I've seen mucho designs like this, I've even made one with chain (don't ask how, it'll take forever to explain), but you generally want to offset the cones so that the belt is always contacting at 90 degrees with the cone. What I mean is for you to offset the cones enough so that the belt runs at a diagonal to the frame, but at 90 degrees to the cones. This is done so that the belt isn't running crooked on the cones. Also, you want to keep the belt as narrow as possible, since as you go up or down the cones, no matter how little, the ratio changes. Theoretically you want one contact point, or an infinately narrow belt, but that doesn't work. If the belt is too wide, the edges of it will be consantly slipping and will get worn out really fast. This design works and all, but you also need to put tension on that belt or it will slip. Other than that, it seems like a very cool design, very makable, and it should work.
My question is, how are you going to move the belt up and down the cones? If you had 2 such transmissions on tank drive, it might be hard to make the thing go straight forward since they probably won't be in exactly the same gear.
Tell you what, if you want to see the one I designed, I could show you some pics and describe how it works, maybe we can help each other out. Just email me at
sixkdollars@yahoo.com.