ESC

[Malcolm Fisher]

Peter,

I returned to slope soaring after many years of power. The site used to have a power strip as well as the slope areas until antisocial behaviour led to a ban on power flying. A similar situation occurred on another site I had used for over ten years. Another club negotiated access to the field with the farmer. Within a few weeks there were restrictions on times of flying and some "no go" areas where previously there had been none. Before the season was over there was a complete ban...

 

The electric model was bought to ensure some flying as I had had several trips only to find that conditions were so different by the time I reached the slope that there was no lift. It has solved that problem - sort of. 

 

Chris,

I don't think that there is a case for suspecting interference. If there was any, I'm sure the other controls would have been affected, but there has been no sign of that. The model continues to soar under full control apart from being able to apply power if desired or needed. The radio is a 35MHz JR set supplied with the package. I am going to try one of my Futaba sets to see if that makes any difference.

 

Malcolm

[Chris Bott - Moderator]

Hi Malcolm, there's every chance I'm wrong but you can't discount it just because other channels aren't affected.

 

On JR throttle is Ch1. So theres a chance the Rx is struggling with frame lock and Ch1 is randomly affected. Also, it could be such a quick glitch that the ESC notices but servos can't respond so quick.

 

Using different radio will be interesting. Trust its a different Rx too?

 

Chris 

[Peter Beeney]

Malcolm,
Yes, I can have a lot of empathy with you, I’ve been there myself, also on more than one occasion. Oddly, we were slightly different, it seemed there was always a feud going on between the farmer and his neighbours. We just became just one more piggy in the middle of a hornet’s nest. My little throwaway comment was only meant as a jest but certainly i/c really does seem to have it’s problems.

With the greatest respect to Chris, I too would be suspicious of the interference angle. Whilst not entirely ruling anything out, if you consider how the radio works it’s very difficult to see how one channel could be affected. Plus a range check would start to identify this straight away.

I’m sure that any results you get, good,bad, or indifferent, are going to be very interesting! PB

[Chris Bott - Moderator]

Well I am probably wrong. But I have had interference on one channel. On more than one model. Always Ch1...  make yr own mind up.

[Peter Beeney]

Chris,
    I’m sorry, I’d posted before I’d read your post of 05 : 05. It’s just that I’ve never seen any interference that affects one channel, and I certainly don’t understand how that can happen. However, I’ve long since learned that nothing’s impossible, so it could well be. I would not rule it out.

I’m sure Malcolm will tell us what he eventually finds is the culprit.       PB    

[Chris Bott - Moderator]

Hi Peter, no probs as I said, it's probably wrong anyway. Maybe there's a glitch from the brushed motor (sparks) getting directly back into the ESC?

 

The one bit I can't understand is why its so good on the ground and why it only happens in the air. I've even been thinking that the hand holding the model is involved!

 

I'm sure it will be simple when resolved. Or possibly something will be changed, it will cure it and we still won't understand why. 

 

Something else to try (if it is BEC powered radio) might be to remove the BEC red wire feeding the radio, and try a Rx battery. (apologies if this has already been tried or suggested)

[Peter Beeney]

Chris,
It seems to me the difference here is between the glider moving and not moving. When the motor is not running it won’t cause any interference to the ESC anyway, so the motor should restart. And then stop again?
I’ve also considered that the power supply must be secure, otherwise it would surely fail completely, but adding a battery for test purposes is certainly an option. I’ve never been a ‘cut the red wire’ man anyway, I personally wouldn’t do that, and I do also know I’m a bit of an heretic and should be burnt at the stake, or at least given electric shock treatment, I don’t have any problems with that. But I’d be surprised if it did make a positive improvement, with or without the notorious red wire.

However, I am constantly being surprised, I’m always finding that things are not what they seem to be, but I think by now I think I’ll not be very surprised at whatever Malcolm finds is the answer to his very intriguing problem.           PB

[Ed Anderson]

This is like a Sherlock Holmes mystery.  I think I know who did it, but I am wrong.

 

So, here is another thought.

 

What changes between ground and air?  The dynamics of the model.  We have all tried to look at that to find a clue.  

 

Look at the motor mount and the spinning parts of the motor.  Is there any play in the mount?  Is there any play in how the motor sits in the aircraft?  How much clearence between the spinner and the fuselage?

 

Is there any part of the motor/drive train that goes through the motor mount?

 

I am looking for something rubbing that would increase the load on the motor, thus drving up the amp draw causing the LVC to kick in.  Naturally the motor would stop, but could then be restarted again.

