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Jeep bikes, with AWD!!!  

post #1 of 11
Thread Starter 
Now I was looking at earlier posts about Jeep bikes and see that they are crap, but look at this,
this one has AWD!!!! Pretty fu*kin cool!

http://www.jeepbikes.com/rubiconawd.html
post #2 of 11

Re: Jeep bikes, with AWD!!!

>"santa" santa@ss.com wrote: >The thing is that this is not a jeep bike, this
is a christini

And here's a used one that didn't get a single bidder.

http://cgi.ebay.com/ws/eBayISAPI.dll...category=27947
post #3 of 11

Re: Jeep bikes, with AWD!!!

Not again!

> http://www.jeepbikes.com/rubiconawd.html

Besides having open bevel gears that do not work with dirt, the drive is transmitted by a 5ft long
shaft no more than 1/2" in diameter and apparently a flexible shaft, there being no universal joints
at curves in the shaft line. If these guys are serious they ought to answer the question of
torsional stiffness of the drive between rear and front wheel. That shaft is a long floppy torsion
bar that will most likely exceed its torsional strength if the rear wheel slips on the level with
the front wheel on dry pavement. Besides that, such a load will generate a large steering torque.

You'll notice that there is no steer tube in the head tube because it is occupied by gears and a
shaft drive. Therefore there is a curved (torsionally flat) plate bridging from the handlebars to
the fork crown. That plate is turned aside for the center close-up.

That people so mechanically inept design machinery, is an interesting side light. They are
apparently adept at making things look right but the concept is wacko in every detail!

It's been here before.

Jobst Brandt jobst.brandt@stanfordalumni.org Palo Alto CA
post #4 of 11

Re: Jeep bikes, with AWD!!!

jobst.brandt@stanfordalumni.org wrote in message news:<rBX4a.67307> >
http://www.jeepbikes.com/rubiconawd.html
>
> Besides having open bevel gears that do not work with dirt, the drive is transmitted by a 5ft long
> shaft no more than 1/2" in diameter and apparently a flexible shaft, there being no universal
> joints at curves in the shaft line. If these guys are serious they ought to answer the question of
> torsional stiffness of the drive between rear and front wheel. That shaft is a long floppy torsion
> bar that will most likely exceed its torsional strength if the rear wheel slips on the level with
> the front wheel on dry pavement. Besides that, such a load will generate a large steering torque.
> Jobst Brandt

I note that it is claimed that there is an "Internal, rigid drive shaft system". I can't really make
it out, but it could run fairly short and straight through the down tube (with just one joint as
shown in the head tube), with drive taken from the bottom bracket axle. This would give no curves.

What I can't fathom is how the front suspension would work. It looks like any travel here would
really mess things up.

In any case, I thing you have summed up the "advantages" of this arrangement admirably.

> jobst.brandt@stanfordalumni.org Palo Alto CA
post #5 of 11

Re: Jeep bikes, with AWD!!!

I'm with you... They've got every bit of the geometry and mechanicals outlined and the weight
is "n/a"?!

Maybe N/A stands for "not acceptable"

I wouldn't discount the idea at all, but given the materials one can work with vs the cost, I think
this proposal is still a decade or so off... I'm certain that in the past, the first designs for
full suspension mountain-bikes got laughed at as well...

For right now, I think this AWD bike idea would be more suitable if you put a motor in it

David

"Bob Denton" <bdenton@soytek.com> wrote in message
news:cur45vk03k6bgv0ah0ifcbapctrn5oq1vj@4ax.com...
> On 17 Feb 2003 06:05:19 -0800, summitlt@yahoo.com (TJ Poseno) wrote:
>
> >Now I was looking at earlier posts about Jeep bikes and see that they are crap, but look at this,
> >this one has AWD!!!! Pretty fu*kin cool!
> >
> >http://www.jeepbikes.com/rubiconawd.html
>
> Hmmmm:
>
> WEIGHT: N/A Bob Denton Gulf Stream International Delray Beach, Florida www.sinkthestink.com
> Manufacturers of Sink the Stink
post #6 of 11

