Is their a hub where you can 'lock' the the hub and still be able to switch gears?
Sturmey S3X has a spline fitting for its fixed cog, A Shimano established BMX hub pattern.
But that's just 1 cog.... the 3 internal gears offer the other ratios. .75. .63 ..
Is there a way to lock/convert a regular hub so it functions as a fixed gear hub?
By welding the moving parts together.