Trex450 Sport - First Crash - Electrical Failure

[dam74]

Well was flying at the end of the day today after having a lovely morning session. I was about a minute into flying at about 10-15m high and I think no more than about 30-40m away. I know I might of said closer in the other thread but have had time to reflect on distances. I know it was no more than half a football pitch width away from me as I was standing in the center of a football pitch and flying it away along the width of the pitch.

Anyway to describe what happened it seemed to loose power, not instant loss but kind of spasmodic like the motor was getting short bursts/pulses. Tried adjusting the cyclic to level it out as it was slightly tilted but no joy so I flicked TH but I'm gathering that wouldn't of done anything as there seemed to be no helicopter response from cyclic input.

The heli landed on the front of one skid which snapped and a blade. Lucky they were cheapo PRO 3D FRPs.

Anybody got any suggestions to what might of caused this issue. Just for an insight on to my setup. Trex 450 Sport Combo with the Align Servos that come with this package. Align ESC also part of this package, a GP750 and an AR6100E (2nd Hand from these forums). The battery in use was an Align 11.1V 3S 25C 2150mAh.

Some background, the batteries have been getting stupidly hot since building but have hopefully resolved this issue by adjusting the meshing as per suggested by the lads at the Totton meet and also I slackened off the belt this morning and it moves over to the middle with a bit of pressure. Unlike before it was a guitar string/piano wire.

The other thing I noticed when testing servos about a month ago was without spooling the motor up the ESC capacitors were extremely hot. For the guys at the Totton meet, as hot as that battery I first let you handle if not hotter. So I'm wondering if I have binding issues and the ESC just cutout???

Or does what I described sound like it could be the RX playing up?

[R1stu]

Had sim issues with the 250, esc overheating and the heli having not tail control. Turned out one of the servos had seized and was now binding. check all the servos after about a minute of playing with them all. if any are really hot, then thats the issue!!

[dam74]

Will have to do a bench test I think one servo at a time and check the ESC temp.

[acwman]

does sound like it could be the esc overheating.

At the moment with the temperature as it is.. I can fly quite a few packs back to back, with no concern with the temperature of the esc or the capacitors on it. Both are barely warm to the touch, even after the fifth pack.

[Farmer Giles]

How much power are you putting back in your Lipos after each flight ?
Are you observing the 80 / 20 rule ?

The Stock align ESCs have built in protection (well the 500 does so assuming the 450 is the same) for when the flight pack get low on power, they start pulsing the power to the motor to give you a chance of landing before a total loss of power happens..

[PsiLo]

If the ESC is getting real hot then it is almost definitely a problem with binding or servos. Check them all thoroughly and make sure there is no binding anywhere.

[dam74]

How much power are you putting back in your Lipos after each flight ?
Are you observing the 80 / 20 rule ?

The Stock align ESCs have built in protection (well the 500 does so assuming the 450 is the same) for when the flight pack get low on power, they start pulsing the power to the motor to give you a chance of landing before a total loss of power happens..

Up until I corrected meshing and tail belt tension I was having to put back in about 2005 units so draining about 98-99% of the battery on a 4-4.30min flight and that is in a hover and a bit of forward/backward and side to side cyclic flight with the odd left/right piro on the spot added into the flight. No 3D is involved so no heavy drag on the blades with extreme pitch changes to cause the motor load to increase.

After adjusting the meshing and the tail tension this morning I recharged the batteries and I put back in 1800units and 1670units (never timed this one just guessed it based on sound) and the 1800units was on a 5min flight.

So now I'll be able to achieve the 80/20 rule now that I've eliminated the drive running too tight.

[Mart61]

Bad luck on the crash.

[PsiLo]

I have an eagletree logger with cable that I am happy to send up to you if you want to see what is happening electrically. You could run it up on the bench with the motor disconnected and see what each of the servos pulls in amps.

I would expect to get 8 minutes + of that kind of flying with that setup so would definitely say that you have an issue somewhere with either binding, servos or a setup issue. I had a slight bend in a flybar once that was hardly noticeable but caused a HUGE pull in amps, so much so that the ESC low voltage cut in after just 30 seconds!

[dam74]

Bad luck on the crash.

Mart, I was long over due. Just placed an order for skids, feathering shaft and main shaft as I think I'll need them on standby.

One thing I'll make note of for anybody thinking about buying a heli. Get an Align Trex 450 over a Blade400. Same sort of crash on the B400 and I would of been buying a new gears, servos, tail boom, feathering shaft and main shaft.

Just checked the gears and none stripped. Will have to pull out the main and feathering but I'm guessing they're still straight seeing as when I ran an Align Trex450 feathering shaft on the B400 the blade grips snapped instead of the shaft bending.

I'm really surprised from the height that it survived so well. I'm really glad the ground was muddy

[xygax]

OK... you can test an ESC for a shorted FET. it may be.... using a multimeter on continuity check between all three phase cables to the motor and battery+ reverse the leads and repeat. (one way you will see the diodes the other way will be open) then go from the phase cables to the -ve and do the same. if any are continious both ways then the mosfet in that quadrant is NFG and you will need to repair or replace the speed controller.

Also connect an ammeter between battery and speed controller without the motor connected and check the servo currents (as said already)goto max pitch and all four corners on the cyclic check for current increase in all positions this should identify bad / binding servos.

Steve

[dam74]

OK... you can test an ESC for a shorted FET. it may be.... using a multimeter on continuity check between all three phase cables to the motor and battery+ reverse the leads and repeat. (one way you will see the diodes the other way will be open) then go from the phase cables to the -ve and do the same. if any are continious both ways then the mosfet in that quadrant is NFG and you will need to repair or replace the speed controller.

Also connect an ammeter between battery and speed controller without the motor connected and check the servo currents (as said already)goto max pitch and all four corners on the cyclic check for current increase in all positions this should identify bad / binding servos.

Steve

Yeah was going to do an amp check but both of my multimeters that I use for work (Sparky) I think only go to 10A max. I'm guessing that the motor will draw most of the current. So I'm thinking if I exceed 10A with the servos I have something wrong

[xygax]

10A is ok you will do this without the motor connected and the servos should be less than 2A total on a 450...

Once you have confirmed the servos remove the blades and run the motor with just the paddles on it will be less than 10A


Steve

[dam74]

Cheers Steve, I was going to go out and buy a clamp meter with a high A rating but wasn't sure if it was necessary to do so given the tests performed were going to be in a no load situation.

I did suggest one of our other forum members to do so aswell as I know he's blown a few ESCs but he said it sounded like too much hard work and decided to just buy new ESCs

You know who you are.

[xygax]

there are several things that go on a speed control but limited mainly to either the 5v reg for the servo / raido or a mosfet and if you have a lot of HF refelected onto the capacitors they will get well hot. make sure if you disconnect the motor pull all three cables not just one some controlers dontlike that and do the spontainous combustion thing..

Steve