Why are my motors getting so hot?

[BurningArmada]

I am on the 6th or 7th version of my tricopter scratch build and have been trimming weight with each successive version but it seams that no mater how light i go, I'm still getting hot (cant keep your hand on them) motors after each flight. Sometimes they stay cooler if the ambient temp is cool but that is not too often in Texas.

Ive got the machine trimmed down to about 560 grams dry weight and 755 with a 2200 MaH battery. Im using MT2213-935KV MultiStar motors swinging 10 x 4.7 props. ESCs are Afro 20Amp controllers.

Im able to hover just a click under 50% throttle and this setup gives me TONS of trust and throttle response but the heat of the motors is freaking me out. Any issues with this setup?

Im new to the ideas of prop pitch and efficiency so need some guidance on this. The motors came in a motor/prop combo pack with 10 x 4.5 pitch props but i quickly changed them out for higher quality props from my local hobby shop. The replacements where 4.7 pitch... how big of a difference would this make? do i need a prop with more pitch. Are the motors working too hard because there is not enough lift per revolution?

Here is a pic of my machine before i buttoned it all up.


Thanks for any input!

 

[rcspaceflight]

How many cells does the battery have?

 

[rcspaceflight]

The heat is going to be from 3 possible issues. A) The "C" rating on your battery isn't high enough. B) The amp rating of the ESCs aren't high enough. C) The propeller is causing the motor to draw more amps than it can handle.

Basically the motor either isn't getting enough amps, or it's drawing too many.

Using a smaller propeller will automatically solve the issue no matter what the issue actually is. But it would be better to get a better battery or high amp ESCs if those are the real issues.

 

[BurningArmada]

The heat is going to be from 3 possible issues. A) The "C" rating on your battery isn't high enough. B) The amp rating of the ESCs aren't high enough. C) The propeller is causing the motor to draw more amps than it can handle.

Basically the motor either isn't getting enough amps, or it's drawing too many.

Using a smaller propeller will automatically solve the issue no matter what the issue actually is. But it would be better to get a better battery or high amp ESCs if those are the real issues.

Thank you for getting me in the right direction. I have 2 x 25C X 2.2 Amps batteries and 1 2 x 30C X 2.2 Amp battery. The ESCs are 20 amp and the amp rating for the motors are "Max.current(10s): 15 amps". I will pick up some 9 inch props on the way home and see if that helps.

 

[Tritium]

Motor pulling too many amps = Hot motor and possible motor / esc damage instantly or over time! Possible causes. Interference with rotation of motors....Too big a prop (too long or too much pitch)....Craft too heavy.

Info at site states 10X4.7 props on 3S so props are not the issue so carefully check for bearing issues, Clearance for bottom of motor shaft on boom or trash in the motor.

I have seen some inefficient or damaged ESC's that do heat the motors quite a lot (doesn't provide the proper timed rotating magnetic field to propel the rotor properly).

Check Motor timing in ESC's. See if Set low medium or high. Try a different setting and see if it changes anything.

In summary, Your ESC's are sized correctly and your Props are also correct for a 3S battery. Almost has to be a motor timing issue or an issue with free motor rotation.

Thurmond

 

[BurningArmada]

Thank you Tritium! I figured if the motors came with 10 x 4.5 props, 10 x 4.7 wouldn't be an issue. Is 755 grams fully loaded a heavy setup? seems really lite to me. I will defiantly pick up some 9 inch props on the way home and see if that is the issue. Really going to miss the power of the 10" props!

 

[Tritium]

No, not heavy at all. I have a small quad (255mm) that weighs just as much.

If the smaller props do not help then check the Timing and rotation for drag.

If you notice the HK listing they say 10X4.5 in the title and 10X4.7 in the specs. .2" of additional pitch in this case is not anything to be concerned about.

If you can find an IR Thermometer then measure the motor temp after a flight and report back. Most motor magnets (Neodymium) max operating temp is around 80 degrees C. There are exceptions and higher temp rated magnets available but they are rarely used in cheap hobby motors. Above 80 degrees C the magnets will be damaged and the higher the temp goes the worse the loss of magnetism till the Curie point of the magnet is reached where there is no longer any magnetic force.

Thurmond

 

[cranialrectosis]

I was using 6mm M3 screws that over heated some of my Suppo 2212s. I added a 1mm washer and the issue went away. The motors spun great. I had lots of power but they got really hot really fast until I added the washer.

 

[Tritium]

Screws were shorting windings it sounds like! I destroyed a motor like that in my earlier days of building craft!

Thurmond

 

[RichB]

Are you using 2-cell batteries or three-cell?

What flight controller are you using?

 

[BurningArmada]

Screws were shorting windings it sounds like! I destroyed a motor like that in my earlier days of building craft!

