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Old Jul 24, 2006, 06:20 AM
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United Kingdom, Aberdeen
Joined Sep 2000
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AXI 2820/10 burn out on 3s Lipos

Looking for a few clues here men.

I've been running AXI 2820/10s on 10 Nicds and 10 NimHs since the motors first came out, usually with 11x7 APC "e" prop and they have worked superbly for me in funfighter type models at 3.25-3.75lbs weight.

Yesterday I tried one of my old 2820/10s in an aerobatic model, the Esprit Models Supra-E, at about 4.25lbs weight. I'd previously seen the second hand model fly well on a 2820/10 and 10xCP1700s. The set-up I'd arrived at was a 3s1p 3300ma FP Lipo pack, Jeti Advance 40 esc and, in view of the better voltage hold up expected of the pack under load, had propped down to a 10x6 MA wood prop.

We put the meters on the model before flight and the static numbers came out more or less as expected = 37amps WOT, fresh off the charger, 9000 rpm and the voltage settling down at something around 10.7v. Take off was brisk and the climb out was fine. The model had no shortage of power and I flew around for five minutes or so, being very happy with the performance.

Then, as the model was pulled vertical and the vertical held, she hung in the air for a couple of seconds and suddenly all power was lost. I still had radio and landed the model deadstick with no damage. On recovering the model there was a strong smell of something burning and I initially thought that the ESC had burned out- further investigation showed that the motor had burnt out a winding and was dead as a dodo. It's the first problem of that type that I've encountered.

The battery was cool, the speed controller was cool but the motor was very hot indeed. The motor has an abundance of cooling supplied, through a big open hole in the front of the cowl, with good airflow through the model.

Two other factors that might be relevant, or not, are that the motor had been in a model that had crashed and this was the first time it had been used since that crash. There is the merest hint of a wobble in the rotation of the can, which might be a very slightly bent shaft, towards the rear. However, even if that was the case, I'd have thought that the current draw of 37 amps WOT static, really ought to be well within the limits for the motor and I can't envisage a situation where that current draw would be increased in the air.

The other thing was that a cable tie, located through the motor box to hold the speed controller was found to be touching the rear or the motor. It hadn't melted or shown any sign of any mechanical damage but I wonder if friction from contact with the tie could have been involved in any way.

I'm going to remotor the model, as I was very pleased with the performance. However if there is something inherently wrong with the set-up, that I'm missing, then I don't want to burn out another of my 2820/10s and would maybe go for a 2820/12. If someone with experience of using either of these two motors on 3s Lipos could chip in with their prop size, current draw and the details of the models that they are using them in then that would be great.
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