Blowing up esc with my SK720 installed

[DJG24]

I just finished building a T Rex 450l dominator (3s version) and installed an SK720be. All the setup went well following the wizards and on the bench.

First test flight to make adjustments, the helicopter lifts off and at about 15 seconds the motor shuts down and the heli drops. ( no damage) go back over the setup and everything still seems to be working fine but speed control is dead. I chalked it up to a bad esc.

I installed my castle Phoenix edge lite 50amp.everything working fine, motor spooled up, servos working,etc.... Again, took it out and hovered. At about 20 seconds it shut off and the helicopter fell from about 1ft up. I left it plugged in and went to look it over. The castle esc burst into flames on the ground! Pulled it out with only a minor burn on the esc mount.

This is the first skookum product I have used and I'm sure there must be something I'm missing here but with 2 speed controls down I figured I better go out and ask for some help.

Both times the heli flew great for 15 seconds and then just simply shut off. Any ideas?

[Hardsy]

I would probably be looking into the motor first, and make sure that it is not causing your your issue.
Possible dead short or mounting bolts touching the windings etc.

Sucks when you get a new Heli and stuff starts burning up, also gets expensive!!

[Luvmyhelis]

The Sk units themselves pull almost nothing as are as amps go. If you know what you are looking at on the esc board you can identify if the fail was bec or motor related.

[omerco]

+1 for the motor. need to check shorts between phases but maybe only when working/vibrating.

[DJG24]

I pulled the motor and hooked it to another heli and it spooled up fine. Of course it was not under load as it had no pinion attached but it did work. That is why I originally figured the esc was bad. Motor windings look fine and it spins free. I guess I could order a spare motor to try out.

I was just wondering since I flew it with the 3GS first and only started having problems after I set up the sk. I figured I just set something wrong.

[georgi UK]

=] was there any heat or smell from the motor? as always we have playback logging for this type of issue, it's really recommended to use this on any type of maiden, please keep us posted!

[DJG24]

First I would like to thank everyone for the responses. I also have to say, I emailed skookum as well and Art responded to me quickly asking for a log file. I have to say, I love customer service like that. Job well done.

I decided to experiment a little tonight first and removed the sk720be from my dominator and set it up in my other bird. Went through the setup again and everything worked perfectly. No shutdowns, perfect flight. I then put the 3GS back into the dominator and hovered quickly. At about 10 seconds it dropped down as the motor shut off.

The obvious conclusion is that it must be the motor! I was surprised as it was brand new with the kit. The good news is that the sk720be is perfectly fine and performing awesome in my other 450. Now to get the new dominator motor in so I can put the skookum back into the dominator!

Thanks again for the help.

[tfrotor]

Did u double check ur gear mesh,it may be to tight

[georgi UK]

=] would love to see the motor amp draw here!

[DJG24]

Well got the new motor in and reset the SK720 to the dominator. Everything went perfect! Thing flys amazing now! Turns out the motor was the issue all along.

I had checked the gear mesh before and it was fine but that original motor would just shut off every time! After putting in the new motor everything flys great.

With that said, I do have a spike on the vibe report. It's in the 400hz range, around 29000rpm in the fore/aft acceleration frequency. Given that data, I'm assuming that it is the motor causing the vibe, correct? It spikes to about 6.4, everything else is sub 2.

So do I put some aluminum tape on one side of the motor and see if it gets better or worse? Repeat until its gone?

I'll see if I can get you some amp draw data from the first motor but the new one definitely seems to be working much better!

[Luvmyhelis]

Can you post up a pic of your vibe log? Separate out the frequencies also (up/down fore/aft side to side) and eliminate the overall black line? Or better yet for the guys here that can read logs. Post the log? Just a fore aft vibe doesn't indicate a motor balance issue. We should be seeing equal side vibes.

[georgi UK]

=] this will be a TT issue...

[DJG24]

First, good call in the TT. Made sure everything was balanced and added another bearing to the TT. Vibes went down without a spike over .2 !! Nearly perfect, I was so happy.

Then it all went bad again! Brought the helicopter into a hover, switched to idle up, and just as I started to move forward the motor just cut off and it fell straight down to the ground from about 10 feet. Both motor and esc are completely dead again! I know a lot of people flying the dominator but mine is the only 3s version. Im really at a loss here but 2 motors and esc's blown with a good crash thrown in. This thing is turning into a nightmare!!

[georgi UK]

=] it's good to hear the good news, but not so much the bad?

so what on this heli could load-up the drive system enough to blow the motor/esc? a partial seizing bearing would tend to slip on its supporting shaft (a screech can be heard here), a gear-mesh issue? anything obvious? must be driving you nuts??!

[DJG24]

It is really making me crazy! I tore the whole thing apart today to check crash damage. Chipped a tooth on the torque tubed drive gear a broken dfc link and blades. I'll replace the feathering shaft and the main just to be safe. Really at a loss on the motor issue as the drivetrain is smoother than any heli I have.

All that said, the skookum works great in the blade 450x but I can't seem to get that rear belt to run without crazy vibes. Got high spikes in the up/down around 7 and shuts down the self level. It has to be that darn belt! I balanced just about everything else on the thing! Lol

[tfrotor]

Originally Posted by DJG24

It is really making me crazy! I tore the whole thing apart today to check crash damage. Chipped a tooth on the torque tubed drive gear a broken dfc link and blades. I'll replace the feathering shaft and the main just to be safe. Really at a loss on the motor issue as the drivetrain is smoother than any heli I have.

All that said, the skookum works great in the blade 450x but I can't seem to get that rear belt to run without crazy vibes. Got high spikes in the up/down around 7 and shuts down the self level. It has to be that darn belt! I balanced just about everything else on the thing! Lol

Whats ur playback telling you at the time it shuts down,you might
should check solder joints really good,If u have been running
the SK in playback mode there would be something in that to
direct you to your problem,not being rude or anything but u
might should practice AUTO's that way if ur just hovering an
it quits on you.you have a really good chance of making it
to the ground without crash damage,forget the vibe analy.
for now turn playback on go fly an find ur problem good luck

[Luvmyhelis]

Originally Posted by DJG24

It is really making me crazy! I tore the whole thing apart today to check crash damage. Chipped a tooth on the torque tubed drive gear a broken dfc link and blades. I'll replace the feathering shaft and the main just to be safe. Really at a loss on the motor issue as the drivetrain is smoother than any heli I have.

All that said, the skookum works great in the blade 450x but I can't seem to get that rear belt to run without crazy vibes. Got high spikes in the up/down around 7 and shuts down the self level. It has to be that darn belt! I balanced just about everything else on the thing! Lol

Unless the cogs in the belt are stripped or severely worn. We don't see vibes out of belts when tensioned properly. Again, we need to see your log. Then we will most certainly 0 in on what the issue is here.