http://www.gizmag.com/steve-durnin-ddrive-d-drive-infinitely-variable-transmission-geared/15088/

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Steve Durnin's ingenious new gearbox design is infinitely variable - that is, with your motor running at a constant speed, the D-Drive transmission can smoothly transition from top gear all the way through neutral and into reverse. It doesn't need a clutch, it doesn't use any friction drive components, and the power is always transmitted through strong, reliable gear teeth.

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What do you think? Video of the working prototype in the link.

Honda hx civic had something similar...kinda like a 4 wheeler i guess

not really infinite... just continuous...

like a bobcat, or a Deere...

[This message has been edited by TexasRebel (edited 5/15/2010 5:47p).]

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not really infinite... just continuous...

like a bobcat, or a Deere...

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Did you watch the video / read the link?

Don't know enough about it to comment on how revolutionary it is, but it looks cool.

His claim of an order of magnitude increase in efficiency seems dubious, but I hope he's right.

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Did you watch the video / read the link?

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I have now, and stand by what I said...

with a variable displacement hydraulic pump and a fixed displacement hydraulic motor you have a continuously variable transmission from full forward through neutral to full reverse...

This is also true with the reversers on Steam locomotives... although at one point they ended up going to defined steps instead of continuous gearing to save money and effort...

a true "infinite" transmission isn't limited by a "top" gear... This one, along with the others listed in this post are all limited by the highest ratio of levers, displacements or gearing... while infinitely continuous between high and low, they are still limited.


EDIT: it is true about diesel-electric locomotives, too... the steam specification was just to show the age of continuously variable transmissions.

[This message has been edited by TexasRebel (edited 5/16/2010 3:26a).]

Variable displacement pumps/motors use swash plates where you have sliding friction and have efficiencies around 85~90%. The video shows something new because its all gear driven which should have higher efficiencies. The part I'm not sure about is how much power does it take to control the second shaft? Still very cool in that he shows it's possible to have a variable transmission while using only gears. The only downside is it looks like it requires two power inputs.

I felt like it was implied in the video that the second shaft would require an almost negligible amount of power compared to the main input, but who knows what you would actually need.

He also mentioned that the system could produce "unlimited" torque, provided you could build a big enough set of gears. I wonder how big it would need to be before it was useful for a car. Still very interesting though