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Old Jan 12, 2008, 04:20 PM
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near disaster

hi guys
well, today my friend and I maidened our super miss for our highschool senior project. The takeoff was textbook. I was flying the plane for around 3 minutes and then all of a sudden the motor would stop spinning then start back up again. I though it must have been interference or something so I brought the plane closer to see if the glitching would stop. Well it started easing up but we decided to bring her on in just in case. On our final approach, the motor completely cut out. Now keep in mind this was only 5 minutes into the flight. The motor cut out, so I though to myself " this isnt a big deal i have practiced landing deadsticks in simulators all the time." upon thinking tha I lost all control, and our plane was at the mercy of the wind. The plane was heading straight for the woods off to the side of our soccerfield but at the last moment a gust of wind pushed the plane down a mere 15ft from the tree line. the landing didn't look to bad so we headed on over to inspect the damage. As we were running towards it I shouted, "Its smoking." My friend responded, " yeah that was a smokin flight." But the plane was actually smoking. My physics teacher approaced it and threw his jacket over the smoke to try and choke the possible fire. At this moment I looked over at a shed that was 20ft away and saw several fire extinguishers on the ground. I picked up one of them and brought it back to the plane just in case this "benign" white smoke burst out into an actual fire. Well inevitably the plane shot up in flames. I aimed the fire extinguisher but nothing came out. I ran back and picked up another one but by that time it was too late, the plane was a complete loss. I am just tremendously grateful that the plane did not land 15ft away in the woods and ignite an all out fire in the woods.
wow, i never realized just how volatile these lipo batteries were. When you hear about all these lipo fires your first instict is believe that "that couldn't happen to me."
Geez what a hear pumping day..Sorry for my ramble here
I just want other people out there who are considering lipos to understand just how dangerous these batteries are and that they need to be handled with the utmost care. This project might not have turned out like we had hoped, but we emerged from this project understanding to always be vigilant and take extra precautions when working with dangerous things such as lipos. My outlook on handling electronics has completely changed. And from here on out Safety really will be my number 1 priority.
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Old Jan 12, 2008, 05:17 PM
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Do you know what happened? I was thinking low volt cutoff, but if it burned after that, it seems it was bummed from the get-go. Glad you missed those trees. Every time I crash (except if I hit a house) I think "Oh well, just my property, it's not big deal." Always good to merely hit the ground
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Old Jan 13, 2008, 08:55 AM
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We found the motor 10ft away from the crash site and the motor leads were completely burnt to a crisp ( we found the motor before the plane caught fire). I am thinking that the batteries discharged too quickly and caused the motor to overload and eventually burn through the wires then that might have ignited the balsa near the battery then the spectacular flames started.
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Old Jan 13, 2008, 11:38 AM
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Quote:
Originally Posted by skate5290
We found the motor 10ft away from the crash site and the motor leads were completely burnt to a crisp ( we found the motor before the plane caught fire). I am thinking that the batteries discharged too quickly and caused the motor to overload and eventually burn through the wires then that might have ignited the balsa near the battery then the spectacular flames started.
Short circuit in the motor, possibly.
It may have a million reasons (bad luck among them). Also, such can happen, if the screws are turned too far into some sorts of motors. For example, the manufacturer may specify that screws may not be longer than 4 mm or so.
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Old Jan 13, 2008, 01:41 PM
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Quote:
Originally Posted by skate5290
We found the motor 10ft away from the crash site and the motor leads were completely burnt to a crisp ( we found the motor before the plane caught fire). I am thinking that the batteries discharged too quickly and caused the motor to overload and eventually burn through the wires then that might have ignited the balsa near the battery then the spectacular flames started.
Sorry to hear about your bad experience. But a "battery discharging too quickly" is not the root cause of the problem -- the root cause has to be something that's making the battery discharge too quickly

As gravitykills has mentioned, it could be a short-circuit in the motor windings which has caused it to draw more current than it should and, thus, burn out the windings and then overload the battery so that it too catches fire.

