In article ,
says...
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


Maybe it's a 12DP inch gear, which would have a PD of 279mm.

Ned Simmons

"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:
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

yourname wrote:

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






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

stan

stanley baer wrote:
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

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