[CR]Re: [Frame] frame tolerances, etc.

(Example: History)

Date: Fri, 28 Sep 2007 20:09:40 -0400
From: "Doug Fattic" <fatticbicycles@qtm.net>
To: Jan Heine <heine94@earthlink.net>, "classicrendezvous@bikelist.org" <classicrendezvous@bikelist.org>
In-Reply-To: <a06230927c32310293162@[]>
Subject: [CR]Re: [Frame] frame tolerances, etc.

Jan, if I understand what you are doing at Bicycle Quarterly correctly, it is to try and quantify various frames dimensions so you and your readers can understand what characteristics have the quality they like and, perhaps even, best . I applaud this effort and believe your research can lead many of us to deepen our understandings of how to design frames for various purposes. I've been on this quest since the 60's and don't feel like I've learned it all yet.

I've often debated positions with you on the I-bob list and felt you were respectful of different opinions and while I didn't always (read seldom) agree with your point of view that didn't mean I thought they didn't have validity. I think my experience of having been a European trained framebuilder means I look at what is important from another perspective.

Here are some of my random thoughts about the question of "what makes a great riding frame?" 1. I, like some others, get a little nervous about stating preferred dimensions because a one-off custom bike is built to a specific individual preference and - like saddles - what one person wants or even needs may not be to the liking of another. I don't mind your documenting the dimensions of frames you test. My vote is for the standard Don Ferris suggested. 2. I've felt like you haven't put enough emphasis on accurate frame alignment when discussing ride qualities. A large part of good framebuilder technique involves how to keep things straight. To me this is not a side issue but a central one. Now this is a can of worms worse than recording frame dimensions because we often choose different points of reference. Remember that is where this subject thread started. 3. Americans framebuilders probably arrived at a mature understanding of design later than their ability to make a good structural frame. What we did in the 70's has evolved (as has our customer needs). Like a teenager growing up, I don't want my work that I do now evaluated by what was done some time ago.

Where I believe not enough information has been provided is in a different area and that is understanding the history and background of the American framebuilding history. We are greatly influenced by where we learned, what equipment was available to us, who are customers were/are. Just like the development of the derailleur can't be understood outside of the cultural milieu it hatched from, neither can we completely understand what we are doing now without knowing where we came from and who we were selling to. I think your magazine is uniquely placed to provide some perspective on this. I think a lot of customers would be more interested in builders on this side of the Atlantic then they would the past French builders for example. You comment on this from time to time.

Eventually I hope to get a chance to talk about custom design.

Doug Fattic Niles, Michigan

On 9/28/07 5:08 PM, "Jan Heine" <heine94@earthlink.net> wrote:
> At 2:06 PM -0600 9/28/07, Don Ferris wrote:
>> Measure what it is. Your current rounding gives you a 1cm & 1-degree
>> tolerance.
> There appears to be a misunderstanding. My current rounding gives me
> a 0.25 cm and 0.25 degree tolerance. If I measure 72.7 degrees, I
> report 72.5 degrees. If I measure 72.8 degree, I report 73.0 degrees.
>> I'd say cut that in half to start with, make the
>> dimensions accurate to 1mm on the lengths and at least 1/4-degree on
>> the angles. Those are easily achievable and reasonable.
> Does any builder design their bikes to a 72.75 degree head angle
> instead of 72.5 or 73? What about the effect of the rider's weight on
> front-center - should we measure the bikes loaded or unloaded? Will a
> millimeter really make a great difference?
>> My problem with rounding to the nearest 5mm or 1/2-degree is that
>> you're claiming, or at least others are claiming for you, to be
>> lifting the veil off of the "frame geometry mystique" and how that
>> translates into ride/handling characteristics. I can't see how you're
>> improving over the "rule of thumb" methods without having better
>> control of your data.
> If we find that the handling difference between a bike with 30 mm
> trail and one with 40 mm trail is minor, then I do not see why a
> measurement error of +/-3 mm is going to affect our conclusions. If
> one bike has a trail figure of 27 mm and the other of 43 mm (the
> worst-case scenario), our conclusions still are valid. The handling
> differences we describe are between bikes that are radically
> different - say 65 mm trail vs. 45 mm trail.
> In most cases, this is a non-issue anyhow, as we agree with the
> builder's spec and report that. Only if we come up with significant
> differences to the spec do we report our measurements instead. (In
> some cases, the builders don't have a spec for certain measurements,
> and then we report our measurements.)
>> Have them test ridden by yourself and your mates, and try to include
>> some test rides by those who don't share your biases.
> We do. The problem is that these riders begin to share our biases
> pretty soon. Mark Vande Kamp rode high-trail sport-touring bikes all
> his life, and liked them a lot. Then I put him on the Weigle
> randonneur bike, and he immediately decided he needed to re-rake his
> fork as a first step, and order a new bike as the second step. He is
> very, very happy with his new Goodrich, which I currently am testing
> for the next issue. BTW, the Goodrich's angles appear to be spot-on -
> 73.0 for head angle, 72.0 for the seat angle, 0.0 for the top tube. I
> haven't asked Curt whether that is what he wanted to build, so maybe
> our measurements are way off, and he intended to build a 72.693
> degree head angle. I'll send Curt the report next week for comment,
> and will find out then.
> Alex Wetmore was another rider who'd never been on a traditional
> randonneur bike. After being involved in our tests for a while, he
> decided to order a new custom bike with a traditional geometry and
> standard-diameter tubing.
> If I need new testers for every issue, I soon will run out of riders
> who are of similar size to ride the bikes that fit me, can ride well,
> are perceptive, can write reasonably well and are local...
> If you can point me to a magazine that does better bike tests than we
> do, I'd gladly take a look and see whether we can improve what we do.
>> It's a lot like the "planing" term/characteristic you coined. The way
>> it's used it appears to be an abstract thought or judgement based on
>> ill-defined criteria or personal perception. I don't see how this is
>> scientific or lifts any veils.
> As for the planing, it's nothing new. Riders for decades have said
> that some bikes felt livelier than others, climbed better, etc.
> Nobody ever liked the performance of drainpipe, even on flat courses,
> yet though those frames were the stiffest available. When I
> complained about the lackluster performance of an American production
> frame many years ago, Peter Weigle suggested that the frame might be
> too stiff for me. That got me thinking - I never had given much
> thought to frame stiffness, figuring that if Tony Rominger could race
> on Alans, any bike was going to be stiff enough for me. It never
> occurred to me before that a bike could be too stiff, until I
> experienced that frame, and shortly thereafter, a superlight,
> superstiff Italian carbon/aluminum racing frame that felt as
> unresponsive.
> All we have done is give it a name so we can talk about it, and look
> for possible physical explanations for this phenomenon. We try to
> figure out which parameters in a bike might be responsible. The
> advantage of riding many bikes (large sample size) is that you begin
> to see parallels between apparently dissimilar bikes, and thus can
> distill the factors that seem to matter. However, I never have
> claimed to have all the answers for this, just some ideas. It's an
> area that requires further research. We are working on it.
> Jan Heine
> Editor
> Bicycle Quarterly
> 140 Lakeside Ave #C
> Seattle WA 98122
> http://www.bikequarterly.com
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