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HomeAircraftHelicopterMain Discussion › Tuning Gassers
03-06-2008 09:46 PM  10 years agoPost 1
Soarin77

rrNovice

castle rock, CO

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Hello everyone;

Im new to this site, but ive heard so much about it and ive actually gotten quite a bit of info from it from searches on the web.

Ive got some questions and or concerns regarding the tuning of the Zenoah 26.
First a little background on myself:

Ive recently started an aerial photography company in Denver Colorado. I am using the Bergen Intrepid EB equipped with a standard muffler and the AP-2000i (which I haven't tested yet), but finally got set up (Thanks Mark!). My radio is the Futaba T7CHP.

I have already perfomed some test hovers and basic maneauvers with it and it hovers like a dream. My questions are as follows:

I am having serios vibration issues with the machine. Among many minor hardware issues is a serious issue, which if I don't fix fast, could cause some serious issues down the road. I recently had the two bolts that hold the tail rotor gearbox to the boom shear off. Luckily, I noticed the tail rotor putting off some minor diaganol motion from time to time when in a hover and landed it quickly. Of course the bolts where held in with loctite, so the removal of the remaining bolt portions from the blind holes on the gearbox was a little tricky.

I am contributing this to what I think is a engine problem. I have read a post on here stating to monitor the landing gear when in a hover for clarity. If the gear appears blurry, then there is too much vibration. Well I performed this test today and the gear was clear as can be in a hover, but the T/R gearbox was pretty blurry. Which indicated to me there is severe vibration in the aft of the machine. I have also read in a forum from Chris Bergen, stating to remove the idle screw from the carb, which I have not done yet. Is this recommended?

Additionally, during the throttle up procedure, when at about half stick (just prior to lift off) the engine boggs down pretty dramatically. If I give it another stick positoin of positive power it recovers and regains rpms. If left at that position, the engine will die. Now, during idle through half stick, the engine is perfect, and during a hover the engine is perfect. Perhaps my thottle vs. Pitch curves are off.

My curves used in idle 1 are as follows:

Throttle curves and points: 1-0% 2-45% 3-90% 4-92.5% 5-95&

Pitch curves and points: 1-30% 2-40% 3-50% 4-75% 5-100%

My blade pitch at full negative is about 3 degrees and full positive is about 9 degrees.

Are these sufficient curves for this machine?

Any help with these issues would be greatly appreciated!

Thanks in advance everyone

Kelby

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03-06-2008 11:02 PM  10 years agoPost 2
jschenck

rrProfessor

La Vista, NE.

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I'm still learning myself. I do know from experience that if the engine sags ANY, AT ALL land immediately. Don't even think about it, hit hold and auto it in if you are in a position to do so.

http://runryder.com/t113089p1

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03-06-2008 11:34 PM  10 years agoPost 3
3dwanabe

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Huntersville, NC

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Your Throttle curve looks to be way off. Mine is set to 1-0%, 2-23%, 3-42%, 4-51%, 5-100%. These percentages were set to get the head up to hover rpm at 1/4 stick and maintain that rpm all the way to full collective.

The G26 has a reputation of creating more vibration than the G231 (which is a very smooth engine). A good start for needle settings is 1 3/8 turns for the low needle and 1 1/2 turns for the high needle. This should be a very rich setting that can be leaned until the engine starts to run smoothly. Just make sure that you don't go too lean or the engine will hammer badly and parts will start falling off your helicopter.

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03-07-2008 11:57 PM  10 years agoPost 4
Soarin77

rrNovice

castle rock, CO

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Great, thanks guys. I will try that setting and adjust from there.

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