[CR] Williams cottered crank question

(Example: Framebuilders:Doug Fattic)

From: "Bob Hanson" <theonetrueBob@webtv.net>
Date: Sat, 8 Jul 2006 22:24:26 -0600
To: classicrendezvous@bikelist.org
Subject: [CR] Williams cottered crank question

Hi Tom,

The steel Williams chainrings I have are all "threaded". They have square headed bolt which pass through the crank arm holes to attach directly to the rings themselves. [When I say square headed, do note they fit the open end of a 1/4" combination wrench - but not the "closed" end... ie: hex bolt required opening].

On the inner sides of the actual chainrings there is a slightly raised section surrounding the threaded holes which measures 0.2955 inches or 7.51 mm. in its outer diameter. It is this part of the rings which would nest precisely into the crankarm's holes... This would be in place of a separate nut like we're familiar with on more recent alloy cranks like the 49D and the TA 5-vis.

Once the chainring is bolted to the crankarm, all that would be visible looking onto the front of the right crank would be the very ends of the actual bolts (or, more properly, "screws", since they have no accompanying bolts).

All very simple, and effective. With steel crank, steel screw, steel chainring there was no need to use the more modern style of nut passing through the crankarm which both protected the more delicate alloy holes and also gave them a strong steel threading to lock the bolts into.

Hope this makes sense. Personally, I would not modify the cranks; I'm sure there are far too few of these around already... since my chainrings are all dated coded from the 1930s & 1940s as I recall.


Bob Hanson, Albuquerque, New Mexico, USA