Electric flight query

[andy watson]

Now I don't understand the first thing about electronics and the like, but I really don't understand why the title of this thread is Futaba 2.4........Oh no not again and why it is in the Futaba section?

[Former Member]

[This posting has been removed]

[Tim Mackey]

Well it did start off with Erfolg having problems with his 2.4G Fuby gear, but then kinda drifted .... it is now looking less and less likely that it was radio fault as such...but the thread is a bit large to move, and probaly almost dead by now anyway.

[David Ashby - Moderator]

Moved for sake of neatness. Does anyone know I amend every post that starts with a small letter to a capital?

[Erfolg]

This thread started as a Futaba 2.4, as the crashes appear to be the result of non-functioning RC gear.

 

I am still trying to resolve, if the issue, is

 

1) Gear suffers a "brown out", if possible for Futaba and for how long

2) The ESC stops supplying power, for some reason to the RC equipment.

3) There is a fundemental problem with the aerodynamics of the wing.

 

I tend to dismiss option 3), as the crashes all occur at about 5 minutes into a flight, all the crashes have been long drawn out affairs, there is no responce from the model, however much stick waggling, all occur immediatly after using power, but in differing attitudes.

 

As for 1 and 2, I am still trying to shed light on the problem. Yet I still do not dismiss option 3. Why. Because I no so little. Other than the gear and motor work immediatly after each crash.

 

Erfolg

[Peter Beeney]

      Erfolg,  This might be a very long shot in the dark but you might like to pop over to the thread 'Spektrum AR500 recovery time slow' by stuey. Quite fortuitously I've recently posted a few comments there, which may be worth a little read.
 
    I'm out for a while now, but I'll be back later. If you wish, a chinwag might then be useful.

    I'm already thinking of up-dating that post anyway.                    PB     

[Erfolg]

Peter

 

I have read the Spektrum thread.

 

What appears to be fundementally different, is that my shut downs (if that is what they are) occur after switching the motor off. If my understanding is correct, this should cause any suppression of voltage to recover, hence reducing any tendency for the receiver to shut down.

 

I will try an experiment, after securing the propeller, which involves, switching the receiver on first, then the Tx. The objective is to establish how quick the Rx is to lock onto the TX.

 

I do suspect that there may be an issue with the ESC, yet again, it could be an il-conceived predjudice.

 

I have some douts abou the aerial also. How important is it, that they are set at 90 degrees to each other? Being so short, do they really work? The long 35 aerial, was reassuring in that it had precence, and you felt some part of it would pick up something.

 

When the other half goes out I will try some experimentaion.

 

Erfolg

[Peter Beeney]

     Erfolg,   I'll have to start by saying that I've not done any experiments with this, so to some extent I'm guessing. But I've seen this happen before, at least 3 times and one absolute classic case, which would be worth repeating sometime.
    The bad news, I know very little about your model. However, there are some clues.
You mentioned the heatshrink that had shrunk. I've seen this before, too. That might imply that something is getting very hot. So it could simply be that the the regulator, (BEC), is just shutting down because of the load of the radio and servos. It certainly can happen. The motor would add to it only by any heat generated by the FETS that control the motor. Is this ESC in a nice cooling draught or is it completely surrounded (my guess) by foam? If it is completely enclosed that might be the trouble all on it's own. Any voltage changes would not make any difference, this would not shut the regulator down. Do you know what the BEC is rated at? 1A - 2A - 3A maybe?
    One experiment that would be nice to try is running the thing as you would if you are flying and seeing if the ESC does get hot. A very useful piece of kit is a contact thermometer, this soon helps to work out what is going on. Heat increase also sometimes seem to be exponential, it takes a while to get going but when a piece of equipment gets up to near it's full rated load, just a tiny increment more can result in a massive heat increase.
    Have a good look at the ESC and see if you can decide if it has been hot. Heatshrink sometimes starts to melt slightly, and that takes a lot of heat!
    I'm afraid I know nothing of 2.4, other than flying other people's models. But no one seems to take any special precautions. In the main, it seems trouble free. I am getting even more sceptical about brown outs though, the answers are in the spiel I recently wrote. But that's all for the other thread.
    I'll be very interested to know what you find.                  PB        

Edited By Peter Beeney on 10/07/2009 22:44:36

Edited By Peter Beeney on 10/07/2009 22:45:36

[Erfolg]

I have now tried switching the Rx on first, followed by the Tx. This has been repeated 5 times.

