Re: single-sided stresses, was [CR]New photos to RH project : Schultz and monobras Labor

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Date: Sun, 16 Jul 2006 00:42:03 -0400
From: "Joseph Bender-Zanoni" <>
Subject: Re: single-sided stresses, was [CR]New photos to RH project : Schultz and monobras Labor
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I was surprised by the Labor-Manobras, and I suspect it was a terrible rider. A lot of early lightweight bikes were quite whippy and merely doubling up the frame components does not begin to get you there with a monofork. As Harvey says, it is an engineering problem and I have a certain experience with it as shown in slides about 12-14 in this slow loading set for the Comanche helicopter gun turret:

As the Comanche turret project engineer for a period in the early 1990's, I had to defend this single trunnion (fork in gun turret talk) design to our very skeptical customer. Keep in mind this was all carbon fiber, with a complete ANSYS stress analysis and notice the large bearing diameter to deal with the moment. Trust me, the Gatling guns you see in the movies are a physics fantasy in terms of the loads imposed on a gun mount.

Anyway, as I got of the defense business because I foresaw that projects like the Comanche would never come to fruition, my very practical example of a successful monofork is the BMW K-100 motorcycle. I spent many miles almost wishing for a rear tire problem, but of course I only had issues with the front forks.

Joe Bender-Zanoni Great Notch, NJ

Harvey M Sachs wrote:
> gabriel l romeu wrote:
> took me a while to find that, quite amazing! I can't imagine the
> stress on that axle. [This refers to the Labor-monobras bike, with
> single-sided support for both front and rear wheel axles].
> ++++++++++++++++++++++++++++++++++++++++++++++++
> First, it is a lovely site; the bikes are stunning, particularly the
> Labor-Manobras.
> But, I'm not sure why we should be so concerned about the stresses on
> the single-sided wheel support. Yup, seems to work on Cannondale's
> off-topic mountain bikes. More importantly, I think the loads I put
> on pedals are comparable to the loads (but perhaps not the
> frequencies) that I put on wheels, and the only double-sided pedal
> supports I've ever seen were on "sociables" (side-by-side two person
> bikes, which can't legitimately be called "tandems," since that
> implies one in front of the other). There may be a weight penalty,
> but this approach is ust putting the bearings all on one side of the
> wheel. If it can't be sound engineering, practice, we better
> re-examine our pedals, and the wheels on automobiles and heavy
> trucks. :-) I know it is counter-intuitive, because we're not used
> to looking at it, but why shouldn't it work just fine?
> Actually, in some of my wilder dreams I've thought about a
> single-sided rear with the cogs outside the support bearings, which
> would have some advantages, too. But, I'm not going to do that
> project anytime in the next hundred years or so...
> harvey sachs
> mcLean va.
>>> For those not finding the Labor bike, it's under "Racing" and is the bi
> ke
>>> with the cantilever frame. A direct link:
> -- gabriel l romeu chesterfield, nj, usa ±
> Ø ±