Large Grinding Machine
The 32" F/4 mirror requires a large machine to grind and polish.
Pratte wanted a machine for himself, so we decided to scale it up just
to handle the 32". The machine was built by John in his shop with
from Bob, and the turntable was used to dewedge the blank. After
the machine was disassembled, painted, and brought to my house, where
was reassembled in my basment where the work will be done. Here
a photo of the parts in the van parked in my driveway (with Bob Holmes
John looking on), and a photo of all the bolts that had to be installed
put the machine back together.
The frame was assembled without too many incidents in the basement.
is shown below at the left. Bob Holmes is standing on the left,
John Pratte is on the right. The rest of the assembly of the
bearings, pulleys, gearboxes and other parts went mostly without
but a little "under the chassis" debugging was required to quiet a
coupling, and this work is shown in the next photo.
Finally, below is a photo of the completed machine, complete with
wooden drip pan, and the 32" mirror sitting on the turntable for
Lastly, here are some photos of the drive shafts, belts, and gearboxes,
the drive arm and eccentric.
Bob also built a nice tilting test stand out of steel tubing so that
the mirror can simply be slid off the turntable onto the stand and
tilted nearly vertical for testing.
Now it is up to me to finish the mirror so Bob can finally get his
operational and doing research. It is long overdue (due to no
fault of ours), and I can't wait to see it producing
images. It will be fun to work on a big mirror again!