts. The article was originally
published in 1970 in "Physics Today". I recall the article vividly,
along with an analysis of the article and more experiments done by
Gordon Jennings of Cycle Magazine. I was deeply involved in
motorcycle racing and therefore was particularly interested in the
science behind bike suspension geometry so that article burned itself
into my memory.

Here is a scanned copy of the article.

http://www.phys.lsu.edu/faculty/gonz...9no9p51_56.pdf


Hmm, somehow I managed to leave out the following reference to more
modern work on the unrideable bicycle.

http://www.rainbowtrainers.com/default.aspx?Lev=2&ID=34

Even here they failed to make an unrideable bike. Even the rear steer
bike that the author says was unrideable isn't. I used to crank a
2-stroke bike in reverse and ride it around sitting backwards on the
seat as part of my exhibition of stunt riding.

I don't think that it's possible to make a completely unrideable bike.

Reminds me of a bike one of my nephews owned. Both wheels were
steerable. You could use the seat to steer the back wheel. It was rideable,
but there were some combinations of wheel position that would flip the
thing. If you weren't in the mood for doing stunts you could lock the rear
wheel in position.

TB

"Robert Bonomi" wrote in message
communications...
: In article ,
: AZ Nomad wrote:
: On Wed, 27 May 2009 16:13:39 -0400, Dave Smith
: wrote:
: Zane wrote:
:
: Wheel size doesn't influence bicycle stability. One guy famously
: illustrated this by building a bike with wheels the size of skate
: wheels, which rode and maneuvered just like a regular one, much to
: people's amazement.. (I don't have a cite for this-- this was before
: the internet.) The dominant stability factor is trail on the front
: wheel assembly. The notion that gyroscopic forces are involved has
: been debunked long ago.
:
: The notion that gyroscopic forces are involved has not been debunked,
:
: D*mn right it has not been debunked. It has been _proven_ to be a
significant
: factor in readability. Scientists have built bicycles where there was
some
: not-so-simple gearing that spun a rotational mass exactly matching that of
: the wheel at the same speed in the opposite direction. The
'counter-rotating'
: mass was capable of being enabled/disabled, thus the _only_ difference was
: in the two modes was the gyroscopic effect, or lack thereof.
:
: As I recall, the longest distance anyone managed to traverse on one of
: those bikes (Which went by the name of the "Unrideable Mark IV" *with*
: the gyroscopic effect zeroed out, without falling catastrophically
off-balance
: was around _3_ meters.
:
: They also investigated other design characteristics of bicycles, including
: the effect relative placement of the axle of the front wheel, relative to
: the axis about which the wheel was turned for steering. If the wheel axle
: trailed the axis of rotation, the bicycle was inherently unstable, and
: would not steer a straight line.
:
: This testing was reported on, more than once, in _Scientific American_.
:
: Unfortunately this research was around 40 years ago, and is not in their
: on-line archives (which only go back to 1993). One would probably need to
: visit a real library, and check the hard-copy "Readers Guide to Periodical
: Literature" for the late '60s, early '70s to find the stories.

Stability of a bicycle is due to the off set of the wheel axel from the
inline axis of the steering mount not gyroscopic stability. There is a
component of gyroscopic stability but any meaningful stability requires
either a LOT of mass or considerable RPM often both.

An aside enough gyroscopic stability to hold the bike upright and you would
be unable to safely turn the bike.

One of the reasons a gyro is gimbaled is that an ungimbaled gyro will either
rip itself out of the mount or destroy the bearings often both.

http://en.wikipedia.org/wiki/Gyroscope

On Thu, 28 May 2009 11:25:39 -0500, NotMe wrote:

Stability of a bicycle is due to the off set of the wheel axel from the
inline axis of the steering mount not gyroscopic stability. There is a
component of gyroscopic stability but any meaningful stability requires
either a LOT of mass or considerable RPM often both.

Try balancing on a stopped bike some time and tell us how gyroscopic
stability isn't a factor.

Anybody who has ever locked up the front tire of a motorcycle can attest
to the importance of rotational motion. The instant the front wheel
stops, there is no stability and the front tire will slip out causing the
bike to crash.

On Thu, 28 May 2009 11:25:39 -0500, NotMe wrote:
An aside enough gyroscopic stability to hold the bike upright and you would
be unable to safely turn the bike.

Nope.

When the force is applied lateraly to a spinning wheel, the wheel will move
through procession. Lean left and the wheel will turn left. Try it while
the bike is stopped and you'll simply fall over.

Try this experement: remove the front tire from a bike. Give it a good spin.
Move it around. It will fight your expected motions (that is where the
stability comes from), but you can move it to any position by applying force
through the axis of motion.

On May 28, 10:05*am, AZ Nomad wrote:
On Thu, 28 May 2009 11:25:39 -0500, NotMe wrote:
Stability of a bicycle is due to the off set of the wheel axel from the
inline axis of the steering mount not gyroscopic stability. * There is a
component of gyroscopic stability but any meaningful stability requires
either a LOT of mass or considerable RPM often both.

Try balancing on a stopped bike some time and tell us how gyroscopic
stability isn't a factor.

Anybody who has ever locked up the front tire of a motorcycle can attest
to the importance of rotational motion. *The instant the front wheel
stops, there is no stability and the front tire will slip out causing the
bike to crash.

At least on a bicycle I can stop with only the front brake. Front
brakes have considerably more braking effectiveness than rear brakes.
I was taught to brake mostly with the front and lean the body
backwards to prevent loss of stability. I've even seen some bicycle
setups which only have a single front brake.

However - nobody here seems to have responded to my post on Moulton
bicycles. Alex Moulton did wonders with small tires coupled with a
(then revolutionary) suspension. They worked with Dunlop to develop
special 17" tires. Apparently they don't conform to many racing
rules, but I've heard incredible things about them.

Apparently someone competed in the Race Across America in a Moulton:

http://members.localnet.com/~milliken/liner/raam.htm

"Neon John" wrote in message
I used to crank a 2-stroke bike in reverse and ride it around sitting
backwards on the
seat as part of my exhibition of stunt riding.


The old Zundaps with sidecars had a "secret" reverse.
At an idle you could retard the spark enough to make the engine run
backwards.
Then you just put it in gear and moved backward.
When you backed up enough you advanced the spark and it would return to
running forward without missing a beat.



--
JerryD(upstateNY)

I guess I should read my posts before I send them.
You ADVANCE the spark to make the engine run backward and then retard the
spark to make it run forward.

--
JerryD(upstateNY)

"JerryD(upstateNY)" wrote in message
The old Zundaps with sidecars had a "secret" reverse.
At an idle you could retard the spark enough to make the engine run
backwards.
Then you just put it in gear and moved backward.
When you backed up enough you advanced the spark and it would return to
running forward without missing a beat.