Excuse me... I've got Gas! Trex 600 Helibug Gasser

[Doozer]

Maiden Video up.

[Solitaire]

Ah, just in time before the trek to the west coast.
Moves pretty quick for less than half throttle. And not quite as noisy out there on the bald prairie. You could always try diesel in your next one.

[Doozer]

Yeah, that's why the throttle curves are so low. Much past 50% and your head is screaming. The carb on a gasser doesn't operate in a linear fashion. Most of the power in a gasser comes from the lower end of the curve. Though, you can set it up linear by putting mechanical expo into your throttle servo. By increasing servo resolution at the bottom of the curve, your throttle will react in a linear fashion much like a glow. I've read about that and I'm thinking about trying it, but right now I'm just trying to get the hang of flying it as is.

With the 17t pinion, I can't get a head speed much above 1900 without risking the engine. 1900 is plenty fast for me though. Without having a reliable tachometer, I can't get there using my curves. At 40% I can save it from a bog or a sag, and it doesn't overspeed. Keeping it from overspeeding at this point is my main concern. So my curve looks something like this:
0, 5, 10, 12.5, 15, 17.5, 40

This way I can get my self out of trouble by pegging the collective without damaging the engine. Next payday, I'm going to get a Sky Tach, so I should be able to work out my curves. I'll have to put my pipe on hold though. Sky Tachs run about $150.

[Doozer]

Alright, I'm pretty much done here. There are probably still some mistakes that eventually I'll get to, but i think as far as a build goes, it's complete. Feel free to ask questions here if you would like to.

I added a few things here and there, including my switch to synthetic oil to the end of the build. I also thought it was important to note, at the beginning of the thread, that this build thread is meant to be read in it's entirety. Because it's a build thread and not a guide per se, I've including my mistakes. To pick off information here and there without reading the entire build thread could end up costly to you.

That having been said, I hope people enjoy the thread and find it useful.

[Solitaire]

And a job well done. Thanks for the extra time and effort you put into this thread, Dooz.

It almost makes me want to go out and get a gas motor to play with...

...almost.

[Doozer]

Though I said I was finished with this thread, I feel compelled to add this post. More like a caveat/warning.

I spent a whole bunch of time, and money hammering out an electric conversion. It was expensive. I spent more money than I needed to. This morning on Heli Freak, in the "For Sale" forums I see this:
www.helifreak.com/showthread.php?t=315544

All the donor parts needed from the 600N are there. How much? $100 dollars. This includes a head (read "spare parts"). I spent a lot more... more than twice that converting this heli with new 600N parts. That doesn't include trips to the LHS (gas) and my time.

Don't do what I did. If you have an ESP, great, you can use the head (without the shaft), landing gear, complete tail assembly, tail drive, tail drive gear, boom, torque tube, and that's it. You'll need to purchase everything else. Even the main shaft is a different length. Look for used parts and get your ducks in a row before you start this build.

My next order of business is to change up the list in the first post to better reflect cost. I might not get to that today, but I'll try.

[oldkiwi]

May 6, 2011 23:22:41 GMT -6 Doozer said:

Well I have to buy a new pinion and clutch bell, and it comes at a hefty price tag. I have heard that if you clean the threads on the pinion with a wire brush it should thread easy. Guess what? I didn't, and I got the pinion about 3/4 of the way down an it got stuck. I tried to back it out.... nada. I hit it with the mini torch.... nothing. I finally broke out the channel locks and a rag. I tried with everything I had..... nothing except I chipped a pinion tooth.

So I had to order up a new one, and they aint cheap. My screw up though. Anyway, if Ali sent the pinion today, I should have it by Monday. I could be in the air by Monday if that's the case. I'll have the rest of the build up by Sunday, except for the engine bearing block/clutch bell/pinion.

Evidently gassers do not have linear throttles so I want to go over throttle curves for Zenoah engines in the build. Eventually I'll put a governor on it, but my need at this time is not great (read: Money I can spend elsewhere... like my new paint addiction )

Yep

cross threaded pinion into clutch bell , luckily new bell available locally and was able to save pinion. even new one was tight. slowly threaded it on as using a tap  i.e 1turn back off, another turn back off etc