Any one watching the webcast of the new jersey regional has probably noticed the astounding speed with which the elevator of team 25 moves up and down. I was wondering what motor they are using and how it works so quickly compared to many of the other ones ive seen
We use a CIM minibike motor with direct drive (ie no gearing on it). Our pulley system uses one long (about 30ft) belt with needle-bearing pulleys to reduce the friction. It’s really simple; if you get a chance to see it in person, it’s much easier to understand.
Any chance of video of your robot from the regional? :yikes:
Well, you may be using the Big CIM motor without an actual gearbox, but the size of the pulleys give you an “effective gear ratio” Much like using a direct drive transmission for your drive train, the size of the wheel makes a dramatic difference in overall speed. Do you know the size of your pulleys in your belt system? Are they all the same size?
I’ll make an assumption to give some example numbers. If you use a 2" pulley, the elevator stage will move 3.14" per rotation. So, at 1/2 of the free speed (or at max power) the elevator will be moving at about 5ft per second. [20rps x 3.14"/rotation] That’s VERY fast. However, you need to balance that speed with the available torque. Again, at max power (1/2 of stall torque) the motor provides ~18 lbs-in of torque. Since the pulley has a 1" radius, the motor can effectively lift 18lbs, at a rate of 5ft / sec.
A larger pulley provides more speed, but less torque. A smaller pulley does the opposite. As you can see, that Big CIM is a VERY powerful motor to use on an elevator. If you can keep the weight down, you can move it vertically very quickly. We tried to use a couple Globe motors to lift our elevator, but eventually switched them out to use the Big CIM as well. It’s a GREAT motor for this application.
I’m interested in seeing some video as well. Although, I can’t say I’m looking forward to competiting against them in Hartford! 
Another great robot from Team 25. Congrats on another victory!
BEN
Based on what I’ve seen, wow! Props to simplicity and recycling the 2006 robot effectively!
This is no recycle. There robot this year has 4 wheels on each side vs. 3 last year. They use all gears in their drive system and get the most out of the 4 CIM’s for both speed and power. If I remember corectly they are using 1 1/2" xl sprockets and belt on their arm and are usin g a 10 turn pot and programming to maintain position. I was told that they use 9 1/2 of the 10 turns for this elevator. Ano0ther awesome machine. Congratulations.
our elevator will go about the same speed (for general use it is massively slowed down) we have our elevator with a gear ratio of 12:1 off a big CIM… don’t worry this motor does more then just our elevator up and down, it has a servo clutch that switches between that operation and lifting the 2 robots (we have two platforms that they drive onto and we lift them up using that) the final gear reduction for that is 144:1. This ended up saving us a tonne of weight and we have a super quick elevator… reliably the quickest I as a programmer could get it to the top without overextending and possibly ripping off our tube manipulator was 1/2 sec… but our mentors wanted that toned down a bit
Now, are you using a timing belt, or just a regular belt. And is there any advantage of using a belt over a cable? Also, how you do achieve a fast descent of the elevator, if the motor only pulls it up? Surgical tubing?
I’m going to guess that gravity does this one for them:p
We are using a timing belt. I don’t know about the advantages of disadvantages of going with timing belt over cable, but we felt like trying a timing belt system because we made a cable system in 2005. The timing belt system is designed such that the motor can pull it down also. Because of needle-bearing pulleys and precise machining of the mast there is very less friction involved so gravity does do some of our work in bringing the elevator down. Surgical tubing was used to keep the gripper from swaying left and right violently during a match.
www.thebluealliance.net … go to match archives… type in 25 in search, you willl get matches from NJ and UTC.