Monday, 26 May 2008

Hop - and then problems

I am sorry I have had no other helicopter or field stories to share with all of you. I have not been able to get to the field because of this build and because the weather has been so bad lately here in the Midlands. Most of the time I wish I had never left Southern California, but that is another story.

So, the Protos was finished Saturday night. A friend, let's call him JS, came over with a few parts for the electronics and drank a beer with me while I slaved away. A while after he left it was ready to spin up. So I did. The helicopter spun up nicely and quite quitely for this size of helicopter. The real noise came when it was at it's full 2500 RPM and was beating the air around it into oblivion. Nice.

Then the Helicopter shut down.... I thought it must have been the motor over heating since I was just spinning it up on the ground for about a minute. Strange. I also noticed that the servos were twitching like crazy. I moved the BEC away from the ESC and tried it again. The next time I tried it the same things happened. Random shut downs and servo twitching. I thought maybe I was drawing too many amps fRom the BEC because of stalled servos, so I reamed everything out some more with the ball-link sizer (that comes in the kit). Again it shut down and the servos were twitching like crazy.

I wish I had started taking video or at least pictures at this point... I figured I had tried everything else, and even though I had been told by Corrado at MSH that there was no chance of Static on this helicopter* I should check it out anyway. So, I connected a ground cable to the tail boom and to the motor mount.

Grounding the tail boom made it worse! It actually became so bad that I could have the helicopter on and spin the main blades with my hands and the servos would twitch!. So, I unhooked the ground cable from the motor mount and it stopped doing it when spun by hand. I figured I better test it properly.

I took off the blades and left the ground cable connected to the tail boom but loose. I spun up the helicopter to the lowest throttle point. I then took the ground cable and slowly touched it to the motor mount. I saw sparks and the helicopter went crazy again. I was convinced. This was the worst static I had ever seen. Connecting the ground strap made it worse and so I had one choice... I sprayed the belt with WD40**. Problem solved. I had no more glitches, twitches or shut downs.

Too bad it is not a happy ending though. Before I found the problem my AR6200 remote receiver got cooked. I e-mailed the Corrado and he simply said they never had a problem during testing. Well I am sure that was the same story with the T-Rex 500. I sure hope he remembers what I said when he starts getting more reports.

I hope to fly this helicopter this week and report. Maybe some video at the weekend?

* He actaully said it a few time in teh design thread, but he said once specifically "I forgot to mention to say goodbye to any static current belt problem, belt obviously touches the metal pinion on the motor so it is grounded the best way possible". My self and others doubted this since rubber is not conductive and actually will transfer charge from what ever it touches to the metal that comes near it, in this case from the plastic pulleys to the metal tail boom.

** Yes, I know WD40 can degrade rubber, but i have used it on my 450 for ages and it never caused a failure.

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