Neil, I'm glad to have been of help, and will be willing again in the future. I think your reasons for wanting to know the angles are perfect. My interest in frame geometry started in exactly the same way, wondering why these different bikes are different.
I am amazed that Carlton offerred such options in frame ordering, back in the day. Seat angle is driven primariily by leg proportion, the rider's need for a certain front/back saddle position, and consideration of weight distribution. The head angle is much more connected to performance, toe clearance, upper body comfort, and handling of the bike - rather more complex.
"Short rake Russ" certainly suggests small rake, which (depending on head angle) could result in a larger amount of trail and some toeclip overlap. Of course, this also is related to the amount of top tube length that is not behind the BB.
Best regards, and please let us know what you discover.
On Sat, Oct 10, 2009 at 4:37 AM, Neil Foddering
<neilfoddering@hotmail.com>wrote:
>
> Again, I would like to thank everyone who has replied to my query.
>
> The reason I want to measure the angles accurately is to try to find some
> correlation between my perception of how well my bikes ride and their frame
> angles and fork rake characteristics. For example, my 1939 Carlton Flyer*
> rides very well indeed; the catalogue quotes standard head/seat angles of
> 75/73, 73/73 or 74/71. In addition to these options, the customer could
> specify the angles he required if the standard offerings didn't suit.
>
> The wheelbase is quoted as 40 inches, and the forks are described as "short
> rake Russ". There is considerable toe clip overlap on my machine, which was
> used by the original owner for time trials. The Flyer is described in the
> Catalogue as "The last word in hand built road racing machines".
>
> I'm curious to know the actual angles on my machine, given the range of
> options offered, and indeed, on all of my 1920's, 30's 40's and 50's
> lightweights.
>
> I realise that ride quality is more than the sum of frame angles (I had a
> beautiful Curved Seat Tube Model Jack Taylor, with a 37" wheelbase, which
> rode superbly, and which I sold to a CR listmember some years ago. I still
> miss that machine! On the other hand, I had another short-wheelbase machine
> (which I won't name) with an unusual frame design, which rode like a dog:
> twitchy steering, bumpy ride, pitched and tossed on an uneven road);
> however, I have to start somewhere.
>
> * http://www.classiclightweights.co.uk/
>
> Neil Foddering
> Weymouth, Dorset, England
>
>
>
>
>
>
>
>
>
> > Date: Tue, 6 Oct 2009 12:21:15 -0700
> > From: verktyg@aol.com
> > To: neilfoddering@hotmail.com; Classicrendezvous@bikelist.org
> > Subject: Re: [CR] Measuring bike frame angles
> >
> > Neil,
> >
> > Measuring the frame angles is just a starting point based on the idea
> > that the top tube will sit parallel to the ground (on a frame without a
> > sloping top tube).
> >
> > The important thing about frame angles is how they will affect the ride
> > and handling of the bike. The fork rake (or trail) is also an important
> > factor.
> >
> > The measurements need to be taken with a set of same size wheels in
> > place and the bike standing upright with the fork straight ahead.
> >
> > I've been using an inexpensive plastic dial protractor with a magnetic
> > base to make these measurements for years. I also have a more expensive
> > digital protractor but they give about the same results.
> >
> > Here's a link that shows a lot of different types:
> >
> > <
> http://www.thefind.com/
> >
> > The only problem with these protractors is on small framed bikes with
> > short head tubes and sometimes frames with a head tube badge. It those
> > cases you can sometimes measure them from behind the head tube with some
> > accurately ground square steel bits as spacers between the tube and
> > magnetic base.
> >
> > Chas. Colerich
> > Oakland, CA USA
> >
> > Neil Foddering wrote:
> > > I have tried, without success, to measure the frame angles on my 1930s
> and 40's bikes; does anyone know whether a purpose-made tool is available to
> do this (preferably idiot-proof)?
> > >
> > > Neil Foddering
> > > Weymouth, Dorset, England
> >
> >
>
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--
Ken Freeman
Ann Arbor, MI USA