The Mirror-o-Matic 20 is my response to the many requests for a larger version of the original Mirror-o-Matic. It has been designed to fabricate concave mirrors up to 17.5 inches. There is room to expand the turntable up to 24 inches so that 20 inch mirrors can be accommodated.
For the many builders that have already constructed the original Mirror-o-Matic , the design allows for the reuse of the entire power head assembly, eccentric, eccentric push rod, swivel and rod assembly and hinges. Even the one inch blower shafts can be reused if they can be removed.
On this CD is the Conversion Manual. It explains how to convert the original machine into the larger version. Some people have also built both machines and just relocate the power head, eccentric, and pulleys from one to the other as needed.
The original Mirror-o-Matic had a turntable that doubled as a slurry drip pan. Because of the increased effort of removing larger, heavier mirrors on this new bigger machine, I have added a stationary drip pan under the turntable. This will allow washing the mirror in place and attaching a drain pipe to the pan. If you will be using this machine to make small mirrors up to 12 inches, you may want to incorporate the original lift off turntable design into this machine. The lift off turntable is much easier to clean.
The over-arm assembly has been modified to be more rigid and there is now a slot running the length of the arm to allow for tool positioning while figuring.
Even though the machine is bigger and capable of handling larger mirrors, the recommended electric motor size is still 1/4 to 1/3 hp.
The advantages of this machine are similar to the original. It can be built for about $400. It is constructed entirely of 3/4 inch plywood and hardware store items. It needs no machined parts and only basic tools are required for construction. Although this machine is physically larger than the original, it is still very compact for a grinding machine with its capacity. It can be broken down for storage and transportation very quickly.