Re: Jeep bikes, with AWD!!!

awebster@littleheath.org.uk (Andrew Webster) writes:
> jobst.brandt@stanfordalumni.org wrote:
> > > http://www.jeepbikes.com/rubiconawd.html
> >
> > Besides having open bevel gears that do not work with dirt, the drive is transmitted by a 5ft
> > long shaft no more than 1/2" in diameter and apparently a flexible shaft, there being no
> > universal joints at curves in the shaft line. If these guys are serious they ought to answer the
> > question of torsional stiffness of the drive between rear and front wheel. That shaft is a long
> > floppy torsion bar that will most likely exceed its torsional strength if the rear wheel slips
> > on the level with the front wheel on dry pavement. Besides that, such a load will generate a
> > large steering torque. Jobst Brandt
>
> I note that it is claimed that there is an "Internal, rigid drive shaft system". I can't really
> make it out, but it could run fairly short and straight through the down tube (with just one joint
> as shown in the head tube), with drive taken from the bottom bracket axle.

One of the smaller pictures seems to show a gear on the back axle (inside the brake disk). It's not
clear, but it looks like maybe a flexible shaft behind the rear shock absorber, linking the back
axle to the bevel gears shown in the cutaway view of the headset/ steerer area. (Though how it copes
with changes in length because of that rear suspension I don't know - flexible shaft has splines and
can slide into a shaft inside the top tube? Front suspension is even less clear.)
post #7 of 11

Re: Jeep bikes, with AWD!!!

Alan Braggins writes:

http://www.jeepbikes.com/rubiconawd.html

>>> Besides having open bevel gears that do not work with dirt, the drive is transmitted by a 5-foot
>>> long shaft no more than 1/2" in diameter and apparently a flexible shaft, there being no
>>> universal joints at curves in the shaft line. If these guys are serious they ought to answer the
>>> question of torsional stiffness of the drive between rear and front wheel. That shaft is a long
>>> floppy torsion bar that will most likely exceed its torsional strength if the rear wheel slips
>>> on the level with the front wheel on dry pavement. Besides that, such a load will generate a
>>> large steering torque.

>> I note that it is claimed that there is an "Internal, rigid drive shaft system". I can't really
>> make it out, but it could run fairly short and straight through the down tube (with just one
>> joint as shown in the head tube), with drive taken from the bottom bracket axle.

> One of the smaller pictures seems to show a gear on the back axle (inside the brake disk). It's
> not clear, but it looks like maybe a flexible shaft behind the rear shock absorber, linking the
> back axle to the bevel gears shown in the cutaway view of the headset/ steerer area. (Though how
> it copes with changes in length because of that rear suspension I don't know - flexible shaft has
> splines and can slide into a shaft inside the top tube? Front suspension is even less clear.)

Rigid is a fuzzy word in this description since all practical materials have substantial elasticity
in the dimensions of this design. A 5-foot long 1/2 inch rod is a twisty spring that could absorb
as much as two revolutions twist... if it were steel. If it is a flexible (speedometer cable)
drive, then it is at least twice as torsionally soft and have insufficient strength to turn the
front wheel.

Also visible is the cumbersome and ineffective steering link from upper head bearing to the fork
crown, there bing no steer tube on this fork. This slightly curved plate has no torsional strength
and will act as a spring between the handle bar and the wheel. Beyond that, the fork is suspended
entirely by a pair of bearings under the head tube (aka a 2-inch long steer tube). Things like this
that make me doubtful of whether this bicycle has been ridden or is just a design exercise.

This is not a practical feature for the future or one for bicycles. Just its weight makes the
device ungainly and its execution makes it useless. By the way, slip joints in shafts do not absorb
length changes when under torque unless they are roller sleeves (heavy). I suppose, for special
events, like monster trucks, a two wheel drive might have an application, but it is not in the
future of MTB design.

Jobst Brandt jobst.brandt@stanfordalumni.org Palo Alto CA
post #8 of 11

Re: Jeep bikes, with AWD!!!

