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HelicopterThunder TigerOther › Raptor 90 how to get 8.18:1 ratio
12-21-2003 09:48 PM  13 years agoPost 1
iachia

rrVeteran

Milan, Italy

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Wich pinion/main gear do you use to get the 8.18:1 ratio?
thanks

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Synergy N9

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12-21-2003 10:49 PM  13 years agoPost 2
Unbalanced

rrVeteran

Melbourne, Australia

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Ah - I have the 3 pinion's and 2 maingears and can't come up with this ratio. You can get 8.27 or less than 8 (7.9 or something from memory).

Jeff

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12-21-2003 10:58 PM  13 years agoPost 3
iachia

rrVeteran

Milan, Italy

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Thanks Unbalanced I suspected that! I currently have 7.91 but feel that I should change it. I'll try 8.27 and see what happens
bye

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Synergy N9

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12-22-2003 01:31 AM  13 years agoPost 4
Heli-Driver

rrElite Veteran

Arlington, TX

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For 8.18 gearing you need an 11 tooth pinion and a 90 tooth main.

I ran 8.27 in mine. I think that was an 11 tooth pinion and 91 tooth main. That ratio is fine for the OS, TT or YS 90s.



Raymond

Predator Gasser SE/231 X 2
Century Helicopters

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12-22-2003 10:39 AM  13 years agoPost 5
iachia

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Milan, Italy

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thanks raptordriver for the info!

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Synergy N9

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12-22-2003 11:46 AM  13 years agoPost 6
Raptorite

rrApprentice

Wiltshire, UK

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I run the standard 93 tooth main gear with a 12 tooth pinion, this gives a ratio of 7.75:1 which means that with a head speed of 1800rpm, the engine is doing 13950rpm which is as near to the magic 14,000rpm as youre going to get.

I flew it yesterday and with the combo of the OS 91 SXH (non C Spec) 60b carb and a 90 size zimmerman quiet pipe it was fantastic, very quiet engine, in fact it could barely be heard above the noise of the blades, the climb out rate is increddible pulling 10 degrees at the top and is exceptionally smooth.

Im not getting any of the vibe problems this older motor suffered from quite allot either, I guess because the engine isnt running that fast.

Cheers,

Pete.

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12-22-2003 12:32 PM  13 years agoPost 7
Reesy

rrKey Veteran

In the doghouse ... Nottingham UK

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12/95 gives 7.91 which looks about closest BUT big pinion and spur means a lot of engine re-aligning.
11/91 should be a direct fit replacement for the stock gearing.

I trashed an early SXH after forgetting to realign

Paul

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12-23-2003 03:32 AM  13 years agoPost 8
Unbalanced

rrVeteran

Melbourne, Australia

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When I fitted the 8.27 pinion/main gear the mesh was way too loose - in fact it would jump gears if you turned it. I had to bring the engine a long way back towards the maingear to get the mesh right. The 91T maingear (white) must be a fair amount smaller.

Jeff

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