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HomeAircraftHelicopterHelicopter Main Discussion › gear ratios for dummies
02-08-2008 11:49 PM  10 years agoPost 1
lrogers

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Mobile, Al

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Okay, the dummy is me! I've never been able to grasp the concept of gear ratios and number of teeth etc. so I need some help.

To lower the head speed by changing the pinion gear (all else stays the same) to you use a gear with more or less teeth?

I want to try a multi blade head on my T-Rex and assume I'll need to lower the head speed to compensate for the 5 blades.

Larry Rogers - R/C Helicopter Pilot

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02-09-2008 12:04 AM  10 years agoPost 2
Jeff polisena

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westpalmbeachflorida usa

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Depending on air frame sometimes you need to replace pinion and main gear on others you need to replace just pinion it sounds like you want to change pinion to a lower # .Take # of teeth on main and divide by # of teeth on pinion this will give you a gear ratio but like I said different air frames require different options

To answer question lower teeth count

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02-09-2008 12:28 AM  10 years agoPost 3
stocky

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Taxachusetts

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(Motor pinion Teeth / Main Gear Teeth) X Motor RPM = Head RPM

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02-09-2008 12:34 AM  10 years agoPost 4
Chuck Bole

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Tulsa Ok. U.S.A.

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if you reduce the tooth count on the pinion head speed goes down.
if you increase the tooth count on the pinion the head speed goes up.
oppisite on main gear tho.
if you reduce the tooth count on the main gear the head speed goes up
if you increase the tooth count on the main gear the head speed goes down.
chuck

Team Synergy Field Representative / Scorpion / Thunder Power

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02-09-2008 12:44 AM  10 years agoPost 5
lrogers

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Mobile, Al

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Thanks guys, I knew I could count on you for an answer.

Larry Rogers - R/C Helicopter Pilot

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02-09-2008 12:49 AM  10 years agoPost 6
GimbalFan (RIP)

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Big Coppitt Key, FL

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Helis with fixed motormounts require buying a pinion and maingear as a set in order to maintain ideal clearance.

Helis like the T-Rex 450 and others where the pinion/main clearance is set by positioning the motor before snugging up can just use a different pinion, but I believe you have to be careful to match the tooth shape (profile?) to minimize wear.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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02-09-2008 12:54 AM  10 years agoPost 7
Yug

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UK. Herts

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Helis with fixed motormounts require buying a pinion/maingear set in order to maintain ideal clearance
and you can shim it for unusual ratios in order to maintain perfect alignment.

Vegetable rights and Peace

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02-09-2008 12:55 AM  10 years agoPost 8
GimbalFan (RIP)

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Big Coppitt Key, FL

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True enough, but only when the set's too tight, eh? And what do you do about the pinion bearing alignment -- enlarge the frame holes?

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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02-09-2008 01:06 AM  10 years agoPost 9
Yug

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UK. Herts

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Yeah, elongate them.

Vegetable rights and Peace

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02-09-2008 02:17 AM  10 years agoPost 10
jongam0

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ft. wayne, in usa

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02-10-2008 05:48 PM  10 years agoPost 11
stocky

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Taxachusetts

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02-10-2008 06:01 PM  10 years agoPost 12
WiscHeli

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Wisconsin USA

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the math is good but when you really want to know a Optical head speed Tach is the way to go ,,, just found out yesterday math said 2050 real headspeed was 1770 ...

T-Rex450seV2,, 600N-Pro ..500CF... Jr 9303 Syn 72Mhz

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