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How many rpm's is manageable for an FRC robot? And also, does anyone know the speed reduction in a 2007 KOP transmission box.
Basically I'm trying to figure out whether a KOP transmission box is provides sufficient speed reduction... And sorry for the multiple questions, but is it possible to mount a wheel directly to a globe motor? (specs)
or are globe motors more for arms and lifters?

thank you! :]

Math error: see post below.

Quote:

Originally Posted by neoshaakti (Post 659340)

In general the KOP transmission does not provide enough reduction to directly drive your wheels without an additional chain-sprocket reduction.

However, there are sprockets provided in the kit (2007) for this purpose, which will give you enough of a reduction to drive at a reasonable speed.

You could mount a wheel directly to the globe motor, but it is not a good idea for two reasons.

Reason one: Globe motors are more for arms and mechanisms like you said, rather than drive motors. They rotate at about 90 rpm, iirc, which is very very slow for a drive system. In addition, they need to be geared down further to provide any sort of torque.

Reason two: Globe motors are notoriously bad at handling side loads. Mounting a wheel directly to the output shaft is asking for trouble, as eventually the motor will go bad.

In general, the drive motors in the KOP consist of the 2 small CIM's, the 2 large CIM's, and the 2 Fisher Price motors. You'd have much better luck using any of these.

Quote:

Originally Posted by AndyB (Post 659345)

Depends on the wheel size. The KOP Transmissions have gear reduction of 12:1 and kind of set the standard for speed reduction. I believe on a 6" wheel with the KOP transmission (which has an output RPM of 292.5 with small CIM motor), it would give you around 7-8 FPS.

I don't believe this is correct. Assuming it has a 12:1 reduction, it outputs ~442 rpm which works out to 11.6 ft/s with a 6" wheel.

Quote:

Originally Posted by Cory (Post 659346)

You could mount a wheel directly to the globe motor, but it is not a good idea for two reasons.

It has been done. 330's 2002 robot used them to drive a mini-robot for extra points. However, that was maybe 4lbs of metal and wheels. More than that I wouldn't do. (We also used them on an arm in 2004--we used two of them for that particular arm.)

CIM Motor RPM = 5310
Reduction = 12:1

Reduced RPM = 442

How'd i mess that one up... :confused:

6 * 3.1415 = 18.849" circumfrence

18.849 * 442 / 60/ 12 = 11.5 Feet Per Second

Wow, must have hit the wrong button somewhere. Thanks Cory.

Quote:

Originally Posted by AndyB (Post 659356)

Remember that this calculation is for the CIM's free speed. The motor will never achieve that speed on a robot because of load, so the actual output speed is probably something closer to 45/50% of this.

Quote:

Originally Posted by Cory (Post 659346)

However, there are sprockets provided in the kit (2007) for this purpose, which will give you enough of a reduction to drive at a reasonable speed.

hmmm so according to AndyB, the reduced free RPM's or a 2.5'' CIM motor would be 442 rpm...so how much more reduction would a sprocket provide?

That depends on which sprockets you use, but 2:1 reduction is typical.

actually lots of RPMs do the work for our team- our Raider Parent Mentor organization....

Quote:

Originally Posted by Wayne C. (Post 659443)

actually lots of RPMs do the work for our team- our Raider Parent Mentor organization....

haha very funny Mr. Cokeley :P
just wanted to let you know that this question is a result of the KOP gear box you lent us...thanks a bunch :)

Something like this inexpensive digital tach might be useful for measuring and calculating a robot's actual top speed:

http://www.meter-depot.com/tacho.html