Re: [CR]Pedal x front/wheeel overlap


Example: History:Norris Lockley

Date: Tue, 10 Jan 2006 19:35:42 -0800 (PST)
From: Fred Rafael Rednor <fred_rednor@yahoo.com>
Subject: Re: [CR]Pedal x front/wheeel overlap
To: Norris Lockley <norris@norrislockley.wanadoo.co.uk>, classicrendezvous@bikelist.org
In-Reply-To: <000801c6164d$fc5af4b0$b9604254@Norris>


Norris,
     Thanks for the informative post. By the way, do you know a pub called the "The Frog and Frigatte" in Southampton. If we can all meet there this weekend, I'll be on the next flight over.
     One thing I noticed about the 1970s era frames you mentioned, is that they seem to have more fork offset than is currently fashionable. Also, Lucien Van Impe's frame must have been designed around his shoe size, too, which I suspect were no larger than a Euro 40.5. Anyway, it would be nice to be in contact with his frame builder.
     Your comments about the frames sold by Merckx were also illuminating. If you look in their old catalogues, although the seat tube angles and top tube lengths are provided, the front end geometry is always listed as "Proprietary." I used to think this was marketing drivel but now it makes some sense.
     By the way, the one frame I have which comes close to Van Impe's in terms of geometry, is the Richard Sachs that I've mentioned in other posts. I bought this secondhand directly from Richard and when I asked him about frame angles I expected him to rattle them off from memory. Instead, he quoted the front-center dimension and top tube setback. At the time, I thought he was challenging me to get out the algebra books and work it out on my own. Now it actually makes sense.
     Cheers,
     Fred Rednor - Arlignton, Virginia (USA)


--- Norris Lockley wrote:


> This topic really is the stuff of a cycling club meet, during

\r?\n> the wet

\r?\n> off-season, around a fire in the local public - house!

\r?\n>

\r?\n> >From what I know of quite a few French frame-builders,

\r?\n> constructeurs,

\r?\n> and bike manufacturers, this overlap factor is one of the

\r?\n> most critical

\r?\n> ones that they consider when

\r?\n> designing a bike frame. The maxim that they adopt is to avoid

\r?\n> overlap at

\r?\n> all costs, although I admit that on some massed produced

\r?\n> bikes, given

\r?\n> the restrictive nature of certain lug angles, the cost of

\r?\n> labour in

\r?\n> manipulating them to more suitable angles, some bikes do come

\r?\n> out of the

\r?\n> factory with built-in overlap...but always as little as

\r?\n> possible.. The

\r?\n> term Chasse Avant ie the front end centre length is all

\r?\n> important.

\r?\n> However some manufacturers managed to overcome the

\r?\n> restrictive nature of

\r?\n> lugs by adopting bronze-welded construction techniques,

\r?\n> thereby allowing

\r?\n> themselves to vary the head and seat angles far more easily.

\r?\n>

\r?\n> I was involved with the TVT company around the time when they

\r?\n> started to

\r?\n> produce TVTs instead of just supplying tubes to LOOK, and was

\r?\n> impressed

\r?\n> by the measures to which the designers went to produce frames

\r?\n> with no

\r?\n> overlap...these frames ...are essentially racing machines,

\r?\n> remember,

\r?\n> and we cannot expect a rider, when descending the Col de

\r?\n> Galibier. to

\r?\n> have to wonder where he should place his pedals in relation

\r?\n> to the front

\r?\n> wheel...he clearly has other more important considerations on

\r?\n> his

\r?\n> mind...

\r?\n>

\r?\n> This was the philosophy adopted by the TVT team, as expressed

\r?\n> to me by

\r?\n> M. Guigneaud, the frame designer who is still, I believe,

\r?\n> designing for

\r?\n> the TIME company.Such was the company's preoccupation with

\r?\n> this aspect

\r?\n> of the frame's design..and the rider's safety, that when they

\r?\n> came to

\r?\n> design the two frames at the small end of the range, the 47

\r?\n> and the

\r?\n> 48cms, and it became abundantly obvious that it wasn't

\r?\n> possible to build

\r?\n> frames of those sizes, with suitably short top-tubes, both

\r?\n> 50cms C-C,

\r?\n> and also avoid overlap..that the designers took the radical

\r?\n> decision to

\r?\n> use a 26" wheel at the front instead of a 700c. This decision

\r?\n> also

\r?\n> produced a frame with a longer head-tube..and a much better

\r?\n> balanced

\r?\n> handling bike altogether The front end C-to-C was

\r?\n> 560mms.Nowhere in the

\r?\n> TVT range is there a front end measurement less than 585mms,

\r?\n> and that

\r?\n> appears on the 49cms frame....and TVTs are reckoned to be

\r?\n> something of a

\r?\n> bench-mark in handling terms for a road-racing bike. All TVT

\r?\n> frames were

\r?\n> designed using combinations of just three angles. All head

\r?\n> angles were

\r?\n> 73, all seat angles up to the 54cms frame were 74.5, and over

\r?\n> that were

\r?\n> 73.5. The company also offered a custom service. I once

\r?\n> ordered a 51cms

\r?\n> frame with a 51 cms top-tube. After various attempts to

\r?\n> design the

\r?\n> frame, the company declined the order claiming that without

\r?\n> shallowing

\r?\n> off the head angle to an unacceptable angle or increasing the

\r?\n> seat angle

\r?\n> to a far too steep one in order to retain sufficient

\r?\n> clearance at the

\r?\n> front end it would not be possible to produce a frame to the

\r?\n> dimensions

\r?\n> asked for.

\r?\n>

\r?\n> However I can't have been the only frame builder on the List

\r?\n> who has

\r?\n> been approached by customers seeking winter bikes built to

\r?\n> the same

\r?\n> design as their best road-racing bike. Almost every time that

\r?\n> I

\r?\n> undertook this task on small frames, particularly Franch and

\r?\n> Italian

\r?\n> ones,I would make certain desin assumptions but would end upI

\r?\n> being

\r?\n> amazed at the mixture of angles chosen by these continental

\r?\n> builders. I

\r?\n> recall 49 and 50cms frames with 75/76 seat angles, merged

\r?\n> with 70/71

\r?\n> head angles...but very short top-tubes...but no overlap. I

\r?\n> believe,

\r?\n> however that Merckx used to build a stock 52cm frame with a

\r?\n> 75 head

\r?\n> angle..but there again he always used a long raked fork...but

\r?\n> managed

\r?\n> the mix without the front-end juddering or wobbling at speed.

\r?\n>

\r?\n> Van Impe, the pint-sized Belgian ace climber, used a frame

\r?\n> with a

\r?\n> 50.5cms seat tube, and a 52.5 cms top-tube, the front-end

\r?\n> clearance

\r?\n> being 585mms...60mms trail..and no overlap. Zootemelk rode a

\r?\n> 54.5cms

\r?\n> square frame with 595mm front end and 60mm trial..and no

\r?\n> overlap..Merckx

\r?\n> rode a 59cms with 57cms top-tube, 600mm front end and..60

\r?\n> trail..and no

\r?\n> overlap.

\r?\n>

\r?\n> Some one once told me that it is possible to obtain a degree

\r?\n> in

\r?\n> cycle-frame design at some college or university in the

\r?\n> States. Is that

\r?\n> really the case?

\r?\n>

\r?\n> Norris Lockley..Settle UK