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Acro Wot Foam e ESC Failure

ESC Burnout on 3rd test flight

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Delta Foxtrot18/06/2012 20:05:04
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566 forum posts
91 photos

Hi,

I took delivery of the new Acro Wot Foam e last week, tonight was the first opportunity to test fly it.

I had two 5 minute flights at moderate throttle setting aimed at trimming the aircraft and flying gentle circuits. The aircraft flew well and I started to feel like I had made a good purchase. On the third flight I was making a gentle descending turn when at around 100 ft I lost all control of the model, no response!

I retrieved the model from a cornfield where it nosed in and split split the nose open. There was a strong smell coming from the ESC which was still hot to the touch after a 4 or 5 min walk back to the benches.

The model came with a 40 amp ESC and I measured 300 w / 30 amps at full throttle before flying it, so on paper the ESC should have had some margin, but in flight it failed without prolonged running at anywhere near full throttle.

I plan to contact Kings Lynn models to try and get this rectified, but I am dubious about accepting a replacement model given, the saga of the WOT 4 foam e ESC problems.

I would be interested to hear from anyone else who has had a similar problem with this model.

dave f

Rusty C18/06/2012 20:19:56
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452 forum posts
29 photos

Oh dear the saga continues! I guess there will always be a few failures in anything, But Its getting a little to common with ripmax. I think I will just throw the esc in the bin and replace when I get mine.

Out if interest what was the rest of the kit like? ie is the hardware of a good quality?

Rusty

Peter Beeney18/06/2012 20:38:20
1549 forum posts
59 photos

David, - This happened to me, on a beginners, (a youngster), model that he was learning to fly with. On take off, as it happens, this one came down with loss of control and with the ESC really well alight, flames spurting out. Not on the third flight, but not long after. His father contacted Ripmax direct and they replaced it instantly. Dad repaired the damage and the second one has been going strong ever since. It’s certainly been broken again, and repaired, once or three times or more but the accidents are now getting very infrequent.

I think it is a well known problem, so I would say that any replacement will be fine.

Good Luck.

PB

Delta Foxtrot18/06/2012 20:44:04
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566 forum posts
91 photos

The kit quality was general OK. The fin and rudder hinges were showing daylight so I used glass fibre tape to reinforce these as I have done on the WOT 4 foam e.

The stickers are very sticky and I would advise not fully peeling off the backing when applying. Just peel off the edges and smooth on progresively.

The outer part of the elevator snake was protruding too much and limited down elevator movement. It is simple enough to remove the control rod and trim it off.

Generally the quality was similar to the WOT 4 foam e with perhaps a few early production areas that could be improved.

The other issue I noted was that the ESC cables where cable tied to both sides of the engine mount. This meant that the ESC had to be positioned just below the motor which I thought might potentially be a problem. This does position the ESC in the cowl vent flow so I decided to fly it as suppied. I doubt that this was a contributary factor to the overheating as the motor was only slightly warm to the touch, but the ESC was too hot to handle.

I had to trim it with a bit od down elevator to stop it climbing. I had a 3s 2200 mAh pack sat where it should be and the CoG was just a little forward of the position recomended, perhaps it needs a small amount of weight in the nose, but it was not a big issue.

hope this helps

dave

Delta Foxtrot18/06/2012 20:46:53
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566 forum posts
91 photos
Posted by Peter Beeney on 18/06/2012 20:38:20:

David, - This happened to me, on a beginners, (a youngster), model that he was learning to fly with. On take off, as it happens, this one came down with loss of control and with the ESC really well alight, flames spurting out. Not on the third flight, but not long after. His father contacted Ripmax direct and they replaced it instantly. Dad repaired the damage and the second one has been going strong ever since. It’s certainly been broken again, and repaired, once or three times or more but the accidents are now getting very infrequent.

I think it is a well known problem, so I would say that any replacement will be fine.

Good Luck.

PB

Peter,

Thanks for the feedback. I have emailed Kings Lynn, but I will take your advice and contact Ripmax if that doesn't work.

dave

Simon Chambers18/06/2012 20:53:35
789 forum posts
42 photos

The ESC should be a Hobbywing unit (branded SkyWalker) - i.e. one of the best Chinese ESC's out there.

Not built my Acro Wot yet (only got it yesterday, so it joins the build queue), however I've had a good look over the parts. I've put my thoughts into the main thread about the AcroWot.

Si.

Edited By Simon Chambers on 18/06/2012 20:55:44

Bill_B02/07/2012 12:57:54
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1145 forum posts
11 photos

Plenty of ground running and two flights have yet to produce any 'magic' smoke. Fingers crossed then.......

Delta Foxtrot04/07/2012 21:34:46
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566 forum posts
91 photos

Update on my ACRO WOT Foam e problem.

