HELP!!!!

I've finally successfully installed my 32 cc McCulloch saw engine on my 1.20 size stick, (took like 3 weeks), and can't get airplane to pass "range check". With the engine at idle, antenna collapsed, all servo's go crazy at about 6 feet, and about 12 feet with antenna extended on transmitter. I have a resistor plug installed from a G-26 (champion), plug wire shielded and grounded to motor, the closest component (servo's) are 11 inches aft of firewall, no help. I went as far as applying "aluminum tape" to the entire inside of the fuselage, all servo leads, receiver, and battery pack, all to no avail. I removed all the tape, and am ready for the next solution (if any). The engine runs great, and there's no "metal to metal" linkages anywhere. Servo's are rock steady with engine not running. I'm running a new hi-tec FM receiver pack, with a JR 642 transmitter. Some say PCM will eliminate problem, others say it will make it worse. Itching to fly the airplane, but don't want to crash!!! Any help from anywhere would be greatly appreciated, I have too much time in this project to give up now.......I am currently using a 1200 mah Nickel-metal receiver pack, and have tried the 600 mah Nicd, no help either...Will it be feasible to purchase a PCM receiver, or another entire engine? The airplane is'nt really worthy of a new G-26 (test bed only), so I don't want to sink a whole lot of money into it, as this would defeat the whole purpose of the project. Both receiver and transmitter are well aft of firewall (17 inches), and closest servo is 11.5 inches....Thanks again....

It sounds like you've covered all the bases. I'm wondering if you don't have a bad receiver. Don't go to PCM however. PCM can mask interference problems until it's too late and they just drop out or go into fail safe. I would try another resistor plug, double check everything, and it that doesn't work try another receiver. You don't have your antenna routed inside near metal or carbon fiber pushrods do you?

Good luck, but whatever you do don't fly it until you get it sorted out.

AV8TOR

one thing you don't mention is your throttle pushrod. it should not be metal. also try tapping on your receiver with radio on and engine off, this will tell you if the crystal is bad of if there is a loose solder connection.

dave

As Av8tor said PCM is NOT the answer! Your component setup sounds perfect. I'd look to the reciever as the problem first. Also could be marginal connectors, mabey the switch ? How about trying another reciever, borrow a known good one from a friend just for a test ?

Thanks for the info guys, I replaced the carbon fiber throttle push rod with plastic yesterday, to no avail. There ARE 2 metal pushrods going aft to the elevators, and 8 metal "guy" rods supporting the tail feathers, I have removed the guy wires, also no help, however, I have not yet replaced the 2 elevator rods, that are near the antenna. Will try that and the receiver out of my 1/4 scale Decathlon (FM also)...All connections are tight into the receiver, and running without a battery switch (strait from battery to receiver) also no help......will update.....

Unless i overlooked it i did'nt see anywhere that your using a resistor plug.You must use one with ignition engines.Also please send me rpms readings and possibly a picture of your conversion.I did one but had trouble with muffler.Did you make it or what?Thanks and good luck with it.

You didnt mention range check with engine stopped.

-ZM

Throttle return spring: tension reduced, clipped hook end or removed entirely? If the the hook was clipped off the spring and it was left in place, could it be vibrating?

Not just to maybe carb mount bolts?

Couple things you can try...

Inspect the ignition wire VERY closely...look for any cracks in the rubbery parts...

Try wrapping the ignition lead very tightly with aluminum foil or aluminum tape.

I've had a bad receiver do the same thing your explaining as well make sure its wrapped in latex foam (vibes will kill a rx).

Good Luck!
CrazyHerb

UPDATE: Removed ignition coil/plug wire, found 1 of 2 wires coming out of coil cut. One obviously goes to ground for "kill switch", the other was diked off. New ignition (from neighbor) had one of the leads going to ground. Installed new/grounded coil and wire assy, Range check good. Carburetor (rubber boot mounted) fell off in process because boot cut itself into. Modified intake pipe with rubber hose and 90 degree PVC pipe, Carburetor and ignition system now rock solid, and runs good, hoping to fly Friday!!!! Thanks for all of your help!!!

9-24.......It flies!!!! Took the monster to the field (1.20 size stick) with the McCulloch 32 cc,
made 8 laps, then nice dead stick for a perfect landing!!! Significant "up" trim on elevators required, Still need minor tweaking on fuel system, but all involved had great time!!! Very satisfying feeling after 3 weeks of major engineering.......I highly suggest this type project for anyone that likes to work on small engines....

Congrats on your success! It is great when "A plan comes together" isn't it. These little motor conversions are great fun and I love it as well. Gave me a whole new interest in the hobby when I started doing them.

Keep us posted,
AV8TOR

12 October 04---went out to field with "contraption" Sunday afternoon,,,,at this point, engine has been on firewall approximately 1 hour total flying time (actually thats quite a bit) and operating well......after about 7 laps, engine sounds unusual, I'm at about 60 feet and 50 or so mph, engine "burps" and without warning, totally separates from firewall. Throttle linkage holds on for about 1.5 seconds, causing "full throttle" situation, while 18x10 prop is steadily eating at over-engineered landing gear. Engine departed at 2.0 seconds, leaving me with an extremely tail heavy 1.20 size stick. At this point, I'm between total surprise/awe, and fighting off hilarity of situation. All other witnesses are making curious sounds, which add to the once in a lifetime event they are all looking at. Everyone is voicing advice at me all at once---"keep the nose up",
"you need more airspeed", I'm thinking "No ****, I also need an engine!" At full elevator down, on high rate, the airplane has about a 2 degree (thats two) nose down, and an airspeed just above that of one of those sea turtles you see on animal planet, and somewhat resembles a drunken seagull contemplating suicide, the airplane actually "autorotated" strait down onto it's belly, sending the over-engineered aluminum landing gear through the fuselage, but cushioned by the half full fuel tank, the damage was minimal, and VERY much worth the entertainment. The poor engine, as if it had'nt been through enough at this point, didnt fair so well. After impacting the earth, at only god knows what telemetry, the exhaust "deflector" was smashed beyond recognition, taking 3 cooling fins with it, our PVC intake system simply separated and was spared, but the intake "manifold" was destroyed, along with the spark plug boot that had the end of my $8.00 resistor champion precariously peeking through it and the 18x10 prop was reduced to mere stubs by attempting to "saw" the gear in half. Needless to say, all very entertaining, aircraft repaired now, other engine ready, and awaiting Plan "C" of mounting method. My neighbor is going to "forge" 2 aluminum plates, one for the engine, and one for the firewall, that will have 3 "posts" on each, to accomodate 1/2 inch rubber tubing that will connect the two to absorb the high vibration being generated by this engine. We will also step up mounting holes from 10/24 to 1/4 24 and safety wire. This should be a hoot! Will update progress of said project. [][][] (I'm already scared)

that part had me rolling on the floor


dave

Hey 717doc, Sure sorry abt all of your proublems but you conveyed in greate detail and I just had to laugh. Please report back with your progress with the repair. I am glad to see you have cleared up uour interference trouble any way. If You Have any other radio/interference trouble please "e" me at [email protected] and I will try to assist you with some of my 45 + years of "ham" radio mobil experence. I think I have seen everything and then along comes another one. That's what makes it interesting. HI HI. Sorry for your loss and thank you for the intertaining report!

fly the airplane first

please excuse the spelling, but I am from TEXAS

73 Lee K5MRC