Rare and expensive.

[Guinessisgoodforyou]

I have never seen one in the flesh.

https://www.ebay.co.uk/itm/27563672...JnEN7JzZjZYqhAKM%3D|ampid:PLX_CLK|clp:2047675

 

[eric_james]

How did they stop the chain coming off back then? I've wondered it for a while. There's no narrow wide chainring

 

[Guinessisgoodforyou]

How did they stop the chain coming off back then? I've wondered it for a while. There's no narrow wide chainring

Correct chain tension.

 

[eric_james]

That chain looks very slack

 

[Guinessisgoodforyou]

That chain looks very slack

Not correct chain tension that said if the chainwheel and sprocket have worn eccentrically (Always) 1/2" at the tight spot is fine.

 

[eric_james]

Thinking back to BMX days, we never had a chain drop much. I know if you convert a multiple rear speed bike to a single front chainring that the chain needs to be slack enough to get into other gears
Just thinking out loud

 

[Guinessisgoodforyou]

Thinking back to BMX days, we never had a chain drop much. I know if you convert a multiple rear speed bike to a single front chainring that the chain needs to be slack enough to get into other gears
Just thinking out loud

I think the chain needs tensioning. Looks slack as you say. I wouldn't run a chain that slack.

 

[eric_james]

Yes that particular chain does look slack

 

[oldave]

If the 4 speed SA is the alu shell version then it's lasted well! Mine exploded in c. 1963, and threw me onto the A6 near Stockport.
Only replacement I could afford was a fixed hub/sprocket built into the rim. To which I returned many years later!