Thunder Chickens CVT?

Someone mentioned that “The Thunderchickens” had a CVT (in this thread ). Anyone know anything about this? It’s an interesting idea and I’d be curious to know how they pulled it off. There are a lot of different ways to do a CVT, and I’m impressed that someone pulled it off.

Here’s the White Paper.

its patent…so…we cant use it?

Other teams have used a CVT in years past. Team 64 had one last year. They had trouble getting it working. I have no Idea how it worked something about planetary gearsets, I never really got to see it.

Here’s a pic: 64’s 2003 CVT

This isn’t really a CVT :frowning: , although I must admit it’s interesting. It seems as though this design is far too complicated a heavy to be worthwhile. I was thinking about something like this:

cvt5

Just as the disk CVT evolved into the cone CVT, the toroidal CVT has evolved toward a cone-shape as well. The result is a much more compact transmission. This type is peculiar in that the speed ratio may be controlled by directly rotating the wheels, or by moving them slightly up or down, causing them to rotate and change the speed ratio on their own. - Taken from http://www.gizmology.net/

Has that ever been done before in FIRST?
More importantly, is there a good reason it hasn’t been done?

Team 190 did this a couple or three years ago. As I recall it worked pretty well. You’ll have to ask them why they haven’t used it since.

It says in the white paper that we ask that you mention credit to us if you base your transmission off of it. One team used our CVT last year and got a design award for it, even though they didn’t design it - we did.

Basically, you can use it, just don’t say that you invented it :wink:

The thunderchickens planetary CCT inspired us (701) to build a simplified version of one this year and from the little testing we have done it seems to work very well. I absolutely credit Team 217 for inspiring our design - but it is different from theirs. Our planetary transmission is not really a CVT, just as the thunderchickens transmission isn’t a true CVT either, it’s closer to being a two speed transmission that doesn’t require any mechanical shifter. Basically, we use the CIM as our sun and the drill drives an external ring gear which is connected to an internal ring gear. The planetaries (output) rotate between the sun and internal ring gear. Thunderchickens (as explained in their white paper by Paul C.) use the drill and FP motor driving a worm gear on their external gear. This was to prevent backdriving of the motors when the output is stalled. We are able to overcome the backdriving effect by gearing down both the CIM and the Drill motor to the almost the same output torque. We thought this would be much simpler than incorporating a worm gear system. Since it is next to impossible to perfectly match them up we compensate for backdriving by using the current sensor to monitor the CIM current. As it begins to spike, we reduce the power to the Drill motor. Important Note: we are a small outfit that had to machine many of the parts ourselves on a mill / lathe that we got just after kickoff - thus we didn’t finish it until Feb. 20!! There is so much more testing we need to do - but we did test it briefly and it supplied a high torque and low speed when the sun and external gear were moving opposite of each other and low torque and high speed when moving in the same direction (an effect the Thunderchickens CCT doesn’t provide according to Paul C. - I’m still confused as to why…). We were able to manually adjust the backdiving effect and sure enough were able to stall both motors together. The one part of the system that was never finished was the programming of the current sensors - we’ll give it a shot at competition and see what happens - but we are very pleased with the results so far. And it required very little machining (housing is probably the hardest part!). We’ll provide more info after the Sacto Regional. Regarding the Thunderchickens patent pending design… If we are presented an award solely on the planetary design - we would not except it. If we are presented an award for the overall drive / control system, we would graciously except it. I would very much like some feedback on this sensitive issue from the CD community.

Good job! It sounds like you put a lot of effort into this. I hope it works great, and hopefully I’ll get to see it at the Nationals. :slight_smile:

Thanks…haha…its funny we designed it a while before comp. got our mill a week into competition…spent a while learning to use it …then around Feb. 20 we finally got it working and man…it is even faster then our calculations…we’re pretty happy for it…
btw… unfortunately we won’t be at Nats but hopefully if we win a regional or something we could get some $dollars$ and make it …kind of a long shot tho