crazy idea: geared vari-drive

[stryker]

Anyone here familiar with vari-drive. It was the idea of having a belt driven by the engine, round a pully one end and round two inwards facing cones at the other. As the revs went higher centrifugal forces pushed the belt further out on the cones, thus giving variable gearing.

Well I had an idea. I'm not talking about a total vari-drive for a bike, but a partial one.... basically whatever you could fit in at the rear wheel in place of the rear sprocket. With the space available you'd only get a small ratio perhaps from 0.5 of whatever gear X is up to 1.5/2x. But imagine.... it would do away with the often low rev flatspot. While in 1st gear it would be like having 6 gears dedicated to <30mph.

Thoughts? this is so damn obvious I can't belive no-one has tried it.
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Now what?

[G]

To start with, you have a clutch that can do that .
You shouldn't really have a problem with flat spots the majority of bikes when ridden properly.

If you can get it working like that, you can probably get it working with a full system.

If you could have seperate controls of the drive and the rpm then there is a lot of possibilities (not just the drive increasing with rpm)... You can be at full rpm all the time, then increase and decrease the drive to change speed, making full use of the engine.
Or you can set the power lower for exiting a corner, and be fairly safe in the knowledge that when set right you'll be on the limits of traction however much you up the speed.

You'd also have the option to use it like standard gearing would be used.

I however believe there is serious problems with using vari-drive style things on high power machines.

I have considered various designs for sprocket systems that can dynamically adjust their size, but haven't come up with any serious practical ideas.

The part on a scooter that actually eliminates flat spots is the centrifugal clutch really. This only engages at a certain rpm and can be set to 'slip' more or less to get better drive or a smoother launch.
I believe centrifugal system are available for mx bikes; this means they can have maximum power from low down without having to play with the clutch when they're navigating a berm. Also means their bike won't stall if they drop it .

[stryker]

Aww so stryker idea not good? stryker sad.
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Now what?

[G]

[pipnet11]

This sounds very much like a scooter style variator to me. Variomatic things were used on various small cheap cars with quite a lot of success, getting it small enough to fit on a bike would be a bit difficult though
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[mr jamez]

Didn't they do that on a formula 1 car, or something similar anyway.

Was quite succesful from what I can remember of it.

[Lone-Wolf]

Wotcha.

Once again the old git casts his mind back . . ah ... Raleigh Runabout & Mobylette mopeds. They used this very system. The engine was suspended from the frame by its cylinder head, and moved back and forth as the effective diameter of the drive 'conical pulley' increased and decreased.

There was a slight drawback with this system, as a mate of mine found out. He was happily riding away when the bolt that suspends the engine gave way . . . the engine promptly made a dash for freedom, the drive belt snapped, the throttle cable snapped and the engine, now happily revving its head off went spinning all over the show until it had used the remaining fuel in the float chamber.
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[loply]

Continuously Variable Transmission. My dads car has it (Honda Jazz). You neednt use centrifugal force to move the belt, you can do it with a motor.

The system cant handle very much power and is quite inefficient. Honda Jazz 1.4 produces 80bhp.
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[Bendy]

Unkie Wolf always has the coolest stories.

[stinkwheel]

Hmmm, Daf variomatics. We haven't seen the last of those

I liked the way you could bang them into reverse when you were doing about 60mph and the whole car seemed to go Boooiiiing then shoot off backwards.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Retro-Man]

one word


VOLVO.........


Anything that belongs on a volvo has no place on anything I would even loosely term a motorcycle

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[stinkwheel]

[Retro-Man]

[Git]

One of the scrapheap challenge challenges had a small daf car with the vari-drive gubbins, never knew about it untill I see it, rather different to say the least.

[stryker]

Hm, I can see how belt drive could suffer under 120BHP of bike engine. Pitty.
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Now what?

[G]

Buell's use Belt drive, though we're only talking around 100hp or a tad less from an ex-harley based engine.

On these thoughts, the ideal would be to have two adjusting 'sprockets' that change size. Would save weight and friction losses in the gear box as well.
I've had a few ideas along these lines, but nothing that would be able to handle anywhere near what is required I suspect.

[yohomiesmelly...]

There also used to be a DAF or DAS truck that had the vari drive system and it could go as fast forwards as it could back lol. Weird stuff eh?

[binge]

Just like if you managed to start a scooter up in reverse it would go full speed backwards...

My mate Bill has got a piaggio APE 50, which he has had kitted out to a 90cc, Its basically lambrettor gear system in a 3 wheeled van...

If he puts it into reverse, he can go up the gears. He went to a carpark and managed to get 40mph in reverse. Im suprised he didnt roll it!

https://www.vehicle-documents.it/schede/piaggio/ape/ape1.jpg
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