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HIROBO Turbulence - SDX - Freya - Sceadu > Vertical vibration on Freya tail boom
 
 
yapjy
Key Veteran
Location: Singapore

My Posts This: Topic  Forum		Hi,
This happens when I flew at a headspeed of 1550 rpm. The vibration is only observed on the tail boom(i.e it goes up and down very slightly). The vertical fin has no horizontal vibration.

The vertical vibration on the tail boom will go away when I increase the headspeed to 1900 rpm.

I have tightened the belt and it seems to help a little bit. But I'm flying F3C and I will like to have a stable tail.

My Freya is very much stock and the only upgrade on the tail is a vertical carbon fin. The engine is an OS70. I bought it new in April 05. No crashes, only a couple of hard landing from autorotation.


Please advise.
06-18-2005 Over year old.
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DOKEY
rrProfessor
Location: Northampton UK

My Posts This: Topic  Forum		Have you used a dial indicator on the start shaft ?
06-18-2005 Over year old.
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white chocolate
Key Veteran
Location: Baltimore, Md.

My Posts This: Topic  Forum		1500 is kinda low for the head. It will wobble alittle. Make sure everything is balanced and your shaft is good. But that headspeed is low for a freya.

Team Raptor
Radix
Perfect Regulators
06-18-2005 Over year old.
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yapjy
Key Veteran
Location: Singapore

My Posts This: Topic  Forum		I increase the headspeed to 1600 rpm plus.
Now, the tail boom vibration is limited to the section between the horizontal fin and vertical fin.

Same thing, when I go idle up at 1900 rpm, the vibration will go away.

Thinking of moving the boom support to the lower hole on the main frame.
06-19-2005 Over year old.
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z11355
rrMaster
Location: New England

My Posts This: Topic  Forum		not a bad idea.

make sure the screws & locknuts do not interfere w/ the fuel tank
and punch a hole in it.
06-19-2005 Over year old.
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yapjy
Key Veteran
Location: Singapore

My Posts This: Topic  Forum		Worse now. After I moved the tail boom support to the hole on the lower part of the main frame, it vibrates rapidly in idle up 1 (~1900rpm) but not in normal (~1600rpm)

I replace the rotorhead spindle and the vibration is slightly lesser.

Will check on the tail shaft and spindle.
06-25-2005 Over year old.
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dkshema
rrMaster
Location: Cedar Rapids, IA

My Posts This: Topic  Forum		Balance your entire tail rotor assembly.

Do the head and flybar while you're at it.

Dave
06-25-2005 Over year old.
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tchavei
rrProfessor
Location: Portugal

My Posts This: Topic  Forum		One question... how do you achieve 1900rpm headspead with a stock freya?!... on a 9,5:1 gear thats 18050rpm on the engine... over max recommended rpm?

Cheers, Tony


--------------------
"Perfection and patience usually walk side by side..."
06-25-2005 Over year old.
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TMoore
rrProfessor
Location: Cookeville, TN

My Posts This: Topic  Forum
Quote 
One question... how do you achieve 1900rpm headspead with a stock freya?!... on a 9,5:1 gear thats 18050rpm on the engine... over max recommended rpm?


Who says?

TM
06-25-2005 Over year old.
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Hirobo St.Louis
Veteran
Location: St. Louis

My Posts This: Topic  Forum		Straight from os's website


.70 SZ-H Ring 3D Heli Engine
SPECIFICATIONS
Stock Number: OSMG1972
Displacement: 0.702 cu in (11.5cc)
Bore: 1.016 in (25.8mm)
Stroke: 0.866 in (22.0mm)
Output: 2.5 hp @ 16,000 rpm
RPM Range: 2,000-18,000
Weight w/o Muffler: 19.5 oz (553.5g)
Requires: Muffler & fuel
17000 .70 SZ-H Ring Parts Listing

A.K.A. J.O.
06-25-2005 Over year old.
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TMoore
rrProfessor
Location: Cookeville, TN

My Posts This: Topic  Forum		I'll betcha that you can get more rpm out of the 70 than the range that is listed on the website.

TM
06-25-2005 Over year old.
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Hirobo St.Louis
Veteran
Location: St. Louis

My Posts This: Topic  Forum		I'm sure. What's 50 rpm compared to 18000 anyway.

A.K.A. J.O.
06-25-2005 Over year old.
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TMoore
rrProfessor
Location: Cookeville, TN

My Posts This: Topic  Forum		Agreed.

TM
06-25-2005 Over year old.
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yapjy
Key Veteran
Location: Singapore

My Posts This: Topic  Forum		I used a 8.45 gear ratio.

Optimum rpm for OS70 is 16000. That gives about 1900 rpm on the rotorhead when using 8.45 gear ratio.



I was advised at the flying field to get the top bearing block for the tail shaft assembly at the end of the main frame. Wonder if that would help?
06-26-2005 Over year old.
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Ron Henry
Senior Heliman
Location: Atlanta area, GA - USA

My Posts This: Topic  Forum		Just a suggestion, but if you're getting a vertical bounce in the tail boom, that normally point towards something not running true in the mainshaft assembly or a bent tail output shaft or hub. Has this machine been crashed lately? If so, and you replaced all of the typical parts (mainshaft, spindle, flybar, etc..) I would also consider replacing the center hub as well. If the machine hasn't been crashed, take a look at your tail section. The Freya tail hub is extremely easy to bend. I've bent them by just tapping the tail against the wall while walking down stairs. The way that I check it, is to remove the hub from the output shaft; tail blades grips and all. Then flex the tail blades towards each other. The hub should not rotate. If it does, then it's bent. Go through those things checking/changing one thing at a time, and you'll find the problem. I hope this helps.

- Ron Henry
http://kaizenrc.com/forum
06-26-2005 Over year old.
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Detroit Steve
Senior Heliman
Location: Michigan

My Posts This: Topic  Forum		Boom Support.

Check to see that the plastic ends are secure in the aluminum boom support tubes(I JB Weld mine in). Check also to see if you have the boom supports tight to the frame and fin band. Also make sure horizontal fin band is tight to boom and not broken, I run a piece of trim tape under my fin band to help it clamp down.

Steve

Feeling the Difference
06-26-2005 Over year old.
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yapjy
Key Veteran
Location: Singapore

My Posts This: Topic  Forum		Thanks for the helpful advice.

The culprit is a bent tail shaft. Replaced that and the vibration is gone. Must have damaged that shaft during a hard landing.

07-02-2005 Over year old.
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HIROBO Turbulence - SDX - Freya - Sceadu > Vertical vibration on Freya tail boom
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