30 January, 2007

Frame Quality, part 1


It can be difficult to judge just how well a lugged steel frame is built. The average cyclist probably has a hard time seeing the difference in quality between a top custom frame and a good production frame. There are those who think that a production frame from Toyo, Colnogo, Waterford, or Maxway is virtually as well made, if not as well painted, as hand built frame by Peter Weigle, Johnny Coast, Richard Sachs, or any number of top custom builders. But if we look below the paint we'll soon find a lot that distinguishes good custom frames from even the best off-the-shelf frames.

Among the things that distinguish the best frames is preparation of the lugs, careful selection and mitering of the tubes, good brazing techniques, and near perfect alignment. Let's take a look at some of the details of a top quality frame:

One of the things that's easy to spot and that distinguishes a production frame from a fine custom frame is the way the lugs are finished. As one of our regular readers put it when I asked about one of his American production frame, "It's never been in the same room as a file."

A good custom builder files, shapes, and thins the lugs. Of course this is done not only for aesthetic reasons. The edges of lugs form stress risers. These are areas where a tube is most likely to fail do to the sudden transition from a stiff area to a flexible one. From Wikipedia:

"Geometric discontinuities cause an object to experience a local increase in the intensity of a stress field. The examples of shapes that cause these concentrations are: cracks, sharp corners, holes and, changes in the cross-sectional area of the object. High local stresses can cause the object to fail more quickly than if it wasn't there. Engineers must design the geometry to minimize stress concentrations."

By thinning a lugs points the builders is able to make a more gradual transition and lessen the stress riser. But filing lugs is done by hand and takes a great deal of time. This is time the production builder can't afford. Besides, the frame probably won't crack if you don't file the lugs.

Likewise you'll notice that some points under the tubes of custom frames are, in fact, not pointed. Rather the builder has rounded them to minimize what is sometimes called the "can opener effect". The frame probably won't fail if those points are not rounded, but then again, why take the chance.

Thinning lugs also saves a little weight. It may not be much, but little details do add up. And finally, thinned lugs look a lot better. They show that the builder really cared. So next time someone tells you their production frame is as good as a custom, look at the lugs.

In future posts I'll write about tube selection, mitering, alignment, and brazing.

20 comments:

Anonymous said...

"Geometric discontinuities cause an object to experience a local increase in the intensity of a stress field. The examples of shapes that cause these concentrations are: cracks, sharp corners, holes and, changes in the cross-sectional area of the object. High local stresses can cause the object to fail more quickly than if it wasn't there. Engineers must design the geometry to minimize stress concentrations."

That's what I always assumed, but didn't want to disturb anyone.

Joel said...

Informative and interesting. Thanks. Look forward to the future chapters.

neil m berg said...

I have a couple of handbuilt bikes with beautifully filed lugs and I really appreciate the craftsmanship. However I do think that a lot of the filing tradition goes back to pressed lugs which really required to be worked to have a "finished" bike. I don't think it's necessary with modern well designed cast lugs. For instance, I don't think Richard Sachs files them much, other than basic clean-up. Maybe he will share his thoughts on this.

e-RICHIE said...

if i have too -

all parts are thinned and filed as much as they have ever been. the only labor missing on a frame with i.c. lugs is the pre-treatment that was needed to blacksmith the parts into fitting over the tubes and conforming to a frame geometry. i still do those types of frames too, mebbe 3-4 times per year, when the order calls for a re-enactment era aesthetic. ya' know - the vintage stuff with the n.r. and s.r. parts atmo!

e-RICHIE said...

oops - meant:
if i have to -

neil m berg said...

Thanks for the info...and all the gorgeous bikes you have built. Maybe some day...

Anonymous said...

Nice piece. I too look forward to the next installment; I appreciate a well-finished lug as well as anyone, and like to read about it. BTW, RS's comments on all this in the old Bridgestone catalogs as well as the Riv reader were the best source of info I've ever read. I still get those out from time to time.

One question I have would be on the whole labeling of custom vs. production. What does that mean, really? I have a Paramount built by defunct match bicycle which has superb worksmanship. Sacha White had one and has spoken about how he still strives to emulate certain details. It was an off the shelf 853 bike made by Pacenti, Isaac, Bulgier, Hampsten and the rest of them in a big state of the art shop, and around 700 of these frames were finished to world class standard. For instance, the inside of the seat tube was ground by stone, not reamed, so the post slides slick as snot. Was that production? Yes, of a sort.

Similarly, I don't see bikes such as Waterfords as second tier to anyone, and I don't believe that anyone who owns one would ever say such a thing. I know, it doesn't look like a Baylis or Weigle, but functionally, damn good=damn good.

What is GOOD, anyway? I dearly loved my old factory-made, brass-brazed, unfiled Bridgestone mtn bikes. Those frames took more abuse in deserts and mountains than I will ever dream of giving any frame again. Pound for pound, buck for buck, I don't even want to think about what I put those bikes through, please don't make me.

There's good production, and bad production. For me, loving bikes means loving good bikes that do the job, not some idea of a preferred method. Loving Sachs, letting him do what he needs to do, but also loving all the old rusty Motobecanes, Stellas, Colnagos, Bridestones, whatever, even the candy-green Varsity--everything that got me this far.

best,
michael white

Anonymous said...

I left out Curt Goodrich at the old match bicycle company. sorry.

mw

Anonymous said...

Wow, Johnny Coast is in the company or Sachs and Weigle! That was quick! ;)

PS -I think "Maxwell" should be "Maxway", no?

Chris Kulczycki said...

Next week he'll be in the company of Herse ;<) Come on; I'm giving examples, not ratings.

Yes, Maxway.

e-RICHIE said...

better in the company of herse, as opposed to a passenger in one. is johnny much of a singer?

Joel said...

Hey, on the subject of hand filed lugs, If Chris doesn't mind, thought I would share Tom Oswald filing down some lugs for the expedition camper he is making for me:

http://www.youtube.com/watch?v=fWJhW913Ykc

Anonymous said...

What about the double negative use in last sentence of paragraph after quotation. That's not 'good to the last drop' either.

Joel said...

Actually that is a perfectly acceptable use of the double negative.

Anonymous said...

as a writing professor with English PhD, I ain't got no comment on that.

mw

Joel said...

You may want to take your University to task if you cannot see the difference between the critiqued sentence and your example.

Parsing. It used to be taught in elemenatary school. Try it.

Anonymous said...

easy there, Joel, just kidding. I went to a very good school, trust me, but prefer to downplay all that.

neil m berg said...

If you guys don't quit throwing spit-wads we'll have to separate you.

Anonymous said...

there's me, then there's the other anonymous guy.
Moi, I ain't throwin' no spit wads at nobody!! No way, no how, capiche?

mw

nv said...

Some pix from the 2007 Japanese Handmade Bike show:
http://tinyurl.com/2nftvc

As always, there are some real beauties!

nv