ESC

[Steve Hargreaves - Moderator]

Amen to that Chris....

[Malcolm Fisher]

This has been an interesting thread for me, as I've just dipped my toe into the electric pool..

 

I have returned to flying gliders on the slope. As the site is some distance from where I live, there are times when the conditions have changed by the time I get there and I find that there is no lift.

To get round this and guarantee some flying, I bought an electric glider package which came with a 600 can motor,foding propeller, seven cell Ni MH battery and supposedly matching ESC to which I attached the supplied heat sink.

 

I can't fault the model for performance with regards to power and its gliding ability with power off, but there seems to be some problem with reliability of motor run.

 

On the ground there seems to be no problem with the motor at any power setting, but in the air the motor cuts without warning at varying intervals. Sometimes it will switch back on after closing the "throttle", sometimes it won't.  The propeller doesn't always fold when this happens and I feel sure that sometimes it "windmills" The period of motor run can vary from a couple of seconds up to about half a minute while flying, but when held on the ground I have been able to run the motor for much longer with no hint of it stopping regardless of throttle setting. Back at home after fully recharging the battery, I have run the motor at varying throttle settings, mainly at WOT, until the BEC has operated.

 

Has Timbo, or anyone else, any suggestions as to why this should happen?

 

My thoughts are that there is something wrong with the speed controller, so I'm looking for a suitable replacement and would welcome ideas.

 

At present I don't want to take the LiPo and brushless route which most people now seem to regard as the norm - this set up will do all that I want for the time being if I can solve the erratic behaviour.

 

Malcolm

 

[Tim Mackey]

First off, you too are confusing BEC and LVC - see post at top of this page.

I would say that its the LVC device on the ESC that is cuttting power to the motor, due normally to either overheating, or more likely the battery voltage dropping.

I cant understand though why it behaves on the ground - it sounds like you have given it a thorough testing on the ground?

Only other thought I have at present is radio signal loss causing the ESC to shut the motor ( which many ESCs do ), so are you sure this is not the issue?

[Ed Anderson]

I would bet there is a lose wire somewhere.  You are not seeing this on the ground because the plane is not being knocked around.

 

In the air you are losing power, then regaining it.  This resets the ESC, sometimes turning the brake off.

 

I would look for a bad battery connector, or the battery to ESC or ESC to recever.

[Chris Bott - Moderator]

It is odd that it's fine on the ground but has problems in the air. I would say then that there are two possibilities. On is the loose connection. On the ground you could try running the motor and shaking the model to see if it behaves like when it;'s in the air.

One possible loose connection could even be worn brushes in the motor...

 

The other possibility is radio interference causing the ESC to cut power to the motor. This could be external interference or something generated by the motor or motor brushes. Do you have capacitors fitted to the motor to suppress any sparks?

 

 

[Andy Harris]

There is something odd going on in the world of ESCs, we do not get what we pay for.

 

I keep forgetting my lesson that cheap ESCs are the best.  The three posh ESCs I've bought have all ended in grief.

 

I've not yet worked out why some ESCs get hot and others don't, or why we believe that we need 20% extra capacity on the ESCs.

Yesterday I thrashed a cheap HiModel 60A esc on a 6S//1100W motor (53A peak). It was barely above ambient. (motor hotter!)  Then I cruised around at 1/2 - 2/3 throttle towing a streamer, again barely above ambient. (motor cool)

 

The previous posh 60A ESC got steaming hot and did very very bad things (I do understand timing etc)

 

I suspect the opposite is true of motors, I've just changed a £38 motor for a £65 motor, and gone from 845W to 1100W output but longer durations under real conditions (both quote 84% 'efficient')

 

My conclusion is that there is a lot of difference between published specifications and real performance. 

[Andy Harris]

There is something odd going on in the world of ESCs, we do not get what we pay for.

 

I keep forgetting my lesson that cheap ESCs are the best.  The three posh ESCs I've bought have all ended in grief.

 

I've not yet worked out why some ESCs get hot and others don't, or why we believe that we need 20% extra capacity on the ESCs.

Yesterday I thrashed a cheap HiModel 60A esc on a 6S//1100W motor (53A peak). It was barely above ambient. (motor hotter!)  Then I cruised around at 1/2 - 2/3 throttle towing a streamer, again barely above ambient. (motor cool)

 

The previous posh 60A ESC got steaming hot and did very very bad things (I do understand timing etc)

 

I suspect the opposite is true of motors, I've just changed a £38 motor for a £65 motor, and gone from 845W to 1100W output but longer durations under real conditions (both quote 84% 'efficient')

 

My conclusion is that there is a lot of difference between published specifications and real performance. 

[Malcolm Fisher]

Thanks to Tim. Ed and Chris for their views.

 

Chris, The motor has capacitors on the connections, and the model is only a few weeks old and has had three outings to date.

