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Gasser Model RC Helicopters > After the build..

pgkevet
Veteran
Location: surrey UK

Frustrating..

After a late night finishing off putting the clutch bell and pinion and checking everything..or so I thought..
This am just to recheck - early and found that despite thinkign everything went back as was then for soem reason the pitch range was out.. so I fiddled that to a flyable state with intent to do it thoroughly later..I wanted to try out the new bell.

So I get to the filed.. and find during pre-flighting it that servo is juddering! These are 9252's, hardly been used and it sounds like a grinding gear.

Now they are in the frame pretty tight against each other..I didn't want to set them from outside because that loses the perfect straight shot to the swash levers (so it's partial dismantle to get at them)- looks like i'm gonna have to do that and try some stand-off balls and pull that servo apart and view/change the gears. (means ordering balls and gear set)

If I ever name this heli it's got to be 'Lucky'

Gotta catch up on all the chores I put off doing Preddie yesterday..then see if I have enough time to pull those sevros out and sort it all..and try again tomorrow...

At least I got spare servos with my Spectra kit..and I'm not starting on that until this flies

pgk

06-08-2008 12:54 PM

pgkevet
Veteran
Location: surrey UK

Have a laugh and get it out of your system

So all fixed up, servo repalced and second maiden flights..

Idled my way through the first half tank then started gentle sports flying..small circuits and fig8's and zig-zags..10mins for each 1/3rd tank and allow to cool before next flight for a couple of sessions..
Then I thought I'd try setting an easy idle up curve..85,70,50,70,85 on throttle and hacked around the sky in wide circuits..

That Preddie looked good..a sorta stable twitchy if that makes sense.. very responsive but sits where you put it. As much climb rate as I can handle at my level, piro rate a bit slow (thats just settings).

Then in fast forwards level flight I hear an ocassional 'burble'. There seemed to be enough power still but the third time it happened I thought we'd better come in. Easy with hindsight but I came in quite fast for me from about a 100 feet, tightish turn at about 10-15 feet..heli burbled, started to drop and such a sluggish response to throttle I now have a lot of parts to buy!

Spark plug looks as perfect a chocolate as the pics I see here. No evidence of fuel leaks, tank still 1/2 full...

I'm guessing this was an expensive lesson in what can happen on transition between low and high needle flight when not run-in or tuned??

pgk

06-09-2008 12:48 PM

jschenck
Elite Veteran
Location: La Vista, NE.

sorry to hear about that. Are the frame pieces all good? Hopefully that was 'just' a typical boom strike.

I always set the top/bottom of the throttle to 100%. Figure if I put the sticks there I want all she's got. My 'Normal' flight mode is set at something like 0, 17, 20, 25, 35, 45, 100. May be a bit hight now but the general idea is if I hit full stick the carb is all the way open.

...yep...

06-09-2008 01:12 PM

pgkevet
Veteran
Location: surrey UK

..a lot of damage..main shaft, a couple of lost links (long grass), blades, boom, torque tube, bottom frame and skids (skid ripped out of the frame and twisted it but carbon side frames OK, Cracked canopy.

I'm more concerned with understanding why the burbling and why the failure to give me power..I'm guessing that since it was a fast descent and turn that I had the throttle/cyclic at/below mid-stick so 50% throttle on that setting.

If I'd run at too high a throttle then presume the plug wouldn't be a nice pale chocolate centre or the engine would have seized and not reaked such havoc?

Parts ordered and a spectra to start building. I might even have to go back to work!

pgk

06-09-2008 02:36 PM

TooBizzy
Senior Heliman
Location: Georgetown, Ohio USA

Quote
Then I thought I'd try setting an easy idle up curve..85,70,50,70,85 on throttle and hacked around the sky in wide circuits..

Your center three positions on the curve looks pretty high. If you were running anything like jschenck's curves 0, 17, 20, 25, 35, 45, 100 (which are very close to mine) you'd see something like this in your idle ups:
100, 45, 35, 25, 35, 45, 100

Maybe you were over revving - over heating the engine with your curves?

