FWD with Rear Wheel-Steering??

NYC XYZ said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

Flevobike used to build a 2-wheel bike with FWD and a central steering
pivot, the drive system was lighter (less chain!) that way. A lot of
people do homebuilt copies of it:
http://images.google.com/images?hl=en&q=flevobike&btnG=Google+Search&sa=N&tab=wi

The flevobike is not a rear-wheel steer however.
------
It is generally held (and so far, proven) that one cannot build a
dynamically-stable vehicle that uses rear-wheel steering; the best you
can achieve is neutral steering, which does not "self-correct" to keep
the vehicle in a straight line if it is upset. Such vehicles have a
nasty tendency to understeer and/or experience sudden
spin-outs/rollovers at higher speeds and on loose surfaces. No modern
car or motorcycle company has ever built a rear-wheel-steer vehicle
(intended for higher-speed travel) that I have heard of.

Erik Wannee has a page up:
http://www.wannee.nl/hpv/abt/e-index.htm
The Kalle bike is a front-wheel-drive + rear-wheel-steer example that
(as far as we know) is rideable. So far it seems to be the ONLY example.
Has anyone [reading this] ever rode one???
~

NYC XYZ said:

Just wondering if there's such a creature.

Some have been attempted. The general problem is the successful
rider generally goes by a name like Koko and has a red nose and big
feet...

Quoted message said:

Whatever is the advantage of a FWD design?

Much shorter chain lebgth and no re-routing around the rider necessary.

Quoted message said:

And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

People have tended to fall off the models to date with alarming
regularity!

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

On 14 May 2006 12:51:33 -0700, "NYC XYZ" <[email hidden]>

Quoted message said:

Just wondering if there's such a creature.

Periodically, someone ignores the past results (or doesn't try to find
out about them) and takes yet another shot at this concept. They
swiftly rediscover why they shouldn't have bothered.

Quoted message said:

Whatever is the advantage
of a FWD design?

On a bike, the advantages are not as great as on an automobile; about
all that is achieved is a reduction in the length of the chain run,
and an increase in maneuverability in situations where small
obstructions must be easily climbed. The principal difficulty is in
coupling the power when the wheel is not close to straight with
respect to the frame, and in accurately steering when applying power
if the cranks are mounted on the steered member.

Quoted message said:

And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Rear-wheel steering on a bicycle is an abomination. But please, don't
take my word for it; by all means, build one and find out for
yourself.

Forklifts (and a handful of essentially similar types of vehicle) need
and profitably employ rear-wheel steering. I know of no other place
where it is justified or useful.
--
Typoes are a feature, not a bug.
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On 14 May 2006 12:51:33 -0700, "NYC XYZ" <[email hidden]>

Quoted message said:

Just wondering if there's such a creature.

Periodically, someone ignores the past results (or doesn't try to find
out about them) and takes yet another shot at this concept. They
swiftly rediscover why they shouldn't have bothered.

Quoted message said:

Whatever is the advantage
of a FWD design?

On a bike, the advantages are not as great as on an automobile; about
all that is achieved is a reduction in the length of the chain run,
and an increase in maneuverability in situations where small
obstructions must be easily climbed. The principal difficulty is in
coupling the power when the wheel is not close to straight with
respect to the frame, and in accurately steering when applying power
if the cranks are mounted on the steered member.

Quoted message said:

And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Rear-wheel steering on a bicycle is an abomination. But please, don't
take my word for it; by all means, build one and find out for
yourself.

Forklifts (and a handful of essentially similar types of vehicle) need
and profitably employ rear-wheel steering. I know of no other place
where it is justified or useful.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

"NYC XYZ" <[email hidden]> wrote in news:1147636293.688908.91260
@v46g2000cwv.googlegroups.com:

Quoted message said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

As others have mentioned, the advantage would be a short chain. Aside from
steering problems, the major disadvantage I see is a HUGE loss in traction.
Nearly all practical bike designs weight the rear wheel. Climbing with
something like the Flevobike that has only the weight of the drivetrain and
your feet holding it to the ground strikes me as frustrating at best,
bordering on dangerous.

NYC XYZ said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

If you were completely insane you could build a rear-wheel steering
bike with a robotic drive-by-wire system with a lean/attitude sensor to
counter the instability. Solar powered of course.

Joseph

Quoted message said:

If you were completely insane you could build a rear-wheel steering
bike with a robotic drive-by-wire system with a lean/attitude sensor to
counter the instability. Solar powered of course.

Please, do us all a favor and don't suggest this to anyone in the
military or the Post Office. We really don't need to have the
government spending billions to develop such a device. (Of course,
they'd probably make it AWD with adaptive traction control as well.)
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Werehatrack said:

Quoted message said:

If you were completely insane you could build a rear-wheel steering
bike with a robotic drive-by-wire system with a lean/attitude sensor to
counter the instability. Solar powered of course.