Thurmond

I've got clearance on my front motors and my rear motor is secured with zip ties so i don't think i am shorting the motors out our messing them up in any way with the mounting.

Are you using 2-cell batteries or three-cell?

What flight controller are you using?

3 batteries and an KK2.1 HC

___

Here are some pics of the finished build with 9 x 4.7 props. I wasn't able to find enough 9 inch props at the local hobby shop yesterday so i went with some cheap spares i had laying around. I don't really like spinning all of the props in the same direction, but it will have to do for now.... I think I'm addicted or something . I only got a chance to hover test it last night and will give it a good workout today and see how the motors are effected. I had to replace the rear motor last night because it was getting "weak".During some backyard test flights over the weekend, the machine would do a back flip without warning and hit the ground. After spinning the motors up with the props off, I noticed that the spinning rear motor could be easily stopped with one finger unlike the other motors. Not sure what the problem was but I'm assuming it has to do with the overheating and magnet strength. Replaced it with a spare motor and now it is good to go.

 

[RichB]

During some backyard test flights over the weekend, the machine would do a back flip without warning and hit the ground.

Afro ESCs with early-2013 SimonK firmware have an issue with certain motors where they will get out of timing. This depends on something I can't remember but it's certain pole count / kv combinations and would happen at certain RPMs. I know that the DT750s were affected by this because I experienced it. Basically, the timing would run off until the wrong phase was energized on the motor, causing what's called "cogging". It would present itself as very flaky motors where the props would stop for a split second and cause a crash if you were low enough to the ground. The issue would get worse the longer you flew. Landing and disarming would reset the clock.

I got 30A Afro ESCs from Hobby King in March and again in July that had the affected firmware versions pre-installed. In both cases the tri would suddenly dip an arm as the motor stopped. If you didn't land it was bound to happen again worse very soon and likely cause a flip/crash. In both cases, updating the ESC firmware to the latest SimonK fixed the issue.

Having a motor stop mid-flight sounds exactly like what I was running into. It would also make sense that you are seeing this after changing props because you are running at different RPM that with the larger props.

It's also possible that running the motors slightly out of timing could explain the heat buildup.

 

[Cyberdactyl]

Rich B is right on. I had issues with the AfroSlims and 4S before flashing to the latest Afro NFET. I was even thinking of trashing them at one point. But after flashing it was night and day.

One very small tip about prop balancing. If you put the tape as close to the tip of the blade as possible, you don't have to use nearly as much. Probably close to half as much as you currently are using.

 

[BurningArmada]

Great info! Thank you both.

Looks like i will be putting in an order for a flash tool. I have actually never experienced this issue until the other night. Strange thing is that the flips happened with my regular 10" props. When I changed out the motor and ran it on the same ESC, there were no issues with the new motor. Im sure flashing to the latest software in any case would be a good idea though.

 

[Invid]

I have actually never experienced this issue until the other night. Strange thing is that the flips happened with my regular 10" props. When I changed out the motor and ran it on the same ESC, there were no issues with the new motor. Im sure flashing to the latest software in any case would be a good idea though.

Sometimes something as minor as a temperature change is enough. I did a build over the winter that I tuned and set up to fly quite well, then packed it for a vacation in Costa Rica. When I got down there I couldn't get through an entire lipo without my motors desyncing and the quad flipping to the ground.

There aren't words for how mad I was. I still won't buy Afros to this day. Too fussy.

 

[BurningArmada]

Sometimes something as minor as a temperature change is enough. I did a build over the winter that I tuned and set up to fly quite well, then packed it for a vacation in Costa Rica. When I got down there I couldn't get through an entire lipo without my motors desyncing and the quad flipping to the ground.

There aren't words for how mad I was. I still won't buy Afros to this day. Too fussy.

What would be a better pre-flashed alternative?

 

[Cyberdactyl]

Not sure in that price range. I don't shop for ESCs much. I found the HK F20-As, DIY flashed, to serve my purposes well and I have stuck with them. I only purchased the Afroslims because I wanted to shed about half the ESC weight for my mini.

However, I see many people have been happy with the ready-to-fly F20As that come flashed with simonK for $8. However, those are "regular" fixed wing ESCs. Afro's are made for multirotors. And I can't promise you the results I got from flashing Afro's to at least Afro NFET V2014-06-18 but you ...should... get MUCH better results.

 

[Invid]

I use KISS ESCs now for weight sensitive but still high power builds, and the Witespy ESCs linked above for other builds. F30A and F20As are not the lightest but they are reliable. If they're going to fail, they'll fail right away, which I can live with.

I'd flash your Afros and see if you can get them working but I did the same and had them fail after appearing bulletproof so I won't use them any more.