Re: [CR] Crank cotter filing, now cotter direction

(Example: Framebuilders:Dario Pegoretti)

Date: Fri, 14 May 2010 19:55:24 -0400
From: "John Betmanis" <johnb@oxford.net>
To: classicrendezvous@bikelist.org
References: <000101caf303$85ba21e0$912e65a0$@com> <4BECFEE5.3050303@aol.com> <4BED1556.7000007@m-gineering.nl> <4BED7E84.2020806@aol.com> <4BED9CD9.6090308@oxford.net> <AANLkTim8Azb2CFaX6WO2tuavb9ts7HBs-W6M063LFfKY@mail.gmail.com>
In-Reply-To:
Subject: Re: [CR] Crank cotter filing, now cotter direction


On 14/05/2010 5:30 PM, Derek Athey wrote:
> The 'head' of the cotter always 'leads' the stoke, thereby giving the
> strongest point of energy on the down stroke using the strongest point
> of the cotter against the flat of the axle to reduce stress.
> That way one also ensures that the cranks align perfectly.

Derek, that does make sense, although they would be perfectly aligned either way, provided both sides are the same direction. However, I just did an image search and still see it both ways. In fact, one image was on Sheldon Brown's site, where he says this:

"Some older books speak of installing the cotter so that the pedaling load is taken by the thick end of the cotter. This is an error, because if you do the right side that way, the left side will be stressing the thin end, and vice versa. It really doesn't matter which way you put them in, as long as they face in opposite directions."

His reasoning is correct, because it's only the *left* crank that transfers load to the BB axle, then the axle transfers it to the right crank and chainwheel, through the *thinner* end of the cotter pin.

--
John Betmanis
Woodstock, Ontario
Canada