EXTRA 300S RR motor problem

[Jiihoo]

Hi,
My old Extra started to have problem which with earlier planes has solved by replacing the ESC but not now;
Original motor and ESC, 4S battery, original propeller: ESC started to lose motor out of sync, (that screamlng sound like stones in gearbox). It became more common and so I changed ESC to Roxxy BL control 755 S-bec. It worked OK for a while but problem is back: worst when testing motor in ground, but after giving more gas this "coughing sound" diasappears and starts to work and I can take-off. Plane in air (regardless if I add gas , also with steady motor gas stick position) it has started to do this more often now. Motor stops and comes back to operation after screaming a while.
-Can broken motor cause this ?
-Can both ESC's be broken ?
-why it worked a while without problems with new ESC but problems is existing now more often ?
- if there is issue with ESC timing, to which settings I should change it ?

Could somebody help with this ?

Regards,
Jussi

[Schwintz]

Hi Jussi,
have You got an other engine to test it? How does the engine feel, when You turn it by hand? Does it feel good and smooth or does it feel sandy and/or rough? Did You check the cables between engine and ESC? It could be a loose contact or a broken wire inside, too. So it could happen that, when You connected the new ESC, You incidentally pushed both parts together and they got loose after some time again. It is hard to find a failure and a solution via the Internet without doing some tests.

Tom

[Jiihoo]

Hi Tom,

I don't unfortunately have another motor to test with.
I took motor off from plane, it feels ok, goes around without any extra friction etc.
Also the cables looks ok and no loose solderings in any of three connectors.

Jussi

[Schwintz]

Hi Jussi,
have You got a friend with a test-engine? Maybe You can find the issue on this way. The last option is to buy an other engine and to replace the old one. What type of radio do You use? Is the transmitter
and the receiver ok? Did You install the ESC in the correct manner?
You will have to exclude all failures. Might take some time and some money.
Sorry

Tom

[Jiihoo]

Hi Tom,

I have Cockpit SX12, has worked all time without issues. Installation happened like I have done it always. As everything worked ok for approx 5 flights, I assume that there were no faults in my installations.
I think I need to buy new motor and test with it.
Maybe there is something inside the motor which causes the problems.

Jussi

Jussi

[Schwintz]

Hi Jussi,
yes, but You see: it is so hard to find failures and mistakes via the net. There are a lot of issues You will have to eliminate to come to the right solution.
Sorry for that.
Could You please give me some feedback, if You found the problem?

Tom

[Jiihoo]

Hi Ton,

You are right, in most cases it is just needed to test with different combinations and try to locate the problem cause.
I will check if there would be a suitable replacement motor for original Permax as it seems to available only at Multiplex own web shop in Germany

Jussi

[Schwintz]

There are many alternatives in the net. Try not to overdo. Take an engine with similar data. Weight, RPM, power ... So You have no problems with ballance, and You can use Your old stuff like ESC and propeller. By the way - is Your prop still ok? Did it have contact with the ground? An other possible reason for strange noise.

Tom

[Jiihoo]

Yes, I will check what replacements there are available.
Prop is new, I changed it some time ago because the old started to be worn-out.
The cause for the problem is not mechanical, it is definitely electrical. (Have had same earlier but as said, they were solved by new ESC)

Jussi

[Jiihoo]

I looked at the motor more carefully and noticed that in the yellow wire the insulation (where the three cables go inside the motor) was not as long as in the others and copper wires easily touched the metal shell of the motor when the cables were bent. I put shrinking tube around it and now it is covered to the end like the other two cables.

In two test flights no issues anymore, so hopefully this solved the problem.

Jussi

[Schwintz]

Very interesting issue, Jussi.
A problem like this is not easy to detect. Thank You for the feedback.
Have a nice Sunday.
Tom

[Jiihoo]

Yes, first time when I noticed this kind of thing in any of my motors. I took a photo of it where it is easy to be seen.

Have a good Sunday afternoon too,
Jussi