Changing Gear Pitch

[Grizzly4x4]

I was just looking at a thread that got me to thinking. Here.

Sal wanted to switch from 48 pitch gears to 32 pitch gears but didn't know what size gear to get. It's really a simple calculation.

Gear pitch refers to the distance between teeth as measured around the circumference of the gear. We all talk about changing number of teeth to change gear ratios but that only applies when you are staying with the same pitch. Changing the number of teeth changes the diameter.
It's really the diameter of the spur and pinion that is important.

An 87 tooth/48 pitch spur gear is 1.8125" in circumference. (72 teeth / 48 teeth per inch)

To find a 32 pitch gear that is the same size (and therefore gives you the same gear reduction) as the 87 tooth/48 pitch spur:
Step 1) Divide the number of teeth on the gear you have by the pitch.
Step 2) Multiply the number from step one by the pitch of the gear you want to use. This tells you how many teeth on the new gear you need.

( 87/48 ) x 32 = 58

You need to find a 58 tooth/32 pitch spur gear. Do the same thing with the pinion and you are ready to order gears with a different pitch.

Hope this helps some of y'all.

 

[sloppy]

so just to make sure I understand correctly a 58t 32p spur should measure somewhere around the same size as 87t 48p gear? 1.8125
thanks for the math its a good formula. now some one needs to figure away to make 32p a little quiter.

 

[Grizzly4x4]

so just to make sure I understand correctly a 58t 32p spur should measure somewhere around the same size as 87t 48p gear? 1.8125
thanks for the math its a good formula. now some one needs to figure away to make 32p a little quiter.

You are correct, on both points.

 

[Mnster]

Or you can use this calculator.

http://scriptasylum.com/rc_speed/_gear_calc.html

 

[TunaMaxx]

This might even be easier:

Convert 32p to 48p tooth count: teeth * 1.5
Convert 48p to 32p tooth count: teeth * 0.666

So, a 58t 32p gear equals an 87t 48p gear. (58 * 1.5 = 87)
Or, an 87t 48p gear equals a 58t 32p gear. (87 * 0.666 = 58)

 

[Ohio_Danimal]

Holmes Hobby gave me a real simple way of doing this, regardless of pitch.

Aim for a 5:1 gear ratio for crawling

For instance, I am using 32 pitch

13 tooth pinion
60 tooth spur

4:6 to 1