Hello,

I have zero knowledge about mechanics and would like to understand how an IGH work.

I read several articles* and watched some videos (mostly those from Dan Burkhart, especially the one of the Sturmey Archer 3 speed AW) and would like to check that I basically got it right:

1. The chain or belt-drive is connected to the sprocket
2. The sprocket is connected to the gears in the hub
3. The axle is fixed; To make sure it doesn't move, its ends are semi-flat so they don't rotate in the drop outs; As extra protection, non-turn washers are added; The axle has a fixed gear in the middle ("sun gear"); The axle nuts must be screwed at around 35-40 N.m
4. Other gears, called "planetary gears", revolve around the sun gear to provide different speeds; They are changed by pulling/releasing the speed cable
5. The planetary gears are connected to the gear hub
6. The gear hub is connected to the wheel through the spokes.

In short: pedals → chain → sprocket → gears → hub → spokes → wheel

Is that correct?

There are also springs and prawls in the equation, but I don't know how they fit.

Thank you.

* The articles:
Internal-Gear Hubs
Internal Gear Hub Theory
Gear train - Wikipedia, the free encyclopedia
Hub gear - Wikipedia, the free encyclopedia
Epicyclic gearing - Wikipedia, the free encyclopedia
File:Bicycle hub gear.png - Wikipedia, the free encyclopedia