Oh no not another ESC question

[Chris Walby]

This might challenge the grey matter

Just prior to the aborted maiden of my BH Mosquito (taxing out) the port motor would very occasionally stutter (as in stop rotating and then pick up again). It seems to only do it say every eighth time and once above 1/2 throttle both motors operate up to full speed okay. If I throttle up quick and vary tings about it seems okay (kept above 1/2 throttle and almost seems to be most frequent with the gentle throttle movements when taxing!

I have not changed any of the factory ESC settings & disconnected both red leads on the ESC's as I am using a separate SBEC. Both ESC's are on the throttle Y lead.

Motor KMS Quantum 2814/06 1290KV, ESC's HK 40A 2-6S, Prop 10 x 7, 5000mAh 3S

Any and all suggestions welcomed (as long as its constructive!).

PS the only other odd thing is the port motor will sometimes initially swing the wrong way (say 45 degrees) on start up and then sort its self out.

[PatMc]

What current is each motor pulling ?

I would expect a 40A ESC to be overloaded with that motor/prop/battery combo.

[Dwain Dibley.]

Some simple elimination tests would be useful.........Swap the esc's over to see if the fault moves to the other side, then replace suspect esc with a known good one.....stuff like that Matey. That will narrow it down a bit, but it does sound like a dodgy ESC, which can happen straight out of the box. The motor reversal points to a fault too.

Do you use two batteries ? one per motor and esc ?

D.D.

[Capt Kremen]

I've had a motor intermittently stutter and then work at other throttle settings, turned out to be a duff solder (dry?) joint on one of the connectors. All, (factory soldered) connectors re-soldered, all resolved.

[Chris Walby]

Thanks guys, I'll carry out a few tests suggested and see what happens. If I need to strip the pants fitting cowls off I'll put the motor & ESC on my test rig that way I can change parts around and recheck the static load tests (IMHO red herring as the fault is on very low loads).

Don't think I'll be going back to HK for ESC's as that be the second with a fault out of the box.

I'll post an update once progress has been made.

[Chris Walby]

Update.

Stripped cowls off port motor and inspected installation with no signs of an issue, checked connections and then removed ESC/motor to bench.

Test run on the bench with no prop and fault seemed to be at very low speed settings where it would occasionally lose synch, stop and then restart, but we are talking way below 5% throttle setting.

Visit to LMS with comment that its not unheard of + could the spinner be touching the cowl (its a very tight fit so possible). Back home and a couple of washer under the motor mounts has the spinner clear of the cowl.

Up to the flying field and forgot the battery Y lead, revisited the field last night and tested across the entire speed range with no issues.

Taxied out and did some ground runs at low and short full power with no issues

So went for it... took off ok but needed a bit of 1/ 2 throttle flying around to trim it in + sounded like a noisy cowl vibrating, but nothing major.

All trimmed in so dropped height and up to full power across the field so away from me, then short squeal 3/4 down the field followed by yaw and dropped port wing. Buy the time I had throttled off it was at the end of the field pointing vertically down!

Full up elevator and low glide across the field (did consider gear down, but thought not!)

No major damage and only three skid marks (two visible on the field!)

Re-inspection found one of the motor manufacturers lead to connectors failed and burnt through the thick heat shrink sleeving. I will ditch all of the bullets and solder all motor leads to the ESC cables

Question? as ESC's seem to be supplied without bullet connectors is it better just to use in line barrels for the number of times they will be disconnected/connected in there life?

Thanks to all those that gave advice and help.

 

 

Edited By Chris Walby on 06/09/2017 10:32:16

[Martin Harris - Moderator]

Fit a couple of nice IC engines and get away from all these electriliability problems!

(I think I just made up a rather wonderful new word - googling it produces no results but feel free to use it!)

[Dickw]

Removing connectors improves "electriliability" and reduces weight so is an option I often use.

I don't use the 3.5mm connectors most motors come with, so always either replace them with 4mm or just solder direct to ESC - that way I never have a problem with the manufacturers soldering!

Dick

[Nigel R]

On my tiny sample size of two electric airframes, one recently had a motor lead fail at the solder connection, ending up being held together only by the heatshrink.

It's a manual phase during manufacture/assembly I would guess, so perhaps subject to being a bit rushed.

[Simon Chaddock]

Chris

You do really need a Watt meter reading as the current draw with a 10 x 7 at full whack may be getting close to both the ESC and motor limit.

For a couple of reasons but mainly weight I tend to solder the motor to ESC connections directly. Ideally with the bare un soldered wires 'worked' together so there are lots of individual solder connections.

It helps to use a big, hot iron as the thick copper wires conduct the heat away very fast so unless there is a lot of heat applied quickly the solder does not run properly throughout the joint.

It is amazing how many times what looks to be a perfectly soldered bullet (or sleeve) connector can actually be fairly easily pulled out. The solder has simply not 'adhered' properly to the inside of the connector.

Of course you never see any un reliabilty problem with IC, Yeah right!

[Martin Harris - Moderator]

It was slightly tongue in cheek I'll admit but I've lost 2 twins to (mishandled) engine/motor problems and as one was IC and one was EP it's honours even so far...although as the IC was in a deliberate flat spin when I think an engine quit at low level and I failed to recover, the only provable incident was with the electric.

[Dave Bran]

Posted by Chris Walby on 06/09/2017 10:31:33

Question? as ESC's seem to be supplied without bullet connectors is it better just to use in line barrels for the number of times they will be disconnected/connected in there life?

THE place where IMO bullets twixt ESC and motor are essential is on Helicopters where some of the setup has to be done with blades on and you REALLY don't want them turning under power!