Ken has understood my point exactly, I wasn't trying to open a technical discussion, just get an idea of "trends" i.e. the use of high BB by Woodrup or by British builders in general versus typical French or Italian builders. One good point that was made was that frame angles do affect standover, and my Woodrup does have rather steep angles. The Mercian I spoke of was advertised as 54 cm, but the eBay seller was quoting the official Mercian size, which rather unusually is measured to the top of the seat lug I believe, so ctc was more like 52 cm. But the BB is so high that a 55 cm frame with the same BB height would have been too tall, even though I can usualy ride a 56 cm frame OK. Regards,
Jerry Moos
Ken Freeman <freesound@comcast.net> wrote: Interesting, John, but to simply look at the frame as a free body does not address all the possible concerns. The OP was asking about apparently more standover height in a Woodrup v. a (presumably) similarly sized Italian or French frame. There are as you correctly say several variables, and in the case of Woodrup a particularly odd one. SOH is equal to wheel radius minus BB drop, plus seat tube c-t times the cosine of the seat tube angle. For many of our vintage frames we can assume radius is essentially constant because of the ubiquitous use of 700C sewups in most vintage racing lightweights. Woodrups, however, seem to have been sold with 27 inch clinchers into the early '80s Ten Speed Drive era.
I interpreted Chuck's comment as "give me some numbers, I can't get your discussion into context, darn it!" I might have been right, or not.
If someone wants to publish an email documenting a standard set of frame measurements with a reference diagram to enable uniform definitions for on-list discussion, I would be glad to adopt such a standard. As a systems engineer I believe in appropriate standards. At least a list of what "describe fully" entails. Without that, I depend on constructive criticism.
Did I contradict anything Brian Bayliss wrote on small frames? Please educate me if I have. I have not read all that he's read. Another good source on the small frame problems is Tony Oliver, a retired UK framebuilder who published a book on frame and bicycle design, called Touring Bikes. I'd recommend CR listers to consider this an important part of their reference libraries. Not all that is good is on the Web, and as we know, not all that is on the Web is good.
Ken Freeman Ann Arbor, MI USA
-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of jj and kk Sent: Saturday, December 30, 2006 9:33 PM To: classicrendezvous@bikelist.org Subject: Re: [CR]Re: Stand-over height for Woodrup
Regarding the mis-measure of bikes.
In the 70's and into the 80's many British racing style frames had higher bottom brackets than say, an average Italian road frame. Note many, not all. There was a time in the early to mid 70's that those looking for a British frame seemed to be looking for an ultra short wheelbase, high bottom bracket mount.
Now, may I suggest keeping to bottom bracket drop. NOT height, for describing a frame's geometry, height is subject to influences of tire size and or wheel size. So, it is hard to compare when the datum is moving about. 650 wheel size is a whole other matter, but the vast majority are not that size.
Chuck was alluding to this measurement problem I think earlier. Also do not forget that seat tube angle will modify the "stand over height" as well, a slacker angle will provide a lower height above the ground for an equal sized frame of the same BB drop.
Also it was mentioned that the frame size will have direct influence of dimensional characteristics. Brian Baylis has often written about the compromises made on small frames frequently to hit a dimension, such as top tube length or front center length.
Front center is also not measured the same way by all, depending on the fixture and or methodology of the builder it could be measured parallel to the ground through the centers of the BB and front wheel, where at the bike shop level is often measured as the direct line from the BB center to the front wheel center.
So, when measuring a frame for others to understand well, please describe fully.
John Jorgensen
Palos Verdes Ca USA