We’ve been starting to have consistent drive practices, and our drive motors tend to get really hot(especially the 550s). After running the robot for 45 minutes we’ve been having to take breaks to let the motors cool. Considering we have been running 2.5 hr drive practices, this can get annoying, not to mention less effective because the robot doesn’t drive as well as it did initially(incorrectly simulating real world drive conditions). I was wondering what tips people have to cool the robot off. We have been considering adding fans, but I was wondering what other ideas people have. Something offboard that we could use while we are switching batteries would be nice too.
971 puts big ol muffin fans right over their drive motors every year. From what I’ve heard, they cool down the motors pretty well in practice and elim matches. I’ve also seen 1323 just blow a regular plug in fan into their robot between elim matches while charging their tanks. A lot of teams (like 254) turn canned air bottles upside down and then spray them on their drive motors. This really does cool motors down quickly, but is quite wasteful environmentally speaking.
We’ve always just grabbed some cool gel packs from the fridge and wedged them on top of our compressor and between out drive motors. It’s a sort of janky fix, but it’s mobile, quick, and works pretty well.
For one you should probably be taking breaks, its good for the motors and every part of the system. Probably good for your drive team as well so they can discuss what they are doing well and what they need to improve on. No use in just running a lot, if you’re not actively getting better.
However if you need to you can blow canned compressed air into the 550s. We did this on our shooter after each match to keep them running consistently. At one point we had to go down the University of Arkansas bookstore to resupply during Razorback. We would see the difference in the shots when the motors were cooled and when they were still hot from the previous match. Also you can get cheap RC car heatsinks and they seem to help a little though not as much as the canned compressed air.
Instead of using cans of compressed air you could use a vortex tube for cooling. http://www.stream-tek.com/products/vortextubes/buy-vortex-tube.php
They use a pressurised air supply to generate very hot and cold air
When using canned ‘air’ upside-down, remember that the ferrite magnets react a lot like glass when subjected to rapid cooling. They shatter.
What Roger said,
We use two fans that we put on the robot. One normally goes on the drive and the other one to other systems that get hot.
Our battery will last us about 3-7 minutes before it dips below 12V. So a part of our routine is to:
-Put fans on the robot
-Fill up air tanks
-New Battery
-Fix anything broken (hopefully nothing!)
The 971 method of putting permanent fans is also a great solution, we’ve been wanting to do it for years but we for some reason don’t… Probably cause we are lazy.
-RC
It is really easy. Just bend a flange off the gearbox plate and add some mounting holes to that. Or you can zip-tie them around the CIMs without doing any engineering if you really want. We put small fans on all the other motors which heat up.
Do you just use 1 large fan from the kits per 2 CIM motors, or do you have a special setup?
You can only use fans from the kit, so we just use the 2 large fans with one per side as you guessed. The 3rd CIMs this year did not have a fan.
We added 2 permanent large fans to the drive motors today. We didn’t get to test them out because we were working on adding a couple other things for Fall Classic this Saturday, though they seemed like they will work very well. I don’t think we will be able to test it for drive practices before then, but we’ll get to test them in competition/elims on Saturday. We also purchased a couple compressed air cans to test those out too.
These are useful in industrial environment, but they are energy pigs. They use a lot of air.
Am I really the only one?
In 10+ years of FRC experience, I’ve never found a need to actively cool a CIM.
Their cases are pretty good heatsinks all on their own.
Only once in my FRC history can I remember killing a motor due to overheating, and that was a 550 used as a drive motor (the only drive motor on that wheel) in 2009 at the Waterloo Regional when I was with 1075. It was actually pretty spectacular, watching that robot drive around the field trailing a stream of smoke until the field crew made us E-stop it (the robot was otherwise operating just fine). I should have a look and see if I can find video. (Looking at TBA? I think it must be one of the 4 missing qualification matches.)
To me, the better question is why are you using 550’s in your drive, particularly with the advent of the miniCIM and BAG motors in 2013?
This is one of those problems that needs multiple solutions…
The armature dissipates most of the electrical losses in DC brushed motors and only connects thermally to the exterior through the end bearing surfaces and convection within the motor.
CIM motors have no way to cool the parts that get really hot. Even dropping these in cooling liquid will do little to remove that heat. The motors are generally intended for intermittent use, originally designed into trailer lift mechanisms.
The 550 and similar motors (like the previous FP motors), are designed to have some cooling air move through the motor from one end to another. Some designs will include a small but inefficient fan near the commutator to help move air. If you block the end where the mounting holes are located, no air will flow through the motor. Blowing air onto the motor frame with a small fan will help but it will not get cool air into all of the motor. Look carefully at the motor and be sure to keep all openings free to move air in your designs.
My recommendation is to practice for 30 minutes and cool down for at least 15. Use the 5 second finger test to determine the actual length of time needed. If you can keep your finger on the surface of the motor for at least 5 seconds, it is likely cool enough to continue. The robot is talking to you, you really just need to listen to what it is saying.
The 6 CIM drive rally helps us accelerate better. We modified the backplate for the WCP DS gearboxes, so we couldn’t fit a mini CIM. Bag motors are significantly less powerful than 550s. Bags are about 150 watts. 550s are 250 watts.
But why would you use 550s for that purpose over 775s?
What gear ratio are you using? 550s have a free speed of 19,300 RPM. They need much more reduction than a CIM would. Without the additional reduction you are overloading (and overheating) them.
We are running the 550s on a 4:1 I believe(might be a 5:1, I will check later). We chose 550s over the 775s because we didn’t want to deal with the case shorting problem.
We cook CIMs in drive practice, we’re planning doing fans for the next season.
For the speeds we gear, in back to back elims we also get a little hotter than we like. We aren’t failing CIMs, but it’d be nice if they were cooler.
There is also nothing inherently wrong with adding a 550 alongside two CIMs. Many teams avoid 775s because the widespread case shorting issues in 2011. It seems like they’re failing at a low rate now, but many teams will likely never use them again.
Be a little less deadset in your own thoughts, and a bit more accepting of what other people are doing.
Yeah, extended drive practices can really heat CIM’s up.
When we run a series of practice matches, or back to back elims, or just trying to repeat maneuvers over and over again, it can take some time for those to cool down. I’ve heard some teams use ice packs, not the most elegant solution but it seems effective.
Is there an additional reduction due to sprockets (chains) or pulleys (belts). What diameter wheels?