Epicyclic Gearbox

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.


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.

Your e-mail address will not be displayed in public and will not be added to mailing lists. Please see our privacy policy for further information.

Please wait while we post your message…