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Author Topic: Mommy told me there would be days like this...  (Read 895 times)

Offline John Hammonds

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Mommy told me there would be days like this...
« on: September 17, 2010, 05:51:54 PM »
Picture 1, me looking pretty smug after posting the highest score in the 1st round of the Old Warden Modelair P40 competition last weekend. Picture 2? Erm me looking not quite so smug after going straight in in round 2.  HB~> "Spring Chicken to Sh***hawke in one easy lesson"  ::) The "Post crash" shot was taken after John Benzing had dashed back to the pits for his camera and returned to the scene of the crime, so at least 45 seconds or more after the event, the flames had died down and the smoke had largely petered out by this stage. It was voted the most impressive pile in of the weekend.  b1 Oh well, it's only money......

TTFN
John.
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Offline Tim Wescott

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Re: Mommy told me there would be days like this...
« Reply #1 on: September 17, 2010, 05:54:09 PM »
On the bright side, three out of four pieces were well away from the flaming electronics.
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Offline John Cralley

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Re: Mommy told me there would be days like this...
« Reply #2 on: September 17, 2010, 07:04:23 PM »
Wow John,

That is sad! Hope some of the electric parts survived! Was it the ESC that smoked?? If it was a CC Phoenix you need be sure to set the current overload cutoff to sensitive, NO make that VERY SENSITIVE for next time (with your new ESC)!! If it was the battery there is not much to do about that.

John
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Offline John Hammonds

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Re: Mommy told me there would be days like this...
« Reply #3 on: September 17, 2010, 07:38:46 PM »
Thanks Tim, that makes me feel a lot better. (Not).  :)

Hi John, No, it was just the battery which went up. As far as the ESC is concerned, I don't mess around with "Sensitive", I've always set mine to "Very Sensitive" from the start and never had one cut out during flight yet.. The result of the crash though surprised even me, The motor (A Scorpion 3014-16) was around 3" under the ground to the mounting plate and literally had to be dug out. The battery leads were never found and the solder on the connectors to the ESC  melted. The insulation on the ESC battery leads also melted away as did the covering around the battery mount and the wood was badly charred, the leading edge of the wing likewise was badly melted. (Foam Wing).

Took the whole lot home (Apart from the battery which was disposed of). An evening inspecting the remains and replacing ESC Battery leads resulted in the amazing discovery that it all still works. The Fm9V timer needed the pins straightening out but it talks to the programmer as normal, The ESC (Phoenix 45) worked both with Castle Link and later during an extensive bench test. The motor continuity checked out and after a strip down and clean again runs. It's very noisy and I'm sure the bearings are totalled probably the shaft as well so I'll replace those and see how I go.

So, It basically cost me a battery and a (Repairable) airframe plus of course the "Embarrassment factor".  b1 This was no glancing blow it went straight in on a wing over. Makes me realise just how unlucky some people are when I hear of smoked ESC's due to a simple prop strike. Someone did suggest the battery may also have survived if I had used a fuse.  LL~

TTFN
John.
 
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Offline Dennis Toth

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Re: Mommy told me there would be days like this...
« Reply #4 on: September 18, 2010, 10:20:38 AM »
John,

I have had a couple booms of my profile ship and never had the battery smoke. I have the ESC set for normal and all components have always survived. I had one incident were the battery separated from the fuse but still no smoke. I didn't go straight in from the top though. Did the battery pack hit another component? It would be useful to all if you could describe what you think caused the battery to smoke so we can design around it in the future.

Best,                   DennisT
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Offline Tim Wescott

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Re: Mommy told me there would be days like this...
« Reply #5 on: September 18, 2010, 02:14:48 PM »
Quote from: John Hammonds on September 17, 2010, 07:38:46 PM
Thanks Tim, that makes me feel a lot better. (Not).  :)
I live to serve.  ;D
Quote from: John Hammonds on September 17, 2010, 07:38:46 PM
Hi John, No, it was just the battery which went up. As far as the ESC is concerned, I don't mess around with "Sensitive", I've always set mine to "Very Sensitive" from the start and never had one cut out during flight yet.. The result of the crash though surprised even me, The motor (A Scorpion 3014-16) was around 3" under the ground to the mounting plate and literally had to be dug out. The battery leads were never found and the solder on the connectors to the ESC  melted. The insulation on the ESC battery leads also melted away as did the covering around the battery mount and the wood was badly charred, the leading edge of the wing likewise was badly melted. (Foam Wing).

