450 Sport sucked a kumar, but why?

[Guest]

My beloved 450 Sport had a bit of a motivational issue at the top of a loop, coming to earth in a vertical descent with a bit of a crunch at the bottom. It's had ~500 trouble-free flights, never any hint of a problem, always ending each flight as strong as it started. Can you help diagnose its sudden loss of enthusiasm?

I think I still had servo control and got it down with minimal damage, but that may just have been the grace of the gods. Afterward, on the ground everything seemed fine. Servos still doing their thing, didn't try the motor, FBL still levelling, there was no yawing during the descent, no suspicious lights flashing on the speed controller, microbeast or rx. In fact, it all seems quite flyable except for a fusable-link style servo horn out on the elevator and a bent boom. Battery had all balanced cells at 3.80v and was slightly warm and very slightly bulgy. Motor and ESC were cool but I forgot to check until about a minute afterward. Connections all seemed mechanically sound and solder joints don't appear to be bad, but very difficult to inspect (save that for another day).

Might be a coincidence, but a few flights before, one of my batteries developed a tired cell (not surprised, it probably had a hundred cycles on it and was only a £20 jobby). I've started flying it a bit harder and in windier conditions (I think we all have recently ), but I'm still only putting 70% back in and the others have behaved.

Equipment:
450M motor
Microbeast v2
CC ICE 50 (not lite), SET RPM at about 3000 (can't remember exactly).
tx 8FG
rx R6106 with aerial along a boom strut (ahem.. does that sound daft?)

Do you think I can blame this on a collection of tired packs? What else should I look at?

[trillian]

Ouch! 'Sorry to hear about that. Hope the damage wasn't too bad. It's hard to say really. Did it sound like it was bogging badly
at the top of the loop?

When I first got my 450SE I crashed due to the pinion coming loose at the top of a loop, suddenly no power and rapidly slowing
headspeed and then crunch.

Regarding Lipos, I have at least one older one that will indicate decent voltage when checked but then drops off severely
under any kind of load. I have been using it in my Align starter but it's going in the bin soon.

[nicobec]

I had my one way slip in the housing. Took all the power out as well. It took off fine but any thing more than a hover it will slow the head speed fast. It seemed fine but if you try to turn the motor with the head it would slip every now and then. I stuck it in with the green stuff in the kit. Hope you find the prob.

[Guest]

Ouch! 'Sorry to hear about that. Hope the damage wasn't too bad. It's hard to say really. Did it sound like it was bogging badly
at the top of the loop?

Not too bad at all thanks. I happened to be videoing the flight (first one for months, how's that for an omen) and just reviewed it. The audio wasn't that clean because of the wind, but I think it sounded fine all along, up until I lost power - at that point the motor noise just stopped and never came back. Then I can hear the clunk of the throttle hold a second later, a few feet off the ground.

Will check pinion and OWB as kindly suggested. I don't expect the ICE logging features will be any good as I believe they stop once the buffer is full rather than wrapping round, shame as I'd love to see what it thought was going on..

Cheers, Tom.

[waveydavey]

Of no help whatsoever but I love your crash write up, loss of enthusiasm, lmfao. The ESC didn't over current and lock out did it. Not sure how you would check this post crash but if you still had servo control that is what it soulds like.

[Guest]

The ESC didn't over current and lock out did it

Could well be! But I can't think of a reason why. I can sort of see how the current load might go up on a sagging lipo to maintain a governed output, but it doesn't seem plausible to me that this alone would cause a large over-current on the controller.

[alioth]

When I had unexplained power losses (complete) on my T-Rex 500, turned out it was the power cable to the receiver had become chafed, and if all the servos were moving it would cause sufficient sagging in the input voltage to the receiver that it would failsafe and kill the motor.

[Guest]

Gave it a going over at lunch time. Can't see anything wrong, seems to fire up ok with the motor out of mesh. So it's not drawing much current, but I didn't see any voltage sag on any cells. Gave all the connections a wiggle and it all seemed good.

I'm thinking my aerial is the problem. It's the thing I've most recently changed (Spekky to Futaba, how ironic!). By the book, it's in the most stupid place you could put it I suppose, right alongside a CF boom support. The orientation at the top of the loop might just have created the pathological condition for shadowing and being end-on with the tx aerial. The rx would have fail-safed the throttle, and then maybe the ESC would have gone into soft start on recovery.

Easy thing to change anyway..

FoolishAerialLocation.jpg

[Guest]

Deja vu

"Fixed" it, flew it again - 3 packs, did a few loops and stall turns (even my first ever bit of inverted) .. and then a perfect repeat of the original problem - chronic loop apathy.

I'd improved the aerial location, but I can't believe a FASST rx at this range would have a problem.
RxAntenna.jpg

The breakable horns saved my servos again
Breakaway.jpg

I did notice that my main gear still has a bad habit. I've tried to adjust how sunk into the OWB sleeve the tail drive gear is, but I'm not sure there's really anything to adjust. I've no idea why there's now not enough clearance for the main gear, but it's been like it for months and doesn't really seem to create any extra resistance, at least on the ground. Tried a new main gear but no difference. It does have the spacer between the OWB and the shaft bearing block, and the bearing block is put in the right way round. Just likes to grate on the frame a bit
BadHabit.jpg

So I'm thinking I'm going to buy another 50A ESC to eliminate that as a cause. I'd default to the ICE 50 Lite, but maybe there's something more interesting (and not too much more expensive) I should consider? Can't live without a governor..

All thoughts welcomed

[Guest]

Don't think anyone really wants to hear more about this but since I've found out what the problem was, I thought I should wrap up..

I've no idea why there's now not enough clearance for the main gear, but it's been like it for months and doesn't really seem to create any extra resistance, at least on the ground. Tried a new main gear but no difference. It does have the spacer between the OWB and the shaft bearing block, and the bearing block is put in the right way round. Just likes to grate on the frame a bit

Yep that was it.

I've tapped the OWB into the main gear housing so it's flush with the top of the main gear hub. There's 1mm or so of clearance now. Looks much better. I can only imagine that making the 450M motor drive a lathe, facing a main gear with a wide carbon fibre cutting tool was not in the job description of the ESC.

On the advice of a mechanical kiwi, the spacer was reduced 3 thou to provide a clearance fit between the OWB and the main bearing. Under a simulated load, the auto-rotation is now much more free

Thanks all, and if there isn't another post this time next week then it's nailed