 

Perhaps the spinner could be brushing the fuselage in some way, causing drag. 

 

My first and strongest impulse was an electrical problem, but now I am looking for mechanical issues.  Something that is different in the air than on the ground.

 

Case in point.  A poster on one of the other forums had a similar problem a while back.  He was flying an outrunner.  Turned out that the shaft was somehow contacting the side of the motor mount, but it was only happening in the air.  He could not see the issue till he removed the motor. Then the rub area became obvious.

 

Another had an outrunner mounted in front of the motor mount.  Turned out that when he attached the motor, the back of the shaft was being lightly pressed into the motor mount.  This was causing drag.     It seemed that on the ground the motor would pull away from the fuse and mount just enough to unload this contact point. But in the air, where the fuse can move to "catch up with the motor", the motor could not "pull away" from the motor mount.  Again, pulling the motor off revealed the issue.

 

Watson, this is a real head scratcher.  I still think the buttler did it!

[Malcolm Fisher]

Thanks guys for all your input.

 

Chris, with this particular JR set, throttle is on channel 3,. The Tx has two sticks - rudder on the right and elevator on the left. Throttle is a small lever on the right side of the TX.

 

This afternoon I changed the Rx for a Futaba linked to my 6EXAP Tx. there was some problem somewhere and I couldn't get the rudder and elevator to work independently - they behaved as though they had been "mixed" - a function I have never used. There had been no problem with the gear in the model I robbed.

 

Playing around to try  to solve this and reversing the elevator at the Tx because it was operating in the wrong sense, I inadvertently switched model memories.

 

The throttle servo on that one must have been the opposite sense because the motor burst into life, the model shot forwards and broke the prop.

 

I know, I should havemade sure the model; was securely held, and that I should have  removed the prop - lesson learned and re-inforced by the need to get a replacement..

 

I did however, manage to separate the rudder/elevator so that they worked independently.

 

Regarding the motor, there is a very small amount of for and aft play in the shaft, and following the mishap I noticed that one of the capacitors had become unattached at one end. The motor has been taken out of the model and this has been rectified.

 

There is no sign of any.rubbing anywhere and the motor was securely mounted.

 

Next chapter will be written up when I get a new prop and, hopefully, get another session sometime next week.

 

Malcolm

[Chris Bott - Moderator]

Malcolm I really feel for you, these things do happen and that split second when you realise it didn't need to, is just so annoying.

 

But, it does sound like you have come across a  possibility for you fault. I look forward to the next instalment. I do hope you've cured it.

 

Cheers  

Chris

(at the fly in) 

[Malcolm Fisher]

Chris,

 

Thanks for the condolences which, in reality, I don't deserve as I've read many times that an electric motor is always "live" unlike IC.

 

After this incident, I've decided to try once more with the original radio, but be prepared to do a swap next time out - it wouldn't be the first time that I've changed radio gear on the slope as many years ago in my learning days I had only one radio and used to change that from one model to another if I "bent" one. 

 

During the removal of the motor to resolder the capacitor, I discovered that there was a loose "sleeve" round the motor casing. It might have happened during the removal, but this sleeve was covering the cooling slots at the rear of the motor which appears to have a small internal fan. As there is an indent which seems to locate the sleeve in a particular position I put it back to where it seems it should have been, although I can't be sure that it had moved before I attempted to take the motor out of the model.

 

This is part of my reasoning for re-instating the original radio - I just might have changed two variables and don't need the complication of a third while trying to track the fault down.

 

At least I did learn something - part of the broken prop revealed that it was 8" x 4.5" so I know what has been used to date.  Now I need to know what sort of size prop I would need to make the motor pull fewer amps - even at the risk of less pulling power - to see whether that would make a difference in future trials.

 

I have what I believe is a Graupner folding propeller which I bought many years ago to use with a 600 motor I had been given, but have never used either. Prop diamter is fractionally less than the one I broke and the pitch looks similar but there is nothing marked anywhere to say just what it is. Checking this motor over shows that it works with the NiMH battery, but there is no evidence of suppression capacitors so I am reluctant to do a swap with that. Can anyone tall me what sort of value the capacitors need to be so that I can amend this lack as another "string to my bow"?

