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Other › what pinion gear to use on motor?
10-14-2005 02:08 AM  13 years agoPost 1
FDNY260

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Suffolk County New York

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i am new to this and was wondering how you determine what gear to put on the motor?
is there some sort of equation or does it depend on the motor

Helicopter Enthusiast of Long Island (H.E.L.I.)

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10-14-2005 02:40 AM  13 years agoPost 2
Ozydego

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Westerville, Ohio

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target rpm * teeth on main gear / motor kv / voltage / motor efficiency

OK, example now, I want a headspeed of 2400rpm, the main gear on a Trex has 150 teeth, I have the align 420LF which is a 3200kv motor, and I use an 11.1volt lipo. For funnies, lets assume the Align motor is ~80% efficient, here we go:

2400 * 150 / 3200 / 11.1 / .80 (80%) = 12.668, or roughly a 13 tooth pinion.

If your still confused post your setup and we can get you squared away....

But Honey, I can't live with just stock.....

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10-14-2005 01:34 PM  13 years agoPost 3
Pirre_GW

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Lier, Belgium

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Ozy, works for me (also have the 420LF motor etc)

But how/where do you get the target-headspeed?

(is there like an 'ideal' headspeed to match the blade type or how does it work?)
I'm currently using the wooden blades that were in the 450XL CDE kit..

Trial-and-error doesn't seem a good method, viewing the posts here of 'exploding' choppers 'n such ... :|

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10-14-2005 02:35 PM  13 years agoPost 4
darkmask

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Chesapeake, VA

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how can you tell on how efficient your motor is? just pull a number out of the air?

Helicopters shouldn't fly, they are just so ugly they repel the ground.

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10-14-2005 06:17 PM  13 years agoPost 5
Ozydego

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Westerville, Ohio

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Most brushless motors are at least 75% efficient, most likely more, 80% is usually a good ballpark for efficiency, but you can find out from the manufacturers...

The target headspeed, comes from align. They say the max the blades can safetly be turned at is 2400rpm, most will say a good stable hover comes in at or above 2000-2100, and 2400 is good for sport flying. 3D people, sometimes go higher... like 2800-3000 rpm, and some still use the woodies, while others use carbon blades.

But Honey, I can't live with just stock.....

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10-17-2005 03:47 PM  13 years agoPost 6
darkmask

rrNovice

Chesapeake, VA

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What if you run a higher tooth pinion and drop the curve? would it keep the motor and battery cooler since you are drawing less amps?
e.g.
11t @ 90% throttle curve= 2450 rpm
13t @ 75% throttle curve= 2450 rpm

there are probably efficiency problems running it this way but if you wanted to run at a higher rpm you could just increase the curve w/o having to swap out the pinion gear.

Helicopters shouldn't fly, they are just so ugly they repel the ground.

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10-17-2005 05:37 PM  13 years agoPost 7
Ozydego

rrKey Veteran

Westerville, Ohio

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I already do this, I keep my curves the same, and just change the endpoint on my transmitter. Right now I use 75% upper max and change it between that and 85% on a regular basis, depending on what I am doing.... This is how I slow down the head without changing out the 13t... I am actually thinking about doing this with the 15t.

The only drawback i have heard is yes, these motors and ESC's are at their peak efficiency above 85%, so to each his own.....

But Honey, I can't live with just stock.....

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10-19-2005 06:02 PM  13 years agoPost 8
darkmask

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Chesapeake, VA

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Do you get longer runtimes? cooler temps?

Helicopters shouldn't fly, they are just so ugly they repel the ground.

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10-19-2005 06:06 PM  13 years agoPost 9
darkmask

rrNovice

Chesapeake, VA

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Oz,

Also, not to go out on a tangent... so you still have your antenna rolled on a tube... I remember an earlier post with that config... I need to do something with my antenna, I use a standard size rx Futaba 148 and it has a pretty lengthy antenna.. I rolled part of it and the ran the rest through the tube. I get about 2 glitches per flight, but it's not bad.. it just twitches... my brothers helo though... man his glitches are pretty bad... one time he had a hardover with a servo at hover altitude... man... what a wreck..

Helicopters shouldn't fly, they are just so ugly they repel the ground.

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10-19-2005 07:48 PM  13 years agoPost 10
Ozydego

rrKey Veteran

Westerville, Ohio

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yeah, I figured it was better than having it always get in the way, so I opted for the decible cut. Its rumored to be about -12dB, but that just cuts down on the 2.5 mile range... I usually have no glitches while flying, but I use a pretty big ferrite choke....

My runtimes are about average, 10-12 minutes and temps never exceed 150 deg....

But Honey, I can't live with just stock.....

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