RunRyder - 7.91 8.08 or 8.45:1 for the old OS91

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HIROBO Freya - Sceadu - Shuttle > 7.91 8.08 or 8.45:1 for the old OS91

MoneyPitVictim
Veteran
Location: Dayton, Ohio

I am running an old OS 91 SH with an MP5. Curently my Freya X-Spec has the 7.91 gearing (95t-12t pinion)

It bogs downs when doing easy tic-tocs at 1800 head rpm. I have toned down the cyclic and collective. Should I run higher head speed OR increase the gearing? (I am using V-Blades)
tnx

Santiago

06-29-2008 03:07 AM

Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

Your best option would be an 11 tooth pinion in your bell and the new 91 tooth maingear to yield 8.27:1 . ESPECIALLY if this is an original SXH91 (pre C-Spec), avoid 8.45. It places the engine well out of its powerband. Oh, BTW, 1900 would be fine with 7.9:1 if you care to play with rpm a bit.

Ben Minor

Representing
MRC Hirobo Helicopters and Team Futaba for Radios
Morgan Fuels
OS Engines

06-29-2008 05:44 AM

MoneyPitVictim
Veteran
Location: Dayton, Ohio

Dr Ben,
Thanks for the advise.
At 1900, would I be in danger of stressing something, like the tail, tail blades?

06-29-2008 04:48 PM

RICH.L
Key Veteran
Location: east springfield p.a.

Anyone out there know the part number of the new 91 tooth main gear?
or perhaps where one can be bought?

santiago,nice to see you are flying a hirobo still,I flew with you guys last year when I was down at school in troy ohio.

rich

06-30-2008 12:08 PM

Jafa
Elite Veteran
Location: Sydney, Australia

06-30-2008 01:12 PM

MoneyPitVictim
Veteran
Location: Dayton, Ohio

Also,

Which is the part number for the 97tooth gear? and is it a direct fit over the 95t?
thanks

06-30-2008 04:54 PM

Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

The model will hold together fine. I'm flying mine day in and day out at 1900 rpm. Unless a plastic grip has been cracked/damaged in a crash, Hirobo models don't come apart in flight.

Ben Minor

06-30-2008 06:46 PM

Agilefalcon
Veteran
Location: Fort Worth, Texas

I agree with Dr. Ben.
I have mine set at 1920 RPM using the CY ATG V3.0 governor. (select the 8.0 gearing during setup).

Loads of power and a nice responsive heli too.

By the way, I am also flying with the beautifull CCPM conversion on my model which is an X-spec with Evo head and the large Evo fuel tank.

Main blades are Radix 690mm and Radix 95mm on the tail.

Even with fairly slow JR8231 servos, the machine flies beautifully.

Chris.

Chris Berardi
MRC/Hirobo Representative
Amsoil Synthetic Lubricants Dealer

06-30-2008 09:23 PM

HOMEPAGE

MoneyPitVictim
Veteran
Location: Dayton, Ohio

Can anyone help me with these questions?

I found these 2 part numbers for the 97t gear, 0404773 and 0404057. Which one is correct?
Is it a direct fit over the 95t?

I am comtemplating the option of using a 97t gear or even the new 99t if it fits.

I have not had a chance to fly the X-Spec since I posted this and give it a go at 1900 rpm.
Hopefully tomorow.

07-01-2008 12:09 AM

MoneyPitVictim
Veteran
Location: Dayton, Ohio

I took care of a vibration from the main blades, leaned the main needle a bit and cranked the head speed to 1850 and now it holds the rotor speed no matter how many tic-tocs I throw at it.

The cyclic is sick fast. Nothing rolls so axial like an
X-Spec, not even my planks, well maybe.

Still I have the question:
Which of these 2 part numbers is correct for the 97t gear, 0404773 or 0404057 ?

07-06-2008 08:01 AM

Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

I'm about 99% sure the one to order is the EX 0404057 97T gear.

Ben Minor

Representing
MRC Hirobo Helicopters and Team Futaba for Radios
Morgan Fuels
OS Engines

07-06-2008 04:24 PM

MoneyPitVictim
Veteran
Location: Dayton, Ohio

Head wobble, blades too tight or not equally

Thanks Ben,

New Problem
I noticed today under full positive pitch at 1830rpm the heli started fast wobbling, kind of like the one you see when the head dampeners are very stiff and the rpm is to low. It was not doing it on normal/hover head speed 1600rpm.

Only thing different today, I tighten the blades lag bolt more than usual. I did not get a chance to fly again and with the blades not-so tight
Any ideas?

07-07-2008 06:05 AM

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HIROBO Freya - Sceadu - Shuttle > 7.91 8.08 or 8.45:1 for the old OS91

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