Please, do us all a favor and don't suggest this to anyone in the
military or the Post Office. We really don't need to have the
government spending billions to develop such a device. (Of course,
they'd probably make it AWD with adaptive traction control as well.)

Some industrious hobbyists could sure pocket a chunk of change if they
got billions to make something like a drive-by-wire bike steering
system with about $500 worth of parts!

It would be basically the same as this unicycle, just sideways, sans
motor:

http://tlb.org/eunicycle.html

Joseph

My limited experience in warehouses is that in long high speed
(remember we're talking fork truck speed) runs, the drivers go in
reverse so that they are in effect front steer vehicles.

Hank Wirtz <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

"NYC XYZ" <[email hidden]> wrote in
news:1147636293.688908.91260 @v46g2000cwv.googlegroups.com:

Quoted message said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

As others have mentioned, the advantage would be a short chain. Aside
from steering problems, the major disadvantage I see is a HUGE loss in
traction. Nearly all practical bike designs weight the rear wheel.
Climbing with something like the Flevobike that has only the weight of
the drivetrain and your feet holding it to the ground strikes me as
frustrating at best, bordering on dangerous.

That's exactly what I've always understood to be the case in automotive
design.

When light-weight, compact cars came out, the advantage to front-wheel
drive was that most, actually almost the only, mass was over the front
wheels in the form of the engine and transmission. To maintain traction
with such a mass distribution, there were clear advantages to moving to
front-wheel drive. That basic fact overrode the normal considerations of
the physics/dynamics of the larger, better-balanced designs under
acceleration along with those caused by transient situations like
steering.

In the bicycles case, the very fact that the rear wheel loading usually
predominates except in braking, combined with the possiblity of losing
steering/balancing whenever you lose traction seems like the 'double-
casualty' that most emergency planners dread facing to the point of
decreeing that their plans assume only one problem at a time needs
addressing. And, those planners deal with an ice-age timelines compared
to the reflex-driven casualty situations on a bike.

Talk about a divergent system response!

NYC XYZ said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

Go here to see a CALPOLY student riding one.

http://home.earthlink.net/~wm.patterson/index.html

Click down to the 2nd and 3rd photos.

I think the high seat provides a time constant that allows him to ride
the unstable bike. Low seat bikes weren't rideable by us.

I had many students try. This is the only one that succeeded

--
See bikes at: http://home.earthlink.net/~wm.patterson/index.html

See bikes and the first human powered helicopter at:

http://www.calpoly.edu/~wpatters/

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Bill Patterson said:

Quoted message said:

Go here to see a CALPOLY student riding one.

http://home.earthlink.net/~wm.patterson/index.html

Click down to the 2nd and 3rd photos.

Oops, I got sick of that old web site and deleted it. Hope you got to it
before it was gone. I'm into helicopter avionics now. sorry.

Bill

--
Some thoughts on Apache helicopter avionics
http://home.earthlink.net/~wm.patterson/helicopterthoughts/
http://home.earthlink.net/~wm.patterson/helicopterthoughts/id17.html
http://home.earthlink.net/~wm.patterson/helicopterthoughts/id16.html

See bikes and the first human powered helicopter at:
http://www.calpoly.edu/~wpatters/
Single Track controls at:
http://home.earthlink.net/~wm.patterson/

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NYC XYZ said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

I am sure that you have never driven a forklift w/ rear steering. Even
w/ 4 wheels they are damn unstable.

Regards, John

NYC XYZ said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

Use this and get back to us......

T = K5 (B/M)(1/(Kx*Kx) +1/(h*h) )

john said:

NYC XYZ said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

I am sure that you have never driven a forklift w/ rear steering. Even
w/ 4 wheels they are damn unstable.

Regards, John

Is that because the wheels tend to keep turned from friction and swing
out more and longer than expected.

Taunto said:

john said:

NYC XYZ said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

I am sure that you have never driven a forklift w/ rear steering. Even
w/ 4 wheels they are damn unstable.

Regards, John

Is that because the wheels tend to keep turned from friction and swing
out more and longer than expected.

I alsways figured it was mostly because of gyroscopic precession.

With front steering, if you start to lean to the left then the front
wheel precesses counterclockwise, causing the bike to turn left so it's
still under you. This is why it's possible to ride no-handed.

With rear steering, leaning to the left also causes the steered wheel
to precess counterclockwise, but since it's a rear wheel this will
cause the bike to turn right, throwing you down to the street HARD!

Stop cross-posting the recumbent chat in the marketplace forum.

"Taunto" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

john said:

NYC XYZ said:

Just wondering if there's such a creature. Whatever is the advantage
of a FWD design? And why not couple that somehow with rear
wheel-steering eliminate the steering issues of FWD designs?

Just curious.

I am sure that you have never driven a forklift w/ rear steering. Even
w/ 4 wheels they are damn unstable.

Regards, John

Is that because the wheels tend to keep turned from friction and swing out
more and longer than expected.