Took the whole lot home (Apart from the battery which was disposed of). An evening inspecting the remains and replacing ESC Battery leads resulted in the amazing discovery that it all still works
Quote from: stuntguy13 on September 18, 2010, 10:20:38 AM
It would be useful to all if you could describe what you think caused the battery to smoke so we can design around it in the future.
From the fact that the ESC survived, that it was set to "very sensitive" current shutoff, that John didn't mention the motor leads melting, and that he did mention the battery leads melting, I'm guessing that the crash caused a short circuit somewhere on the ESC side of the battery wiring, but not on the motor side.

John, did you see anything consistent with the above theory?  Any signs that the battery wiring at the ESC may have jammed together?  Enough current flow to melt the insulation on the battery leads would be enough to burn the traces on the ESC, or at least scorch the solder mask on the circuit board -- if there's no sign of overheating there, the current almost had to be flowing somewhere else.
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Offline John Hammonds

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Re: Mommy told me there would be days like this...
« Reply #6 on: September 18, 2010, 05:43:42 PM »
Well, I always mount the ESC and timer on the inboard side of the fuselage and the battery outboard, so I'm pretty sure the fuselage acted as a fire screen which saved the ESC and timer from any heat damage. The gap between the leading edge of the wing and mother earth after the crash was about an inch less than the length of the battery so it would have suffered considerable "Trauma" on impact. The insulation on the battery leads from the ESC were only melted for the few  inches which again supports the theory that it was heat from the battery rather than a pure electrical short in any other component. (The rest of the lead would have been on the other side of the fuselage). There were no burn marks on the ESC or electrical smells. I think the battery just suffered an catastrophic internal short. The motor leads were OK but again the leads were on the other side of the fuselage (And the motor itself had dug itself a bunker to hide in).

The reason for the crash was simply brain failure, I was flying in both Vintage and P40 and as a relative newbie (Only my 2nd full year) I am still using a crib sheet to remind me of the manoeuvres, I entered the wingover and as I went to recover to level flight remembered I was not flying vintage. Instead of bailing out and writing the wing over off I attempted to recover inverted with the predicable result seen above. I'm not one to normally offer advice in such exalted company  H^^ but.....  While you are learning don't even think about entering multiple disciplines on the same day, especially when even some of the the common manoeuvres are different. There is more than enough to do concentrating on just one pattern and model preparation. I've made a resolution. I'm still going to fly but vintage and P40 but not on the same day. I've come to the conclusion this was just too much for my brain to handle.  b1 At least until the pattern is 2nd nature.

TTFN
John.
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Offline Tim Wescott

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Re: Mommy told me there would be days like this...
« Reply #7 on: September 18, 2010, 06:58:36 PM »
Quote from: John Hammonds on September 18, 2010, 05:43:42 PM
The reason for the crash was simply brain failure, I was flying in both Vintage and P40 and as a relative newbie (Only my 2nd full year) I am still using a crib sheet to remind me of the manoeuvres, I entered the wingover and as I went to recover to level flight remembered I was not flying vintage. Instead of bailing out and writing the wing over off I attempted to recover inverted with the predicable result seen above. I'm not one to
Been there, done that.  Fortunately not in competition, although I'm sure I'll get around to it.

Last time I did that it was a wingover, at the bottom I suddenly realized that I hadn't decided whether to do a forward or reverse wingover, so instead I tried to do a wingunder but the earth got in the way.

Now, before I do any maneuver, I vocalize to myself: "I am going to do a forward wingover" "I am going to do a reverse wingover" "I am going to do a lazy eight".  Etc.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dean Pappas

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Re: Mommy told me there would be days like this...
« Reply #8 on: September 18, 2010, 08:13:36 PM »
All these exotic conjectures about where the short was.
If the battery hit the ground that hard, especially on the end, then it shorted internally, or the plastic envelope got ruptured and let oxygen in.
Either way ... Whoosh ...
On the other hand, I have seen a battery ejected from a Pattern ship at 150 feet altitude and maybe 80 miles per hour.
It landed in a grassy field and did not do anything.
After we brought it back to a safe corner of the pit and watched it for an hour, it was re-charged and flown another 50 flights before being retired.
After that, my flying buddy and I resolved to eliminate velcro from our setups.
This has carried over into Stunt and we probably saved a bit of weight.
later All,
  Dean P.
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