doctor ed

Call me a retard, but I've never come across this before...

Yesterday I picked up a new 18T pinion + clutch bell, and in the midst of installing things, lo and behold its got some funky tooth profile. Pitch is fine, and meshes ok, but is a pita setting the mesh clearances, and just seems 'wrong'. In my mind the pinion and spur should have matching tooth profiles?!

interchangeable? reason?

Looks like this:



Normal looking old one looks, well, normal:

Roelof

There is somethig like over and under pitching.It means you can have a different tooth count with a same diameter.

Rather Race

iTrader: (5)

You were able to get it mesh properly it shouldn't be a problem.

doctor ed

It meshes ok, but it's pretty difficult finding the sweet spot when it comes to clearance. Either too tight, or too loose... back and forth, and eventually settled, but has a hair of backlash, but it's as good as it was going to get

mercfocus

iTrader: (3)

I do believe there's less wear & tear with the squared off teeth.

I havn't noticed if they're harder to set backlash but SOME of mine are. I always thought it was the car but now I want to look closer at that.

I just now looked at my busted CBs and I see the only CBs I ever chipped a tooth on had pointed teeth.

My ST-RR EVO

iTrader: (5)

In my opinion it is best to have you c/b and spur made by the same manufacturer to avoid that issue.

1/8 IC Fan

iTrader: (102)

+1,

Always run the same profile tooth gears in your Pinion and Spur setup. It will ensure correct gear loading, prevent slippage and ensure longevity. The square sytle, will point load your spur, i.e. it only engages at a point vs. the involute curve of a traditional gear.

There is a lot more too it, so here is a bit of technical reading...

https://www.cs.cmu.edu/~rapidproto/m...sms/chpt7.html

fdjizm

Good info on gear teeth I've seen all different clutch bells, for HPI (2 speed) they make aluminum ones with the square teeth, seems to fit more teeth in the same area as a similar sized bell.

burnnitro

iTrader: (2)

I think it's the wrong pitch. losi has a weird pitch that almost matches a mod1 gears mesh together fine too.
but once on the ground it eats the spur up in a few feet.

doctor ed

i dont think its the wrong pitch, im starting to think its just a normal tooth profile with the point taken off. the contact face of a tooth is never in flat contact, theres always point loading through its range of motion. the squared-off teeth seem to have a facet that would be the point of contact on meshing, the tip is missing though (which is rarely, if at all loaded) and the valley is extra deep for whatever reason. i dont think the load transfer actualy ends up being much different.

the missing tips and the extra deep valley certainly makes setting backlash clearances tricky though

token

Agreed.