Home Racing World

Before researching what components to use on the upcoming midget proxy, I had never even heard of gear pitch. Then I began to see "48 pitch" mentioned in reference to certain Parma and other 1/24 scale gears. That sent me on a quest to uncover exactly what "pitch" means.

From what I understand, gear pitch is the number of teeth on a given gear over the span of one inch. Basically, to find out a gear's pitch, you can either cover the gear in ink and roll it over a sheet of paper, or roll the gear through something like silly putty. Either way, you then measure one inch in length and then count the number of tooth impressions that you see. Ta-dah! That's your gear's pitch.

The reason that this is of interest has to do with what is commonly referred to as gear mesh. Gears with the same or similar pitch mesh well, whereas ones with dissimilar pitches may struggle to get along, often resulting in anything ranging from a minor inconvenience such as noise to the very much unwanted resistance.

The difficultly in pinning down exactly pitched gears is that it seems the pitch varies even throughout a given manufacture's line. Slot.it pinions seem to vary between about 47 through 60, and NSR pinions vary between 45 and 60. The variance comes in to play not only due to the amount of teeth on a gear, but also in its diameter.

It seems that gear pitch is something of a concern in the larger scales, (and the R/C world) but I have yet to find a 1/32 manufacturer who publishes this information. So, my question is this- is it worth going nuts over, or should I just forget the math of it all and just play around with various gears until I find a mix that fits a given application?


My problem is that I often need to know how something works, instead of just that it does. Perhaps that aspect of my personality is causing me to lose my mind over this…
:confusion-questionmarks:

My thoughts exactly. Believe it or not, there was another set of info I left out that was mind-bogglingly worse! On this, I'll trust Slot.it and a few others. I will say, Slot Car Heroes is still my favorite universal pinion. Used my last one recently.

You are losing your mind over nothing. ALL 1/32 cars sold for home track use EXCEPT the TSRF use .5 module metric gear pitch. The TSRF uses 64 DP.

Now, where you are getting messed up here is, everybody "cheats" on the gear diameters. The cars have no adjustability for different gear sizes. So, everybody makes different gears at one spacific diameter.
Let's say a car comes with a 9/32 gear set. Hopup gears would be made 8.9,10 made on the diameter of the 9, Axle gears would be made 30, 31, 32, 33, 34 all on the 32 diameter. Now you can mix an match gears to get a ratio you like and it all fits.

When I raced 1/24 commercial raceway cars I used 48 or 64 pitch gears. With 1/32nd nearly all of my cars have Slot.it gears. I don't worry about the actual pitch because at the end of the day the gears either mesh well or they don't. If your gears are quiet they are probably OK.

I stocked up on the TSRF 64-pitch 14x45 sidewinder plastic gears before they disappeared; they're incredibly quiet. No screaming!

Waays diagram of the gear teeth is really very informative. Most people use the outer diameter in calculating the pitch circle diameter. That is not correct. The the pitch circle is the (nominal) point at which the gears touch each other. That is the intersecting point between the tooth flank and tooth face.

If you look at the different slotit gears (i.e. 19 or 18mm diameter) you will notice that the overall diameter doesnt change but the tooth's profile (i.e. the flank and face of the teeth) do change significantly. By reshaping the flank and face slotit are able to change the pitch circle diameter while maintaining the same overall diameter.

cheers
dr fabio