 

It takes the Rx 2.7sec to go green. That is perhaps a little longer than i thought it would. Yet I feel reasonably confident that is shorter than the durations of the crash. On the assumtion that the aerials were for some reason unable to pick up a signal, I think that the time taken for the model to re-orientate itself so as to be able to get a signal, would be less than a second.  So I would guess that 4 seconds is the longest, it would take.

 

What causes "Brown Outs", is it a none model transmission on the frequency band  of 2.4, where the signall strength is so high that all the model Rx hears is noise? 

 

Although it seems incredible, the heat shrink has shrunk by half. That is when a tube it must have been 20mm dia, that is approx 60 mm  circumference, it is now about 30 wide, the speed controller being flat and 25 mm across

 

I have also done my power tests.

 

The duration was just 20 minutes.

 

It consisted of 30sec of power and approx 1 minute off power. During all this time the Tx sticks were moved.

 

It statred drawing about 268w @ 23 amps

 

it finished at about 200ish  w at 21 amps.

 

I should have had a peice of paper to log the watts etc. But my engineering training has failed me, or is it the other way round.

 

The run finished when the motor power began to decline, down into the 50-60w.

 

Both the speed controller and motor became warm, the receiver  stayed apparently at ambient. At no time was there any sign of radio link failure. 

 

The first 30secs heated the controller up substantially, subsequent power ons, did not seem to heat it as much. Without a surface thermometer it is rather subjective. At a guess I think that the temperture rise could well have been substantial enough to compromise some of the components in the ESC whilst enclosed, when drawing close to 400w..

 

I am now thinking of how i could aid cooling to the ESC, in a way that does not increase drag, in any measurable way.

 

I did not enjoy these tests at all, constantly fearful of the propeller disintergrating, with me close by.

 

Erfolg

 

 

 

[Tim Mackey]

Erfolg said

What causes "Brown Outs", is it a none model transmission on the frequency band  of 2.4, where the signall strength is so high that all the model Rx hears is noise? "

 

Erfolg we have been discussing brown outs at great length - however you maybe have not followed this as your question indicates that you wonder if it is connected with signal /non signal

- its nothing to do with radio signal Erfolg

Also...if the current at start ( on WOT ) was only 23A and your ESC is rated at 45A then it is barely ticking over, and should not have got more than warmish.

Edited By Timbo - Moderator on 11/07/2009 15:46:07

[Peter Beeney]

   Erfolg,   Thank you for your reply.   I can understand your fearfulness, I always try and treat these things with the same respect that I would give a bunch of gorillas armed with chain saws. And that they'd found out how to start them.
    First observation - I would forget the radio for now. I would not be convinced that it is a problem at the moment. 
    First question -    Were your tests done with the model assembled, EXACTLY as if you were flying? I'm assuming not, because you might have had some test equipment connected. Also you were able to touch the ESC, I think. If that is correct, then the temperature rise when it's sealed in could be considerably higher. And, in fact definitely would be!
    Second observation - As I understand it, a brown out happens when the rx supply voltage drops to 3.5v, at the rx. That's not necessarily the voltage at the source of supply. However, for this exercise I think they are pretty well the same. I remarked before that I thought the brown out might be a red herring, after reading again wot I rote in the other thread, I'm now considering it could indeed be a purple dogfish! I think we can ignore that also for a while.
    Second question -   Is there any ventilation at all to the ESC when you are flying? If not, that makes sense in that it is another clue.

