Does motor temp affect performance?

[Conor Ryan]

Going back to the problem at hand.

Originally Posted by Joe Johnson

By the way, your gear ratio is probably not high enough but that cake is already baked. From what I saw of you at the MSC, you guys are doing just fine with the too tall of gearing you have. You just need to make sure your motors are cooled down between matches and you'll do fine -- next year, consider a bit more ratio ;-)

If you have the ability to do it, gear down your motors a wee bit. All of these high temp scenarios can lead to some ugly consequences in the heat of competition (pun intended). You really are playing with fire (also intended).

[JamJam263]

Originally Posted by Conor Ryan

Going back to the problem at hand.



If you have the ability to do it, gear down your motors a wee bit. All of these high temp scenarios can lead to some ugly consequences in the heat of competition (pun intended). You really are playing with fire (also intended).

I can defiantly agree with that. We burned out a couple CIMs and ended up blowing out a victor. And I don't mean that beautiful magic smoke. They had to get the fire extinguisher because the fire was spreading down out electronics board. Defiantly an important lessoned learned.

http://www.youtube.com/watch?v=hJMuKH9WkZo

Granted we really did push the CIM way way too far with that design.

[Ether]

Originally Posted by Conor Ryan

If you have the ability to do it, gear down your motors a wee bit. All of these high temp scenarios can lead to some ugly consequences in the heat of competition (pun intended). You really are playing with fire (also intended).

And the irony is, more often than not you will get better performance AND less heating with a properly-geared system.

~

[sanddrag]

Originally Posted by Don Rotolo

Avoid bundling wires up too tightly; allow some space around them for cooling.

If the wires are heating to the point where they need cooling, something else is wrong. Circuit breaker not tripping, too small of gauge, etc.

[EricVanWyk]

Originally Posted by sanddrag

If the wires are heating to the point where they need cooling, something else is wrong. Circuit breaker not tripping, too small of gauge, etc.

Actually, I have to agree with Don here.

Take a look at http://www.powerstream.com/Wire_Size.htm - The rated currents for Chassis (unbundled) and Power Transmission (bundled) differ by about a factor of two.

Tight wire bundles can have an effect. I usually tell students to put it on the "nice to have but don't panic about it" priority level. I just don't recommend that teams put their entire power flow through those wire guides.

[Al Skierkiewicz]

For those of you that are interested, the tables that Erik has linked to are also derived from the National Electrical Code and in some locations, the NEC is the rule rather than local codes.
The transmission numbers derive from voltage drop in the wire for different currents. The desire is to have less than a specified voltage drop for a given wire length. This insures that your wall outlet maintains the 110 or 120 volt output when you plug in a toaster, space heater or hair dryer.
If Art Dutra happens to lurk by, he could be more specific than I on this subject.

[Damaku250]

Hm. After frying a CIM at Waterloo, me and a teammate were discussing something like this, and as paintballers we discussed the possibility of spraying liquid CO2 onto the CIMs after every match or so. Would this work? Or is there something special about the freez-it spray?

[Al Skierkiewicz]

Craig,
Freez spray or CO2 work by evaporating from the hot surface and taking some of the heat with it. Unfortunately, the heat is inside the motor, stored in the steel armature and windings and to a lesser extent in the case and magnets. If teams use this approach they must also be aware that making cold surfaces in Atlanta humidity will bring about condensation. Water may not be a desired effect if it drips into controllers or Crio.

[Joe Johnson]

Originally Posted by Damaku250

Hm. After frying a CIM at Waterloo, me and a teammate were discussing something like this, and as paintballers we discussed the possibility of spraying liquid CO2 onto the CIMs after every match or so. Would this work? Or is there something special about the freez-it spray?

Cool is cool.

The thing I like about the Freez-it stuff is that it comes out as a liquid if you hold the can just so and spray with the right velocity. This is important (or rather, nice) because it lets you direct the coolness right to the bits you are interest in.

For example, if you want Thing A cool, you drizzle some liquid out of the Freez-it (or equiv) and onto Thing A. Thing A causes the liquid to boil, which sucks heat out of Thing A like mad (it is a phase transition thing -- gobs of energy are required to go from liquid to gas).

I have no experience with CO2, but I don't THINK it comes out as a liquid but again, cool is cool. Expanding CO2 takes energy (though I don't know how it compares to the liquid->gas transition of Freez-it) and that energy comes from the surrounding environment. If you can control the CO2 such that you can get the heat out of a particular part or group of parts, it should work fine.