 

On the very first flight, the motor cut after a short time, but always responded when I opened up again. Soaring conditions were pretty good and the motor only had a few seconds run at a time to regain height and continue flying when a non powered model would have been committed to land so it's possible that if the problem was overheating, it didn't happen and the intervals between running could have been sufficient to cool things down.

 

Ground running has been tried at various distances while shaking the model around and operating all controls with no apparent glitches and the motor responding to control as one would expect, yet when committed to flight I get the motor cutting even though it has run faultlesly for much longer while being shaken about. This is repeated after each time I've landed the model following a motor cut i.e. there seems to be no trouble until the model is at a guessed height of around 100 feet.

 

Tim, my reference to the BEC operating should have been with regards to the LVC - that part is what I meant. As there has been no sign of loss or lack of control of the flying surfaces I don't think it is loss of signal causing the shut down.

 

During a ground run where I ran the motor until the ESC cut power to the motor, the motor got quite warm - too warm to hold for long, but it turned freely at all times and the ESC didn't seem to be hot. I had again given the thing a good shaking and varied the throttle setting but mainly kept it at WOT with no hint of it missing and it opened up again briefly after shuitting down as I'm led to believe is possible for an aborted landing following a LVC operation. At the end of this test, the battery showed a no load voltage of 8.2v. After my last outing it read 9.2v following the flying session. It had been fully charged beforehand for each session.

 

I will check all the connections and probably replace the connectors to make sure that there is no loose wire as Ed suspects, and report back after the next outing which, sadly, might not be for a week or two..

 

Thanks

 

Malcolm

 

[Steve Hargreaves - Moderator]

Just to lob one in from the sidelines so to speak does your radio have a failsafe set up on the throttle? Might some interference somewhere in the system be fooling the failsafe to act & shut down the motor?

[Chris Bott - Moderator]

Sounds like you are being pretty thorough Malcolm. It does sound like the only difference is the environment that the model is in. i.e. it is 100ft in the air. It is also some distance from the transmitter so the wanted received signal is far weaker.

 

It still sounds like some sort of interference, possibly too quick to affect a servo but something that just upsets the ESC for a moment.

 

Can you move the Rx any further away from the Motor, ESC and all power wiring?

 

Also possible is a microwave telecoms link crossing your patch or a faulty high voltage national grid insulator with some arcing going on (more common than you would think).

These can sometimes be mitigated against with tin foil wrapped around the Rx. 

 

 

[fly boy3]

Hi all,  slightly off topic,does the "Twinstar" have a dedicated esc as supplied, or can one use a similar type as far as amps are concerned. Thanks FB3.

[Ed Anderson]

Malcom,

 

I am still going to work the lose wire angle.  Next suggestion is to open the model.  Secure it as best you can.  You won't need full throttle for this test and you can do it with the prop removed if you like.  

 

Turn it on, power up just enough so you can tell the motor is running, maybe 1/4 throttle.  Now go pull, pull, push, twist and wiggle the wires directly with your hand.  that includes the battery wires, and every connection.  Don't forget the antenna wire. 

 

See if you can get it to show a problem.  Remmber to pull, push and lightly twist each wire.  Also check to see that your push rods are not touching any of the wires, especially the antenna wire.

 

Just one more step to eliminate this as an issue.

 

 

Oh, one last thing, and this really happened to a friend.  Make sure that there are no screws touching any carbon that might be in the fuse or the push rods.   I had a friend with a DLG that was having repeated crashes. 

 

I don't recall the exact details but it turned out the screw that was holding down one of the servos would touch the fuse or a rod or something and cause enough interference or a short or something and the model would go dead for an instant.  This was a DLG and it would die on launch from time to time.  It was caused by the extreme stress on the fuse during launch.

 

When you are done with this you can check that off and move on to other things.

 

[Malcolm Fisher]

Thanks for all the input.

I had another session this afternoon, having checked all the connections and replaced the connector on the ESC where the battery plugs in. Battery was fully charged this morning and not connected until I was ready to fly.

 

Motor "fired up" when ready to launch but cut in the air after a few seconds - this time much lower and closer to the launch point. Soaring conditions were good and I managed to gain a reasonable height in the slope lift without power. I made several attempts to start the motor during the flight without succes i.e. there was no motor availabilty throughout the rest of the long flight.

 

After landing, the motor started as one would expect, but I didn't fly again as I had other models which were happy in the conditions without power.

 

Chris, The Rx is as far as possible from the motor with only a little slack in the wires - I don't like things in this area to be too tight.

 

Steve  I don't know if there is a fail safe in the radio, but I doubt it as it is a no frills three function 35MHz set and only has servo reverse capability - not even rate switches.

