hobo_chuck said:what im saying is that pedaling at the same rate on a coker or a geared
24" you go the same speed(or the stupid idea of a stack of wheels).
the large/small wheels act as gears to speed/slow the RPM of the wheels
rotating below,with a 36"wheel on top and a 24"wheel on bottom it is
geared to 36" with a ratio of 1:1.5.
(notice that the numbers i used are the same as a standard GUni)
the stack of wheels act as gears.
Is it not harder to ride the 24" GUni than the 36" standard coker?
You are apparently missing the point. You are confusing an increase in
the speed of rotation with an increase in the speed of movement.
The stack of wheeels idea is not stupid. There are plenty of people
who ride them. One wheel above another is sometimes referred to as a
diverticycle. You pedal backwards to go forwards. On a three stack,
you pedal forwards to go forwards, but the middle wheel contrarotates.
It is possible to use different sized wheels in a stack. If you pedal
a big wheel and it turns a small wheel, then the small wheel will turn
faster. In this limited sense, it is "gearing". If you pedal a small
wheel and it turns a big one, the big one will turn more slowly.
Again, in a limited sense, it is gearing.
There would of course be handling and balance issues, as well as weight
and extra friction, but they are not relevant to the point in
question.
The important point is that in a stack of wheels, the movement is
transmitted from one wheel to another by direct contact between the
tyre treads. There is no magnification of the movement of the tyre
treads. Ultimately, it is the movement of the tyre tread that dictates
your road speed.
Let's take a simple 1:2 ratio. Let's say an 18" wheel stacked with a
36 inch wheel. (Both sizes are available, so it's not a daft
example.)
The 18" wheel has a circumference of 2 x Pi x radius, or Pi x
diameter.
Diameter = 18 inches. Circumference is 18 x Pi = 56.52 inches
(treating Pi as 3.14.)
So, in one revolution of the 18 inch wheel, a point on the tyre (or the
contact patch with the road/the next wheel) moves 56.52 inches.
The 36" wheel has a circumference of 36 x Pi inches = 113.04 inches.
A moment's reflection will show you that 113.04 is twice as much as
56.52. So in one revolution, the 36" wheel travels twice as far as the
18" wheel.
However, if the wheels are stacked, the number of rpm is "geared".
Pedal the 18 inch wheel and the 36 will turn half as fast. Pedal the
36 inch wheel and the 18 will turn twice as fast.
So, pedal the 18" wheel and in one revolution the tread turns 56.52
inches. It turns the 36" wheel half a revolution. The tread moves
half of 113.04" = 56.52 inches.
Conversely, if you pedal the 36" wheel, in one revolution, the tread
turns 113.04". The 18" wheel turns twice as fast, and the tread moves
2 x 56.52" which is exactly the same.
So in the sense of translating movement of your feet into movement
along the road, the stack makes no difference to your speed. In a
complex stack, you could have several different sized wheels all
spinning at different rpm, but the net effect would be completely
neutral, and you would be travelling at the same speed as if the wheel
you were pedalling were in direct contact with the road. (Ignoring
friction, weight and balance issues.)
Now, considering the geared uni, what happens is that you turn the
pedals one revolution, and the wheel turns more than one revolution.
For simplicity, call it 1.5, but other ratios are technically feasible.
Something fundamentally different is happening here.
You could only achieve this effect with a "stack" by having side by
side wheels with different diameters on a common axle somewhere in the
stack. Now that would be silly.
Here is a link to a photo of a three-stack unicycle.
http://www.costlowcorp.com/images/personal/three_wheel.jpg
--
Mikefule
I once had a bad experience with a bigot. Now I hate them all - even
the ones I haven't met.
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