P-Gasser Se, Raptor 50 Se Hyper, Raptor 30v2, Trex450se, 3dx450...

06-09-2008 05:19 PM

pgkevet
Veteran
Location: surrey UK

Quote
Your center three positions on the curve looks pretty high. If you were running anything like jschenck's curves 0, 17, 20, 25, 35, 45, 100 (which are very close to mine) you'd see something like this in your idle ups: 100, 45, 35, 25, 35, 45, 100

I was significantly over those figures at the middle. Engine sounded happy apart from those few short burbles..hmmmm...Ph, well - lesson learned the hard way.

pgk

06-09-2008 06:27 PM

jschenck
Elite Veteran
Location: La Vista, NE.

It might be a tuning issue. I don't know much about tuning these gas engines yet but I had to raise my middle numbers quite a bit to get to the 1800 headspeed. I think I'm rich on the L needle yet.

I wonder if your engine coughed a bit when it transitioned to the H needle. Does it normally transition and accelerate clean from hover to full throttle? Kind of thinking out loud here. Could this have been caused by a rich L needle so the engine loaded up?

I've decided to put my old gasser airplane back together. It's a Bud Nosen trainer (10 foot wing) - quite a monster. I have some ancient 38cc conversion on the nose of it, a "Bennett" conversion as I understand. I bought this several years ago at an auction and flew it for about a year before breaking the firewall on a bad landing. Won't take long to put it back together. Now that I'm learning a bit more I hope to use this to get an ear for tuning gas engines. I've even given thought to a G-26 powered airplane such as a CG Tiger-120.

Anyone have thoughts on learning gas engine tuning with a prop, how that experience translates to rotating wing'd aircraft?

...yep...

06-09-2008 06:41 PM

xcellgasman101
Elite Veteran
Location: WOODWARD, OKLA....

Yep,, you can learn allot,, smooth idle, transtitions, and full power, by sound, and plug reading,, XGM/VGM

I have a 35% Carden Cap, with a Brisson 6.4 twin, Awesome plane,

John Crotts
www.soonerhelicamproductions.com

06-09-2008 06:46 PM

HOMEPAGE

jschenck
Elite Veteran
Location: La Vista, NE.

The interesting thing about my BN gasser was I didn't fiddle with it. Didn't know enough to question what oil and how much so I just ran the same mix I had for my snow-blower and weedeater. Thinking back it was too much oil. I did play with the needles but sure didn't know what I was doing. It has lots of power, make a huge amount of noise and the coolest part is channel-5 is a bomb-bay door trigger. The fuse it almost a foot tall and wide so I can carry a lot.

As has been noted here before, I now have one of the best running weedeaters on the block

- just be virtue of my heli experience.

...yep...

06-09-2008 06:53 PM

pgkevet
Veteran
Location: surrey UK

Quote
I wonder if your engine coughed a bit when it transitioned to the H needle. Does it normally transition and accelerate clean from hover to full throttle? Kind of thinking out loud here. Could this have been caused by a rich L needle so the engine loaded up?

That's honestly hard to answer. Remember this has had a maiden flight sries of short hovers, one day out when the pinion thread sheared and then today. My experience with helis is 2 electric and almost a massive 9mths flying!

Today after each start I gave it a few moments to warm up and then gently into a light on skids then lift-off. As it lifted off it did give a sl hiccup which i put down to the slow spool up.

Hovering and lazy 8s at 30 feet it sounded nice and I'd guesstimate headspeed no higher than my 600e in a hover. no-one around to tach it for me.

any explanation for the 'burble' in fff?

It did look super up at 150 feet creaming along though and great climbing form there to stall turns. Id thye Spectra looks that cool in the sky then I'll be a double happy bunny - just need to sort these teething issues (and fix it up again)

pgk

06-09-2008 09:18 PM

pgkevet
Veteran
Location: surrey UK

Base plate

For those folk that remember Profwiz's build thread on the predator and issues he had with the base plate.

I had no such problems and I've just changed baseplates (after the 'episode'

and the new one fits fine too.

Implies his was engine variation?

pgk

06-16-2008 09:09 PM

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