Re: [CR]weinmann vs. universal centerpulls

(Example: Production Builders:Frejus)

Date: Fri, 08 Jul 2005 09:15:01 -0700
From: "Steve Maas" <stevem@nonlintec.com>
To: classicrendezvous@bikelist.org
Subject: Re: [CR]weinmann vs. universal centerpulls
References: <42CDBEBA.7020401@erols.com>
In-Reply-To: <42CDBEBA.7020401@erols.com>


Another posting that sent me out to my garage with a steel ruler.

I compared the Universal 61s on my Hetchins to the Weinmann 999s on my Carlton. Interesting to note that the caliper dimensions are nearly identical. I can't confirm the lever ratio you quote, though. My measurement of the levers is 2.5 cm from the pivot to the cable connection, and 9.8 cm to the point on the lever where your fingers rest. This is almost identical for Universal 58 and 61 levers. So, I get about a 4:1 ratio.

The length of the straddle cable is longer on the Universals, however, so the peak of the cable is almost twice that of the Weinmann, 4 cm vs. 2.5. This might give them a little harder feel (lower mechanical advantage), but not hugely different. I don't find mine particularly different from other brakes.

I took out the Hetchins today for the first time in a few weeks, and I actually was surprised at how positive the brakes feel. They do not require an extraordinary amount of force. The Matthauser pads I'm using might have something to do with this, but I can't see the Universals having an unusual overall ratio.

As for toe in: I have stopped trying to bend caliper arms of all types of brakes. This is not so much because of the fear (probably overstated) that it might weaken them, but because it's hard to control precisely where and how much they bend. You really don't want the arm to bend near the pivot. Instead, I use a piece of shim stock between the caliper arm and pad to adjust the toe in. A package of assorted sheets of brass shim stock is not expensive and is one of the most useful things you can have, in my opinion.

Steve Maas Long Beach, California

HM & SS Sachs wrote:
> It happens that a few years ago I actually measured the lever movement
> and cable pull for some levers. The results, as a ratio of lever throw
> per unit of cable take-up, are below. What you will see is that the
> Universal has a very low ratio. Roughly speaking, moving the lever 2 mm
> shortens the cable ~1 mm. In contrast, with the Weinmann "red-dot" of
> the early 60s (a personal favorite), it takes 3 mm of lever travel to
> pull a mm of cable. As Joe B-Z says, the Universal has uncommonly low
> mechanical advantage. Lots of cable pull, very little force transmitted.
> It is not "powerful," but it is very direct since it takes up slack
> amazingly quickly and then has full contact. Then it is up to brute
> strength to get it to convince the pad and rim to get intimately
> acquainted.
>
> Ratio, lever
> 3.2 DiaCompe
> 3.9 Weinmann Delta
> 3.0 Weinmann Red-Dot
> 2.1 Universal 61/68
> 4.2 Sachs "Ergo"
> 2.4 Shimano 105 Road (not sure which one)
>
>
> AT the other end, the caliper, you can do the same sort of measuring.
> Let's ignore the straddle cable geometry for now, and just think about
> the relative lengths of the lever arms (pivot is the fulcrum). It's
> roughly 2:1 for the CP-61 and 1:1 for the SP-68. So, a mm of cable pull
> moves the brake pad roughly 1/2 mm with the 61 and 1 mm with the 68.
> That is one heck of a big difference. So, all other things being equal,
> the 68 SP calipers are easier to modulate and require less pressure than
> the 61 CPs.
>
> My Hetchins came with Universal 61s. Even with the original pads, they
> inspire confidence by their combination of good feel/modulation and
> adequate power with the force my 60 year old fingers can maintain. Last
> week, I set up 68s on my NOS Weigle, which wants longer sidepulls than
> the modern fashion, with Universal levers. It was a bit scary, and I
> will change to levers that need more lever travel to take up cable, so
> they have more mechanical advantage.
>
> Like most of us, Universals are quirky. In this case, great when set up
> right, impossible to adjust toe-in (guaranteed to break), lousy hood
> rubber but fine pads, poor chroming on the CP hardware... My own quirks
> are somewhat different.
>
> harvey sachs
> mcLean va
> Met a smiling chap on my morning commute today, at Key Bridge, NoVA. He
> gets to ride his only bike, a '72 chromed paramount, to work. My
> commuting bike would have a half-life (before theft) measured in hours
> parked outside where I work...
>
>
> _______________________________________________


>

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