Unexplained crash!! Help

[icarus]

Just got my Trex exactly how I wanted it, super stable, will fly in fairly windy conditions and cope with gusts, brilliant....or so I thought.

Flying it tonight it was sat in a perfect hovver about 5ft when it started twitching and the tail swung out wide. So I landed it and had a quick look, nothing out of place, all servo's appear to be ok so I took it back up.
Back into a perfect hovver about 10ft then all hell breaks loose, it was twitching, tail flapping from side to side and the power surging then sounded like it was cutting out, power seemed to be coming in and out about 5 times a second.......I managed to get it down without too much damage but the blades touched down when it landed, ripped the end off the blades and looks like its slightly bent the main shaft.

Back in the garage I took the blades off then wound the motor up to observe the glitch, but nothing, it was perfectly smooth again?

I'm a beginner with heli's and can't understand whats caused this, ESC, motor?

[LipolyGone]

How old is the heli?
If it has had alot of use I would guess a bearing is breaking down causing the glitching had this on my raptor recently it wa a tail pitch slider bearing that had broke up.
Cant see that it can be anything else so long as you havent changed anything on the heli that could have caused this problem.
Martin

[robgt]

How long had you flown the heli on this charge of the battery pack?
Surging is usually the ESC's method of telling you the pack has run out and you should land. If the motor surges, the tail could wag and cause the general mayhem you encountered.

Cheers,
Rob

[icarus]

Its not the battery, I should have added I changed the battery after the first set of glitches because thats what I thought it might be.

This was happening on a smaller scale a few weeks ago, small glitches that couldn't be explained, I took it to the shop and they fitted a BEC for me, it seemed to sort it out but now its happened again much more dramatically.

[robgt]

This could be down to interference - whats your electrics layout like?
Can you post a picture of receiver, gyro, battery and ESC locations?

Cheers,
Rob

[chugga-bug]

If your using a PPM rx then component & cable placement is critical in achieving a glitch free set up. It took me ages to get mine right. I ended up with a Shultze RX in the back right side of the frames, gyro under boom mount, ESC on left front side of frame with battery on top front mount (carbon frame). Keep all servo/ESC-RX wires away from ESC & motor as much as possible.
I also fitted a MAP micro ariel to the right rear underneath the frames. This gave me a virtually glitch free heli.

[icarus]

Ok....thats the battery, ESC underneath, BEC tie-wrapped on at the front of the frame, receiver sat in its usual place, Li-po voltage indicator tie-wrapped on rear of frame and GY401 sat in usual place above.
On the other side is the little polo mint shaped thing that is supposed to limit interferance.

[chugga-bug]

Is there a reason why you're running a separate BEC?
Unless you're running 4 cells you don't need one. That's one possible source of interference gone.
Also the Hitec rx's are not the best at blocking out glitches. I tried a couple of different Futaba ones and couldn't even get them to work well.
The Schultze has circuitry that helps stop glitches getting through, a bit like PCM without the dreaded lock outs. It also has an LED which flashes to show how many hits it's detected which is handy as they don't all get through but you'll know they're there.
Try doing a really good tidy up of your wiring. I shortened servo & gyro wires where necessary to keep them out of the way. The cable route can make a big difference, so keep them away from ESC & motor as much as possible.

As a side note, i'd advise you to move your gyro under neath the boom as it's been known for them to get smashed by the flybar in a crash when mounted on top.

[robgt]

Keeping your high voltage wires away from your low voltage wires is a good idea.
High = Battery and Motor wires
Low = everything else.

Also, aerial routing is critical - I used to coil mine around the aerial tube in a fairly tight coil, 0.5 to 1 cm apart and evenly spaced along it, leaving enough length to tie-wrap it to the horizontal fin (used a piece of fuel tube over the wire, then tie-wrap to fin). Try to avoid doubling aerial wire back on itself (I can see you haven't - I'm just mentioning it )
Cheers,
Rob

[chugga-bug]

Just noticed that your aerial runs very cose to the motor and ESC. Try getting that away if you can.

You can wrap the aerial round a drinking straw (don't over lap the winds)
and cover it in heat shrink. This is all the MAP antenna is. This gives you more chance of mounting it away from motor etc.. Doesn't seem to have any effect on range either (Can't see a Trex that far any way).



Easiest and ONLY real option to cure your problem is to get a 2.4gig radio!

[icarus]

Is there a reason why you're running a separate BEC?

The guy in the model shop suggested it.
I'm a beginner and tbh don't really know my way around the control systems on these, I just took his advice and they fitted it, only cost me a tenner.

Easiest and ONLY real option to cure your problem is to get a 2.4gig radio!

How does this work?


Thanks for advice so far.....

[chugga-bug]

Basically there's nothing on the heli that can create any RF at anywhere near that wave length. Hence no more glitches, period...

This is new tech that's only been legal over here since Jan this year.
Spektrum DX6/DX7 was the first, Futaba now have sets out as well.

[Randall]

but be carefull its not yet proven to be 100% i fly with a guy in aldershot on some pretty damm big fields, i can fly there on my 35mhz fine he has a spectrum dx7 and he cannot fly there it glitches all over the place and almost cost him the model ! the only thing we can put it down to is its near a army base and they use a lot of equipment on 2.4ghz in theory it should not affect it but take it from me it does affect it bad yet mine is not affected

[marktigere1]

I had glitches on my tail until I started spraying Mr Sheen on the tail belt.

This removes any static build up which discharges through the tail servo and Gyro causing glitches or worse equipment failure.

Mines a Trex 450XL CCPM so may be different from your SE.

Just a thought.

Cheers

Mark

[moyesboy]

randall
That DX7 certainly should not do that.
I should get in touch with the importer and give them details of the location - that is assuming the same DX7 works fine elsewhere.
Is he using a single part or two part rx? That makes a difference. Using the two part with 4 antennas at 90 degree angles is supposed to be a lot better.
Also the antenna on the tx should be angled up and not point at the ground, or at the model.
I heard of people losing the model by pointing the tx antenna down toward the ground and getting it back immediately by holding it up in the air.
I just bought a dx7 (on the door mat at home now) and I've been doing some background reading!

To some extent the reliability is only assured if the other 2.4Ghz devices in the area conform to legal requirements. The military may well have licence to operate differently but this would have grave implications for flying models on military airfields if true.