Re: [CR]BB Shells and Dave Bohm

(Example: Framebuilders:Alex Singer)

Date: Wed, 7 Jun 2006 09:38:00 -0400 (GMT-04:00)
From: "Nick Zatezalo" <nickzz@mindspring.com>
To: Norris Lockley <norris@norrislockley.wanadoo.co.uk>, classicrendezvous@bikelist.org
Subject: Re: [CR]BB Shells and Dave Bohm


Norris I am so glad you made this contribution. I have often wondered what mechanical benefit is derived from the efforts to customize stock frame building components.

I am a strong believer in the less is more approach to craftsmanship.

Nick "keep it simple" Zatezalo Atlanta,Ga

-----Original Message-----

>From: Norris Lockley <norris@norrislockley.wanadoo.co.uk>

>Sent: Jun 7, 2006 9:23 AM

>To: classicrendezvous@bikelist.org

>Subject: [CR]BB Shells and Dave Bohm

>

>It's been a difficult day so far..and it became even worse when I saw

>Wayne's contri about Dave Bohm's reworking of the RGF bottom bracket

>shell and the Bocama lugs. In retrospect perhaps I am over

>reacting..it's just that the contri caused me to revew much of the work

>I have done on bike frames for nigh on 50 years and to revisit some of

>the principles on which my working procedures have been based.

>

>Like many frame-builders I have always been more than happy to use RGF

>cast bracket shells because they are accurately made, the castings are

>sound, the threads are usually well-formed,and they contribute to a

>stiff and responsive frame. I have never known one to ovalise in use or

>to crack or deform in any way, being ultimately very dependable and

>suited to the purpose for which they were made. They were often the

>first sign of a quality frame made by a builder who knew his materials.

>I have never thought that they were "rough", just in need of a little

>cleaning and smoothing, but far far better than the cast brackets of the

>50s. in all respects.

>

>Similarly Bocama lugs were always robust, well thought out for the

>purpose in hand, but did require some refinement in terms of filing down

>and profiling...but never anything drastic.

>

>The purpose of this email is not in any way to criticise Dave Bohm's

>skills because he clearly has immense talent with his jeweller's saw and

>needle files, but instead I wish to ask quite simply "Why?" Why take

>that bracket shell and lugs and then set about wholesale alterations,

>alterations that although rendering the components more artistic, might

>in fact lead to them being weaker than they were at the outset thereby

>jeopardising possibly the integrity of the construction and the ride

>quality of the finished frame? Would it not have been more sensible to

>take a blank one or if none were available, to weld one up, and then

>cut the profiles.

>

>Most Bocama lugs arrive with a ring of metal attached to the headlugs,

>in the same way that Nervex Pros did That ring has a function - to help

>to prevent the ovalisation of the head bearing sockets, thereby reducing

>or removing judder. Dave appears to have removed those rings. If they

>appear slightly ugly, it is always possible to run a bead of weld

>material along them and then file them into an elegant concave curve

>that not only enhances their appearance but strengthens the headlugs

>against ovalisation even further.

>

>The removal of the outer tube socket walls on the bracket shell and

>their replacment with longer tangs seems not a bad idea, but if those

>tangs are only brazed or bronze-welded into place rather than fusion

>welded thereby producing at least a semblance of homogeneity and

>structural integrity, it does bring into question whether the end result

>was worth all the effort. My own experience suggests that such tangs as

>these and those brazed to the lugs are little better than

>window-dressing.."ars gratia artis". Presumably Dave will use

>silver-solder when he eventually "brazes" the frame together, otherwise

>there would be a risk of the added-on tangs, floating off under the

>torch. Should the frame be chrome-plated there would also be a risk of

>the acid etching slightly into the tangs' b/o joints, and of

>under-cutting the filed and dressed weld.

>

>I came across this contri about two hours after I had put to one side

>the Bernard Carre-built Sauvage -Lejeune frame that I had been cleaning

>up. This is the 1965 frame that carried Henri Anglade to the French

>Champion's jersey and to 4th on GC in that year's Tour, together with a

>number of high placings in top-ranking races.

>

>Coincidentally this frame has an RGF bracket shell, but neither the

>shell nor any of the Prugnat short-point lugs have had any reworking

>nor, I suspect ,even the stroke of a file gently across their surfaces.

>The front and rear drop-outs and their joints into the blades and stays

>are just as the torch left them.

>

>Membership of the List and the privilege of being able to read all the

>contris has made me very much aware of the vast gulf that exists between

>perceptions of a custom frame in the States and those held in the UK.

>Clearly the clientelle for custom frames over there demands and is

>willing to pay for far more "art" than a British builder could ever hope

>to find stepping through his workshop door. Perhaps that is the

>difference..American builders have studios and British ones have

>workshops...I suppose, on reflection I am firmly rooted in the "form

>follows function.." school of framebuilding.

>

>Norris Lockley, Settle UK