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Home > Articles > Other Articles > Equipment/Optics > Ultra-Low-Cost Fine-Focus Gear-Reduction Drive

Ultra-Low-Cost Fine-Focus Gear-Reduction Drive
By Ron Masters - 5/29/2009

Please refer to the series of photographs.
Follow the sequence from left to right along the top, and then again along the bottom

This is a differential gearbox available in the radio control car section of your local hobby store, and also available through online auction sites. This particular unit, a Traxxas 4910, cost me $10 plus shipping. It contains all steel internal gears and shafts, a robust plastic housing, and smoothly operating bearings. The photographs show how to disassemble the unit and modify it to be used as a 3:1 fine focus reduction drive that can be attached to the focuser drive shaft of any scope. Another benefit is the change in angle that puts the fine focus knob within easy reach, especially when a camera is attached for imaging. I hope this provides an easy, low-cost option for those who do not need the more professional 10:1 systems that are commercially available. Perhaps it will inspire a manufacturer to provide a lower cost option than what is currently available. I certainly would be willing to pay double to triple my current investment to buy professionally manufactured units designed for my scopes.

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