Joe J.

[Joe Johnson]

Originally Posted by Al Skierkiewicz

Craig,
Freez spray or CO2 work by evaporating from the hot surface and taking some of the heat with it. Unfortunately, the heat is inside the motor, stored in the steel armature and windings and to a lesser extent in the case and magnets. If teams use this approach they must also be aware that making cold surfaces in Atlanta humidity will bring about condensation. Water may not be a desired effect if it drips into controllers or Crio.

Very good point. I recall that the motors can get a bit frosted if you cool them too much in the humid air of Atlanta. The good thing about the CIMs being a closed can I guess is that the water won't get inside the motor but you need to be sure not have any dew drops drip onto Victors, Jags, and/or crios.

Joe J

[Damaku250]

Originally Posted by Al Skierkiewicz

Craig,
Freez spray or CO2 work by evaporating from the hot surface and taking some of the heat with it. Unfortunately, the heat is inside the motor, stored in the steel armature and windings and to a lesser extent in the case and magnets. If teams use this approach they must also be aware that making cold surfaces in Atlanta humidity will bring about condensation. Water may not be a desired effect if it drips into controllers or Crio.

Shouldn't be too bad I suppose, we only have our pneumatics tanks around the CIMS...

What I meant was that the freez it seems to be "antistatic" or something, and I read on their site that it's non-frosting, so i was wondering how important these features were.

I figured if you attach a Co2 tank to the reciever valve and turn it upside down, you should get liquid as most tanks aren't anti-siphon.

[Ether]

FWIW:

http://www.vapco.com/prod_freezeitspray.html

Freez-It contains menthol, camphor, eucalyptus oil, and isopropyl alcohol.

Menthol, camphor, and eucalyptus oil are mostly harmless in small amounts, but have a strong odor. Same ingredients are in Vicks Vapo-Rub that Mom used to rub on your chest when you had a cold (oops, am I showing my age?).

Isopropyl alcohol, unlike ethyl alcohol (the drinking kind) is toxic if ingested or inhaled in sufficient amounts. If you get an unexplained headache that should be a warning sign.

Get enough folks using that indoors and it may get banned. Although I suppose the venue at Atlanta is large enough it might hardly be noticed?

CO2, by contrast, is relatively safe, except for the stored-energy concerns.

If you've got enough room around your CIM, try attaching an aluminum or copper heat sink with lots of surface area (fins).

[Alan Anderson]

Originally Posted by Ether

If you've got enough room around your CIM, try attaching an aluminum or copper heat sink with lots of surface area (fins).

With or without the additional surface area, airflow is key. You want to get as much hot air away from the case as you can. The earlier suggestion of adding a fan is a good one.

[Andrew Schreiber]

Originally Posted by Ether

FWIW:
If you've got enough room around your CIM, try attaching an aluminum or copper heat sink with lots of surface area (fins).

Heatsinks do have an effect, in 2008 we attached one to our compressor to help it stay cooler during long practice periods. It worked but only because it was mounted in such a way that at speed our robot's motion caused airflow over it. Heatsinks aren't helpful because they provide extra thermal mass they are helpful because they provide a lot of area to dissipate heat from.

Either way, you are addressing a symptom and not the issue. 1918, my suggestion would be double check your transmissions, make sure they aren't binding anywhere. Double check your wiring for any loose connections (loose, not out). If you can you might want to tweak your ratios a little bit. Obviously THAT may not be feasible. Perhaps replace your fuses too. They might not be tripping when they should. I know no one wants to pop a fuse but they are a safety precaution, burning a motor or starting a fire is much much worse. Plus if they pop you know you did something wrong. Perhaps try replacing the motors too.

Next step would be adding the fans/heatsinks/CO2 baths to alleviate the symptoms until you can figure out the root of the problem in the offseason.

Worst case, ask your driver to tone it down a bit.

[Ether]

Originally Posted by Alan Anderson

With or without the additional surface area, airflow is key. You want to get as much hot air away from the case as you can. The earlier suggestion of adding a fan is a good one.

Yeah, a fan is probably the first thing to try.

But the converse is true too: with or without fan-forced airflow, surface area is key. So if more cooling is needed, adding a heatsink could make a big difference.