Cooling the PTC's within the motors...

I know it’s in the rulebook somewhere, but It’s just a quick question, so i won’t bother to quote directly from the rulebook. I believe the rule states that Motor modification is strictly prohibited…

In the competition, many, many teams burn out their motors in a match, So my question is would it be legal to drill a small hole in the motor that is close to the PTC, so we can cool it with “Air Duster” or compressed air after a match?

This would not Directly interfere with the motor’s threshold of power, it would just be restoring it quicker than the estimated time of roughly 30-40min (at least for us).

Thanks in Advance!

I think you may be looking for the Q&A Zack:p…

It has not been legal in the past, but I am in full support of it becoming legal now. I can’t think of a good reason why it shouldn’t be as long as the rule is specific that this would be the only legal motor modification. Almost all teams have access to a drill so it isn’t a matter of funding/richer teams having an advantage.

I think allowing this would be in the best interest of everybody.

Similar things have been asked in the Q+A in previous seasons.

Modifying the motor housing to help with ventilation is definitely not legal.

I should also point out that if your goal is to selectively cool the PTC then you’re hindering the ability of the PTC to do its job. Your goal in this situation should be to cool the motor.

This question would violate the Q+A usage guidelines, because the answer is in the manual:

Lobbying for changes to well-defined rules is not really what the Q+A is for.

Hmmm, Ill think about it, but for now i like unofficial…

Yes i have cooled motors (outer housing) in the past, but when you’re in eliminations, theres always that chance of it not being cooled properly or something…But then again there’s always a chance right? In my opinion i just believe that directing the cool air more directly, will decrease the wait time for gain-back of optimum performance, and it would be nice to have… and I thought it had been answered before, but just thought i would double check if anything had changed.

I don’t have a motor with me at the moment, but if my memory serves me correctly, are the motor and PTC not directly adjacent? Attempting to cool the PTC would cool the motor as well. When you cool your PTC with whatever you’re using, you’re cooling the motor at the same time.

Being able to drill holes in the motor housing could definitely lead to getting better performance out of overheating motors. The relevant component inside the case though is the motor and not the ptc:

The big silver thing, not the little yellow thing.

There are a couple of downsides to letting teams drill holes in their motor cases for this purpose:

  • It could slow down events as teams spend time cooling motors in preparation for matches. Anything that increases prep time slows down match cycles.

  • If one team does it and it works well, every team would have to do it to avoid losing their competitive edge. It would add an extra layer of complexity and cost to competing.

  • A lot of Vex is about working within a set of limits. From a competitive point of view it doesn’t really matter where those limits are set, because everyone is on the same level. Change the rule and you’re back at square one but with cooler motors.

On the other hand, if teams were able to cool off motors more quickly then events could run tighter eliminations schedules with less down time for robots and potentially fewer time outs. And motors might last longer.

Well from what i Know it is the PTC that heats up before the motor, and by cooling the PTC, you would also be cooling the motor much more efficiently than just cooling the plastic outer casing. Let me elaborate; if you spray at the PTC, then some of the coolant will go around the PTC and also cool the motor, plus it would be more effective because there isn’t plastic in the way to stop some of the thermodynamics that should be happening. Again, just my thoughts.

Hummmm… never thought about this issue. My first feeling tells me that it is illegal.

Although I do think VEX should design holes on motor shell. Just common sense, your motor can cool faster and easier.

I know PTC sometimes can be annoying, and some of us do think that we can push the motor to a higher limit when it comes to overheating. But I have always accepted it as a rule. I agree that we need to learn to work under limit.

It seems to me though that we are missing the point of vex robotics at this point in the conversation. The point is to perform well on the field using the vex design system, and any legal components there of so it seems to me that we need to back up from this post and look at what exactly we are doing. Saying we need a new way to cool down the motors (which I have tried and it works fairly well) is like saying we need a new size limit to make it easier to score, this is all part of the challenge. However there are certain things that can be done,

  1. know that just about any robot over 13 lb and with 4 motor high speed will have risk of overheating easily
  2. know all the rest of the general rules of thumb like this
  3. use designs and driving techniques to keep the motors from getting warmed up in the first place, eg. chaining the motors together for more even distribution of load, using helpful software such as slew rates and Smart motor library, and just not jamming in reverse as this draws double current as opposed to the hitting of a stable object.

all of these things we fought last year but found that you can stretch the capability of your motors considerably if you try and find ways to keep them from getting hot in the first place.

