module of VW flywheel gear

"stanley baer" wrote: (clip) This results gear module of about 2.1(clip) ^^^^^^^^^^^^^^ I have always specified gear teeth in therms of "pitch diameter," which is apparently the reciprocal of gear module. Diametral pitch, as I know it, is always a whole number, which allows a system in which all gears of the same diametral pitch mesh properly. The reciprocals of most whole numbers are not whole numbers. BUT, I have never dealt with metric specs--could you fill me in? Since they specify thread pitches differently, I wouldn't be surprised if they do it also with gear teeth. I'm hoping to learn something here.

I am making some plans for my VW generator project. I have to use a different starter and flywheel than the one that came from the engine. I have been trying to figure out the correct distance between the new flywheel and starter motor. By my rough measurements the pitch diameter of the flywheel is about 276mm and the number of teeth is 132. This results gear module of about 2.1. I was expecting something more standard like 2.0 or 2.5. What gives?

stan

starter gears are not normal gears, they are too small for their tooth count. Also most starter gears are the same inch/metric, IOW the metric ones are identical to much older inch series. IIRC the vw uses a 1 inch diameter, 9 tooth pinion. This is a wide standard used everywhere. You can also use an 11 tooth 1.15 inch diameter if you offset correctly. YOu will more than make up for the slight mechanical disadvantage with the better tooth form. Grab such a pinion from a electical rebuilder and measure the two together engaged, do the math, add ten thou and be done with it. It isn't that fussy

stanley baer wrote:

Thanks, this is exactly the info I was looking for. My measurements of the starter pinion match yours exactly.

stan

Ring gears mate up with extended addendum pinions. The pitch line of the ring gear is probably at the od or even above it.