The challenge (in the US at least) is finding the right combination of "small parts" to make a internal gear hub work on your frame.
The parts lists provided by Sun Race Sturmey-Archer, at least for their more recent hubs, are hard to decipher because they cover every conceivable bike frame without helping to figure out how they apply to YOUR bike frame.
For example, I have this nice RXL-RD3 rear hub with a drum brake.
This is from their latest catalog dated 2017-2018
View attachment 245825
The Redline has "reversed" dropouts and the catalog lists the matching fulcrum lever and non-turn washers. Critical items to make the hub fit properly on this frame.
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However if you go to the parts list provided on their site for this hub, you'll find this:
View attachment 245827
Problem is that this is NOT correct. Look at the axle, it shows the old "indicator" shifter when my actual hub uses a fulcrum lever [Cassette Joint on a Shimano Nexus]. The correct axle and associated parts can be found on a different hub the XL-RD3 [only 70mm].
View attachment 245828
There's also the SA "special tools" that are often hard to find.
Like this little guy for correctly installing the fulcrum lever to the hub.
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There are awesome resources for the old SA hubs but it's hard to find solid info on the newer stuff.
Sadly I don't know that there is a strong enough market in the US for SA to fully support their products here.
Ok, I'm done whining for now. Back to it.