Alan Braggins <armb@chiark.greenend.org.uk> wrote in message > One of the smaller pictures seems to
show a gear on the back axle <snip>
> (inside the brake disk). It's not clear, but it looks like maybe a flexible shaft behind the rear
> shock absorber, linking the back axle to the bevel gears shown in the cutaway view of the headset/
> steerer area.

On close inspection you are absolutely correct - the shaft is clearly visible entering the top tube
where it bends sharply up. The more I look at it the curiouser it seems - and the more accurate
Jobst Brandt's assessment.
post #9 of 11

Re: Jeep bikes, with AWD!!!

jobst.brandt@stanfordalumni.org writes:
> Alan Braggins writes:
> > to the bevel gears shown in the cutaway view of the headset/ steerer area. (Though how it copes
> > with changes in length because of that rear suspension I don't know - flexible shaft has splines
> > and can slide into a shaft inside the top tube?

> useless. By the way, slip joints in shafts do not absorb length changes when under torque unless
> they are roller sleeves (heavy).

So either the shaft is useless and doesn't carry any torque, or the suspension is useless and has no
real travel.

(I've taken apart a car suspension where I'm fairly sure the spline drive allowed a little movement
(as well as removal of the shaft once bits were disconnected at the other ends). Nothing like the
amount this design would seem to require though.)
post #10 of 11

Re: Jeep bikes, with AWD!!!

Alan Braggins writes:

>>> to the bevel gears shown in the cutaway view of the headset/ steerer area. (Though how it copes
>>> with changes in length because of that rear suspension I don't know - flexible shaft has splines
>>> and can slide into a shaft inside the top tube?

>> useless. By the way, slip joints in shafts do not absorb length changes when under torque unless
>> they are roller sleeves (heavy).

> So either the shaft is useless and doesn't carry any torque, or the suspension is useless and has
> no real travel.

> (I've taken apart a car suspension where I'm fairly sure the spline drive allowed a little
> movement (as well as removal of the shaft once bits were disconnected at the other ends). Nothing
> like the amount this design would seem to require though.)

The spline shaft freedom of axial motion is a common error in industry and cars. It was especially
apparent in a race car accelerating around an uphill bend and remaining tilted to the outside on
the following straight section until the driver let up power to shift, at which time the car
leveled itself.

another massive error is chronicled at:

http://www.spikesys.com/Trains/grd_loco.html

Jobst Brandt jobst.brandt@stanfordalumni.org Palo Alto CA
post #11 of 11

Re: Jeep bikes, with AWD!!!

Gary Young <garyyoung3@hotmail.com> writes:

>> Besides having open bevel gears that do not work with dirt, the drive is transmitted by a 5ft
>> long shaft no more than 1/2" in diameter and apparently a flexible shaft, there being no
>> universal joints at curves in the shaft line.

> There are detailed pictures here:

http://www.christini.com/Manual_vsn_1.4.pdf

> They do claim to use universal joints. Does that change your assessment of it?

Not in the least, but I am impressed with the thoroughness that this document is presented.

The (exposed) gear size alone is foolishness. Consider the contact loading of a bevel gear about
15mm in diameter, at both the wheel axles (in the dirt) and in the head tube. These are connected by
a steel shaft that is in effect a long torsion bar. Imagine a BB spindle 1.5m long and 12mm in
diameter with your weight on the pedal. Besides that, the square shaft slip joint is even smaller,
its inscribed diameter (the diameter that goverens torsional stiffness) being less than the shaft.
The joint will not slip under torque, a common design error made by more famous people than these
inventors.

[Torsional stiffness varies as the 4th power of solid diameter or about the 3rd power of a hollow
shaft depending on wall thickness.]

See "Shay" at:

http://www.spikesys.com/Trains/grd_loco.html

The Shay locomotive of American Locomotive Works (Alco) used such a flawed slip joint, the cause of
many of its derailments. The cause was never recognized during the Shay's years of service. Similar
slip joints were used on automobiles with equally unexplained failures.

Jobst Brandt jobst.brandt@stanfordalumni.org Palo Alto CA
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