Stuttering motor

[Andy G.]

Whilst flying my HK Teksumo yesterday I suddenly lost motor power, so glided in for a deadstick landing, on picking the model up and trying the motor it just stuttered. Battery was still good, esc was cool, motor fairly warm. In. the workshop last night tried it again, exactly the same. Plugged another identical motor onto the esc, everything worked fine. Then checked existing and new motor windings with meter, all good and identical so reconnected old motor, tried again , stuttered again. Powered down then powered up again, but this time with throttle set high, went through esc set up, powered down and up again. Motor works perfectly! Any ideas / comments?

[Simon Chaddock]

Andy G

The "stuttering" sounds like a bad connection between the ESC and motor.

Remember the ESC controls the switching to the motor by recognising the tiny voltage created by the non powered winding. so a poor connection can confuse it.

As it is now working the poor connection was hopefully in the wiring between the motor and the ESC and has been fixed as a result of you remaking the connections. Test it thoroughly and give all the wires a jiggle to make sure there are no loose contacts.

But it could also be in the motor windings them selves and by chance it has made good contact again. If this is the case then it WILL fail again and there is no repair possible.

Edited By Simon Chaddock on 06/06/2016 10:19:51

[Andy G.]

Hi Simon....

All the connections are tight and cabling secured well, the 'original' motor still stuttered after reconnection UNTIL I reprogrammed the ESC.. Even though a new motor had run happily without reprogramming? This set up has had at least a couple of hours of air time to date with no problems, although Sunday was the warmest day I have flown it on.. It may just be imagination, but the plane didn't quite seem to have it's usual ''Punch'' right from the launch, just seemed a few mph slower than usual.. Maybe it was just an off day..

[Biggles' Elder Brother - Moderator]

Bit of a mystery! Until you said that an identical motor worked OK I thought "Aha, he's accidentily altered the timing on the ESC" as that can have that effect. But you've dealt with that.

Then I thought "Aha, duff winding on one phase" - but you then scotched that.

Then, like Simon, I though "intermittant connection to one phase" but you seem to be sure it isn't that. And the the fact that reprogramming apparently sorted it? Mmmm?

The warm day make be a clue. I have a ESC in my Pheonix 2000 that cuts out regularly when it gets too warm (which isn't actually that warm!) mind you my sense of frustration with the P2000's general sluggishness does tend to make me a bit harder in my demands than I might be generally!

BEB

[Andy G.]

A bit of an update on the ' mystery'. Tried the Teksumo out again yesterday, loaded up a fresh battery, quick ground test , everything seemed ok so launched, about 20 seconds into the climb out the motor cut, still had full control so dead sticked down ok. On picking up the model everything was pretty cool, applied throttle input and back to stuttering, BUT this time a little whiff of magic smoke from the front of the motor! So , looks to me like a breakdown of the winding insulation which has become worse. Haven't had time yet to put the meter onto the windings yet but I suspect that this time I will see a problem. Thanks for the comments so far. I'll be fitting a new motor by the weekend so should prove the point soon. Although the watts were within limits I think I may prop the next one down a size!

[Engine Doctor]

I had a similar symptoms on my model . I see you have detected a fault in the motor . My problem was only found by changing the esc as I thought it was defective .All fine for a couple of flight then same thing . I eventually found that one of 3mm connectors on the motor was dodgy . Fitted a new set of connectors and all is now fine. It's hard to find the fault . The only thing you can check for is a very tiny amount of " in out" movement on the duff connector as the spring is not gripping the inner part of the plug.

Edited By Engine Doctor on 08/06/2016 09:42:25

[Peter Beeney]

Andy,

When you say the motor is stuttering I presume you mean it’s actually oscillating, the prop is swinging to and fro? If this does start to happen, particularly with a full throttle setting, then it’s imperative to stop it immediately because full current flow is occurring, albeit in fits and starts, and virtually everything in the power train might start to get a trifle warm, to say the very least! It’s certainly possible that a fault might be on the ESC, say, to cause this, but the motor might be also getting enough current to rapidly start to overheat, the evidence of which you’ve already seen; but maybe it’s not the motor (windings) that are at fault in the first instance anyway.

As ED says, it can be difficult to find the fault. Another problem with the connectors is the ubiquitous dry soldered joint, these can often behave themselves impeccably for a long time and then suddenly strike you down. If it were mine I think I’d most probably fit three new connectors as a starting point; if it then proves to be something else and I have to junk the motor anyway I can always salvage them…

PB

[gangster]

If you have to scrap it make sure you retain the magnets for hatches etc. have you seen the price of such magnets you will get back most of the cost of the new motor

[bruce batten]

HI Chaps Following on from my problems with an ESC and EDF unit I was found that the ESC had dropped phase . Now trying to get my money back from HK appeases to be difficult Is there a rule of thumb for thrust to model weight ratio? Bruce