 

Ed, I'll try your suggestion, but the shaking around I have given the model should have been more than enough to show a loose wire - I reckon I give it much more hammer that way than it ever gets when airborne - its flight is very smooth, and even just soaring is one of the fastest gliders I've had and perfectly responsive considering the controls are only rudder and elevator. There has never been any sign of a glitch in these controls with or without the motor running.

 

My next idea is to try to use a different radio and see if that makes any difference. Following that it will be a case of change ESC, mptor and battery, one at a time and see if that shows where the problem lies.

 

I'll keep posting with progress as and when it happens.

 

Malcolm

Edited By Malcolm Fisher on 22/06/2010 20:44:49

Edited By Malcolm Fisher on 22/06/2010 20:46:33

[ericrw]

First of all I wondered where Timbo had gone , now I know it's Tim Mackey.   What I wuold like to know  about this ESC posting, is, am I doing harm to my ESC, in tootling around the sky at lesser throttle, other than full throttle?   My model is the Multiplex Funcub with the stock motor & ESC.   Eric.

[Tim Mackey]

No.

[Ed Anderson]

Posted by eric loakes on 22/06/2010 21:00:40:

First of all I wondered where Timbo had gone , now I know it's Tim Mackey.   What I wuold like to know  about this ESC posting, is, am I doing harm to my ESC, in tootling around the sky at lesser throttle, other than full throttle?   My model is the Multiplex Funcub with the stock motor & ESC.   Eric.

 

Nope, no harm at all.

 

Ed

[Peter Beeney]

Malcolm,
Just to echo Chris’s words, it would seem that the only things that are really different when you are flying is the fact that you are at some range and the model is moving forwards.
If you haven’t already tried this, and you have a friendly helper, is it worth taking the model 2 - 300 yards away, extending the aerial, and then giving it a try? It can happen, an aerobatic model once had some interaction between elevator and ailerons, but it wasn’t apparent until the aerial was extended, which threw us for a while. It seemed to be only happening when it was flying! It was a capacitor in the tx, it was not nearly as severe as in your case, and so I think this has to be a mighty long shot anyway.
The integrity of the power supply seems to be totally secure right up to the motor, because, as you say, it’s the only thing that fails, is it possible it’s something to do with the motor unloading slightly in the air and it’s a little trick of the armature moving? This sounds highly implausible, almost impossible even, but I think I’d be tempted to suspect the motor and work back. Again, if you haven’t done this, is it possible to very lightly press the the spinner back with a piece of wood with the motor running? You would certainly think the the shaking etc. that you’ve already given it would have the same effect!
The capacitors can give trouble, but from what I’ve seen in the past it’s far more obvious. I think they short any rf borne interference and that causes total havoc, with all the servos! I’m sure it’s not there.

It would seem to be one of two things, the motor going open circuit, when moving forward, flying, that is, or the ESC shutting down, also when moving. Ultimately you may have to crack it by substitution, one bit at the time, to get the answer.

A very remote chancy poke here, the throttle control signal wire from the ESC? The two power wires are ok but is there any strange remote chance there is some sort of intermittent break on this? This really is clutching at straws now!

Good Luck.               PB

[Malcolm Fisher]

Peter,

 

I've been clutching at straws and scratching my head since the first time out with this model. On that occasion, there was a motor cut when at height, but it always started again when required. I don't know if it would have cut again as for the rest of the session I only opened up for a few seconds as and when needed.

 

Each time out since then ,I've tried operating at some distance on the ground, admittedly not as far away as you have suggested, with no apparent problems. The motor has always responded to running at all throttle settings and starts again after being stopped - until committed to flight.

 

The motor will run for ages, and has been run without faltering until the LVC on the ESC cuts power to the motor. However, when committed to flight I can't be sure that it will continue to run or, when cut, start again whether or not there has been a ground run before committing to a launch.

 

I can't detect any forwards/backwards motion on the motor shaft, but will try your suggestion about putting pressure on when it is running

 

As said I intend to try a different radio next time then substitute components one at a time until I find out what is the culprit.

 

My best guess is that the problem lies with the ESC somewhere, but only substitution would determine that, and at present, I don't have another one.

 

Thanks for your comments,

 

Malcolm

 

[Chris Bott - Moderator]

Malolm, I'm not sure if you've tried this: How about getting someone else to hold the model, or restrain it, and do a range test. See if the motor falters when at some distance from the Tx.  i.e a range test with the Tx aerial retracted, or if 2.4 then on range test mode.

Mainly, replicate the exact conditions on the ground that you have in the air when it falters. Then reduce the distance 'till it's not faltering again.

[Malcolm Fisher]

Chris,

We did a range check on the ground with aerial retracted before the first ever flight and no glitches occurred.

 

It is impossible to replicate the in flight conditions as distance can only be an estimate -- there is no reference point against a clear blue sky...

