Originally Posted by
luker
I think that the rear dropout is a cyclo...the dropout allows for multiple rear wheel positions, in case you want to switch off to fixed. The tang on the front keeps the cogs from hitting the striking fork when you remove the rear wheel to fix a flat or whatever, and also acts to guide the rear wheel into the dropout when changing the wheel. Claud Butlers also came with the downward tang - a Butler would be stamped CB somewhere on the dropout.
This drop-out is totally bizarre. It look like the tang is there as a sort of chain guard or limit to prevent shifting off the small cog. Since the drop-out opening is rear of the pictured axle position it wouldn't be much of a guide, would it?
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1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear