[CR]Curved crank sets...Why

(Example: Racing:Jacques Boyer)

From: "NIGEL LAND" <ndland@btinternet.com>
To: <classicrendezvous@bikelist.org>
References: <MONKEYFOODxq1kv33SM0000364c@monkeyfood.nt.phred.org>
Subject: [CR]Curved crank sets...Why
Date: Sat, 1 Jul 2006 07:12:43 +0100


John, from my early engineering training I recall that curved spokes in cast wheels were that way to avoid casting cracks, when the molten metal cooled. Cast iron, in particular, has little strength in tension, and the curves gave just enough flexibility to, as you observe, relieve the stresses in the cooled casting. They also look more decorative and would appeal to Victorian aesthetics.

Nigel Land sunny east coast UK

Date: Fri, 30 Jun 2006 12:09:11 -0400 From: John Betmanis <johnb@oxford.net> To: Classic Rendezvous <classicrendezvous@bikelist.org> Subject: Re: [CR]Curved crank sets...Why Message-ID: <3.0.6.32.20060630120911.00827100@mailhost.oxford.net> In-Reply-To: <75d04b480606300846v7f4314d5qd549ce5632f9909c@mail.gmail.co m> References: <20060630143027.1352.qmail@web52510.mail.yahoo.com> <000e01c69c49$b3a134f0$e453ff44@ts> <20060630143027.1352.qmail@web52510.mail.yahoo.com> Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Precedence: list Message: 7

At 08:46 AM 6/30/06 -0700, Kurt Sperry wrote:
>Curved crank arms have no engineering merit, but the reactions here show
>they potentially have marketing merit.

Old iron hand wheels and flywheels on old machinery had s-shaped spokes, probably to releive stresses and help with shock absorbtion. Old meat grinders had s-shaped cranks. Perhaps these curved cranks gave the impression of being "high tech" at the time. Also, it would seem that the curved section might help keep pant cuffs from being caught in the chain.

-john