Re: [CR]Weinmann 999 centerpulls

(Example: Framebuilders:Alex Singer)

In-Reply-To: <c1.1903076b.29549fb2@aol.com>
References:
Date: Fri, 21 Dec 2001 10:41:25 -0500
To: RaleighPro531@aol.com, classicrendezvous@bikelist.org
From: "Sheldon Brown" <CaptBike@sheldonbrown.com>
Subject: Re: [CR]Weinmann 999 centerpulls


Pete Geurds Douglassville, PA
>For some (a lot?) of us we wouldn't want to change the calipers, or the
>levers.

I was specifically advising _against_ changing the calipers.
>Not because they're better but because they "belong" to the bike.

Certainly for a museum piece or a show bike, you would want to keep the originals.
>That leaves the cables and brake shoes.
>Lined cablehousing works wonders and is not obviously new looking; as do
>better pads or sometimes new, fresh versions of the old pads.
>What about the straddle wire on Weinmanns and similiar calipers?
>Is there anything to be gained by trying to make this adjustable as on Mafac
>or changing the yoke to a wider one?

This works pretty much the same as with cantlevers. Shorter, shallower transverse cables generally increase mechanical advantage ("power") at the expense of lever travel. The effect is not as pronounced as with cantilevers, though, due to the way the arms cross over from one side to the other.

Transverse cables are available in various lengths, though the selection isn't what it was.
>I have a couple straddle wires of uncertain origin which are doubled, that is
>two wires doing the job where normally there is one. Maybe they were trying
>to increase stifness or the liability lawyer was helping design?

Those are rare and highly specialized. Center-pull brakes of any type have a problem on the rear of small frames. If the distance from the brake bridge to the seatpost bolt (where the housing stop is usually located) becomes too small, it becomes hard to fit everything in place and still leave sufficient bare cable to allow the yoke to travel up and down without bumping into the bottom of the adjusting barrel.

There used to be a special "compact" yoke that had a shorter distance from the anchor bolt to the crossing of the transverse cable. This would gain you maybe a quarter-inch of extra clearance.

Because the vertical dimension of this yoke was so short, it would be unstable in the "pitch" axis and tend to tip forward or backward. This problem was addressed by the use of the double transverse cable and an extra lip on the yoke, providing a bit of triangulation in this direction so that the yoke would stay lined up with the main cable.

The whole thing was a bit of a kluge. +-----------------------------------------------------------+ | The difference between science and the fuzzy subjects | | is that science requires reasoning while those other | | subjects merely require scholarship. | | --Robert A. Heinlein | +-----------------------------------------------------------+

Sheldon "Hopes That's Clear" Brown Newtonville, Massachusetts
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