Re: [CR]Widening the classic handlebars

(Example: Component Manufacturers:Cinelli)

Date: Wed, 17 Sep 2008 16:45:44 -0700 (PDT)
From: "david snyder" <dddd@pacbell.net>
Subject: Re: [CR]Widening the classic handlebars
To: Classic Rendezvous <classicrendezvous@bikelist.org>
In-Reply-To: <3.0.6.32.20080917184014.0171fd28@mailhost.oxford.net>


As a mechanical engineer, I find such discussions scary. Would a future rid er of a structurally modified bicycle necessarily be aware of such a modi fication?

The issues with such overlap joinings (using adhesives) are many, including the extremely uneven shear stress distribution throughout the adhesive reg ion due to the flexing inherent in lightweight structure, even if (especial ly if) one half of the joining were solid and relatively flex-free.

A typical failure with such torsionally-stressed joinings is one of creep ing bond failure from one end to the other, the rate of which is very diffi cult to predict without testing, even if the entire joint were free of any adhesive voids. Such joinings may show remarkable impact strength over a low number of cycles (as with the motorcycle bar end extension, which likel y didn't have much torsional loading at all) as repeated (cyclical) loadi ng may be needed to spread the separation (a rather complicated technic al discussion in itself). Even the most elastic of adhesives will do little to even out the shear-str ess distribution when modest-diameter parts flex torsionally and the cl earances are too small to allow movement without tearing the bond near  one or both ends of the joined area of overlap.

Ted acknowledges he may have gotten lucky with that modification, and I not e that the injured user may have used her bike under very low stress co nditions.

A proper use of such joinings typically makes use of a relatively short ove rlap over a relatively stiff, larger-diameter area of the tubes. Such joini ngs are widely and reliably used in the cycling world today.  It goes wit hout saying that such designs are engineered with quantitative data at ha nd, then tested and manufactured under strict conditions of quality contr ol.

David Snyder
Auburn, CA  usa


--- On Wed, 9/17/08, John Betmanis wrote:


From: John Betmanis <johnb@oxford.net> Subject: Re: [CR]Widening the classic handlebars To: Classicrendezvous@bikelist.org Date: Wednesday, September 17, 2008, 3:40 PM

I'm glad to see someone who knows what they're talking about respond positively to this idea. If everyone in the world had poo-pooed every idea out of hand based on politically correct blanket safety concerns, we would still be walking, not to mention riding bicycles, driving cars or flying in airplanes. Of COURSE handlebars can be widened if done correctly. The centre part could even be solid aluminum because it would add negligible weight and each side could be glued on over a couple of inches turned down to the correct diameter using an appropriate engineering adhesive. Years ago I extended the ends of a pair of motocross handlebars using a similar technique and they survived numerous crashes.

John Betmanis Woodstock, Ontario Canada

At 01:53 PM 17/09/2008 -0700, ternst wrote:
> My experience was different and I may have been lucky with no problems
  
>at all.
>A lady touring sport rider already a customer came into the shop with her
  
>arm in a sling.
>She got her arm caught in a car door closing and tore her arm up most
>nastily.
>Her arm was healed and with therapy was starting to come around but she wa s
>about 3" short on reach with her bad arm.
>Much like the old fabled longshoreman with their bale hooks and one shorte r
>arm of occupational injury.
>So, after thinking a little I decided to go to my favorite machine shop an d
>have piece made that was standard length on one side and about 2" closer on
>the other.
>This piece fit in the stem and gave me a double length insert that had about
>2-1/2" of peg sticking out on each side.
>I then cut a bar in half and had the inside smoothed out to match the pegs
  
>with a nice snug not quite tight press fit.
>I glued it in place after testing it and the lady picked up her bike and
  
>started her comeback.
>It took about a year for the arm to feel strong and flexy again.
>We removed the custom therapy fitment and the lady is still riding today 1 0
>years later, fit and happy!
>Take your chances, use the best and strongest materials and the rest is up
  
>to you.
>The new tough alloy is so strong, I would be hard pressed to not trust the
  
>job.
>It worked for my customer.
>Even though you may be bigger and stronger, get a shear and stress estimat e
>on the diameter and I'll bet you get a rupture before it could be made to
>fail with lunging testing as in hard climbing for instance.
>How many times have we seen pics of the Euros riding bikes with bars and
  
>stems drilled through and a 5-6mm screw and nut holding the damn thing in
  
>place?
>Ted Ernst
>Palos Verdes Estates
>CA USA
>----- Original Message -----
>From: "bruce thomson" <masi3v4me@yahoo.com>
>To: <Classicrendezvous@bikelist.org>
>Sent: Monday, September 15, 2008 11:34 AM
>Subject: [CR]Widening the classic handlebars
>
>
>> Has anyone either thought of or experimented with the concept of widening
>> t
>> he classic handlebars? I don't mean by a stretching process, but I mean
>> a using a tubing cutter and center cut and then adding a central extension
>> of either solid or heavy alloy tubing that would be step cut to fit inside
>> the cut off bars and have a central section that would match the original
>> c
>> lamping section.
>> I am considering experimentation with a addition of Permanent Lock-Tite
>> and/or knurling the sections together. I have too often felt scrunch
>> ed up on those old 39cm bars and miss some of the classic randonner curves
>> of some of the old bars.
>>
>> Bruce Thomson Spokane WA 99204
>> (509) 747 4314
>> Masi3v4me@yahoo.com rapidfire10ring@hotmail.com