[CR] Help needed - spoke length for Martano rim on NR small flange rear hub

(Example: Events:Eroica)

Date: Sat, 31 Oct 2009 18:40:37 -0400
From: "David G. White" <whiteknight@burlingtontelecom.net>
To: Classic Rendezvous <classicrendezvous@bikelist.org>
Subject: [CR] Help needed - spoke length for Martano rim on NR small flange rear hub

I don't have much wheel building experience -- maybe a dozen or so wheels over the years. I can manage a basic 3x build reasonably well (albeit slowly). My current problem is that for the build I'm about to undertake I'm uncertain about the proper spoke lengths. I've downloaded and used spocalc.xls but am uncertain about my measurement of the rim's ERD (effective rim diameter) and thus am uncertain of my results. I'd appreciate someone with more experience double checking my effort.

Here are the facts:

I plan to build a rear wheel with a Campy Nuovo record small flange hub and a Martano tubular rim. In case it makes a difference, the rim has the newer "bowtie" decal, not the older pyramid one. I measure the ERD at 623. It is 36 spokes and will be 3 cross.

I used spocalc's built in database for the hub measurements, as follows: OSB: 0.0 WL: 37.0 WR: 20.0 dL:44.0 dR:44.0 S:2.3

The spocalc results say the left spokes should be 302.2 (I presume I should use 302s) and the right spokes should be 300.6 (I presume I should use 301s).

I'm most uncertain about whether I've measured the ERD accurately. Can someone who has a Martano rim double check this?

Confirmation of the overall results would be appreciated too.

If the results are correct, would it be ok to use 302s on both sides? I've got plenty of those on hand, but no 301s.

Thanks for helping sooth my ignorant uncertainty!



David G. White
Burlington, VT