    I still think the problem is one of overheating. First the heatshrink, and then the fact that the radio still works when you pick it up the bits. Difficult to see what other single fault has this combination. For instance, if it were a radio failure, you would not get the heatshrink evidence.
    You will not generally damage the BEC doing this, unfortunately it does you far more damage. Some components, capacitors etc. might be affected by long periods of very high temperature though.
    There is one proviso in all this. Whilst I'm happy about the specifications on the regulators you buy from Maplins etc., I've never tested any ESCs. And maybe they are suspicious. A friend I fly with regularly is all electric, mostly very fast small foam models. Once upon a time he had his latest toy, to which he'd added even more coals. This was haring around at high speed when suddenly the ESC totally disintegrated and came out through the side of his foamy in a massive shower of sparks. It had completely burnt up. For a while it was thought that a new comet, Moltenn-Fett, had been sighted. The battery and the motor were perfectly ok. In the perverse ways of aeromodellers, much merriment, laughter, and quaffing of ale was seen. Well, hot coffee, actually.

    Significantly, I don't think there was very much in the way of inbuilt protection shutdown facilities here. And what was I saying about that exponential heat rise..........  

          

    In the first instance I would certainly go for those cooling vents. 

 

           Good Luck    PB             

Edited By Peter Beeney on 11/07/2009 18:58:46

[Erfolg]

Timbo

When I wrote "a none model transmission", I did mean a signal from another source other than Tx.

 

I have just looked at my account with GC. It seems that I purchased a 40 amp ESC, not 45 amp. Although the drawn 36 amp drawn on the 9*6 prop is below 40 amp, it is a lot nearer to the rated capability. The other issue is the lack of ventilation. So the ESC, may be the culprit, more to do with abuse than an intrinsic ESC fault. 

 

On all my other models, the capability of the system is a lot greater than, the duty I actually use. A normally look for approx. 50% duty.

 

What has surprised me that that when drawing 22 amps aprox, the ESC is a little warmer than I would like. It seems that DYS ESC is perhaps, optimistically rated, and does require provision for cooling, to function at its rated duty

 

I do feel that I now have sufficient confidence to assemble the model for another flight. Although the rocket like climb rate is unlikely to be there now. It could be adequate, on the 8*4.  It was extremely fast in level flight also. It was strange to see a model going along like a rocket in level flight, and then become a frisby, when the power was switched of.

 

If I am wrong, and the model crashes again, it will be a case of "thats life" and another rethink.

 

Erfolg

[Former Member]

[This posting has been removed]

[Erfolg]

Eric

 

Hi, it is atrue flying wing. There are a few pictures in my picture folder. The CG was fa back and I did think I had stalled it.

 

It was the first time I became aware that no amount of stick waggling did anything. The handling, particularly as a glider has always been rock solid, very predicable. It is now after electrification that problems have becpme apparent, although the first 5 or so minutes always rock solid.

 

Erfolg

[Former Member]

[This posting has been removed]

[Tim Mackey]

Indeed yes Tom...but according to Erfolgs info, the speedo was rated quite well above the current being drawn. As for the heatshrink haing shrunk "alarmingly"...well the clue is in the name Erfolg!

How about a picture of offending ESC so we can try to judge whether it has really overheated.

[kiwi g]

Ive always found that you can test and calculate for intermittant problems all you like but never recreate what happened .

Erfolg another thought is what transmitter are you using.

Does it have a plug in module.

Does it have loose rechargable cells .

MY Optic 6 suffered from the module popping loose after a while causing the odd crash.

My dx6i suffers from the battery holder unclipping and cells dropping loose.

Both caused a short loss of tranmission till they were knocked in and the problem discovered.

   its easy to go on a train of thought only to have it be a simple problem.

Has you transmitter been used for other models or is this problem model specific.

[Erfolg]

Tom and Timbo

 

To date, or until this particular model, all my equipment has been, vastly over rated, by approx 50%. That is if I was using a 200w motor, I would endeavour to stay below 150w, I would use a at least a 30amp ESC, better dtill 40 amp. With the battery if a 25c battery, best use it at or below 15c.

 

In this case I appeare to have let standards slip, I obviously dod not use mt watt meter, as I had to make up some conversion leads. I read and believed the data sheet. All still should have been well (excepting the motor). Given the duty that the rest of the system saw relative to the rating.

