2 CIMs -- practical?

Looking around these forums, I have seen a lot of teams complaining that they cannot use the 2-motor transmissions from past years. Also, every drive setup I have seen this year uses a 2 motor transmission. I am wondering if using 2 CIMs with the new transmissions is a practical way to drive a robot, seeing as it has only 1/2 the motor power of many past/present robots. I relize it won’t win any pushing matches, but can it push itself with 2 CIMs with the new transmissions?

but there are parts you can buy for the gearboxes that allow you to place two cims on one gearbox( banebots.com). and you can have a max of 4- 2 1/2 " cims
that makes for a very nice 4 cim motor robot

Teams have run for years with only 2 CIMs driving the robot. There’s plenty of power there to move your robot.

Having 2 CIMs is a little bit of an insurance policy because if something was to happen to one CIM (anything from loose wire, to victor failure, to total failure), you still have another CIM to drive with for the rest of the match.

Many teams have run off of a single motor on each “side” for years. Especially teams who are not designing to be involved in pushing matches :cool:

A one CIM Dewalt gearbox, when in low gear, can still be in a pushing match… and win :smiley:

Thanks guys, I think we’ll be going with 1 CIM per side due to weight/time/budget constraints. Just wanted to make sure we wouldn’t do the first drive test with everything installed and find the robot struggling to move.

AndyMark sells single speed transmissions for a reasonable price ($98), and the upgrade pack to use two CIMs on the kit transmission is $42.50 from banebots.com . I don’t know how well either of these options work, but you can do a forum search on them to see what others think.

If you are just using two motors, then you probably can’t gear the robot for too high a speed, or use too grippy a tire, unless you don’t care about breaking your wheels loose before you stall the motors.

If I were using traction wheels or too high a speed with only a 2-motor drive system, I’d be more worried about blowing a fuse than stalling out my motors.

When using a 2 motor skid steer (tank steering) drive system there is a number of things you need to consider.

1> Traction of your tires: too much traction means you cannot steer.
2> Wheelbase: The longer your wheelbase, the more power you’ll need to turn.
3> Pushing: most robots out there will be able to push your robot around.

To avoid some of this you can:
1> use omniwheels on either the front or back set of wheels as this lowers your sideways traction.
2> use casters on front or back (same as above).
3> use High traction wheels in the back and low traction wheels in the front.
4> Change the orientation of the frame to shorten the wheelbase.

I used to be in the 1 CIM per side is enough camp. BUT… …with the growth of motors in the FIRST KOP, the balance of powers has changed and so too my opinion.

2 CIMs per side is not a must have but it is a very big advantage. And not just in order to “win a pushing match” Yes it can help with that but I have come to believe that the #1 reason is it is a benefit is that it gives you 2 40Amp breakers to push to their limits vs. only 1 40Amp breaker. The power out of the motor (especially the CIMs) is more often limited by the current it can draw than the physics of the motor.

This double path for current is a huge help in accelerating and in turning.

I have been out of FIRST too long to know how I would really choose if push came to shove, but I may actually end up in the 3 motors w/o shifting camp.

Again, I have come to this mostly as a result of the plethera of good powerful motors in the kit. With fewer motors to pick from in the KOP, I would likely choose differently.

Joe J.

DOesnt anyone remember teh days of 1 drill motor per side?? And when CIMs were called Chipawas…lol, the good ol days.

sure do, i was in FIRST in 96-00 before going to college.

I don’t miss the Bosch drill motors and Tekin speed controls.

YEP in 96 we used the old seat motor with chain drive and 8" wood wheels had to ice the motors after each round. Dont think it would work NOW. We now use 2CIMs per side and do not have any problems. GOOD LUCK TO ALL see you sooooooon
:yikes: MOE TEAM 88 TJ2

I remember the drill motors…my freshman year of HS the 2000 FIRST season. we actually installed a couple of muffin fans on the robot to cool the drill motors ^^ Those were the (bad) old days…I like our current setup with 2 CIM’s on each side much better ^^