Constantinesco Torque Converter in Lego

CVT means Continuously Variable Transmission. Unlike a standard transmission, which has several fixed ratios to choose between, a CVT has pretty much infinite ratios. This means smoother acceleration, better power delivery, and less loss of power due to shifting and clutching than a normal trans.

CVTs are nothing new. Dodge has a CVT (http://www.youtube.com/watch?v=8VYPsrOyIdw&feature=fvwrel) that's belt driven and uses variable pulleys. NuVinci has a bike hub (http://www.youtube.com/watch?v=Smijjy832X0&feature=related) that uses swivelling balls and some kind of grippy fluid. Simkinetics (http://www.youtube.com/watch?v=cd2-vsTzd9E&feature=related) has a pretty interesting design as well, which looks quite similar to this design except that it uses cams (?) instead of pendulums.

I like this design because it's relatively robust. It doesn't need special fluids, it doesn't rely on friction, and even in Lego it works pretty well. There may be a better design out there (the Simkinetics hub looks promising), but this system seems like a good place for me to start tinkering.

To see the Wikipedia write-up on what I'm trying to replicate, go here: http://en.wikipedia.org/wiki/Constantinesco_(automobile) or here to read about the inventor http://en.wikipedia.org/wiki/George_Constantinescu or here http://commons.wikimedia.org/wiki/Category:Constantinesco_torque_converter for the pics I worked from.

I built this from two Lego Mindstorms kits (1.5 and 2.0), one Ultimate Accessory pack, a few bits from some monkey kit thing, and a few other bits and pieces I had laying around. Your mileage may vary depending on what parts you have at your disposal. None of the parts were modified, and the only non-Lego part is the string.

Questions/comments welcome.

Category:

Science & Technology

Tags:

• lego
• CVT
• continuously
• variable
• transmission
• torque
• converter
• Constantinesco

[boyd868b]

good work,d have you checked out the rexresearch page on him yet?

[Darwinpasta]

@boyd868b The what now?

[caesareor]

Hey man, nice build. Anyway, I was wondering if you can adjust the motor rpm. I would be curious to see what happens at lower rpms .

My concern is that if you reduce the rpm's to 1/4 let's say (the equivalent ratio between the drive and idle rpms in a real car) there will still be a lot of torque in that wheel so you would need quite a strong hand brake to keep a car stationary.

Now I know that the guy actually built the car and it worked fine but I would like to see it too. :)

[Darwinpasta]

@caesareor Thanks. Yeah, torque would be an issue, unless the motor was really slow. Given the idle speed of a gasoline engine, it would need a clutch to stop it from fighting against the handbrake. In fact I think I'd set up a CVT much like a standard auto trans, with the torque converter feeding a few clutch packs. This would also provide for underdrive gears and reverse.

I've dismantled this one to attempt a dual-pendulum setup. I'll try slow input with that one if I get it working.

[boyd868b]

the site is Rex research.com they have quite the story on him plus other good stuff

[matsuri626]

Cool prototype! I wonder, though, about the torsional trepidation at the wheel. I can see in the video that the wheel's rotation is kind of jerky which I suppose is a direct consequence of the one-way clutch. I don't mind the shaking of the entire frame, as the pendulum's motion is obviously not balanced, but I think the torque fluctuations at the wheel (the jerkiness) are harder to eliminate as they are a result of the one-way clutch. What do you think? Keep it up, it's really cool!