 

Malcolm

[Peter Beeney]

Malcolm,
If we begin at the ending, so to speak, I think the capacitors you’re wanting are something like an 0.01uF ceramic disc, such as the BX00A from Maplins. The values are probably not really that important anyway, anything from 0.1uF to 0.01uF. Or perhaps even down to 0.001uF. But I would use an operating voltage of at least 50V. Once upon a time you could buy a ‘motor capacitor kit’, I think from MFA, I’m afraid I cannot remember exactly but I have a feeling this may have been three caps, with something like a 0.1uF between the terminals and one 0.01uF between each terminal to can. But I may be completely wrong there. Certainly as I remember there was the piece of insulating sleeve for the legs, don’t forget that, otherwise sure as eggs are eggs, there will eventually be a short. Again, from memory, and this is not now totally reliable, some motors had three caps, more usually two, and occasionally none, I think there was one school of thought that reckoned that the caps soaked up too much power. That’s a distinct possibility. I always thought that separation (distance) was a good idea, when I was into powered gliders for a while I used the Fleet Mini 4 channel rx, very light and small, which you could push down the back end of the fuz. Thus as far away from the motor as possible. It always worked for me.

I always used to run the new motors in for half an hour on the lowest voltage that would make them turn but many people did the same thing with the motor in a jam jar full of water. This was considered very beneficial.
Also I think you can glue a schottky diode across the terminals to act a a brake. Although I’m sure a 1N5401 would be just as good.

The loose ‘sleeve‘ you mention is probably what was known as a torque ring. The theory of this was that it concentrated the flux and improved the torque. If you removed it, it made the motor faster. I was never into competition stuff but I think sometimes with these lads there was a bit of a love/hate relationship, you either used them or you didn’t! Also I think sometimes it may have known as a slug, although this may be a bit of an archaic (like me!) term and only used by specific groups of people. As in, - a slugged relay, a relay with a copper ring on the coil, to make it slow to operate. Your sleeve is steel, I believe, and I suspect our old friend Eddy Current, together with Lenz’s Law, is involved here. I think there was some talk at one time that some experts would add another sleeve over the top, or more, even, to increase the effect but I’d reckon you’d need to get that about right. Otherwise the law of rapidly diminishing returns might start to take over. I would have thought that there would be a chance of this warming up to some extent, which is always a waste of useful power!

Have you managed to get any further with tracking down the mysterious cutting-out problem with your motor yet?
I’m still not really convinced that overheating is actually causing this. I’m sure the motor would keep going until it finally stopped, and the ESC would continuously stop - start to some extent, although I’ve never witnessed this. What I have seen, though, is the voltage regulator, or BEC, overheating and shutting down, which instantly results in a crashed model, which is also a bit final.
Coincidentally, yesterday a colleague has told me he’d had a little bother with a motor intermittently stopping, which he was able to trace to the signal wire from rx to ESC. But his was also happening on the ground, which made it a lot easier to solve.
Ironically, if there was a little quirk on your motor, the jolt you gave it with the prop may have sorted it out! But never fear, my odd bits of experience of obscure intermittent faults on electronic equipment says that sooner or later they will come back to haunt you: the second time, though, you can be prepared.

I’m sure you will eventually solve this rather unusual conundrum. PB

[Malcolm Fisher]

Peter,

Thanks for your input., paricularly relating to the capacitors.

 

My memory is certainly not what it was, but I have some recollection of the three caps. I didn't take a lot of notice because, at the time, I had no real interest in electricity as a motive power. I was very happy with my diesel and glow motors when I needed power. I still have a couple of small engines as "power pods" as well as several "proper" power models.

 

The present motor only has two capacitors which are very tiny and look like the illustrations I have seen of tantalum bead capacitors. There is no evidence of any insulation on their "legs". Perhaps I should amend this?

 

When I removed the motor, I was very surprised to see that the mounting plate at the front was just a ply disc. There was no provision for apertures to match those in the front of the motor which are, I assume, intended to allow cooling air through the motor.

 

I have made a new mounting plate which does have matching holes and had hoped to have another try on Tuesday of this week. It was a "comedy of errors" outing. When I pulled the model out of the car, I found that I had forgotten to replace the spinner on the folding prop so the blades wouldn't hold the optimum position. To add insult to injury, I had brought the wrong transmitter - I had put in the one intended to replace the original having forgotten that I had reinstated the original receiver...

 

Ah well, such is life and I might get it right next time.

