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HelicopterMain Discussion › Just purchased an EVO 90 and YS91 - What gear ratio recommended?
11-21-2006 10:53 PM  11 years agoPost 1
Amarjit

rrApprentice

Chicago, IL

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Hi everyone,

I just purchased an evo 90 kit with a ys91 engine. What gear ratio do people recommend for this setup? Should I stick with the factory ratio? If so, could someone also tell me what the factory ratio is?

I am just getting into 3D

Thanks!
Amarjit

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11-21-2006 10:56 PM  11 years agoPost 2
Furious Predator

rrProfessor

Kitchener, Ontario, Canada

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read the YS manual. it recommends a ratio of 7.5-8.0
its sweet spot is about 15500rpm, do NOT go over about 16000, you will destroy your motor. i've done it, and friends of mine have done it.

Shawn
Team Leisure-Tech
Team HelixRC

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11-22-2006 03:21 AM  11 years agoPost 3
RCtaz

rrVeteran

Leander, TX

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the kit comes stock with 8.45 and the only other option for the EVO is 7.92.

Of the 2 8.45 is better for the YS.

~Texas Renegade Rotorz~

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11-22-2006 03:23 AM  11 years agoPost 4
Furious Predator

rrProfessor

Kitchener, Ontario, Canada

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if you run a low head speed then yes. for the motor to run in its sweet spot the head would only be doing 1830rpm.....pretty slow for 3D if you ask me. with the 7.92 gear ratio you would be running at almost 1960rpm, which is really good for 3D and high speed stuff.

Shawn
Team Leisure-Tech
Team HelixRC

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11-22-2006 04:12 AM  11 years agoPost 5
Amarjit

rrApprentice

Chicago, IL

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Thanks for your messages...I too have heard that 8.45 is a better setup for the YS

but, I guess it may be partial to the person flying the helicopter. In any event, if I were to use the stock 8.45, what is a good head speed for this particular ratio?

Thanks so much!
Amarjit

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11-22-2006 04:15 AM  11 years agoPost 6
RCtaz

rrVeteran

Leander, TX

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1830 is right on the money like FV said. My EVO worked great right there.

~Texas Renegade Rotorz~

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11-22-2006 08:43 AM  11 years agoPost 7
DS 8717

rrProfessor

Here wishing i was somewhere else

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We are using the stock 8.45 ratio with 1900 and 1930 headspeed's,it livens up the cyclic and keeps the engine in it's power band better.And of course you need a governor so it wont overspeed.DOUG

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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11-22-2006 01:50 PM  11 years agoPost 8
shlm

rrKey Veteran

West Chester, PA

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YS91 w/SB16 w/8.45 at 1880-1900 w/7.5 cyclic pitch = Fun!!!

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HelicopterMain Discussion › Just purchased an EVO 90 and YS91 - What gear ratio recommended?
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