Re: [CR] dumb design, was A tale of two hubs?

(Example: Racing:Jacques Boyer)

From: "David Snyder 2" <dddd@pacbell.net>
To: <classicrendezvous@bikelist.org>
Date: Thu, 6 Jan 2011 11:22:31 -0800
Subject: Re: [CR] dumb design, was A tale of two hubs?


Could the rear hub in question have been intended for a tandem?

I've built up a couple of Tandem hubsets for road use over the years and they had very wide flange spacing as appropriate to their very long axles (much more of which protruded from the left side of the hub than normal).

I always ended up with very un-balanced spoke tensions, but have had no reliability or spoke detensioning issues as I selected sturdy Module-4 rims, used 40 spokes and tensioned accurately with a couple of rounds of pre-stressing.

Those stiff Mod-4 rims have a lot of spoke hole offset (to alternating sides) and thus allow an annoying amount of rim movement between the brake pads unless wide hub flange spacing is also selected. I had to work getting the off-topic, threaded Phil axle narrowed down from ~140mm to 132mm. The Specialized hubs were much easier to narrow down the rear axle.

So often, a single, "orphaned" rim or hub becomes the nucleus for a complete set of wheels, given the opportunity at various swap meets to match-up those single, stray parts. Both of these wheelsets started with such humble origins.

David Snyder
Auburn, CA usa


----- Original Message -----
From: M-gineering
Subject: Re: [CR] dumb design, was A tale of two hubs?



> On 1/4/2011 1:46 AM, John Betmanis wrote:
>> Here is a pair of unknown hubs I bought off eBay a couple of years ago,
>> described as "vintage".
>>
>> http://i.imgur.com/F34pN.jpg
>>
>> I got them for a 1951 Claud Butler I'm building and the widths are
>> pretty close to what the frame is. If the rear hub is a poor design,
>> should I substitute a more conventional modern one? This is a budget
>> project, so I'm not striving for exact originality, just something that
>> looks close.
>>
>
>
> they look fairly symmetrical to me, so they will be alright. The problem
> with rearhubs where one flange is much farther out from the centreline
> than the other is that:
>
> -the spokes with the best bracing angle need a minimum tension to prevent
> them from breaking
> -the spokes with the worst bracing angle need a much higher tension to
> balance the sideways tension of the complimentary spokes , which kills the
> rim
>
> Or the rim lives, and the undertensioned lh spokes keep breaking and
> loosening
>
> The difference in tension is roughly proportional to the distances from
> the flanges to the centerline
>
> Modern rims are designed for heavier dished wheels, and thus heavier than
> the classic rims designed for more balanced designs
>
> Spocalc.xls (Damon Rinard/ Sheldon Brown) will give you the ratios and the
> angles
>
> --
> mvg
>
> Marten Gerritsen
> Kiel Windeweer
> Netherlands