X-Mozilla-Keys:                                                                                 
Gary Wolf wrote:

Paul,
   Sprockets made by stamping a preform and then rolling are not as easy to
make as you might think. The preform tooth shape is far different from the
final shape after rolling, because the valleys of the teeth open up. I would
not be surprised to find that they had been restruck after welding to
minimise runout. Remember, these parts are made in runs of millions and the
tooling can be justified.
   On the herringbone sprocket, I think you are ignoring the difficulty of
subsequently forming the stamped preform into a circle. A simple roll around
a mandrel is not going to result in an accurate tooth shape. There will be
waving at the edges and the teeth themselves will flatten at their crowns.
Imagine bending a thinwall tube into a small diameter circle. The crown of
the tube flattens to resist stretching unless the shape is contained in a
die and there is a supporting mandrel inside the tube. The irregular shape
of the herringbone sprocket would be a nightmare to bend accurately.

I thought of that Gary and I was not advocating doing it with the 
herring bone. Sorry I did not make that clear. I agree on the forming
of the stright teeth but I think the deflection will deform the valleys,
the sides and tops of the hills more or less equally. The dies in
the press brake stage may have to be modified in form to take that into
account. We are not producing these in quantity so a little adjustment
here and there could be accomodated.

 Cutting a new aluminum sprocket by tracing from an off-the-shelf sprocket
merely reproduces the pattern without knowing on which side of the tolerance
you are. If you are determined to reproduce in aluminum, I would suggest
biting the bullet and writing the code to control the CNC mill. Then the
cutting charge is similar to any machined sprocket of that size.

I agree on this. It should be done on a four axis CNC mill.
Good points. Thanks Gary.

BTW Archie what are the diameter's and RPM's on those roots
blower drives?

Paul Lamar
 
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