As has been mentioned by Andrew Palardy and others, a heat sink will probably have relatively little impact on the motor winding temperature over the course of a 2-3 minute match... See Richard Wallace's data for evidence regarding that (note how, during the test, the motor case temp only rises by about 5-10degC).
Where I do think a heat sink would make a difference - and I think it would - is when you put the usage in the context of practice, elim matches, or short match-turn-around (i.e. districts or off-season), etc. The internals of the motor can't be cooled below the CIM case temperature... so as the external motor housing climbs to higher temperatures, so also do the minimum and working internal temps (since under same power output conditions, the same deltaT will be maintained from motor windings to CIM case).*
So, I definitely recommend that teams consider how to cool their CIMs! I know I'd like to work out a way to put a heat sink solution on our robot!
I haven't used the CIM COOLERS but they look like a neat solution... I do have a few comments about them though:
-The linked video test is neat, but running at free speed is fairly low heat output (32W)... At max power they dissipate 477W, and at stall they dissipate a mind-blowing 1596W**! At only 32W, simply adding aluminum to the case to hold more heat for a given temp increase would have a beneficial impact.
-Heat sinks rely on air taking the heat away... hence the fins. Without a fan (forced convection), it relies simply on the air moving around... which is driven by the fact that air becomes lighter when it gets hotter. In the test the fins are vertical (ideal), while on almost all robots they are at all angles (vertical, horizontal, upside-down)... this means its effectiveness will be significantly lower when mounted horizontally, particularly in a cramped robot.
- If teams use the heat sinks, they should definitely apply thermal paste (I've had experience with silicone grease and other gap fillers... i.e. http://www.bergquistcompany.com/ther...roperties.htm). Interfaces are tremendous thermal insulators... applying a little thermal paste and then bolting the heat sinks together firmly enough so that paste squeezes out will help tremendously. With many Watts being dumped through that interface, you could have a huge thermal rise just in the interface (let alone the motor internals). I wouldn't be surprised if using the CIM COOLER with no thermal compound gives little or no benefit. If you do use a thermal paste, I highly recommend the blue stuff from Bergquist... compared to grease it's extremely easy to cleanup!
So, I would recommend investigating a CIM-cooling solution... but putting some big muffin fans on there to run while the robot's on or off may go about as far (note, the robot's usually on the cart far more than it is powered on). You'll likely want fans somewhere to force the air around, rather than relying on free convection.
*If you're interested in a tidbit about heat transfer... it works the same way electricity does. In electricity, a Voltage drop (i.e. deltaV between two battery terminals) drives/pushes electrical current (I) to move against electrical resistance (R). Similarly, a Temperature drop (i.e. deltaT between CIM internal and CIM case, then between CIM case and ambient) drives heat to move against thermal resistance.
** Note, 1596W is nearly as much as an oven puts out, and well over that of a microwave! Now that certainly motivates me to cool my CIMs and avoid stalling them!