How does this gear set work?

[skeeter]

Hello

Could anyone explain how this unit has infinite gear ratio, and how it handles it. This is pictured in the present issue of Popular Mechanics.

I tried a search at the patent site, but nothing came up, on the topics that I tried.

The picture may not be enough information. Just curious.



This bike is selling in the neighborhood of $3000.

Best regards,

[dp]

It's a friction, not gear drive. The two cupped disks are coupled to balls by friction. The balls are also coupled by friction to an inner hub. As the hub moves left/right the contact point between either disk and the balls shifts toward or away from the equator of the balls while the other disk moves toward a pole.

The ratio is 1 to 1 when the disks are equidistant from the equator of the balls which happens when the axis of the balls is at exactly 90 degrees to the disks.

This looks like a serious attempt to create metalic dust from all these parts rubbing and slipping together. I don't see how this would last on a mountain bike, but the sample bike is not in that category. It would be fine for a beach cruiser that never sees a hill.

There's a video of it here: http://gizmodo.com/gadgets/gadgets/b...nci-247436.php

Turns out it's fluid coupled, still friction drive, but no apparent metal on metal contact.

Here's a direct link to youtube: http://www.youtube.com/watch?v=kVPjhmTThPo and there are several related videos provided there.

[Keith Krome]

It has infinite gears in the bicycle sense. Each "gear" on a bicycle consists of a sprocket. This transmission is infinitely variable, has a maximum ratio and a minimum ratio, and an infinite number of ratios in between. On a bicycle, you have the same maximum and minimum ratios, but only a few distinct ratios in between. It is a infinitely variable transmission. They just like to leave off the variable part.

[Rich Carlstedt]

It's a variation of the very old friction disc drive.
RIGHT ANGLE STYLE
Back around 1900, cars would have a leather disc, like a phonograph turntable on the rear axle, that was driven at right angles by a small wheel (tire) that ran accross the turntable .
The wheel was on a splined shaft and was driven by the motor . When it was on the outside of the turntable, the table turns slow, but as the wheel gets closer to the center of the turntable, the output goes faster.
If you went past the center of the table, you got reverse.
A true variable speed unit.
It's short comings are wear ! particularly with a wide wheel.
The narrrower the wheel, the less wear, but the greater the force needed to keep the unit from slipping.
This was solved somewhat by mounting two parallel shafts, each with a steel cone mounted opposite to each other, with a small space between them.
INLINE SHAFT DRIVE
Think of two such (ice cream cone size) cones about .450" apart .
If you mount a .50" ball bearing between them, and drive one, you get a varible output on the other, as the ball is moved from one end to the other.
The ball must be held vary tightly against the cones to do this.
By having the opening slighly smaller than the ball, lower forces are needed.
CONCURRENT SHAFT DRIVE
Similar to your bicycle unit.
Two discs are mounted as shown with a series of balls mounted around the outside of the discs and the balls have axles. the balls pivot and the contact angle between the pivot point AND the contact point changes to produce the variable speed. In short, you cock the ball and the ball transfers motion to the axle to give the change. Think of a Globe spinning with a wheel driving at the equator, and as you move the constant speed wheel towards the North Pole, the Globe spins faster.
The Japanese have a very fine Gear motor variable reduction unit on the market that uses this principle.

But , the problem is lubrication.
To keep wear down, oil is CRITICAL( type and viscosity), and so is cleanliness.
Hope this helps
Rich

[mechanicalmagic]

Ball drives have been around for quite a while. They were used in 1953, in the McCulloch superchargers. (Later to become Paxton.) They were updated to a variable ratio, and used in the 1957 T-bird.

Yes, lubrication is an issue. But they can take several horsepower.

http://www.paxtonauto.com/history.html

Dave

[2ManyHobbies]

http://www.atcnuvinci.com/overview.php

Movies on the "How does it work" tab on the left.

To me it almost looks like a thrust bearing where the only contact points are the outer edges. It doesn't look like the "balls" move in a raceway or anything. In fact, the "balls" appear to be more like a rod jammed through a sphere.

Looks like the variable bit comes from the variable circumferences you get by tracing two different sized circles around the outside of a sphere. They rock the "ball" element back and forth to alter the contact "latitude" for each disk. The effective gearing ratio increases near the poles and decreases near the equator.

See if this helps visualize it:
1. Fix a sphere on an axis in space.
2. Add 2 disks with axises parallel to the axis of the sphere.
3. Spin the "input" disk against the sphere near one of the poles of the sphere.
4. Touch the "output" disk against the sphere near the equator.
5. Vary the contact "latitude" of either disk to see an increase or decrease in output to input speed ratios.

Substitute cone for sphere if it gives you a headache, I know it gave me one for about 20 minutes.

[John Stevenson]

Saw these at the Canton show last April, they were attracting a lot of interest.

Some of the big ink mixers use this trype of drive, they run a 7 HP motor and run 24 / 6 with only about a pint of ATF in them but they do get hot.
They last about 3 years before they go bang which isn't too bad when you see the amount of work they can do.

.

[kendall]

there is another bicycle drive I read about (somewhere, can't find the links) that uses cones instead of balls, basic operation seems to be the same.

to me it seems like a friction drive is wastefull of energy, especialy when discussing the minute power output of a rider.

better option for a wide gear ratio would be the rohloff 14spd hub:

http://sheldonbrown.com/harris/images/speedbild2.jpeg

or one of the 8 and 9 speed versions.

Ken.

[skeeter]

Hi,

I would like to express my thanks for the information. From what is stated in the answers, I can visualize how it works.

Thanks very much.

Skeeter

[A.K. Boomer]

From what I can tell its a type of variable planetary system, its a fancy shmancy version of the simple progressive cones that are opossed to each other and run a ball or friction disc between the two cones and use the flip flop diameters of the cones as a means of getting variable ratio's, these units may keep something in its optimum range but there is a price to be paid in extremely hard materials that are pre-loaded at all times -- the result is much friction just to make them opperate without slippage, Now many will think that a simple bicycle is immune to this because us humanoids only produce so much power but we are very high torque machines therefore these units have to still keep much pre-load, they did one thing right - they put the unit one the rear wheel and this at least got them by so they could reduce the needed pre-load by 1/3 --- still, it may be fine for "cruising" but this unit is a horsepower eater and you will never see anything like it on a race bike --- there is a reason the almighty chain has been around forever, they are about as direct aproach as you can get, they are about imposible to beat with power transmision efficiency on a bicycle that needs to have them for thier muti-speed changes --- putting the crank directly on the wheel is one step better, but extemely limited, putting a planetary system on the crank thats directly on the wheel pales in comparison to a chain drive...