 

Malcolm

Edited By Malcolm Fisher on 03/07/2010 20:26:20

[Peter Beeney]

 Malcolm,
   Thanks for the reply and I’m afraid my post turned into a bit of a ramble, as it often does!
   Yes, these things all tend to look the same, and if you wanted to use them, I’m sure that tantalum bead caps would be fine for suppression purposes, although they seem to come with very short legs for attaching to printed circuit boards, but they could be extended, another snag is they tend to be in the lower voltage range, which might also be ok. However, I guess the ceramic disc would be made to measure. I’m pretty sure the two capacitor lash-up was by far the most usual, I’d settle for this.
   The insulation on the wires. Again, I’m sure it’s quite possible a lack of this this might never result in a short circuit or similar; however, I am a bit of a belt and braces bloke, though, so I would insulate the leg that goes from the terminal to the capacitor, the other leg, from the capacitor to the can is not so important. Find a piece of insulation, maybe from the wire in some lightweight household flex for instance, cut it to length, slit it along it’s length, a smear of contact adhesive inside and slide it on to the wire. A touch more sticky at the ends etc., - perfect! I personally don’t think it’s a good idea to unsolder a perfectly sound joint unless you really have to!
   Any provision for more cooling has to be good, particularly in a model aeroplane. Some models I’ve noticed seem to have none at all. Electrical components do not like excessive heat, for one thing, which has been stated here before, they sometimes have shutdown facilities which protects the device but not the model! When these little beasties are operating at their top limit any extra load results in an exponential heat increase. Not quite a ‘thermal runaway‘ situation, but perhaps getting close. When you see cases of shrunken and split heatshrink covering, and in one case it was burnt and welded onto a battery in a molten crust, then you know things have been warming up! Aeromodellers are very good at testing the outer limits!
   But it certainly doesn’t sound as though your installation is getting overly hot at all.
I can definitely empathise with your ‘comedy of errors‘ trip, although these days I tend to do a double take before I leave. I would not be surprised if you find there is nothing wrong with your model now, it’s all down to the ‘knock test’ you gave it. This procedure has been used before, in the same spirit of desperation. Only kidding…..
   Good Luck, and I’d be interested in any conclusions you arrive at. PB

[Clifton Park]

Malcolm

 

Last year I had a problem with an IC model which seemed to be  random glitching  during flight, which I could not reproduce on the ground. After one of the many gear removals and re-installations I re-routed the RX aerial from along the axis of the fuselage and hooked it to the tip of the tailplane so that it was about 40 degs to the fuselage. Problem solved!

 

Might be worth trying this on your model, doesn't cost anything or require much effort. I have found in the past that a model on the ground or being held can produce different RX performance than that occurring in flight.

Looking forward to the solution of your problem.

 

Brian 

 

 

[Malcolm Fisher]

Brian,

 

The only glitch is that of the motor cutting. It would possibly be more understandable if there was evidence of other controls being affected.

 

However, moving the aerial outside as you suggest is one of the items on my "change one at a time list".

 

Having sorted out some extra cooling for the motor plus re-attaching the dislodged capacitor I don't want to do anything else until I've had another flight.

 

The aerial move would be an easy one to make on the flying site should there still be a problem. With hindsight, I could have done that weeks ago - didn't think of it until I started listing possibilities when back home, but will be prepared to give it a try next time out which will, hopefully, be tomorrow afternoon.

 

Malcolm

 

Edited By Malcolm Fisher on 05/07/2010 20:37:52

[Malcolm Fisher]

Back again after, at last, another outing with the recalcitrant motor glider set up.

 

Model climbed away to a reasonable height and the motor cut as before and wouldn't restart for some time.

 

After a period of gliding sans power, the motor eventually responded and I flew for quite some time but only gave the motor a few seconds run each time stopping it via the transmitter. and, on the whole, had an enjoyable session with a number of flights before rain stopped play..

 

In spite of my modifications, it looks as though there is no change for the better. The motor will still run without hesitation while on the ground but cuts when airborne..

 

Now it's time to start substituting alternative bits of equipment.

 

Last month I was the lucky(?) winner of the Forum "Giveaways" and now have a new ESC for a brushless motor. Stupidly I didn't take any notice of the spec when I entered as I didn't expect to win - I never did in these situations until now and my power plant is a 600 "can" motor.

 

The prize is an Overlander XP-30A-2  ESC and is, apparently, compatible with the seven cell NiMH battery I have. I now need to know what sort of motor/propeller combination it will serve and if there is one such which might be comparable with the 600 brushed motor.

 

This is totally foreign territory to me and I have no idea where to start but think that a new brushless motor plus this ESC could be a starting point to solve my problems - at least it could be part of the way .

 

I've tried looking at some sources but don't know enough to be able to choose a suitable motor.

 

Can anyone advise me?

 

Malcolm