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HelicopterThunder TigerOther › Gear ratio question
01-25-2007 08:32 PM  10 years agoPost 1
SPB

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Athens - Greece

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Lately I am wondering how much differnce will make the gear ratio so I might ask some of you that probably have already experiment on that.

I am using a YS.91 with 937 (3D) Hatori muffler geared with 8.45 gear ratio (93 & 11 tooth) and I am running 1850 rpm at idle up (15640 at the engine.)

In the Hatori packaging there is a note saying that the 937 is tuning between 11500 and 15000 with the YS. Out of this range the 937 works as a conventional muffler. Based on that I should either lower the rpm to 1770 in idle up (14964 to the engine) or lower my gear ratio to 8.27 in order to have 1800 at the blades (14974 at the engine) and keep my cyclic response alive.

Majority says that the YS likes the 8.45 ratio better. How many of you are flying a combo similar to mine and with what rpm and gear ratio?


Sotiris
myhelis.com Flying Team

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01-25-2007 08:37 PM  10 years agoPost 2
colsy

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Cambridge, UK

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I have 8.27:1 with st4 and 937. last tacked @ 1940.

colin.

Only Quote From Experience.

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01-25-2007 08:43 PM  10 years agoPost 3
SPB

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Athens - Greece

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Colsy have you ever tryed the 8.45 or you went staight with the 8.27?

If yes what difference did you noticed?


Sotiris
myhelis.com Flying Team

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01-25-2007 09:08 PM  10 years agoPost 4
colsy

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Cambridge, UK

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No, this heli originally had a SZH-PS and MP2. and i swapped pipes and engines to overcome bad vibes.

I have the 8.45 but couldnt be bothered to change it.

col.

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HelicopterThunder TigerOther › Gear ratio question
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