I thought I had left problems behind me when I converted from IC Powered models to EL about 18 months ago,. but it seems old 'Murphy' is always there, just waiting to strike you down when he sees an opportunity!
As may have been seen in a previous post, a couple of weeks ago I converted my older IC Powered 'Firecracker' stunt models to EL power.. I haven't mixed any fuel for an IC engine now for over 18 months and thought that era was behind me as far as flying F2B aerobatics was concerned.
I've been running my normal 'comp' models on either a Plettenberg 2510 or Arrowind 2832 motor, a Phoenix ICE 50 ESC, Hubin Fm2 or 9 timers and 4 cell batteries of between 3000 & 3700mah capacity. I had 2 ESC's the above type in my 'current' models and a few weeks ago thought I'd buy another to save swapping them around and to just have a 'spare' ready to go.. So the order from 'Tower Hobbies' arrived early June and yesterday I was out with the model and the new ESC (after being programmed to the identical settings of the previous two) for a test flight.
The FM9 timer was set for a short run of 2.5 minutes - just to check speed etc. I had the RPM set on the no. 2 setting (9200) as this was a starting point and the same Rpm that I was using on my current model of the same type. Everything was set to 'GO' - the model took off and I immediately saw that it was flying nearly a second slower per lap than I needed it to at what was the same set Rpm as my 'normal' model, I was thinking as it flew "
Well, I'll have to change the Rpm to the next speed when it lands for the next test flight" When the model reached what I thought was the end of the flight I felt the motor slow and guessed it was about to stop after the normal 5 second time lapse - however in stead of stopping, the motor accelerated for a few seconds (about half a lap) to what I thought could have been the speed it
should have been doing to begin with. However the motor then stopped and began to 'free wheel' - which it should not have been doing as I had it set to 'brake' at the end of the flight. On landing a friend carried the model to the pits and as I was walking back toward it from the handle another friend called "Hey, its's on fire!!"
Sure enough, there were flames coming out the side of the cowl (underneath is completely open), one of my friends was blowing furiously on it and the flames went down a little, I pulled wires from under the model away and turned it over. There was still a small flame coming from the ESC which I blew out too. So then looking at it all, and so extremely fortunate that the damage appeared not to be serious.
Mainly smoke staining to the paint inside the cowl and also to the battery - which I checked later and found to be working and balancing ok - however the ESC has had it - it is burnt to a crisp and beyond all help and I think no postmortem examination as well.
So understandably this is a concern! Why did it happen? As mentioned - all programming and equipment was identical to that used over hundreds of flights in my other models - the cowl is fully open underneath the model and the ESC was mounted to the rear quite close to the bottom of the fuselage where there would be more than adequate cooling - so overheating just couldn't be an issue. All electrical connections were shielded using shrink wrapping and banana plugs so I don't think any 'short' could have occurred.
I've sent a letter off today to Castle Creations asking that the ESC be replaced under the terms of the Warranty as I'm of the belief that there was some internal issue that caused the problem.. hopefully I'll get a favourable response from them soon..
Anyway, any comments or advice gratefully accepted..
Hoffo