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Sep 24, 2021, 01:30 PM
I just want to go fly!
walter3rd's Avatar
Thread OP
Question

Motor getting warm seconds after run up??


I have this small little motor 1306/3100 kv motor. I don’t have any more info on it. Trying to do a run up test with this little 10 amp ESC and 2H battery. The battery says HV wondering if that’s my problem. Seconds after a run up I can barely touch motor. Is the high-voltage battery the culprit? I don’t want to kill the motor Sounds OK just gets hot and afraid to continue running.Thanks for any help. Walt PS I have no info on this prop set up but it came as a set and I figured a tiny short run up shouldn’t cook the motor that fast.
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Sep 24, 2021, 01:51 PM
An itch?. Scratch build.
eflightray's Avatar
You appear to be trying to use a drone racing motor in a conventional aircraft.

The thing that generally cooks a motor is trying to use a too big a prop, (the load that draws the amps that generates the heat).

If you search on that size motor you may find that it uses no more than 5" diameter, preferably smaller props. Anything bigger is just not suitable.

Decide what size prop you need to suit the model, then buy a suitable motor. The whole power system needs to be considered, motor, battery, prop, type of model and flight style.

.
Sep 24, 2021, 01:52 PM
New to this whole thing...
Are there any markings on the prop? What's the diameter of the prop? Does it spin freely with the prop removed? (Sometimes the motor shaft can rub against the firewall, requiring a central hole to be drilled.)

Looks like on a 2s battery that motor can probably handle at most a 5" prop.
Sep 24, 2021, 02:43 PM
I just want to go fly!
walter3rd's Avatar
Thread OP
prop measures approximately 4 1/2 across I don’t see any pitch markings. I could definitely shave it down and re-balance to make it smaller. It came in a bundle so I thought it would work. But yes I guess the high KV and this prop are not playing well this is just for powered up flights on a glider so I only need it to work a little bit to climb to altitude. I guess cutting down the prop and rebalancing could be an option? I just need it for a short flight up
Sep 24, 2021, 03:21 PM
Entropy is happening!
Jim.Thompson's Avatar
Do you have a power meter Walter?
If so, did you check the current to the motor?
It is excessive current (amps) that heat the motor, not the voltage.
See Ron Van Sommeren's many (qualified) posts on the subject.

I think the kv is too high for powering a glider.

I have one of these little cheapies in an 1800 span glider:

https://www.banggood.com/Racerstar-R...0&rmmds=search

Swinging a 10 x 6. Plenty of power on 2 cell LiPo battery.

Jim.
Sep 24, 2021, 06:21 PM
New to this whole thing...
Is that 4 1/2" the total diameter, or is that just for one of the two prop blades?

If it's total diameter then I would have expected it to be fine. ecalc gives under 5A and 35W, but it's not giving much thrust.

If it's per-blade, then there's no way that little motor will be able to handle it.

A 6x4 prop is the largest that motor can realistically handle on 2s, and only for about 10-15sec at a time. Ecalc estimates around 190g of thrust for that setup.
Sep 24, 2021, 09:35 PM
I just want to go fly!
walter3rd's Avatar
Thread OP
4.5 total span. i have watt meters but not set up to read this little thing. very frustrating, as i power up i can tell its giving off lots of thrust! way too much prop i guess. im looking at less than 1 inch wide fuse so spinner need to be tiny.
Sep 24, 2021, 10:05 PM
If it flies, I can crash it.
rocketsled666's Avatar
That motor ought to be OK with a 4.5" prop on 2S. But that looks like the prop has quite a bit of pitch and a pretty wide chord. The props I'd spin on that motor on a quad would have much narrower chord. By way of a sanity check, I run a 3100KV 1505 motor on 6S with 3" props. The motor size dictates the maximum power limit, but 3100KV is 3100KV regardless of motor size. My 1505s get toasty, but not too hot to touch and not after a short run (and the quad will fly at >100MPH at WOT).

Does the motor turn easily by hand? Do you have a more "traditional" airplane prop vs. a folder? Did you perchance make any programming changes to the ESC, like advanced timing or something?
Sep 25, 2021, 01:22 AM
New to this whole thing...
At 4.5" diameter, theoretically that should work fine. Any difference in pitch shouldn't be enough to overheat it in seconds.
Sep 25, 2021, 06:54 AM
Registered User
walter3rd
Are by any chance the motor bolts too long and are touching the motor windings?
Sep 25, 2021, 08:16 AM
I just want to go fly!
walter3rd's Avatar
Thread OP
It turns free by hand. I added firewall spacers and washers so the bolts would not touch. All good questions. I was told removing the spinner might help with cooling too. I have not done anything to the esc but I can try another one to test that out. Arriving today. Someone posted a picture of what appears to be my motor and same prop set up that they say work for them. Without spinner. I’ll try all the things to try to get it sorted.
Sep 25, 2021, 08:40 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by walter3rd
... Someone posted a picture of what appears to be my motor and same prop set up that they say work for them. Without spinner. I’ll try all the things to try to get it sorted.
If motor heats up that quickly, removing the spinner won't do much I'm afraid.

Current drawn is proportional to pitch, voltage≤ velocity konstant Kv and diameter⁴
You may already have overheated the magnets → weakening magnets (irreversably!) → higher Kv → higher current → hotter magnets → weaker magnets → higher Kv → higher current etc.etc.

Quote:
Originally Posted by cbf123
... What's the diameter of the prop? Does it spin freely with the prop removed? ...
Don't forget to do this test with at least two of the three motorwires disconnected from ESC, and not touching eachother. Otherwise you'd be testing a shorted motor, lots of resistance.
Explanation in video below.

Why sometimes, brushless motors don't spin freely (9 min 5 sec)
Last edited by Ron van Sommeren; Sep 25, 2021 at 11:32 AM.
Sep 25, 2021, 10:01 AM
I just want to go fly!
walter3rd's Avatar
Thread OP
Come to think of it I wonder if some of those motor wire male female unions were in advertently touching. I will double check that there is space between and nothing is touching
Sep 25, 2021, 10:41 AM
Registered User
Some think electrics are simpler than glow, then find out electrics are not really simple at all. Buy a matched power system including motor, prop, esc, and battery or you will discover how complex they are.

A suitable wattmeter is essential to avoid burning stuff up.
Sep 25, 2021, 01:01 PM
I just want to go fly!
walter3rd's Avatar
Thread OP
I fly strictly electric so I realize the game, I have watt meters just not set up this small yet. This was a set so figured it would play nice. I don’t mind the challenge. I love setting up my systems and have not had issues like this prior. First time for everything I guess.


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