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Built by Brian Elvidge
This is a demonstration model of a three-speed epicyclic gearbox designed by Phillip Edwards which appeared in the March 1989 issue of Constructor Quarterly. I have added a gear lever and retaining plate to Phillip's design.
To explain how it works would require a physics lecture and mathematical understanding. Phillip explains it all in the December 1987 issue of Sheffield Meccano Guild Magazine.
The model uses three 2½" gear rings with 95 and 57 teeth, and a system of sun and planet gears. These produce three reductions of 4:1 (1st gear), 2.28:1 (2nd gear) and 1.73:1 (3rd gear). The input is the central rod and the last 57-tooth gear is the output.
It is too big as yet to go in many medium-sized models and needs some development work to solve a top gear issue. It may also require a reverse gear.
My unit appears to work very well, after carefully removing paint from the gear rings with a file, which would otherwise jam the unit badly.
Your Questions and Comments
Alan Wenbourne wrote: Hi Brian, congratulations on building and getting this gearbox to work. I am in the process of generating formula for calculating the ratios and wondered, since I don't have the article, if you can tell me what the article claims the ratios to be, or if you can do an input/output rotational count as an estimation? This would give me a sanity check on my numbers! Regards, Alan.
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