Gearing down motors

[MechaJag]

We're fairly new to the game of robotics and everything that goes along with it. One question we have is: Are the CIM motors a good motor to run your entire robot off of. We were planning on using the CIM motors this year instead of the drill motors. We had a ton of problems with the drill motors last year. Are we going to have to gear the CIM motors down to run two wheels off each motor? Will the CIM motor be efficient enough to pull two wheels? Any help would be greatly appreciated.

[jeremy562]

You definitely need to gear them down. They spin at something like 4000 RPM's... way too fast for a drive train. Geared down appropriately, the CIM's will provide plenty of torque and speed.

This year, however, you may not need as much torque as you did in the past. The ease of using the drill motors is a strong argument to stick with them.

[Jeremy Roberts]

Originally Posted by MechaJag

We're fairly new to the game of robotics and everything that goes along with it. One question we have is: Are the CIM motors a good motor to run your entire robot off of. We were planning on using the CIM motors this year instead of the drill motors. We had a ton of problems with the drill motors last year. Are we going to have to gear the CIM motors down to run two wheels off each motor? Will the CIM motor be efficient enough to pull two wheels? Any help would be greatly appreciated.

Either the drills or the CIMs will be fine as long as they are geared down (we choose how fast we wanted to move and geared accordingly). We are also using the 2 CIMs to to drive our robot.

[rswsmay]

Actually we have already made our calculations for the gearing reduction and are prepared to order parts. The CIM motors are the choice for this years robot.

Guess we need to have a team meeting with EVERYONE attending.

[Andy Baker]

CIMs will work well. Just keep in mind that many of your opponents will be using BOTH the CIMs and the Drills, or maybe CIMS and F-Ps to drive their 'bots.

[Frank(Aflak)]

drill motors are more powerful. I'd suggest stick with them (no need for gearbox, also, use the included tranny!)

[Veselin Kolev]

Originally Posted by Frank(Aflak)

drill motors are more powerful. I'd suggest stick with them (no need for gearbox, also, use the included tranny!)

Well, if you look at the spec sheets, the motors actually have really close power. The upside for the drill is that it comes with a handy dandy gearbox that reduces the crazy speed of 19,670 to something less than that (haha yea, I've never used the drill gearbox on a transmission, so I wouldn't know off the top of my head). The great part about the CIM motor is that it delivers lots of power, is smaller than the drill and its gearbox, and runs at a pretty low speed. Its free load speed is 5346 rpm, and its top load is 2680-ish, so just do the math. Ex: You want to go 10 feet per second, on 6 inch wheels. 10ft/s x pi x diameter = rp/sec. For this example, it would be about 6.4 rotations per second, or 380 rpm, at the wheels. You've got a running speed of about 4800 rpm at the motor, so do the math. You need about a 12.5 to 1 gear reduction. Using that, figure out what gears to use, and throw them together with some aluminum plates, and you've got yourself a drive train. Yea... but put a little more time into the calculations than I did. The process becomes a bit more complicated when you have multi-motor transmission, because you haveto gear the motors together, and that gets ugly. But.. the CIM motors are very good motors to use on a dive train, so good luck.

[Veselin Kolev]

Oh, and just something I had to calculate out of curiosity:
Direct drive from the CIM motor to a 7/16" diameter wheel, you'll get 10 ft/sec!!!

[tenfour]

The CIM motors work great to drive alone. We did this one year and found them to be very smooth. The downside is that they are very fast.

To calculate how to gear them down, you need to do a few things. First, decide how fast you want to move and how much force it will take to do it. Then, take the distance around the robot wheel. Knowing this, you can calculate the required rpm of the wheel shaft. Take that speed and compare it to the CIM motor. It will ikelt be many times, so you will have to do a multi speed gear reduction. This will include possible coming out of the CIM with a large gear, then attacking the large gears shaft to small sproket. Then you would attack the small sprocket to the wheel shaft (most likely with a large sprocket on it).

If you have any questions, e-mail me at cdk@1stnetusa.com

Good luck from 696!!

[Joe Johnson]

Originally Posted by Andy Baker

CIMs will work well. Just keep in mind that many of your opponents will be using BOTH the CIMs and the Drills, or maybe CIMS and F-Ps to drive their 'bots.

There are some a good discussions about the merits of shifting vs. multimotor systems on these fori.

Search for "shifting transmission" or "mutli motor drive"

Joe J.

[Jeff Waegelin]

My team drove our robot with the CIM motors and a custom 2-speed gearbox the last two years. It worked out pretty well. The main advantage they have over the drills, that I've seen, is that you can get into a pushing match, and the CIM's won't overheat nearly as fast as the drills will. That might not be a big concern this year, but it helped us the last 2 years. We never once had a CIM overheat and need to be cooled after a match.

[falconmaster]

Originally Posted by MechaJag

We're fairly new to the game of robotics and everything that goes along with it. One question we have is: Are the CIM motors a good motor to run your entire robot off of. We were planning on using the CIM motors this year instead of the drill motors. We had a ton of problems with the drill motors last year. Are we going to have to gear the CIM motors down to run two wheels off each motor? Will the CIM motor be efficient enough to pull two wheels? Any help would be greatly appreciated.

You need about a 30 to 1 gear ratio to get a good drive of off the CIMs and then use the 2 to 1 gear box provided by first to come close to the drill's 40 to one and 2 to 1 gear box. The CIMs are hard to overheat