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