But it could also be too big a propellor on the motor, or too many battery cells for that particular motor, both of which would cause it to draw more amps than it can stand and eventually burn itself up and then overload the battery. Did you check how many amps it was drawing at full throttle before you flew it? If you haven't got one already, a wattmeter (or an ammeter that can handle the expected amps) is a vital tool for anyone getting into the e-flight hobby.
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Old Jan 13, 2008, 01:55 PM
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Did you find the ESC? It's more likely the culprit.
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Old Jan 13, 2008, 02:18 PM
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Quote:
Originally Posted by Probedude
Did you find the ESC? It's more likely the culprit.
Sounds also plausible, like that it broke and put DC through the motor. But have a look at the motor anyway, it should be quite straightforward to tell.
Thinking of it, wrong propeller sounds very plausible, with spectacular outcome...
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Old Jan 13, 2008, 02:23 PM
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was the ESC well ventilated, if not, the output FETs will get HOT and short out the LIPO pack thru the motor wires
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Old Jan 13, 2008, 02:31 PM
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Quote:
Originally Posted by hall woo
was the ESC well ventilated, if not, the output FETs will get HOT and short out the LIPO pack thru the motor wires
I'm thinking they didn't push the plane hard and likely everything was still cool.
There are stories of ESCs having burst into flames, or just smoldered to a heap even on the tarmac, without the plane even in flight or the motor even turning!

It happens. It's rare, less rare for some ESC's.

I'm guessing the ESC glitched, turned on 2 or more phases at once continuously, overheated the motor windings but the ESC itself was really what went up in flames due to the hard short.

Just out of curiousity and nothing more, can you list the
- battery type and mfgr
- ESC model and mfgr
- motor type and mfgr?

was this a brush motor?

Dave
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Old Jan 13, 2008, 02:44 PM
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U'll be surprised what an overheated 20A brushed ESC can do if not vented, my PKZ P-51 ( no air cut-outs for cooling ) using Electtr-fly 20 amp started smoking, then crashed and burn, luckily I had half gallon of water with me at the time to douse the flames

on the other hand my PKZ FW 190 with cooling louver slits on the exhaust exits runs very COOL
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Old Jan 13, 2008, 03:41 PM
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battery type: 3 cell 2500mah polyquest
Esc: Jeti eco 25 amp
Motor: Atlas 2909/20 brushless
I could not find the esc, as I said the plane was reduced to a heap of ashes.
The esc was mounted behind hte battery and underneath the servos so it was in a small space.
The reason i was thinking that the "battery may have discharged too quickly" was because when I was wrapping electrical tape (shrink wrap ripped) along the solder joints after soldering on the dean's connectors my scissors touched the two gold tips and started sparking.
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Old Jan 13, 2008, 07:13 PM
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Get rid of " Bad Luck ".

Can you or someone you know modify the DEWALT battery packs or the Black & Decker PVX packs ?
No more battery fires. They are that safe.

Rich
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Old Jan 14, 2008, 02:45 AM
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I had one of the two 30-amp ESCs on fire when taxiing my little catalina over the lake.
A lot of white smoke went out of it, cca 20 meters far from the ground, not far but not encouraging.. but remaining left side motor with second ESC were still working, and did bring the plane to the ground, out of the water. 3200mAh Lipos were OK, no harm at all, just the ESC turned into a pieces of black carbon, fallen inside the fuse.
The drop of water inside ESC was most probably my reason why.
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Old Jan 14, 2008, 06:27 AM
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Quote:
Originally Posted by coro
The drop of water inside ESC was most probably my reason why.
Ooooookey interesting... slight rain counts for me as "best flying weather" because it keeps the kids off the football field. Will double check, whether this is really as well sealed as I think it should be...
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Old Jan 14, 2008, 06:57 AM
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Original ESC is not covered neither protected at all, there is just a shrink wrap with both ends wide open. Some brands are offering "W" versions of ESCs, protected against the water.
In water panes like Catalina, I always treat ESC and also all other parts where it doesnt hurt (receiver except servo connectors, electronics inside servos), using "Plastik 70", conform electronics protective coating lack. http://www.mdaelektronica.nl/nl/dept_8.html#item_21
But it probably dont last forever, especially when ESC permanently heats and cools, or perhaps it was not done perfect by myself (ESC shrink was not opened, it is possible that I forgot to even treat this one ESC).
I have seen unprotected brushless esc burn in a flash after water wawe run thru propeller and just one small drop gets inside, passing by the wire. Dont try that.
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