Re: 2012 motors?
 

I am going to go out on a limb here and suggest that water only needs to migrate into the space between the shaft and bearing material for a rapid bearing failure in the CIM. If premature wear, high heat and the resultant shaft runout is acceptable, then I guess the motor might work alright under water.

Re: 2012 motors?
 

Wouldn't the CIM heat up enough under load to make things kinda steamy?

Re: 2012 motors?
 

I bet that if there was water inside the case then you might have a nice steam bomb on your hands :eek: I can easily imagine steam building up faster than it could escape. On the outside of the case... not so much.

I think 95 has a bunch of older/spent CIMs kicking around... we may have to run an experiment soon. ::safety::

Re: 2012 motors?
 

Actually running motors in water to break them in is pretty common in the RC Car market....see the article below...
It is actually showing how to do it with a 540 motor...

http://www.rccartips.com/rc-electric...ning-guide.htm

your mileage may vary...

Re: 2012 motors?
 

I don't think it will steam, even if you run it to a steady thermal state (which most CIMs don't hit during a regular match). There's water outside the case that will ensure substantially better heat transfer away from the motor. Similarly, inside the motor, the windings will be submerged and will probably stay relatively cool.

Even if the steady state thermal condition was high enough to boil water, the mass of water inside (plus the mass of the motor) will have a significant heat capacity. It will probably take quite a while to reach that condition.

Do it. (The best experiment would probably be with a new one, but try an old one first as a proof of concept.)

Re: 2012 motors?
 

We have had CIMs start to have their shafts rust in a basement of our school and no we did not run them in water. I am sure running them under water would only increase the process. You also need sealed gearboxes or lubricant that won't wash away if you don't want 5000 rpm and 1lb-ft of torque (if memory serves)

Re: 2012 motors?
 

As far as I understood, the CIMs have an aluminum chassis? Correct me if I'm wrong, but if it IS an aluminum chassis, it might corrode, but it won't rust.

Re: 2012 motors?
 

But the shaft, bearings, springs, bolts, magnets(?) etc. are all steel/iron.

Re: 2012 motors?
 

Magnets are ceramic, case ends are aluminum, shell is steel as well as shaft and bearing parts I believe are sintered bronze. The armature is nickel/iron and brush assy is partly brass.

Re: 2012 motors?
 

The magnets contain iron though, correct?

I guess I should have said "the following parts probably contain iron, which might oxidize"

Re: 2012 motors?
 

In the new ceramic and rare earth mixes, I believe whatever iron that might be used in the mix is bonded with a waterproof material to prevent corrosion. Ferrite and Alnico mixes are frequently manufactured with exposed iron, and some of our motors do contain these materials.

Re: 2012 motors?
 

I'm not contesting the above, but where do you get all this information? Do you have a set of engineering drawings for the CIM?

Re: 2012 motors?
 

I have pulled a few of them apart. One was "lightened" by a team, one smoked, one was part of a direct chain drive with no external bearings that ended up with nearly a 1/4" of runout.
I do not recommend anyone open the motor if they plan on using it in the future. The brush assy is easy to damage during dis-assembly.

Re: 2012 motors?
 

Can we have the story of the "lightened" CIM please?

Yay story time!

Re: 2012 motors?
 

I dont know about the "lightened" one Al is talking about, but we shaved a few thousandths off of the side of several of our motors. The CIM's are NOT actually 2.500" in diameter, but we had designed a drivetrain with that assumption, so we made them fit by grinding some of the case away.