Sturmey Archer 2 speed kickback hub operation

[MattiThundrrr]

Sachs became SRAM, so they're related, not sure if there's a direct evolution of the hubs though. I don't remember a kickback version of the SRAM, only automatic operation.
Fitchel & Sachs Duomatic

SRAM Automatix

 

[MattiThundrrr]

Oh jeez this is incredibly cool. I didn't know F&S hubs were black in the forties. Must not have been a lot of exports to North American in that decade, for reasons. He suggests that they made millions of them, perhaps tens of millions. Now I gotta keep a secret from Duck Norris, he'd want a set of those

 

[Wildcat]

It made sense to me.

I actually just bought one. Got the idea from this thread. I am working on a friend’s all blacked out beach cruiser. He lives in a flat area (Richmond VA) and mostly rides to the local breweries . He was complaining that he needed his bike to go faster. Well for some reason it came new geared ridiculously low. Like granny gear. It is a single speed coaster brake. Bought during Covid, so maybe it was due to lack
of parts.

Anyways, I am going to re-lace the rim onto the SA kickback and use a smaller sprocket. Goal is to have a fast and 38% faster gear. No cables!

I am really excited about this. Just got the hub yesterday and still need to calculate spoke length.

If this goes well, I may build another.

Thanks for the idea!

Is that bike a 26" bike? Usually one speed generic cruisers have a 44 tooth chain wheel with an 18 or 19 cog, it must have a 36 or 40 on there with a 20 cog. If so, the cog on the wheel it has may work well on the kickback, and you won't have to change the length of the chain. I've changed them out on mine, they are the same size just less teeth. In fact that's the way to go to keep it simple.

 

[Wylly]

Oh jeez this is incredibly cool. I didn't know F&S hubs were black in the forties. Must not have been a lot of exports to North American in that decade, for reasons. He suggests that they made millions of them, perhaps tens of millions. Now I gotta keep a secret from Duck Norris, he'd want a set of those

Yeah this guy has a bunch of fascinating videos. He lives in a “village” in northern Germany and apparently makes a living repairing and refurbishing these old hubs…

 

[Wylly]

Sachs became SRAM, so they're related, not sure if there's a direct evolution of the hubs though. I don't remember a kickback version of the SRAM, only automatic operation.
Fitchel & Sachs Duomatic
View attachment 279429]
SRAM AutomatixView attachment 279430

I just bought a wheel with the duomatic hub pictured above but haven’t messed around with it yet…

 

[twojs.bike]

Is that bike a 26" bike? Usually one speed generic cruisers have a 44 tooth chain wheel with an 189 or 19 cog, it must have a 36 or 40 on there with a 20 cog. If so, the cog on the wheel it has may work well on the kickback, and you won't have to change the length of the chain. I've changed them out on mine, they are the same size just less teeth. In fact that's the way to go to keep it simple.

26” wheels. It came with a 40t front chainring and 22t rear cog. I’m not great with gear ratios. I just go by feel. I’m have a few other rear cogs to choose from.

 

[Wildcat]

26” wheels. It came with a 40t front chainring and 22t rear cog. I’m not great with gear ratios. I just go by feel. I’m have a few other rear cogs to choose from.

View attachment 279444

The Sturmey Archer comes with a 22 tooth cog, so maybe high gear will be a good ratio as is. I'll run the numbers.

The standard 44/18 setup gives a gear inch of 64, that's the usual ratio for cruiser bikes.

That setup you have now with a 40/22 has a gear inch of 48, pretty low. But when you shift to high gear, now it would be 65 gear inches, using the same 40 tooth chain wheel with the 22 tooth cog. You won't have to change any links on the chain. It'll ride like a regular one speed cruiser, with a low gear and a medium gear.
I calculated the gear inches using this site: https://www.bikecalc.com/archives/gear-inches.html

 

[twojs.bike]

That is a huge help. Thank you!! I will probably put on a smaller cog. It is a very flat area and I think he was having a hard time keeping up on group rides to the breweries. Not much need for a low gear.

I think I have an 18t cog. That would give a choice of 56 or 77 gear inches. Will be interesting to see what that feels like. I have never calculated gear inches before.

 

[Wildcat]

I would try it with the 22 first, that might be enough gear and would save you from removing a link or two from the chain. With 18, it might be too high at 77. Cogs are inexpensive so a 20 might be the right one too.