Quote:
Originally posted by Jnadke
There is no way (that I know of) to create a CVT using only gears.
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I'm not sure if it would be considered a true CVT or not. But you can use an epicyclic or planetary gear system to create a similar effect. As GregT mentioned, it does require two torque sources and the ratio is changed by changing their relative rotational speeds.
I have a little hand operated demo version our machinist built that shows the concept pretty well. We were going to use it in 2002 but it didn't fit the robot concept. This year we didn't feel we had the weight available so we haven't put it into practice. Maybe next year, now that we feel a little more confident building gearboxes.
The Thunder Chickens' Crazy Chicken Transmission of 2002 worked on this principle. I think that the Gila Monsters used it this year. There may be others out there that I don't know about, but FIRST teams have done this in the past and it has been effective.
I'm not sure how efficient it is. Paul Copioli posted a white paper a while back that indicated the power of the second motor is basically lost. I went over the equations and didn't see anything obviously wrong, but a different configuration may require the equations to be set up differently and so give a different result. I haven't gone back and checked this myself, yet. I may get around to it someday, but I have a different area of interest at the moment.