Bike Drive

Ok, so you know how a bike works, right? It’s able to switch it’s gear ratio by moving the chain onto different gears. So I was thinking, what if you imitated this on a vex drive? This would have a number of advantages:

It would allow you to unlock more speed as you could use torque just when you need rather than having to have the same ratio all through the match.

You could use a torque ratio to help with controllability while still having speed available.

You could use a torque ratio to accelerate and then slowly switch up to a higher speed as you gain momentum.

You could build up momentum with a speed ratio and then switch to a torque ratio at the last second to get over a bump.

Anyways, this is a very sketchy, however I think it would be cool to develop.

There have been people that have done this. I think if you search youtube for “vex transmission” you should find them.

I’ve seen quite a lot of pneumatic transmissions that work well before but none using a system like a bike. It’s a good idea although I think the vex sprockets have too much of a size difference to make transitions smooth and efficient. Also the sprockets would need to be modified to make sure they are close enough together on the shaft to prevent the chain from going down the middle of two.

I think you are better off using pneumatics for a transmission. Look up the VCAT NBN worlds reveal, and you’ll see a really good transmission. As well as GER’s robot from Toss up

It works just as well to use a motor to shift the transmission if you have a motor available.

Our team created a 3 speed transmission that we used during NBN that used no pneumatic only motors. We had to scrap it due to the last two games requiring more weight. It would skip chain when you turned with a lot of weight.

we had no shifting mechinism

Wait…then how is it a transmission?

It went from 1st gear to 2nd to third without a traditional shifter like a pneumatic. It worked by running certain motors different ways. Its been awhile but i’ll see if I can prototype one later and put a picture on here.

That is actually pretty cool, I’d love to see pictures

We actually have someone who has been working on a transmission just as a fun side project. If you were at Andersonville in Indiana, then you might have seen my team member, Jake, working on it. It’s pretty cool to have around.

O ya that technique is strictly inferior. It has been talked about a lot on the forum in the past.

@Easton Here is an animation by jpearman about this style. We actually found out after we built it that it looked almost alike. Ours had some differences but this is the basic idea.

sorry forgot to put it up here it is
link text

the biggest problem with a bike transmission is that it uses a derailer that also doubles as a tensioner for the chain, this means that you can only go one direction, because when you ride your bike forward it is using the tension across the top of the chain run, however, if you tried to pedal backwards, it would just pull the tensioner out and then you would have a ton of slop in the chain.