Elgin Style Grinding Machine

This is my third grinding machine based loosely on a design by the late Tom Waineo. Instead of a swing arm that moves left to right this one moves back and forth across the table It uses two 24 volt DC, 85 rpm gear head motors. One motor operates the turn table. The speed is controlled via a AC variac that controls the amplitude of the AC applied to a full-wave bridge rectifier and filter capacitor.This controls the unregulated DC voltage applied to the motor. The second motor runs the swing arm. The speed is reduced through a 6.2:1 gear box The gear box is a new unit that was intended for use in a Sears self propelled lawn mower but ended up at Herbach & Rademan surplus from whom I purchased it for $30.00. Much to my sorrow, it's unmodified form made a awful gear box for a grinding machine. I had to remove the hand control drive engagement clutch, fill in the space with nylon and metal washers and bond one of the gears to the engagement mechanism to prevent some major mechanical slippage. If gear boxes were not so hard to come by, and expensive, I would have bought a ready made unit designed for purposes more in tuned with my intended use. Using the variac and pulleys I was unable to create a system that gave me the speed range I wanted for the turntable. With the variac I can control turn table speed and a DPDT center off switch allows me to change direction if desired. I made allowance on the front panel for a second variac for the second motor but I found the swing arm performed poorly if I reduced the power to the motor so it now has a regulated 24 volt 4.2 amp switching power supply. The turntable, at approximately 24 volts, runs at 33 rpm with the 6.5" mirror and 10 pounds of weight and 24 rpm around 18 volts. The swing arm under the same load make 16 strokes per minute.

Below are some JPEG images of the machine and a animation file of the beast in action.

Click on an image to enlarge...Back to return.

Click on ANIMATIONBack to return.

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