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HelicopterHIROBOOther › Freya 7.75 ratio/ YS 91 works great
03-16-2003 02:46 PM  14 years agoPost 1
Tyler

rrElite Veteran

Chicagoland area

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I have just about put a gallon of fuel through my Freya with a 7.75 gear ratio. I am using the 93 main gear and 12T pinion gear. After reading DavidH's posts about lowering the ratios for the YS 91, I thought I would give it a try. Most people are using 7.91 on the Freya, but the YS manual recommends 7.5 to 8.0 ratios. The 7.75 fit perfectly in the middle. I was using 8.45 previously, but I thought I needed a little more head speed and was afraid of over speeding the motor. On the Fury extremes, headspeeds of 1750-1850 seem more than adequate for most pilots, including hard or advanced 3d pilots. However, I have found the collective of the Freya to leave a lot to be desired comparatively. The higher headspeed really brings the heli to life: 1800-1900 idle1-idle2.

I would like to burn some more fuel to make a final decision on this ratio, but the heli sure is lively, quiet, and smooth. I often hear the blade noise much more than I ever expected, and I think this is due to two things: the engine is turning less rpm and therefore is quieter, and the motor has enough power to really make the blades work through the demanding manuevers that may typically bog my smaller engines and reduce headspeed.

I can easily perform climbing tick-tocks and other power hungry tricks. I am still working on tweaking the GY-601 gyro to my taste/style, so I have not explored all the manuevers I am capable of, yet.

Has anyone else tried this ration? I have not noticed any gear wear due to improper pinion/main gear mesh.

Tyler

Enjoy things that money can buy IF you don't lose the things money can't buy.

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03-17-2003 07:21 PM  14 years agoPost 2
Agilefalcon

rrKey Veteran

Fort Worth, Texas

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Great info Tyler. I'm running the 8.45:1 ratio for comparison to the 7.91:1 ratio (12 tooth pinion and 95 tooth main versus 11 tooth pinon and 93 tooth main gear).

The engine is a lot noisier at the higher 8.45 ratio with a head speed of 1750. I agree that the 7.91:1 or 7.75:1 ratios are a lot quieter and have the nice positive response at higher head speeds. Hirobo really did their homework when they selected the gear ratios though it took a while for everyone to see that the big motors really did have more torque than we believed.

I'm switching mine back shortly to the 7.91:1 ratio with an 1800rpm head speed. This is a great combination! Heck I might even give the 7.75 ratio a try.

Chris.

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03-18-2003 12:37 AM  14 years agoPost 3
Tyler

rrElite Veteran

Chicagoland area

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Fuel consumption

My fuel consumption is outrageous right now. If I set the needles to the break in recommendations, the engine is too lean with Wildcat 30% coolaid. I have tried to sneak the needles leaner after 3.5 gallons, but the engine simply will not tolerate it. I am getting very concerned about feeding this hungry engine!!!

Is it common for the engines to reach a certain break in point that all of the sudden will allow the needles to be turned in? I have heard people mention in the past that YS engines really take 8 gallons to get broken in.

I cannot imagine filling the tank to a 8.45 ratio.

Tyler

Enjoy things that money can buy IF you don't lose the things money can't buy.

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03-18-2003 01:12 AM  14 years agoPost 4
JEraptor

rrApprentice

Kankakee IL

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Tyler,

My STII seems to run for hours on a tank of fuel, if you are really concerned about fuel consumption, I can help you out.
I am running 9.3/1 and I'll bet if you ran your 7.75 with this engine you could fly ALL DAY on 1 tank!!

Just think of all the extra dough you could save if we swapped even up.

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03-18-2003 08:14 AM  14 years agoPost 5
helidude

rrApprentice

Sunny California

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X-Spec and YS91

I'm currently running the 7.92:1 ratio in my X-Spec. I'm running my own mix of 22% fuel. I'm currenty getting 12 mins on a tank.

The engine is very quiet. More so than my Extreme at 8.18:1.

I'm very pleased with this combo. So pleased that a bud is buying my Extreme,which will be replaced with another X-Spec/YS91 combo.

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HelicopterHIROBOOther › Freya 7.75 ratio/ YS 91 works great
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