Which motor is better?

I was wondering which motor is good for the drivetrain? Last year most teams used drill motors (which our team found was great but they heated up quickly. This year most teams used the CIM motors (which our team found that was better because they dont heat up fast). Which motor did your team found better CIM or Drillmotor? (If your team used different motors, what kind of motor(s) was your drivetrain?)

While the drill motor had a slightly higher peak power than the CIM, I think EVERYONE agrees the CIM is a better motor. This year, we drove on four CIMS and two Fisher Prices.

what did you use the fisher price motors for?

more power in the drivetrain. http://www.chiefdelphi.com/forums/showthread.php?t=35266

kool thats awsome

Personally, I never got too familiar with the drill motors, so I can’t really choose one or the other. But, the CIM’s are heavy (more than I remember on the drills) and didn’t give us much of any torque till we ran them through our AM’s. Once we had our drive train set up they gave us plenty of torque and never generated a heat problem.

There are pros and cons of some motors… here are some I can think of right now:

Drill: Pro
-Small and light, roughly 1 pound
-Slightly more power than the CIM
Con:
-Evil, hard to find metric gear…
-Burns out a lot
-Very high rpm, so its anoying to make a reduction
-Anoying to mount, seeing as it has no screw holes
-Suck very large amounts of current when at stall

CIM: Pro
-Easy to mount, with standard screws
-Keyed output, so you can put your own gears on it
-Lower rpm, so reductions are less anoying
-Almost as much power
-Never overheats (I’ve only done it once, so its rare)
Con:
-Big, and almost 3 pounds each

FP motor: Pro
-Even smaller than the drill
-Good power for its size
-Standard pinion, so its easy to mate
-Standard screw mount, easy to mount
Con:
-Overheats and melts
-Very high rpm
-Sucks current at stall

I have personally always liked the CIMs better for drive train, but they are sometimes more useful elsewhere. Heck, if we got 8 CIMs I would use them all. But… seeing as how we dont, you gotta go with the FP motor for drivetrain sometimes, or the drill when we still had it.

If you use the drill or FP motor for anything… especially drive train, always buy a bunch of extras. When I used the drill for swivel drive, it burned out roughly every competition. We just bought 10 of them and kept replacing them.

~Veselin Kolev

sorry if this is already posted but we have a question and didnt have time to go through all 500 posts

We were just wondering if we were still allowed to use the old bosch motors and the dewalt motors

thanks

are the CIMs still enclosed?

the drill motors and FP motors have internal blowers for cooling, and openings to let the air through.

Nope, follow the flowchart. The only motors allowed are those provided in the KoP or identical CIMs/servos.

CIMs have no openings in the case, except for mounting screws, the axle, and where the wires come out. It’s the same for both types.

Not quite. The Large MiniBike CIM actually has one more small hole opposite the output shaft, on the plate holding the back of the armature.

The big one is definitely not, but is the small CIM water resistant? If you take the motor apart, you’ll notice that there are rubber gaskets between the different case parts. The only real hole that isn’t gasketed is to the output shaft hole.

There are many things that go into this, but in my opinion, based on power conciderations alone, the CIM motors are the only real choice for the drive train (with the possible addition of the FP if it is not the only motor used).

There are only 2 questions then:

1 motor per side or 2? And Which CIM motor?

If you go with 1 only, the extra power of the 330W motor and smaller size & lighter weight is too attractive too pass up. If you go with 1 motor, I recommend that you strongly consider shifting.

The question of multiple motors per side is tricker.

There are various combinations:
CIM 340W + CIM 340W = 680W
CIM 340W + CIM 270W = 610W
CIM 340W + FP 170W = 510W
CIM 270W + FP 170W = 440W

I think any of them can work but to be honest, I would stay away from the FP in a drive train because they tolerate heat and abuse less well than the CIMs.

It is sort of a toss up for me between the top two above, though I am leaning toward the 680W version.

I used to be firmly in the “1 Motor + Shifter” camp, but I have since become a believer in the merits of 2 motors per side for 2 reasons: it makes your robot peppier in terms of acceleration and it gives you two (2) 40Amp breakers to feed your drive motors.

As to shifters, with the advent of the Andymark.biz shifter and the NBD whitepaper on how to adapt a CIM to a 3 speed XRP Dewalt Drill Transmission, shifters are easier than ever to implement, even for a team with limited resources.

So…

…here is the bottom line advice, **this year’s Stylish Robot will have 2 CIM 340W motors per side + shifters.
**
You read it here first…

Joe J.

Just a side note, The torque at stall on the mini bike motor is almost twice that of the small cim. If you want to keep it simple and not shift you might consider that. And if you want it all Check out the Andy mark conversion kit to run one small cim and the large cim out of the kit transmissions.

Yes it is true that the FP CIM has 66% more stall torque than the smaller CIM, but the Smaller CIM has 97% more free speed.

Stall torque and free speed are accidents of birth. You can always trade more of one for less of the other (by gear ratios).

The Peak Power (=Tstall*Wfree/4) is your immutible figure of merit for a motor size.

For example, I can put an extra 1.66:1 gear ratio on the smaller CIM and get 1.66X the stall torque which will match the FP CIM’s stall torque. BUT, this reduced smaller CIM will be running 25% faster than the FP CIM loaded to the same torque.

I like the FP CIMs, they are nice motors that will probably run nice and cool even when abused (as they surely will be), but they have 25% less power than the smaller CIMs.

Joe J.

I agree sanddrag. Last year our team used a drill motor and it heated up very fast. CIM motors are great. :smiley:

I sure hope you didn’t use a drill motor, seeing as they were illegal last year…

MOTOR SELECTION COMMENT

To: FIRST Committee

From: Martin Kanner

Subject: Comment on FIRST kit content

As possible assistance to rookie teams, let me first introduce myself. I’m an NYU graduate with a long experience base in electromechanical and electrical feedback control systems. I have now mentored for high schools for the past four years and am presently working with Plainview-Old Bethpage. I want to sincerely thank and congratulate the FIRST committee on the kit contents for their variety of content and their sophistication which gives the students the opportunity to learn and make high level technical decisions.

This year the kit provided larger CIM motors than those of last year and an adapter to be used to couple the motor into a gear box which was also in the kit. There were comments made, which I agree with, that the use of these items would result in approximately a 20% loss in performance (torque/speed).

I believe that providing the adapter for the larger motor was misleading to high school students and does not permit them to think and come up with a good application of the larger motor. I believe the larger motor, which runs at a lower speed but higher torque could have been used by eliminating the heavy gear box assembly and replacing it with an appropriately matched, pillar block gear reduction. The students could then design and test both approaches for their application and have the opportunity to make a good decision.

I do not want the comment to be taken out of perspective. This is one small item in a kit which has unbelievable content and opens vistas in all directions for students at all levels.

any one know if you can you connect a globe motor to a spike