Infinity Drive

[Martinez]

I wanted to thank all the teams who wandered into our pits at Nationals to check out Chuck 84's Infinity Drive. You kept our engineers so busy that we missed our first two practice matches!

[Gabe]

Sorry about that...I kept recommending to members from my team to check out your transmission, because it is really cool!!!

I am very impressed by the way your team developed this differential transmission, and used the KOP Banebots transmissions for it. I have had a similar design bouncing around in my mind but that was using bevel gears similar to a car differential.

One idea that I just thought about that might be worth looking into was using DeWalt cordless transmissions instead of the Banebots 56mm planetary gearing. The DeWalt gearing is a lot more compact and their relative design issues have been more thoroughly addressed over the years than the much newer BB 56mm planetaries.

Considering the troubles with this year's KOP transmissions, FIRST might not include them in next year's kit of parts, so DeWalt planetary transmissions might be a good candidate for another Infinity Drive.

[JBotAlan]

I don't think anyone from 68 checked this out. How does it work?

[Guy Davidson]

Could you guys post the flier or some information about it online? I wasn't at nationls, but I am really curious about the idea of the "infinity drive."

[AdamHeard]

From what I saw, it is similar to the crazy chicken transmission 217 used in 2002.

I like the idea, but it seems kind of inefficient to me. Doesn't the power from only one of the two CIMs actually power the wheels?

[Dan_Karol]

Your drive was really cool! Based on what i saw at Nats i think i may try to develop one using the Lego differentials.

-Dan

[AJ R]

I really wanted to get over to your pit, but must have forgot about it when I had free time. Could someone post a pic for those who didn't see it?

Thanks

[Po-ser]

Seconded (or seventhed, or whatever). I didn't get to check it out and I'd love to see how it works.

[POLISH703]

I saw it a few times. Then I directed about 8-12 other people to go look at it too. Sorry to overbear your pit a little bit. But that was a cool tranny, I have never seen anything like it.

[David Guzman]

Originally Posted by AdamHeard

From what I saw, it is similar to the crazy chicken transmission 217 used in 2002.

I like the idea, but it seems kind of inefficient to me. Doesn't the power from only one of the two CIMs actually power the wheels?

From what I understood you only get the power of two motors when you go on the fastest speed. I think this is a gearbox with many "speeds" for the robot. However when you go at low speeds you don't get much torque, since one CIM is working against the other one.

I think the one that 217 made before was actually using the full potential of the motors to get max torque at every speed.

Someone please correct me if i am wrong.

[Gabe]

I looked at it for a long time and understood the explanation given to me pretty well (I think):

In planetary gearing the planet gears rotate inside the ring gear (which is the housing of the Banebots transmission); as long as the ring gear housing remains a fixed part of the drive relative to the motor shaft. Now imagine that the ring gear housing is allowed to freely rotate relative to the motor shaft. If the housing is turned against the rotation of the motor shaft, then the output speed of the transmission will decrease. If the ring gear housing is turned with the rotation of the motor shaft, then the output speed will increase.

I'll have to think a little more on why this is.


[Edit: The reason why is that as you rotate the ring gear the planet gears are being rotated faster on the internal gear, and they rotate in place if the sun gear counter-rotates. This means that the carrier plate will provide a lower output speed. Whn the ring gear housing is moving with the rotation of the input sun gear, then the planet gears rotate faster, which means that the carrier plate will also rotate faster.]

[Alex.Norton]

The idea is actually how the transmission in the prius works. They used a CVT to change the ratio of the ring gear. This means that you can actually get both reverse, stationary, or forward movement with the same input speed.

In the case of the infinity device I didn't see it but based on what has been said I can guess how it works. One motor is used to turn the input shaft to the bane bot and the other is used to turn the gear box itself. In this case it does provide the full torque and power of both motors, however since only one motor needs to back drive to allow this system to fail its does reduce the usefulness of this system. The advantage of 217's transmission was that it used a worm gear to turn the ring gear. This meant that if the other motors stalled then the CIM would get the largest reduction and the other two motors couldn't back drive.

At least that is what I have figured out.