 

Excepting, I do not ventilate the battery or ESC. Why? Because i am so far under the rated performance, regarding the current drawn, thay never even become warm. Except in this case, probably, no ventilation.

 

I will endeavour to photograph the ESC this week and post it. I am not ure that the photographs are conclusive, other than taking on trust, what you see, is what I found.

 

I am not as yet necessarily convinsed, that we have identifified the cause of my problems. As previously I was convinced that the problems were a to far to the rear CG, some inadequate piloting. I was particularly impressed with the flat spin, as I had never ever achieved a truly flat spin. That is the wings horizontal, spinning around the CG. I think I was mesmerised, as it seemed so text book, and so stable.

 

Another club member manged to crash today, having had his ESC catch fire, or at least melt the wire to his seperate flight pack. Anyway there were flames, a crashed model. I guess there will be some head scratching there. I have seen one more ESC catch fire, I thought it was a rarity, or unfortunate or carelesness etc.

 

This sequence of events would possibly have been less protracted if I had used my watt meter. A very important lesson!

 

Erfolg 

[kiwi g]

Why dont you try a bigger speed controller. sounds like youve pushed the limits all the way thru. if its dodgy ,biff it

[Erfolg]

I could try a bigger capacity speed controller.

 

The fundemental problem, was I had overproped the motor, as it was drawing a lot more current than it was rated for. To reiterate, I was drawing 380ish watts, it was rated at a nominal 200w, specifically 22 amp continous.

 

As Timbo stated, by rights, you would expect the motor to go puff and emmitt the aroma of burnt shellac. I was lucky, i guess from only running the motor for very short periods.

 

It was from this basic, fundemental issue, that the ESC, was also pushed. Drawing about 38ish amp., it is rated at 40. But I have no ventillation for the speed controller.

 

Re-proping to draw 23 amps, should, reduce the heat build up with the ESC.

 

I am now thinking how I can, provide some cooling to the ESC, without increasing drag, substantially.

 

The basic issue hear is, the model is a glider, drag is bad news, yet slow speeds, tend not to provide much air throughput.

 

It was a rocket on +300 watts. Quite liked the climb, and even level flight.

 

Erfolg

[Erfolg]

Kiwi

 

It is a Futaba T6ex. There is no module, batteriy is built in, with a simple plug and socket.

 

I would be very suprised if the Tx is the issue, from that point of view. Not impossible though.

 

Erfolg 

[Tim Mackey]

Of all my electric models, I have only ever needed cooling to the ESC on one of them.

As long as you stay well within the current rating ( as you are now doing ) then personally, I dont believe a lot of cooling is actually required. Obviously, the unit should not be packed tightly in foam, or insulation etc. Of course....you may have goosed the unit in earlier use.

[Erfolg]

Timbo

 

You say goosed ( I am almost certain that the phrase, is not politically correct. It is birdist, could be taken to be some sexual deviation, nudge, nudge, aka George Formby). No the phrase, "would benefit from  electronic enhancement", is surely less offensive.

 

From a function perspective, the unit seems to perform as designed. In that it contols the motor and powers the Radio and servos.

 

I am at present charging my Digi Camera, as the batteries are yet again flat. I will then post some pictures of theESC Unit.

 

It is also reassuring, that I am not alone in not providing ventilation. I will also include a shot of where it sits, in the fuz. It seems that 23Amp max for 30s bursts, should be all right.

 

As A tmporary measure, I will wrap some polythene as a protective cover around it. That is until I obtain sme larger heat shrink from GC or similar. The local electronic shop closed down about a year ago. First model shop, then.........................

 

Erfolg  

[Erfolg]

I have now taken the images of the ESC. Hope you can see where the "shrink wrap", has shrunk/gone. I have also included a picture to show  wher it is situated, pretty much by itself.

 

 

 

[kiwi g]

Erfolg Didnt the t6ex  transmitters have a problem with the early production models or was that all fasst radio gear....

I like you would be doubtful that its the futaba gear, but has the receiver been in a crash before. .

I have found that the heat shrink will shrink on alot of ecs when in use it just depends if its quality plastic or not..