I returned the model to Kings Lynn who were very helpful and quickly sent it back to Ripmax. Ripmax sent me a replacement which was not of as good quality as the first aeroplane. There were had a blemishes around the cockpit area and on the tail, but I managed to cover most of these with the stickers. I could not be bothered to send it back to Ripmax as they would not cover the postage costs of returning the original.

I emodied the ESC positioning mod suggested by Ripmax, which makes battery positioning easier, but does nothing for ESC cooling. I do not think lack of ventilation was the problem I had with the first model, I believe it was a faulty ESC as it was cool after the first two flights, but burning hot within seconds of connecting the batter to the ESC after the crash.

I flew it for the first time tonight. Six short flights pf around 5 mins. I gradually used more throttle on each flight and had no problem with the ESC, it was only slightly warm at the end of the session.

Hopefully the ESC problem I had was down to a faulty unit.

Dave F

MZH07/07/2012 23:29:49
1 forum posts

Hi

after flying the wot4 foam-e with no problems apart from pilot error ,I purchased a acro wot foam-e.

like other struggled to get the battery in and fit the cover not a quick job. (what is the mod with regards to the battery compartment to improve acess?)

nice calm day ,first flight all trimmed out very nicelty But on a couple of occasions ,just as if you had totally lost all power motor and radio for a second then ok, same again on landing approach.

checked all connection all seems ok, phoned the model shop that I purchased it from and theer suggestion was to change the esc (skywalker esc as supplied) with the on from my wot for and try again.

have yet to try

MZH

Paul Marsh08/07/2012 14:38:35
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3481 forum posts
963 photos

Not bought the Acro foam e yet, but got the IC one. The wot 4e flys well, but not sure if I want another electric model. I hope the new esc on the Acro is better than the wot4. Mine's still the original, but gets hot and I thought it had burnt out - as I lost radio control last week, I found that the model was ok - apart from the u/c ripped out - but no battery/hatch!

The battery had come out in a spin - hence loss of control. Found the battery and the cover a minute or two later.

Delta Foxtrot08/07/2012 20:17:55
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566 forum posts
91 photos
Posted by MZH on 07/07/2012 23:29:49:

Hi

after flying the wot4 foam-e with no problems apart from pilot error ,I purchased a acro wot foam-e.

like other struggled to get the battery in and fit the cover not a quick job. (what is the mod with regards to the battery compartment to improve acess?)

nice calm day ,first flight all trimmed out very nicelty But on a couple of occasions ,just as if you had totally lost all power motor and radio for a second then ok, same again on landing approach.

checked all connection all seems ok, phoned the model shop that I purchased it from and theer suggestion was to change the esc (skywalker esc as supplied) with the on from my wot for and try again.

have yet to try

MZH

The battery access mod is on the Ripmax website **LINK**.

Dave G08/07/2012 21:23:01
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34 forum posts
4 photos

Well I think there should of been more thought in the design for fitting the battery.face 4

Surley after the debarkle of the early Wot4 Foamie, Ripmax should have made more effort for the Acro Wot. I for one will not be buying one.

Must admit I have a Wot4 Foamie and it is the best value model and fun for the price.

Mine still has the origonal setup and has flown at least 130 times.

Just got the Eflight Carbon-Z Yak 54. Cor now that is an experience to fly. Brilliant.smiley

Edited By Dave G on 08/07/2012 21:24:03

Graham Higgins24/07/2012 21:08:39
1 forum posts

Hi there yes I had the same problem I think , I had one great flight and everything was fine then on my second flight I was about half throttle just about to bank around for a landing when the plane just carried on flying with no response , then I saw it flick onto its back and crash nose down , the only problem is I can't find we're it crashed to find out for definate if I have had the same problem with my esc but it sounds likely

Lukas Ratcliffe09/09/2012 18:17:12
1 forum posts

Dear David,

I was the one Peter was talking about, the wot 4 foam-e I had at 30amp esc which was the primary reason for the crash, in addition, I recommend not using the deans connectors supplied on the esc, I changed to xt 60. The increase in connectivity was amazing. I haven't had any problems in the wot 4 foam e since I got the 40 amp speed controller, and I have flown entire flights at full speed. But I will look out for this issue on my acro wot foam e

Lukas

Delta Foxtrot16/11/2012 18:41:52
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566 forum posts
91 photos

Just to round off

I have flown my replacement acro wot foam e loads since I lost the first one to the esc failure. It is a great aeroplane for the price, it flies very well and I have had loads of fun with this. It is still going strong after 160 + flights.

ken anderson.16/11/2012 18:53:40
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8309 forum posts
768 photos

by all accounts-the esc's get hotter running at low speeds as they have more work to do....and at full belt ..they run cooler.....

ken anderson ne..1 ..... hotter/cooler dept....

Peter Beeney16/11/2012 19:24:14
1549 forum posts
59 photos

Ken, - I need to do some practical tests on this, but I have feeling that ESC’s reach their hottest heat at a point between three quarters and full throttle. This is a bit of a guess at the moment, but I’d think that at low speeds they don’t work particularly hard. I do have some electric kit still on loan from a mate, so maybe I will be able to have a wee dabble tomorrow.

