The drive was made out of a reduction gear trans-axle from an old snow blower.  It has a (speed)gear reduction factor of 28 to 1, which we needed to slow down the movement of the dome,
increase traction, and increase torque.  This decreased the motor speed from 1800 RPM to
64 RPM and the speed was decreased further with the drive pulleys we installed.  We originally
used a chain drive but switched to a belt drive because the chain made too much noise.  In addition,
problems with the grease in the reduction gear thickening in cold winter and bogging down the
motor was corrected by switching to oil lubricant and changing the motor for one with more horse
power. The system is now driven by a 1/2 HP electric motor.

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A double throw on/off/on switch was installed to reverse the motor direction so the dome could
be driven in either direction.  The switch is on a 8 ft cord for remote operation and can extend
to any location in the observatory.  


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We had problems with the original 2 inch standard caster wheels that the dome rides on flattening
out and shifting under the weight of the the dome, making the dome difficult to turn with the drive
or by hand.  To correct the problem we installed 3 inch roller bearing caster wheels each having a
500 lb rating.  This was accomplish by using three automobile scissor jacks to lift the dome off the
building while the wheels were changed out.


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The drive can be disengaged from the dome at any time by pulling a spring actuated pin
(no tools required).

 

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As a back-up to the drive, we constructed a hand lever that retracts up into the dome when not
in use, but can be dropped down to provide the increased leverage that is necessary to move
the dome by hand.

 



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