 

The difference is somehow in the change between the model being held, near or at some distance, or when flying free with no restraint.

 

Whatever it is, it is very inconsistent as the motor might start, could then run for upwards of half a minute or just a second or two or it might not start again at all.

 

If temperature is part of the issue, when I was flying on Tuesday, it was a very hot sunny day - pushing 90 F measured on our garden thermometer when I got back home. Before I flew, I gave the motor a quick blip to make sure that it would start and stop then opened up and launched. The motor cut very quickly and I had a struggle to stay above the launch point until I managed to get through near ground turbulence and soar away in the slope lift. Thereafter the motor never started again until it was back on the ground even on a low pass at head height during an overshoot.

 

I have been considering ways of getting more airflow past both the motor and ESC and to this end have been making a replacement canopy with ventilation, and increasing the sizes of the vents behind everything.

 

Any ideas would be welcome.

 

Malcolm

[Steve Hargreaves - Moderator]

Unlikely this but worth a look......I recently had to shorten the wires from a motor & resolder the connectors. The motor wires were coated in varnish which is hell to shift completely & after resoldering the connectors everything seemed fine...motor spun up nicely. Put it in the model & it wouldn't run. Very odd.....wiggled the motor connectors & it started only to stop a few seconds later...more wiggling (apologies for the technical terms here guys...) & it started again.

 

It seems that the soldering of the connectors was less than brilliant due to the varnish. It looked OK from the outside but was obviously not good on the inside. I re-cleaned & resoldered the connectors & its been fine since (touch wood). This was a brushless motor so a little bit more "sophisticated" than your can motor but might you have a poorly soldered joint somewhere (ie on the motor terminals)

[Chris Bott - Moderator]

I think we're all struggling now Malcolm because it sounds so rock solid when you are holding it.

 

I'll certainly be interested in anything you do try though, and what finally solves it. 

[Malcolm Fisher]

Steve,

The motor wires were pre-tinned so I don't think there's any problem there. Similarly with the ESC wires and there was no difficulty when I replaced the connector between that and the battery, but even that might be worth investigating. I would have thought that if there was a problem in the connection between battery and ESC there would have been problems with the rudder/elevator controls and there has been no detectable evidence of that either airborne or when held.

 

Chris,

That is the biggest conundrum. In the ground run test, the motor case does get quite hot but doesn't falter until the  LVC device cuts power. I would have thought that this would be the most likely situation for overheating and also that there is a possibility of more vibration being transmitted to the ESC while the fuselage is held securely compared with when there is no restriction as in flight.

 

The motor cut has always occurred at WOT during climb out from launch.

 

I have wondered about the feasibility of suspendiong the ESC on something to isolate it from any possible vibration transmitted from the fuselage. At present the ESC is just lying on the fuse bottom as shown in the assembly instructions, heat sink being underneath the ESC. There is an almost straight line between motor, ESC and receiver with all at almost maximimum possible distance which the wires will allow without them being under tension. Receiver is cushioned with foam.

 

Malcolm

[Peter Beeney]

 

Malcolm,

I’ve just caught up with the thread. It certainly all does seem very odd, and, indeed, as you say, there doesn’t seem to be much more you can do without actually changing the bits in the power train.
I think I might be tempted to put my money, (but not much!) on the motor, if for no other reason than simply that it’s a mechanical device, and as such probably has the highest chance of having a fault. Even if it’s the ESC it could still well be a bit mechanical, such as a dicky soldered joint or even a little crack in the printed soldered board. That’s difficult to believe here, though. I was once very lucky, I found this in a rx and much to my amazement repairing it cured the fault. As in your case, finding these faults is always the hard bit; and even more difficult for you, as it only happens when you’re flying!
Improving the cooling is always commendable in my book, but just looking at some models that’s not always easy to do I would think, and I’ll be very surprised if this proves to be your aggravator. This cutting out is too random in nature. If the motor became hot, I reckon it would probably carry on running until some solder started to melt and a joint became unglued, or something else burnt through. In which case, the stop is full stop. Any components overheating on the ESC might shut down but would quickly reset. I’d have thought this would have become an obvious pattern, too, plus also being easy to replicate on the ground.
Even when you’ve isolated the errant item, you’ve still to try and find out was is going on. Very interesting!

You could always try a bit of i/c, though, for a bit of trouble free casual relaxation……….or not!

Hope you crack it ok.             PB

[Chris Bott - Moderator]

I still have my metaphoric money on interference.

What radio gear is it Peter? 

 

I'm thinking you are climbing through some interference or the motor is generating it. When you are near the transmitter, the transmitter signal is strongest. As it climbs away the signal from the transmitter gets weaker, but maybe the interferer stays as strong or gets stronger.

I have had interference on a single channel in the past. Oddly, that was nearly always throttle channel.