PB fw…1 … dabbling dept….

Peter Beeney17/11/2012 22:41:02
1549 forum posts
59 photos

I managed to do a quick run for a temperature check change on an ESC today and so far the results are fairly inconclusive. I used a RS digital thermometer, with a contact probe, it’s quite old, but if it is a bit incorrect it’s probably consistently incorrect. The motor was a Turnigy Aerodrive SK3542 -1000 and the ESC a Turnigy PLUSH - 60A. I used just one 12 by 6E propeller. The power source was a 12V (14.4V) commercial size LiFePO4, which I’ve bought as a field power supply. I did get some data, but it’s a bit mundane, suffice to say that the temperature only varied about 2 degrees from start to finish.

I ran it with no prop on to start with, full throttle down to tick-over, in 6 increments, for 2 minutes at each stage, but nothing really changed. The ambient temperature was 11.4 degrees, the centre of the large IC on the ESC was around 15 degrees all the time. Then I put the prop on and did the same thing again, and once again the temperature didn’t change a great deal. I did try the motor at one stage and that was 50 degrees, and also I did check on the end of the two input smoothing capacitors, they were up to 27 degrees, this could also be a likely heat source. I’ve thought this before, on an Aveox ESC that I used, the capacitors blackened with the heat! They worked really hard. Interestingly, my clamp meter is an AC/DC type, and at one stage I noticed that briefly it was indicating that the battery output was AC. I’m not totally convinced about that, but it might be indicating it’s very lumpy DC!

If I do this again, I will do it somewhat differently. On this cobble up the ESC was in the prop slipstream, which I think could have had a definite cooling effect; and I’ll monitor all the items, such as the motor and the capacitors. Also it might be interesting if someone has a model with an ESC that is actually getting hot. Just to see what the change in temp is; and at what throttle level it’s at it’s maximum.

I would assume from watching quite a number of electric models flying, that in general terms that overheating is not really a big problem? On the occasion that an ESC has gone on fire, this may be due to a design fault, something was allowed to get into a thermal runaway situation. It that happens, a component can get very hot very quickly indeed.

So now I’m still not very much wiser…… just older……

PB

WolstonFlyer18/11/2012 00:17:33
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2104 forum posts
189 photos
Peter

The Turnigy Plush 60 is a very well engineered unit, if you were not putting many amps through it, it probably will not get that hot.

I think the problem with the original 30A ESC in the WOT4 FoamE is that it is a cheap ESC that can probably only just manage 30A in short bursts, if you are flying along at 28A it is putting a lot of load on that ESC so it gets hot, cooks and fails.

I think your test rig was probably too well specified to generate heat for you to measure.

There are a few threads on the forum about how ESC's work but I do understand that they work harder at half throttle than at full throttle.
Peter Beeney19/11/2012 14:25:18
1549 forum posts
59 photos

WolstonFlyer, - You may be right, but I was only actually looking for a trend. The thermometer is quite sensitive, it measures in 0.1 degree increments, and with the prop on there was a 27 amp flow at full speed. I feel it might have been more, but I was using a bit of a raggle-taggle bunch of jump leads, it was a quick cobble up, so this may have been some of the reason. I wasn’t that surprised that it didn’t get that hot, I’ve done checks before, for various reasons, and in general ESCs don’t seem to get that overheated. At least when it’s out in open, that is, where I would normally playing with it. My colleague that owns this kit now often brings the ESC to the outside of the model for maximum cooling on his sport types anyway.

When the ESC went on fire, as in my post, pb @ 18/06/2012 20:38:20, it was on take off, after only just a few seconds of flying. It was really well alight, all in flames, only the fact that the resultant tangle with terra firma knocked the front off and threw it out probably saved the airframe. It may be that something went short circuit, that caused a hotspot, which in turn caused an even shorter circuit which then caused an even hotter spot. Fortunately the young beginner wasn’t fazed by this at all, he’s now lining up for his ‘B’.

When the throttle is fully open I suspect the modulating pulse is perhaps non existent, the motor requires full voltage, but at part throttle the pulses turn the transistors on and off at a given rate. The process of actual switching causes some heat, but it depends to some extent on the switching rate. I have a feeling that the max here may be something like 20 kilohertz, which may not be sufficiently fast enough, whereas a component that is switching at say 1 megahertz, like a switch-mode power supply, may require a heat sink.
I’ve noticed that some of the bigger capacity ESCs now have some credible heat sinking attached, I wonder if this is to disperse the heat generated by the ‘on‘ resistance of the transistors, or the heat generated by the throttle switching, or, most likely, a combination of both.

There are reports that some competition flyers only use full throttle because any other setting causes the ESC to over heat. Is this because they tend to use the physically lightest ESC, in weight, or is it simply the ESC is not really up to the job in the first instance?

PB

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