Gear pitch

[studysession]

Will someone please explain gear pitches to me and why it is important?

Like on my TC3 mostly use 48 pitch pinions and spurs. I think I understand what it all means but need to be sure.

 

[Nitroaddict]

From the Geometry Tech Library:

Essential to prescribing gear geometry is the size, or spacing of the teeth along the pitch circle. This is termed pitch and there are two basic forms.

- Circular pitch — A naturally conceived linear measure along the pitch circle of the tooth spacing. it is the linear distance (measured along the pitch circle ar between corresponding points of adjacent teeth. it is equal to the pitch-circle circumference divided by the number of teeth:

Diametral pitch is so commonly used with fine pitch gears that it is usually contracted simply to "pitch" and that it is diametral is implied.

From the AB Sport Website:

OK – So what is Gear Pitch? Put simply, it is the size of the tooth on the gear. The standard accepted method for working this out is known as the pitch diameter and this, simply means by the number of teeth of a consistent form that may be accommodated on a ONE inch gear.
Therefore a 64 pitch gear would have 64 teeth if the gear were 1” in diameter. Similarly an 80 pitch gear would have 80 teeth if that gear were 1” in diameter. It’s that simple. So basically, the higher the pitch number, the smaller / finer the form or shape of the gear tooth becomes


Here is a chart:

you can read more here:

http://www.abslotsport.com/page8.html

Hope this helps!

 

[studysession]

Thanks - that helps a lot!

 

[Nitroaddict]

no problem - thats why the forums are here!

 

[robriguez]

And for those that cannot read tech-speak basically what this all means is that regardless of the number of teeth on a Pinion/Clutch bell and the Spur/Crown Gear the "Pitch" must be the same.

The Pitch refers to the angle of the cut in the tooth, the spacing between teeth, and the way the teeth fit together. If the spacing or the angle dont match your going to grind gears.

 

[Error401]

Dang, NA busted out the text book (with diagrams to boot).

A simple comparison would be to look at a T-Maxx spur gear and a Savage spur gear. They're both about the same diameter, but the Maxx spur has a radically different pitch from the Savage spur.

Another thing to point out about gear pitch and our hobby, is that nearly all of the gears in the r/c hobby are metric and not ASE. I looked into cutting a savage spur and after doing a bunch of research and measuring, I found out that I would have had to have ordered a $75 cutter from England in order to cut the proper teeth for the spur. ASE cutters would not have worked right. Needless to say, I waited for Robinson to start shipping the spurs.

 

[Wardo]

Running the highset pitch gear you can get away with also helps getting a finer tune on gear adjustments.

64 pitch

23/96 4.17
24/96 4.00
25/96 3.84

48 pitch

17/72 4.23
18/72 4.00
19/72 3.78

32 pitch

13/56 4.30
14/56 4.00
15/56 3.73


With a handfull of 48 and 64 spurs and a set of each pinions, you could make gear adjustments from 2.00-8.00 without a jump of more then .02 in ratio.