One last thing, as Zack said people are going to cool down there motors through the casing, which will make teams that don’t do that lose there competitive edge even without breaking the rules, so for all the reasons I think that people need to find new and innovative ways to stay ahead of the heating curve.

Hey 26,
I completely, 100% Agree, and it seems as if the community is split on this topic, 50/50. I just feel that if there is a more effective way of doing something, we should be allowed to do it.
And yes i can understand that if this is ruled as legal, then some teams will be at a disadvantage, but isn’t that in the spirit of VEX? To learn from experience, and others? Some people may feel that it is unfair, but me personally i believe it will cause the level of competitiveness to increase by a far margin, and cause teams to learn more about the design system. Not meaning that VEX is not already competitive, but we will be increasing it. I remember when i was a rookie team and i looked up to all of the better teams, and went up to practically all of them and used to ask why they were so good, and the answer was always something small, and unexpected, such as cooling the motors, or actually having charged batteries :p.
But, not to sound contradicting (well i kind of already am :)) but i am already on board with learning how to cope with the burn-out problem. Let’s face it; burnout’s have caused teams to lose matches, that weren’t supposed to be lost, and they’ve also have been surprised that they didn’t burn out. I do feel that we are already learning how to somewhat cope with this issue, but i know some teams will just buy new motors, and some new batteries before a competition, which causes them to have a greater advantage. Thats not illegal, but it increases performance by a HUGE margin, and i mean HUGE.
All were talking about is a little hole on each motor, that will just restore the full capacity of the motor. Nothing drastic, just a small tweak.
Not to sound mean, just expressing an opinion.

Probably not really the best idea, as dust, dirt, and water in the motors and internal gears would probably have a considerable effect over time.

Capri sun pouches are a simple alternative. Put cold Capri sun pouches on motors between matches

I like this solution a lot. It reminds me of drilling holes in brake rotors on sports cars to cool them.

+1 to vent holes!

I do not support this idea, however…

I do believe it is a worthwhile experiment for someone to test this theory and demonstrate one way or the other if in fact it makes any difference. You have all made an assumption that a small hole helps with cooling, I would like to see some evidence supporting this.

Which IIRC actually has no effect at all, it’s just cosmetic, I need to try and find the tests one of the motoring magazines did a few years ago.

Insert my picture into here… :facepalm:

OK, the vents in the brakes help with the heat more than the drilling… Sigh. Do spinners not help the wheels either? :smiley:

However on the Vex motor, wouldn’t airflow increase the heat transfer into the air from the PTC making its times between trip conditions tougher? (two holes are needed I guess so you get flow and not an eddy swirling about) Canned air comes out at -13F (from wikipedia so take that for what it’s worth). It would seem the increased flow plus the lower temperature would cool the surface of the PTC rapidly. Cooling the wires would probably have the best heat transfer properties on to the internal parts as metal transfers heat much better than air. Having a cooler shell may not help the PTC that much in performance.

Normal air flow would help somewhat, but putting cold items on the external plastic might not get the internals of the PTC cold much more rapidly (which is the only part that matters for a motor trip.).

Do you still have that infrared camera you used on the PTC tests in the first place? Should the test be under a heavy torque load known to eventually trip the PTC versus a held/stall test?

This is the assumption (which is not unreasonable) that we are making. But does it make a practical difference if there is a 5 minute break between matches? I don’t know. Turn the air can upside down and spray liquid propellant (even colder), would that be legal? I’ve lost track on whether using canned air on the outside is legal, it didn’t used to be but then I think there was a rule change last year allowing it, not sure on that.

Technically not (changed jobs), but I could borrow it.

Whatever the outcome of testing, I still think this is a dangerous place to go and we should just leave the motors alone and use them as they are. Everyone has the same equipment to work with, I don’t see the problem, just design within the guidelines.

Spraying canned air on the motor was ruled legal last year. It was never really demonstrated if/how much it helps, but it was legal.

Perhaps there is a market for peltier junctions that clip on to VEX motors right after a match. Put a heat sink on one side of each junction, and start actively cooling the case.

Or just bring a bar fridge to your pit and stuff the robot in there.

Or perhaps design your gear ratios so that you don’t overheat the motors. Nah. Where’s the fun in that? :rolleyes:


Spraying the motors helps tremendously! We used just a regular air duster can held upside down. We used this during the finals to help keep our robot from over heating and it worked great! A good 15-20 second spray will bring the external temperature of the motor to about 45° F. If you look at the picture in post #6 its shows that the PTC (the small yellow object attached to the motor) is very close to the outside of the case so it also cools that down as well but not sure by how much.