Compressed air for rapidly cooling motors?

[aphelps231]

I've heard of a few teams using compressed air to cool motors between back to back matches. Is this bad for CIM motors on a drive base? Is there any real performance gain to rapidly cooling motors before a match?

[troy_dietz]

Compressed air coolant is usually used in-between back to back matches (such as finals) to cool drive train or other high use motors. Electric motors preform better when they are cool, and have a lower risk of burnout. Some companies do make heat-sinks for CIM motors, which you may have seen in the KOP, but they are bulky and not terribly effective.
There is no real risk of damage, and it isn't likely that you will have to do it more than 1 or 2 times during a competition.
Students from other teams have told me that they've been doing it for years without issue.

[IndySam]

It's not the air that is cooling the motors, it's the super cold propellant that is expelled when these cans of air are turned upside-down.

Very hot CIM motors are not happy motors.

[GeeTwo]

It is interesting to note that (based on a number of posts on CD, not my own experience) that the damaging and performance robbing heat of a CIM is located on the rotor, not the stator or outer case.

The rest is my reasoning, not something proven through experience:

The rotor is only in significant thermal contact with the outer case at the bearings and somewhat less at the brushes; in each case the area of contact is limited or rapidly moving or both. There are also radiation and convection acting within the motor case.

Therefore, the most effective place to cool a CIM may prove to be conduction through the CIM output drive shaft. If your gearbox design allows it, you may wish to try cooling your CIMs by spraying their output shafts and pinions.

I am not familiar with anyone specifically trying to draw heat out through the drive shaft, but it should not be to difficult to design a heat sink that functions as its own fan and which could be attached to a CIM or mini-CIM when they are used in offset gearboxes.

[Jay H 237]

You have less of a chance damaging the motors in this case with a quick cooling off than still running them when they are hot. The CIMs and others lack their own cooling ability like TEFC (totally enclosed fan cooled) and others that have higher duty cycles. We aren't normally using the motors for what they are designed to do in normal operation so some choices have to be made.

[ctt956]

Originally Posted by IndySam

It's not the air that is cooling the motors, it's the super cold propellant that is expelled when these cans of air are turned upside-down.

Very hot CIM motors are not happy motors.

DO NOT use a canned "air" duster to cool it, especially the liquid. Spraying highly flammable liquid that gives off highly flammable fumes onto a burning hot motor near electrical stuff will not end well! Not to mention that the fumes are also highly toxic. Regular compressed air, as in what you get out of a compressor that's used for riveting/nailing/etc, will cool the motors. If the pressure is high enough, it will be cold enough to cause frostbite. Even if it's not cold, passing the cool air over the CIMs will cool them down. It's like a fan blowing on a heat sink.

[GeeTwo]

If you want to cool down your robot and aren't too chuffed about safety, here's a quick way.

[ctt956]

Originally Posted by GeeTwo

If you want to cool down your robot and aren't too chuffed about safety, here's a quick way.

Game Announcer: "Team xxxx just got a red card for using unsafe liquids and shattering a robot..."

Wait a minute...I just got an idea...anyone have a spare boulder?

[dradel]

Originally Posted by ctt956

Game Announcer: "Team xxxx just got a red card for using unsafe liquids and shattering a robot..."



Wait a minute...I just got an idea...anyone have a spare boulder?

Would be kind of interesting to see what would happen to a boulder going through a shooter after being super frozen like that

[Bob Steele]

Originally Posted by ctt956

DO NOT use a canned "air" duster to cool it, especially the liquid. Spraying highly flammable liquid that gives off highly flammable fumes onto a burning hot motor near electrical stuff will not end well! Not to mention that the fumes are also highly toxic. Regular compressed air, as in what you get out of a compressor that's used for riveting/nailing/etc, will cool the motors. If the pressure is high enough, it will be cold enough to cause frostbite. Even if it's not cold, passing the cool air over the CIMs will cool them down. It's like a fan blowing on a heat sink.

In normal canned air there is no flammable liquid. The cooling effect is simply from the rapid decompression of the highly pressurized air.
The "fumes" are just air.... when you see frost on the item that is being cooled it is a result of the cold object's reaction with the humid room air. You might also see condensed water from the air in a humid environment.

