Hi, folks. I just swapped out the high-efficiency Mabuchi 365-size motor (direct drive) in my transport for a geared 280 motor, increasing my torque and hopefully boosting my ship's resistance to weeds. Well, the torque has gone up significantly, but so has the heat. The new motor heats up over time. This is a new phenomenon to me, as every motor I've used previously does not heat up. So I'm wondering, how hot do your motors get? How hot is too hot? And if it does get too hot, what can I do about it?
The smaller motor gets hotter because to do the same work, it operates closer to no-load torque, so the current drawn is greater (relatively speaking i.e. as a proportion of its rating), and it heats up more. Your motor can get hot enough to cause insulation breakdown, and after that it gets very ugly (short circuits in the motor, which can lead to melting insulation elsewhere, if one doesn't have fuses on the motors). The official Navy electrician's guide to 'how hot it too hot?' is: touch the motor casing with your hand. If it's too hot to keep your hand on, it's more than 140 degrees F, and therefore too hot. Call the mess decks and get the off-duty electricians away from the movie to come start troubleshooting. They've seen 'Bordello of Blood' too many times anyway.
Isn't the 280 a smaller motor? I would use a bigger motor geared down. But then I have 550-size motors galore
if it's exceeding 140F, it better be a killer sink. Maybe a pump-driven cooling coil around the motor. Not the DC pump, one that runs allt he time, that has water all the time
Motors heating up generally isnt good but Tugboat is right it in that it depends on how hot it gets. Back when I was driving my cruiser I destroyed a number of motors due to overheating them. At NATS in 2003 I was packing ice on top of the motors to help keep them cool, otherwise I would burn up a motor after about 3 battles. Anyway if you're overheating your motors its normally a sign that you're wanting them to do more work than they are happy doing. Going back to my cruiser it had crappy stuffing tubes(poor alignment so there was excess friction) and I was running a poor gearing ratio thus forcing my motors to work to hard, but I digress. If you motors are just warm to the touch after a sortie I wouldn't worry to much about it. However if they are blazing hot I would suggest changing your gearing ratio, using more powerful motors, smaller props, etc.. to reduce the load on your motors. You can watercool motors pretty easily too if you want to go that route, it doesn't solve the underlying problem but it does keep the motor from getting to hot. An inlet port somewhere infront of the motors in your hard area below the waterline(duh) and then an outlet port right infront of the props will let the suction from the props draw water through the system. Or you could put the inlet ports in the hard area in the bow and let the dynamic pressure from moving forwards push water through the system Ive done that to watercool ESCs and it works.
Or, alternatively, if Snipe's method is too much work, you could just run for a few minutes then get sunk, cooling the motors very effectively.
The motor I am using is the: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXWK50&P=0 with gearbox: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXVY65&P=M Several other big gunners are using geared 280 setups in their ships, and I decided to try one in my testbed ship. The heating process itself is rather slow, and while it does reach very high temperatures, it takes a long time to get there. I am taking it to the pond today, to test things out. If I need to, I can try a heatsink: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHHN6&P=M and if that isn't enough, I will ask again about water cooling. And if it's REALLY bad, I can just switch back to my old 365.
My Yamato runs hot with a pair of J-600s geared down but I use cooling coils and water pick up tubes and the system has performed flawlessly keeping my motors cool for the last 9 years.
I took the ship to the pond today. While I didn't get any chance to test its weed-munching ability, I did discover a tighter turning radius, at least one ship-width smaller. I also discovered that, after five minutes of continuous sailing, the motor was quite hot. After 5 minutes of cooling down, it was cool again. Sail it for 10 minutes, and while I could still hold the motor without getting burned, it was not far from that point. I am ready to try some form of cooling. So here's the question. Are there any pre-made water-cooling coils for 280-size motors? If not, how do I make a water-cooling coil? Pictures of installed water-cooling systems would be appreciated, as well. I'm going to try an aluminum heat sink first, but I want to be prepared in case that doesn't work.
I make my watercooling coils by taking Aluminum (or copper but its easier to get aluminum) tubes and crimping one end. Then I slowly and carefully fill the tube with salt using a "ram rod" every so often to make sure the tube is packed solid and there arent any large air pockets. Once the tube is totally full of salt you can easily bend it around the motor to get the correct size coil with out it kinking. Once you're done just empty out the salt or use hot water and dissolve it out, using something can force water through the tube helps. Im sure there is an easier/better way if you have the right tools, but this way works if you dont.
sand also works well for tube-bending and for small motors, i think it's easier to do it Snipe's way than to try to get a tight-radius bend, consistently. Important because we really really want max contact area between the motor casing and the cooling coils. Has anyone tried used some kind of metallic paste to increase the contact area? Kind of like we do with CPUs and heat sinks?
Ive used thermal compound on water cooling for ESCs but not for motors. Thats the best way i could think of to get really good contact between the water tubes and the ESC heatsink.
