Stuttering motors on a Lancaster

[David Tayler]

I have built a four engine Lancaster out of Depron foam with some balsa reinforcements . The wings are sheeted in 3 mm Depron and contain the wiring for the motors .I tested the motors and theESCs prior to installation. One ESC provides the 5 V supply to the receiver and servos. All the motors run without the propellers but with the propellers fitted, three of them just rotate slowly, unless flicked round when they burst into life- ouch blood to prove it! The ESCs are EMAX 20 amp Simon K-series and are producing lots of bleeps. I wonder if I have inadvertently got them into programming mode, or that the problem is caused by having an inappropriate program for my motors. The behaviour is the same whether I use a receiver or a servo tester. There is one wire to each motor to transmit the servo pulses. I am looking for a reprogramming card to try and solve the problem but they seem to be unobtainable now. Does anyone have a surplus one I could buy? Or has anyone any other clever suggestions which will save me doing major surgery to the wings and the nacelles?. David

[Chris Walby]

Hi,

We might need more information to bottom this, but when you say one wire to the ESC I assume you mean the signal and the negative to three ESC's and the forth with all three wires?

Have you tried teaching the ESC's the RX throttle min and max positions?

Lastly I had a E-max motor that would occasionally flick back 1/8 of a turn before operating correctly...until the maiden when at WOT the motor to bullet solder (manufacturers termination hidden under heat shrink sleeve) parted company....resulting in a dead stick...

Double check all connections, if in doubt cut the sleeve off and inspect the soldering...

[David Tayler]

II have tried calibrating the throttles- indeed when I did this ws the time the problems started.The ESC can also be put into programming mode by powering up with the throttle at maximum. I wonder if this is where I went wrong. As to wiring I have one signal wire to each ESC , connected together in pairs at each wing root.I have two channels for throttles ,one for each wing.,The negative wires are common as are the positive ones. Only one esc provides the positive supply.

[Chris Walby]

David,

The red wires on the other 3 ESC's should not be connected together...just disconnected from the servo plug and taped/heat shrink sleeve.

Each BEC or UBEC on the ESC's will fight or disrupt the others, not sure if it will have caused permanent damage so just disconnect and test.

Hope that helps, if not ask and I'll draw a diagram !

 

Edited By Chris Walby on 05/11/2020 17:29:44

[David Tayler]

Chris, One esc supplies the receiver .No supply to the others-my error in the post above.David

[Robert Parker]

Hi David,

You are bringing memories from my past.

I too had a problem like yours and to the point, it drove me up the wall trying to find the fault. A programming card is a big help here.

A couple of years ago I built a 72" Short Stirling which had ESC/electrical problems, if you are interested in did a build blog on here it was called "Design and Build Short Stirling", I had what turned out to be a faulty ESC AND although brand new a faulty extension lead, see page 11.

Hope this is of some help or do as I did walk away from it for a while and come back with a fresh mind.

Regards

Robert

[Keith Berriman]

David PM sent on Simon King ESC Card

[Dad_flyer]

Are all the negatives connected to the receiver? If you are on more than one battery, and you only connect the signal wire, then there is no zero reference for ESCs on the second battery.

[Simon Chaddock]

David

From the problem you describe it sounds like three of the motors are not returning the 'direction' sensing pulse back to their ESC correctly. It is a minute voltage so it only takes a small resistance or stray voltage to confuse the ESC.

With a prop attached the rotation of the initial pulse is lower so the return voltage created is even smaller so gets 'lost' more easily.

The most robust way is to connect each ESC individually to the rx so there can be no question of stray voltages or poor connections effecting the other ESCs.

I had similar problems with a 4 micro EDF plane with long wires. The EDFs did strange things until each ESC had their own individual wires all the way to the rx and individual ESC power wires to the battery. They then operated perfectly normally.

[David Tayler]

Thank you for your thoughts and help. All the negatives are connected together. I have two batteries but they are in parallel.There is one esc per motor,but the signal wires are joined at the multiplug where the wings join the fuselage.I will try unsoldering these and test each motor individually.I am hoping not to have to do a major rewire as that will involve cutting through the glass covering the wing and a major rebuild!!

[Keith Berriman]

David pm sent with pictures of card and an esc

[Frank Skilbeck]

It maybe that the ESCs are not seeing a strong enough position signal as this is now split between the 4 ESCs, although the position signal is a very low current if you try to draw too much from one receiver channel it can cause some issues. Does each ESC work fine, with prop attached to the motor, if plugged directly into the servo tester or receiver channel.

[David Tayler]

Well I have solved it! When trying to calibrate the throttle I must have inadvertently gone into programming mode for the ESCs. With the aid of an Emax programmer I have now set up the ESCs to be appropriate for my motors.Low advance timing and a higher start torque.All 4 motors run up nicely.each wing has a separate channel so I could use diferential thrust if I feel brave! Thank you all and especially Kieth. David

[Geoff S]

That's good news.

I'm slightly puzzled by your comment that you've divided the throttle channels from side to side. I would have expected a division between inner and outer engines/motors. Are you likely to need differential thrust?

Geoff

[David Tayler]

I may never need differential thrust but dividing the channels between the wings simplified the wiring. I have soldered most of it and used as little wire as possible to try and save weight.I have those green multiplex connectors for the signal wires ,one pair for each wing.The power connectors are xt60 .I have two 22003s batteries in parallel.AUW at present 6and a half pounds.span 72 inches.

[Chris Walby]

Good to hear its sorted and on the subject of RX to motor IMHO there is no right or wrong way. Some use differential thrust mixed from the rudder to help taxiing. I tried it on a TN small twin that did not have a rudder servo and was hand launch. The effect was a very un-scale yaw if used in flight so I didn't bother with it much after testing it out.

One other model I use differential is my Woohoo and that does some really manic spins/tumbles with one on full power and the other stopped...perhaps not scale with a Lanc.

PS - put it on a switch and you can always try it when you fancy something different!