# Mysteries of the planetary gearbox REVEALED!



## Andrew Gorman (Oct 17, 2021)

A lot of people- myself included have had a hard time wrapping our brains around how planetary gearbox/hub like a Sturmey Archer hub actually works.  Here is a US Army training film from 1953 that does a good job of explaining how planetary gears work on a tank transmission which is just larger and easier to see than a bicycle hub. Basic mechanisms are explained well, although the method of locking parts is different.  I hope other folks out there find it helpful- a tank transmission is not the first place I'd look for bicycle information, but there is always serendipity.


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## ricobike (Oct 19, 2021)

Andrew Gorman said:


> A lot of people- myself included have had a hard time wrapping our brains around how planetary gearbox/hub like a Sturmey Archer hub actually works.  Here is a US Army training film from 1953 that does a good job of explaining how planetary gears work on a tank transmission which is just larger and easier to see than a bicycle hub. Basic mechanisms are explained well, although the method of locking parts is different.  I hope other folks out there find it helpful- a tank transmission is not the first place I'd look for bicycle information, but there is always serendipity.




Excellent video.  It helped me figure out how the Bendix two speed kickback hubs can be changed from underdrive to overdrive with just swapping the drivers.  That always puzzled me.  Thanks for sharing this .


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