You, me, and CVT

"RamblinRover Luxury-Yacht" (ramblininexile) 12/13/2018 at 10:23 • Filed to: technology

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Here’s a diagram from the patent application for a cone-drive CVT used by !!!error: Indecipherable SUB-paragraph formatting!!! (1905-1910). It’s fairly elegant - the drive control engages the center cone, and a tension system holds in the driven cone as the drive cone extends.

I think this system allows for a little more power transfer than the simpler one used by GWK, and certainly lower wear. It also in theory allows full speed in reverse... though as this one is configured, you’d have to maintain reverse tension manually, and the driven “normal” output cone probably bottoms out somewhere. You might get to 80% full forward speed before the drive cone hit the reverse cone and the normal driven cone at the same time... which hopefully there was an interlock for, or should have been, as smoking both of them would be bad. Even if driving 30mph backwards is dumb in the first place.

Tekamul > RamblinRover Luxury-Yacht 12/13/2018 at 10:31

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Fun fact : A snow blower friction disc is a CVT if you g rind off all the little detentes at the selector knob. Of course, then you have to hold it in place....

RamblinRover Luxury-Yacht > Tekamul 12/13/2018 at 10:35

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Yep, and the exact same type of transmission is used on classic Snapper riding mowers - has been for many many years. There are other machines dating to antiquity using a similar sort of thing, and as I mention in the post, the GWK automobile (also brass age):

Tekamul > RamblinRover Luxury-Yacht 12/13/2018 at 10:38

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I like the design, because it can be  so damn simple. One of my kids wants to build a little car, and I was trying to sort our how she could m ak e one of these with just basic pieces.

Manwich - now Keto-Friendly > Tekamul 12/13/2018 at 10:49

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That setup looks more complicated than it needs to be.

RamblinRover Luxury-Yacht > Tekamul 12/13/2018 at 10:52

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If you find a Snapper that’s otherwise clapped out, you might be able to cannibalize the trans setup, which might include an auxiliary brake as a bonus. Or, hell the whole back end and some of the steering and pedal setup to - cut it mid-frame, put a pan down in front of the engine/trans box to get the seat lower, etc. etc.

Here’s a classic Snapper:

Chop the sub-box off the rear drive unit box, disconnect the front steering assembly, attach a steering wheel instead of the tall steering stalk and tilt the pedal/kingpin assy back, put new body pan (could even be wood) in the middle:

You could even put bigger wheels on the modified front assembly with some cutting and rearranging.

You can probably get a semi-dead Snapper for a couple hundred bucks and the other bits for not that much. Or, y ou can get a more normal go-kart if you’re boring.

I like cars: Jim Spanfeller is one ugly motherfucker > RamblinRover Luxury-Yacht 12/14/2018 at 13:05

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I had an argument about CVTs with someone online once. They told me I was dumb because I said a manual CVT could be implemented. It’s easy to conceptualize a CVT that isn’t computer controlled- sure, there’s no clutch, but it’s possible to have a CVT where the operator manually slides the drive cone in and out.

RamblinRover Luxury-Yacht > I like cars: Jim Spanfeller is one ugly motherfucker 12/14/2018 at 13:20

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And the thing is, both the GWK and the ABC had manually controlled CVTs in the brass age, and the Owen-Magnetic had something akin to a partially-automatic CVT via electric drive. Automatic CVT control didn’t break into the mainstream until scooters and the DAF variomatic, about 50 years later. Just because with some setups it’s easy to implement and leverages an advantage of the CVT doesn’t mean it’s necessary or even obvious as the preferred way.

Snapper riding mowers since maybe the 60s have used a rubber friction disk on a sliding collar, via a chain-drive swing-arm, so they have had normal clutch use and reverse on the same drive unit of a CVT for a very long time - it’s just stepped on the drive control because it’d otherwise need some kind of balance setup to keep it from creeping into low gear.

I like cars: Jim Spanfeller is one ugly motherfucker > RamblinRover Luxury-Yacht 12/14/2018 at 13:27

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I don’t think I would mind a robust manual CVT honestly. The thing I prefer about driving stick is having the ability to change a gear ratio on demand to multiply torque and being in complete control of what gear I’m in. I think having that ability but with infinite ratios would be fun. Could even toss a clutch in there to disengage the transmission and it would be practically the same, but with more gears.