Loss of power

[Christopher14]

Hi everyone, I just built a 560mm FT Spitfire and when I flew it 15min ago I noticed a large loss of power. When I flew it yesterday it was fine, I could go 70mph without diving and I was doing fine and then I crashed, but not badly at all. But after repairing (I did all my pre-flight checks) it I could not go as fast, maybe 50mph at the most. and also I have lost power completely several times. So here I am flying along and then all the sudden the motor cuts out, but the funny thing is I still have control of the airplane. And when I land the ESC and motor are just slightly warm, and the battery is hotter then normal. Ideas?

 

[Rubicon]

Sounds like the battery is damaged. Even if you can't see any damage, power leads can be fairly easily damaged in a crash.

 

[nerdnic]

Hey Chris,

Are you flying with the Turnigy SK3 2118 3100kv you mentioned in my scaled plans thread? How are you measuring speed? With a 4.75 prop and 2s power I can't see how you'd push more than 50.

Based on your description of the issue it's either your motor or battery. You can test the battery by just swapping out for a new one, does the same thing happen?

 

[Christopher14]

No it is not the battery, I have seven. And I don't have any way of measuring the speed, I know what a car going 70mph looks like, and my plane seems to be going the same speed. Update: I just went out to fly it again and I got about 17 seconds of motor run time then the motor cut out, I shut the throttle for 2 seconds then I had power, it cut out again. This time the throttle shut trick did not work, the plane glided in to a perfect landing (witch is rare for me) but on the way down I still had control of the planes ailerons and elevator (I skipped the rudder on this plane) I think it is the ESC, when I recovered the plane the ESC was hot and the motor cool. And the weird thing is when I did a static test holding the plane the motor ran for 7 seconds and the cut out then came back and the went back out again. And when I tried to throttle up again the motor would only shudder. But when I unplugged and plugged the battery in again the motor would do the exact same thing.

 

[mymaps]

That sounds like your ESC needs replacement, but I cannot think of any measures you can take to be sure, maybe just get a new one as that is not such an expensive part.

I lost power yesterday (luckily just before launching, still on my hand) but it was because the leads in my Lipo are getting loose, time to replace that Lipo.

 

[Christopher14]

Problem solved

Last night I took the ESC out of my plane, took the heat-shrink tubing off and proceeded to examine it very closely, everything looked good. So to test if it was the ESC I got my other 10amp ESC, connected the motor and battery, throttled up and the motor shuddered. Well, nothing wrong with the ESC. So then I proceeded to disconnect the bullet connectors, and one of the wires coming out of the motor seemed to stretch. Well that is not normal! So hastily taking out my scissors I cut the stretchy wire about 2cm form the motor. And taking the stretchy bit with the bullet connector still attached, proceeded to remove the wire insulation. That done I found a cold solder joint with a hole where the wires used to be, hastily taking out the blowtorch and clamping the bullet I proceeded to torch the end of the bullet connector with the solder in it. And presently finding the solder melted, I shoved the bit of wire still on the motor in (don't worry I did strip the end) and held it still. And finding the solder cool I un clamped it and connected it to my plane and the motor worked flawlessly.

My theory for the motor cutting in and out is the small vibrations from the prop and motor where making the wires touch for certain amounts of time, and the motor would cut in and out.

 

[RAM]

nice fix

 

[Christopher14]

Thanks. That was part of my mad scientist side coming out, I don't have a soldering iron.

 

[nerdnic]

That sounds about right! I didn't think it could be the ESC because you said you still had servo control the whole time.

Glad you found the issue in your motor.

 

[Christopher14]

I am glad to.

 

[rcflyer729]

It would ether be your battery or esc. I think the esc. Try a different one if you have one.