pinions....12T, 15T what it means

[RACON450]

Im sorry for all the post but i am on a learning spree to fine tune my brain..can somone explain Pinions for the motors...Like example align gear 12t what does it mean, what should i look for...do i want higher T ratings or lower..what does the t even mean...Helllpppp!!!!!!!

[[X]Outlaw]

T=teeth

example 13T=13 teeth

Changing your pinion effectively changes your gear ratio thereby changing your head speed.

All things being equal (motor KV, cell count, throttle curve) a higher pinion will result in a higher head speed and a lower pinion will result in a lower head speed.

I use this utility to help me determine pinion size for a particular setup.

http://heli.dacsa.net/calcv3/

[CAP21]

There's also Pinion, the great interviewer.

[RACON450]

ok got the whole T thing down but whats up with pinions...

[K2Freak]

whats up with pinions.

That's the name of the gear that is connected to the motor shaft - the little metal one.

[TheBum]

The greater the number of teeth, the faster the main gear will spin for a given amount of motor spin. You sacrifice power when going to a larger pinion though because it loads down the motor more.

[skunkworx]

I'm going to go off your name and use a Trex 450 as examples to explain things.

Your gear ratio is essentially a comparison of the big (main) gear and the little (pinion) gear. You take the large gear tooth count and divide it by your pinion tooth count to get your gear ratio (you would use the diameter of each, but the teeth privide a bit of a cheat).

Anway, the gear ratio is used to determine your headspeed provided the voltage and Kv rating of your motor. First, you'll need your motor speed. Let's say 11.V and 3500Kv.
11.1 * 3500 = 38,850rpm motor speed. <--- Now take your motor speed and divide by gear ratio

To find gear ratio: 150t main gear and 12t pinion. That nets you a ratio of 12.5 to 1 (12.5:1), or for 12.5 turns of the pinion gear, it turns the main gear one revolution. If you were to increase your pinion size, you would get the following ratios:
13t = 11.53
14t = 10.71
15t = 10.00

As you increase the pinion size, it uses more torque/amperage from the motor and will make it run hotter, as well as cause more stress on your batteries, geartrain, and blades, but will get you higher and higher headspeeds.

Ok, so now we take the proposed 38,850rpm divided by selected gear ratio (12.5) and you get roughly: 3108 to 3318 headspeed.

If you increased to the other pinion sizes, you would get approximately:
13t = 3108 to 3318
14t = 3369 to 3827
15t = 3883 to 4147

And so on and so forth. The formulas are universal as long as you get all the aspects I pointed out. Comes in handy, but it's probably easier going through a caclulator like Darkhorse.