Converting an old GMP Cobra to electric

[ticedoff8]

I've gotten back into helis recently.
I've been flying a 400 size heli (Shogun V2) quite successfully - some crashes at first, but now I am ready to step up to the next size.

I have a GMP Cobra that I bought new in '84. I learned to hover with it, but I never got enough courage to try forward flight. I must have burned through 5 or 6 gallons of 12% nitro before I "retired" it to the attic.
I recently pulled it down from the attic and started thinking I could actually fly this again. It was never crashed and it still has the original, wooden, blades on it. I bought a box of spare Cobra parts from eBay and I found a guy that had a NIB GMP Cobra - so I have enough parts in the event I do crash it.
The original rotor head on the Cobra has a 3-degree coning angle - so I am looking for a "Pro" head with the 0-degree coning angle.

The issue right now is this: The original OS Max 50FSR-H motor it gummed up and I doubt I could rebuild it and achieve the needed power to fly the Cobra properly.

I want to covert it to electric.

Regardless of the engine, I will need to do a "ground up" restore / rebuild of the airframe.
And, I will change out all of the electronics and replace with modern technology (2.4Ghz DSM, gyro and servos).

Replacing and updating the IC drive train is about $250 (motor, governor, voltage regulator etc).

I am thinking I should use the power train system from the Align Trex 600 as the basis for the conversion.
I will be buying the Align motor, a Castle Creations ESC and LiPo battery - as if I was going to fly a Trex 600.
Fabricating the motor mount is easy enough - so I am not worried about that.
Overall, I think the ready to fly Cobra with the electric conversion would weigh less than the original heli - no flywheel, cooling fan, fuel throttle servo - etc.

The question I have is this: Is the Trex 600 motor / ECS / LiPo system powerful enough to fly an airframe that still weighs at least 1 to 2 lbs more than the Trex airframe?

[schluterdude]

ah, another vintage dude! check out the builds by dan in the 60 size nitro forum for his heli-baby, and his superior (both schluters). if you goto electric, you're also going to need to look into a new main gear as i would assume the gear pitches are different between the two and thus incompatible. i would just buy a new nitro motor and have at it! keep the old birds alive!

[WiscHeli]

i am restoring a 82 GMP Cobra now ,,,, i am puting a os 50 Hyper in it ,,,, were did you find the parts ,,, i have some spare parts .... and i am tossing the wood baldes and useing Glass or Carbon Blades

[Dan]

The T-Rex 600 electric only gets 4 minutes of flight at its designed weight. Adding a pound to that can only shorten the flight time. You may want to stay with gas.

[schluterdude]

http://stores.rchelicopterworld.net/Categories.bok?category=Vintage+Helicopter+Parts%3ASchluter

these guys sell all sorts of vintage heli parts. if they don't list it on the site, just call or email them. and, of course, there's always ebay...

[ticedoff8]

For spare parts, I just kept looking on eBay.
I found a guy that was selling a box of parts for the GMP Competitor & Cobra (spare side frames, rotor head, clutch, main gear, misc "stuff") and got it for $40USD.

I also found this site: http://www.1017.org/competitor/cobra.html. I signed up for his newsletter, and I am waiting for some parts.

I was also cruising some of the helicopter forums, and I found 2 guys that were selling complete GMP Cobra airframes. One was NIB but only missing the bag of screws - it is packed in the original box and most of the parts were still wrapped in their plastic bags - I bought that for around $75USD. The other guy said he was going to put his on eBay, but I haven't seen it yet.

The Schluter web site has a ton of stuff - for Schluter helicopters. I couldn't find anything for the Hirobo / GMP products (Competitor / Cobra). They have some links for "Cobra", but I think that was a Schluter Cobra, not the GMP Cobra.

After some consideration, I will stick to the IC motor instead of converting to electric.

Now, I am not debating whether to update the rotor head, or stick with the original.
The original has the 6-degree coning angle - great for learning and hovering, but not so great for flying. GMP had an upgraded head - the "Pro" head that had 0-degree coning - but those are as rare as hen's teeth. The GMP Cobra has an old style of cyclic mixing - lots of weird angles and levers - so upgrading to a newer design means a complete redesign of the control linkages.

I'll keep everyone posted.

[olhippie]

I have what I believe is a competitor like in the web site you've shown here. A friend was going to toss it and I grabbed it. I hate to throw stuff out. It has a real nice working head and gears. Looks pretty complete except for the motor. All I have of the motor is the finned heat sink head. It has 4 old futaba servos and futaba fp-r6l reciever and a kraft gyro 2 piece set up. I thought of fixing it up but don't have the time to. I have too much fun and time in my new helis to mess with it so I was going to put it on e-bay just to get it to someone with the time it deserves. I have an old mantis and revolution from american rc that are going, too. If someone is interested in it or them and makes a fair offer I'll deal with them. I'm not looking to make a load of money just want to sell them and make room for more new stuff. Let me know if I can help a old heli guy out.