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/

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?

Rear wheel steering is highly unstable. With computer help it can be made
to work, as on the motorised land speed record holder Thrust SSC. But if
you read the pilot's (Andy Green) comments about it it's not ready for
prime time yet.

OTOH, for very low speed use most fork-lift trucks use it. You're already
complaining that your Streetmachine is not as fast as your old upright
(something is very wrong here ...) but maybe if you're going slowly
enough you could use rear-steer.

[original cross-posting trimmed]

Mike

DougC said:

No modern car or motorcycle company has ever built a rear-wheel-steer
vehicle (intended for higher-speed travel) that I have heard of.

The current land speed record holding vehicle, Thrust SSC, used rear wheel
steering, but with dedicated computer assistance. The driver (pilot),
even with the computer, rating it 8 on a scale of 10 on instability.

[rec.bicyles.marketplace and rec.bicycles.misc trimmed]

Mike

Mike Causer said:

<SNIP>

You're already
complaining that your Streetmachine is not as fast as your old upright
(something is very wrong here ...)

What's very wrong? 'Bents are generally slower than uprights, and the
'bent I have is a tourer while the upright I have is a "comfort
racer"....

Quoted message said:

Mike

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've been around the HPV/recumbent world for about 25 years, and I've
seen this question pop up every couple years. Everyone who has actually
*built* a rear-wheel-steer vehicle has abandoned it after the first
high-speed ride.

It's easy to see why if you understand vehicle dynamics. With a vehicle
that steers with the front wheel(s), the force needed to steer climbs
as speed climbs. This leads to a naturally self-stabilizing and
self-damping system. (OK, OK... it's a gross over-simplification.)

On a RWS vehicle, the force needed to steer *falls* as speed climbs. If
you have manageable steering at slow speed, the force drops to the
point that the vehicle can't be adequately controlled. Above a certain
speed, the steering is so "light" that the rider/driver can't
adequately control it... the vehicle occillates until it turns
sideways.

There's been couple RWS vehicles- someone mentioned the Thrust SSC,
Buckminster Fuller's Dymaxion, the Sidewinder trike:
http://www.sidewindercycle.com/products/sidedet.asp . There's
peculiarities with each: the Thrust SSC was limited to a couple degrees
of steering, the third and final Dymaxion was converted to
front-wheel-steering, and every posting I've seen about the Sidewinder
has mentioned high-speed instability.

Front-wheel-drive does have some advantages, particularly with very low
and/or very reclined recumbents:
http://www.zoxbikes.com/
http://www.challengebikes.com/html/index.php?taal=en#nme
http://www.ohpv.org/albums/bm2004/velox/pages/velox5.htm
http://www.ohpv.org/albums/bm2004/varnas/pages/varnas16.htm
FWD works pretty well with front-wheel-steering.

Rear-wheel-steering has been tried by lots of people... none has been
successful outside of a narrow performance window. I'd love to be
proven wrong- but I'm not holding my breath.

Jeff

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.

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

Mike Causer said:

DougC said:

No modern car or motorcycle company has ever built a rear-wheel-steer
vehicle (intended for higher-speed travel) that I have heard of.

The current land speed record holding vehicle, Thrust SSC, used rear wheel
steering, but with dedicated computer assistance. The driver (pilot),
even with the computer, rating it 8 on a scale of 10 on instability.

[rec.bicyles.marketplace and rec.bicycles.misc trimmed]

Mike

Yea but they "cheated", twice: first they confined the range of steering
to a very-small amount, and then by computer-controlling it.

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!

In article <[email hidden]>,

wvantwiller said:

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.

Front wheel drive in cars has almost entirely been about packaging: no
long heavy driveshaft, no drivetrain hump in the passenger compartment.
It was really a matter of making more space for people and living with
the (in most cases, quite acceptable) dynamics you got. The fact that
FWD has some advantages in low-traction situations has been a selling
point, but I think it was almost always a side-effect rather than a
primary reason for going to FWD.

Quoted message said:

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!

For off-road bicycles, FWD is a non-starter, but road bikes are hardly
ever drive-traction limited. Most of the bikes configured with FWD
(almost all recumbents) have weight distribution and cockpit designs
such that substantially unweighting the front wheel is nearly impossible.

I suppose it's possible a FWD recumbent with cranks high enough for the
rider to pedal in sharp corners could get the rider in trouble if they
poured in the power hard at mid-corner, but that would be stupid.

The problems with current FWD bikes, relative to similar RWD ones, seems
to be mostly a matter of packaging, not dynamics: it's hard to make the
design so it has a good range of motion for the front wheel, an
efficient drivetrain, and cranks that don't move with the front wheel.

--
Ryan Cousineau [email hidden] http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos

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/

Reply to [email hidden]
[email hidden]
[email hidden]

I have personally seen a front wheel drive, rear wheel steer recumbent in
the past.

The bicycle was a simple straight beam that had the front wheel mounted
under it along with the steerable rear wheel being mounted under the beam.
Both wheels looked as if they were either 27 inch or 700c series wheels. I
was too far away and not conversant enough at the time to determine wheel
size on this bicycle.

At the time that I saw this bicycle it appeared to be quite unstable. The
person riding it was given quite a wide area for his maneuvers to keep the
bike upright. Now, I did NOT see the bike out in the middle of the country
side at speed to know how well it was doing. The times that I saw it I was
supporting RAGBRAI at overnight towns. This was before I got back into
cycling myself.

I never saw the bike on the years that I drove sag or rode on RAGBRAI which
started around 1991. It would seem to be counter intuitive to try and
balance a vehicle of this type when the back wheel moves opposite of the
direction one wants to turn. I want to go right so the back of the bike
goes left doesn't seem like it would be something that would be instinctive
to anyone that I know.

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It may have been a Flevobike - which more or less pivots in the middle -
otherwise it sounds home made.

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

Quoted message said:

I have personally seen a front wheel drive, rear wheel steer recumbent in
the past.

The bicycle was a simple straight beam that had the front wheel mounted
under it along with the steerable rear wheel being mounted under the beam.
Both wheels looked as if they were either 27 inch or 700c series wheels.
I
was too far away and not conversant enough at the time to determine wheel
size on this bicycle.

At the time that I saw this bicycle it appeared to be quite unstable. The
person riding it was given quite a wide area for his maneuvers to keep the
bike upright. Now, I did NOT see the bike out in the middle of the
country
side at speed to know how well it was doing. The times that I saw it I
was
supporting RAGBRAI at overnight towns. This was before I got back into
cycling myself.

I never saw the bike on the years that I drove sag or rode on RAGBRAI
which
started around 1991. It would seem to be counter intuitive to try and
balance a vehicle of this type when the back wheel moves opposite of the
direction one wants to turn. I want to go right so the back of the bike
goes left doesn't seem like it would be something that would be
instinctive
to anyone that I know.

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