Trex 500 up in smoke

[Russ]

Well the gremlins finally got the better of my 500 on Monday. The heli had no more than two hours of running and had developed a random glitch in flight - typically only once during a 5-6 min battery run. When Guy was flying the model on Sunday he described the glitch as feeling like a jump into idle up.

Inspections on the ground gave no indication of distress; nothing mechanical was binding, bearings were cool and none of the electrical components were more than warm.

On Monday I decided to hook up my Eagle Tree Datalogger to see if I could get a better understanding of the problem. Sure enough the glitch continued to occur and the data showed both current drops and spikes. Most odd!







 
Having decided to live with the problem I got on with my hover practice and on my 5th flight, fortunately only about a foot of the deck, the ESC started to smoke and the heli lost all power. I quickly moved in to disconnect the battery.

Outcome? ESC shot to pieces and my brand new Spartan Quark gyro wiped out (confirmed by Spartan today). Fortunately the  RX seems to be unaffected. The motor also feels odd - tightens up when held in certain orientations. This may well have been the root cause of the problem, but I'm not 100%.

Burnt out FETs in ESC



Unfortunately nothing is covered under warranty - the heli is 18 months old and the Spartan gyro was not at the root of the problem. Spartan have offered me a new gyro under their crash replacement policy - not cheap at 75% of full price and I obviously need a new ESC and possibly a motor to get in the air again.   

Once the dust has settled I'm tempted to fit a Scorpion 1600 KV motor and a Castle Creations Ice 75 ESC. This seems to be a very popular upgrade and whilst I'm at my level of ability I'm not looking for a performance boost, given this incident I'd be reluctant to fit another stock Align motor and ESC.   

[Jaco - Sir Crash-alot]

Sorry to see your great loss.

I would just like to make one comment regarding your motor. The Align 500 motor is known to be tight and "loosen up" when turned by hand. This does not affect the performance of the motor.

[Chris]

Sorry to hear this Russ, I'd go along with your diagnosis though.   Commutation errors are the no.1 killer of ESCs and a motor which for any reason can occasionally bind slightly (such as with a dodgy bearing which sometimes allows stator and magnets to strike), will cause a loss of sync and a commutation error.  The current spikes which result can be terminal for an ESC.  The other thing which can cause this is when people cut or extend their motor wires and end up with differing lengths of wire on the three phases.

[Guy]

Thats a pain Russ, I've not heard of problems like this before so I cant really help.

I might try and post on one of the heli forums later and see what they reckon.

[Gareth]

Russ, that doesnt sound good. Hope you get it all sorted. Perhaps this could have been causing the problems with the 401.

Gareth

[Russ]

Thanks all, as we've all found these things come with the territory.

Jaco, I take your point about the motor, but the current spikes concern me - Guy will testify to the jump they produce.

Chris, your appraisal is pretty much inline with what the service engineers at Spartan came back to me with.

Guy, I have had a good scan on HeliAddicts & Helfreaks and these occurrences are not uncommon. The pain for me is that I cannot pinpoint the cause, hence the reason I'm considering swapping the motor out. Another contributing factor may well have been the low head speed I was running which suited my learning, but was probably stressing the ESC. The CC Ice 75 ESC has a governor mode for maintaining a constant head speed which most people seem to utilise. Time to up the speed and set a pitch range to suit my capabilities - what do you reckon?

Gareth, regards to 401 I'm pretty sure it's an ebay duff - the Spartan Quark had the tail locked in no problems at around 30% gain. Maybe if returned to Futaba service at Ripmax it can be sorted.

[Guy]

I dont think it was the low headspead, it wasnt overly slow.

I have had several replies just saying that its probably a faulty ESC.

I also got a PM from Angelos the UK Spartan rep.

I'd like to tell you the following not as representing Spartan RC but on a personal level. I also had the exact same problem on a Trex 500 with the same ESC. It fried all three servos and receiver but in that instance the gyro (ds760) survived. I took the ESC apart to see what caused it. Without spending too much time it seems that the microprocessor on the ESC controls the regulator circuit. This is very poor design in my opinion. If the processor does not boot cleanly or for some reason crashes in flight (perhaps due to static) the regulator will pass full unregulated voltage to the receiver and thus all radio gear. There are much better ways to design the regulator so it runs independently and be more resilient but that means more components thus a bit more cost.

I am really annoyed about this, for a start it costed me three servos and a receiver; luckily not a crash. And I have seen numerous people with the same problem on internet forums.

[Smudgyboy]

Hi Russ

I have a standard motor you can have or a Scorpion 1600 KV motor for £30 if that's any help?

Phil

[Russ]

Guy,
Many thanks  for going to the trouble of getting this feedback - reassuring to me that I'm not the only who has suffered this fate. Mind you it's always worth stepping back and reflecting that there are thousands of these models flying problem free all over the world.

Well on the positive front, I have a new Quark already back from Spartan (big + of being made in England) and I've ordered up a new ESC from Fast Lads. I will have a closer look at the motor - probably remove the outer casing - this evening and see if I can find anything untoward. I should also be able to check the continuity of the 3 windings and compare their resistance values. May even lube the bearings if I can get at them.

Smudgyboy, thanks for the motor offer, but for now assuming all checks out with the old motor I'm going to stick with it.   

Hope to be back in the air at the weekend assuming the weather holds out.

[Mike S]

Bad luck buddy but glad to hear your be back in the air soon