IIRC, Wild Bill asked what the pulley was like which I ordered from
DuMore. It is the standard crowned steel one, not the flanged aluminum
ones. I suspect that the aluminum ones were made by someone who got a
grinder without *any* pulleys, and did not know about the self-centering
features of a crowned pulley with a flat belt.

The nominal size was suppose to be 7/8" (0.875"), and the one
which I received measured 0.863" so all the accuracy which I was
maintaining was not needed. :-)

In checking other things out, I discovered that only one side of
the wheel had the proper relieved flange. The other was a flat washer,
and smaller than the pressure diameter of the one which was fitted, thus
it was a time bomb waiting to go off. I've got measurements, and will
be machining up a second one soon. Tonight I made the ring to slide
around the post to set the grinder's shank centerline on the centerline
of the lathe headstock and tailstock, to save fiddling every time I
mount it. (I made one for the smaller Series 11 as well.)

Thanks to all for all the information and help.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
"DoN. Nichols" wrote:

IIRC, Wild Bill asked what the pulley was like which I ordered from
DuMore. It is the standard crowned steel one, not the flanged aluminum
ones. I suspect that the aluminum ones were made by someone who got a
grinder without *any* pulleys, and did not know about the self-centering
features of a crowned pulley with a flat belt.

The nominal size was suppose to be 7/8" (0.875"), and the one
which I received measured 0.863" so all the accuracy which I was
maintaining was not needed. :-)

Just for curiosity, I plotted the logarithm of the pulley diameter
against the pulley number for pulleys #2 through #5, using the
dimensions you provided (#2 being 1.1085" and #5 being 2.9815"). They
fall on a nice straight line, allowing me to predict that the #1 pulley
diameter would be 0.7987". However, #1 may be constrained by the
details of how it is attached to the shaft, and thus be required to
depart from the fixed-ratio progression implied by that straight line.

Now we know the diameter, 0.863", which is 0.863-0.799= 0.064" larger
than predicted.

The other thing I noticed in that data was that the diameters appear to
have been rounded to the nearest 64th of an inch from what the straight
line would predict.

Joe Gwinn

On Feb 13, 9:18*am, Joseph Gwinn wrote:

Just for curiosity, I plotted the logarithm of the pulley diameter
against the pulley number for pulleys #2 through #5, using the
dimensions you provided (#2 being 1.1085" and #5 being 2.9815"). *They
fall on a nice straight line, ...
Joe Gwinn

That's not surprising. They were probably designed to be a geometric
progression.

In article
,
Jim Wilkins wrote:

On Feb 13, 9:18*am, Joseph Gwinn wrote:

Just for curiosity, I plotted the logarithm of the pulley diameter
against the pulley number for pulleys #2 through #5, using the
dimensions you provided (#2 being 1.1085" and #5 being 2.9815"). *They
fall on a nice straight line, ...
Joe Gwinn

That's not surprising. They were probably designed to be a geometric
progression.

Yes, another name for "constant-ratio progression".

It makes sense as the way to get the maximum number of evenly spaced
rotation speeds from a small set of pulleys.

Joe Gwinn

On 2009-02-13, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:

IIRC, Wild Bill asked what the pulley was like which I ordered from
DuMore. It is the standard crowned steel one, not the flanged aluminum
ones. I suspect that the aluminum ones were made by someone who got a
grinder without *any* pulleys, and did not know about the self-centering
features of a crowned pulley with a flat belt.

The nominal size was suppose to be 7/8" (0.875"), and the one
which I received measured 0.863" so all the accuracy which I was
maintaining was not needed. :-)

Just for curiosity, I plotted the logarithm of the pulley diameter
against the pulley number for pulleys #2 through #5, using the
dimensions you provided (#2 being 1.1085" and #5 being 2.9815"). They
fall on a nice straight line, allowing me to predict that the #1 pulley
diameter would be 0.7987".

And two of the sizes that I calculated were pretty close to
that -- 0.7983" and 0.7918". One was the ratio of adjacent sizes, and I
forget what the other was. I also came up with 1.0067" by calculating
the diameter needed to produce the nominal no-load speed of 38,500 RPM,
using the measured size of the #5 pulley to drive it. (That one assumed
that the no-load motor speed with the spindle and belt in place was the
same as with the belt disconnected -- but I didn't get around to
actually measuring that. :-)

However, #1 may be constrained by the
details of how it is attached to the shaft,

The nut is a threaded washer with a pair of flats milled on
opposite sides. I think that the small diameter of the crown ends is
pretty close to the diameter of the majority of the nut.

and thus be required to
depart from the fixed-ratio progression implied by that straight line.

That -- or perhaps a problem with the smallest mounted stones
would be too fast at no-load speed.

Now we know the diameter, 0.863", which is 0.863-0.799= 0.064" larger
than predicted.

The other thing I noticed in that data was that the diameters appear to
have been rounded to the nearest 64th of an inch from what the straight
line would predict.

I think that was for ease of production.

You know -- I probably should measure the crown radius on the
No. 1 before I actually put it into service.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
"DoN. Nichols" wrote:

On 2009-02-13, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:

IIRC, Wild Bill asked what the pulley was like which I ordered from
DuMore. It is the standard crowned steel one, not the flanged aluminum
ones. I suspect that the aluminum ones were made by someone who got a
grinder without *any* pulleys, and did not know about the self-centering
features of a crowned pulley with a flat belt.

The nominal size was suppose to be 7/8" (0.875"), and the one
which I received measured 0.863" so all the accuracy which I was
maintaining was not needed. :-)

Just for curiosity, I plotted the logarithm of the pulley diameter
against the pulley number for pulleys #2 through #5, using the
dimensions you provided (#2 being 1.1085" and #5 being 2.9815"). They
fall on a nice straight line, allowing me to predict that the #1 pulley
diameter would be 0.7987".

And two of the sizes that I calculated were pretty close to
that -- 0.7983" and 0.7918". One was the ratio of adjacent sizes, and I
forget what the other was. I also came up with 1.0067" by calculating
the diameter needed to produce the nominal no-load speed of 38,500 RPM,
using the measured size of the #5 pulley to drive it. (That one assumed
that the no-load motor speed with the spindle and belt in place was the
same as with the belt disconnected -- but I didn't get around to
actually measuring that. :-)

If one uses the harmonic mean of all the ratios of adjacent diameters,
one will get much the same prediction as the fit to the log of diameter.


However, #1 may be constrained by the
details of how it is attached to the shaft,

The nut is a threaded washer with a pair of flats milled on
opposite sides. I think that the small diameter of the crown ends is
pretty close to the diameter of the majority of the nut.

and thus be required to
depart from the fixed-ratio progression implied by that straight line.

That -- or perhaps a problem with the smallest mounted stones
would be too fast at no-load speed.

Another good reason.


Now we know the diameter, 0.863", which is 0.863-0.799= 0.064" larger
than predicted.

The other thing I noticed in that data was that the diameters appear to
have been rounded to the nearest 64th of an inch from what the straight
line would predict.

I think that was for ease of production.

That seems likely, although I don't know why it would matter given that
it is machined on a lathe, which doesn't care about 64ths. Perhaps
there is nothing more to it than people being used to thinking in 64ths.


You know -- I probably should measure the crown radius on the
No. 1 before I actually put it into service.

Yes, to 0.0001", so you can worry about wear.

Joe Gwinn