Sometimes manufacturers add something called a bitterant to the air to deter individuals from inhalant abuse. The can will tell you if it contains this material but it is not hazardous and is definitely not flammable. A common bitterant is denatonium... the name is a reference to the denaturing quality of the substance... denaturing is adding something so it cannot be consumed by humans. You can avoid this in canned air if you purchase canned air without a bitterant.

I am concerned that you are spraying something other than "canned air" which is normally used as a duster. Many things are in spray cans.... and you would not want to spray WD40 or some other petroleum based material for this use but canned air would be fine.

You want the rapid decompression to happen as it hits the motor, this super cooled air will cool the motor. Normal compressed air can work... but the cans are usually a much higher pressure and will cool more and you cannot have a compressor in your pit anyway other than the one on your robot or the one you use in conjunction with your robot to fill your pneumatic tanks.

[Ether]

Originally Posted by Bob Steele

In normal canned air there is no flammable liquid. The cooling effect is simply from the rapid decompression of the highly pressurized air.

Please provide a link where this "normal canned air" that contains only (or even mostly) pressurized air (N2 & O2) can be purchased.

[DonRotolo]

Originally Posted by Bob Steele

The "fumes" are just air....

Not exactly. Air is mostly nitrogen and oxygen with some other gases, while the contents of a can of "Dust Off" is not, instead being a mix of non-flammable gases (with virtually no oxygen or nitrogen).

The permanent magnets surrounding the CIM motor, and in contact with the case, are a ceramic material which, like some glass materials, can shatter when exposed to a very rapid temperature change. So just dropping a hot CIM into liquid nitrogen will case irrepearble damage to the CIM.

That being said, it isn't all that fragile and most cooling methods available to an FRC team are fine - just take it a little easy, OK?

[ctt956]

Originally Posted by Bob Steele

In normal canned air there is no flammable liquid. The cooling effect is simply from the rapid decompression of the highly pressurized air.
The "fumes" are just air.... when you see frost on the item that is being cooled it is a result of the cold object's reaction with the humid room air. You might also see condensed water from the air in a humid environment.

Sometimes manufacturers add something called a bitterant to the air to deter individuals from inhalant abuse. The can will tell you if it contains this material but it is not hazardous and is definitely not flammable. A common bitterant is denatonium... the name is a reference to the denaturing quality of the substance... denaturing is adding something so it cannot be consumed by humans. You can avoid this in canned air if you purchase canned air without a bitterant.

I am concerned that you are spraying something other than "canned air" which is normally used as a duster. Many things are in spray cans.... and you would not want to spray WD40 or some other petroleum based material for this use but canned air would be fine.

You want the rapid decompression to happen as it hits the motor, this super cooled air will cool the motor. Normal compressed air can work... but the cans are usually a much higher pressure and will cool more and you cannot have a compressor in your pit anyway other than the one on your robot or the one you use in conjunction with your robot to fill your pneumatic tanks.

https://en.m.wikipedia.org/wiki/Gas_duster

Note that it says they're filled with fluorocarbons. Quote from the "Safety" section of the article:

Though not extremely flammable in gaseous form, many dusters use a fluorocarbon that can burn under some conditions. As such, there is also a warning label present on some gas dusters. When inverted to spray liquid, the boiling fluorocarbon aerosol is easily ignitable, producing a very large blast of flame and extremely toxic byproducts such as hydrogen fluoride and carbonyl fluoride as a combustion product.

And what caused this if it's not flammable? Yes, a commenter said it was the CPU, but that computer was unplugged.

[Bob Steele]

I stand corrected. At our facility we are using a refillable air duster which does not contain anything but the compressed air I put in.

We also have a couple of these:
http://www.amazon.com/Best-Canned-Co...B03 7HQZK9F4W

As an aside, nothing burns in a liquid form.... it has to become a gas. Of course the concentration of the gas vapor above a liquid amount may be higher than normal fluorocarbon and if it is truly in a boiling state gas is present.

[aphelps231]

To clarify, I'm mostly referencing the second finals match of IRI in 2014, towards the end of the video you can see members of 254 spraying their motors with what looks like compressed air, in order to super cool their motors for the next match.

It had been suggested that we use the same method, since we also had thermal problems with the CIM heat in 2014 in the elims (especially finals) matches of Galileo, but we ended up fanning them with a sheet of polycarbonate since it was a common belief (on 1318) that super cooling CIMs was bad for them. I'm expecting to have more thermal issues this year, even at the PNW District Championship next weekend.