I'm confused by this whole discussion. I've worked with plenty of rims that weren't perfectly round before being built into a wheel, but so what? The tension required to make them round is very small compared to the tension in a properly built wheel. In the final wheel the spoke tension will vary by plus or minus epsilon due to the imperfection in the rim, but I'll bet you can't even measure that.
So I don't see a problem with a rim that's naturally slightly elliptical. Of course, there are real manufacturing defects like dents that won't round out in the built wheel, but I assume that's not what's being discussed here. -- Kurt On Oct 1, 7:50 am, Peter Jon White <[EMAIL PROTECTED]> wrote: > The job of the wheelbuilder is to build a round wheel. To build a > round wheel, you need to start with a round rim. Of course I try to > determine if the rim isn't round before starting the build, but very > often the irregularities don't show up clearly until you have tension > on the spokes. It's not that the rim starts out round, it's that the > rim isn't round, but for whatever reason you can't see the problem. > > There's only one shape of an untensioned rim that I want to recreate, > and that's the shape of a round untensioned rim. > > On Oct 1, 1:43 am, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> > wrote: > > > Well, Swan is clear in what I quoted. and in the rest of his > > post.http://search.bikelist.org/getmsg.asp?Filename=classicrendezvous.1080... > > that the non-concentricities are there, and are best ignored because > > they are hard to correct. He earlier claims that the job of the > > wheelbuilder is to build a tensioned wheel which well recreate the > > shape of the untensioned one. > > > I know, PJW, that you have been building wheels for many years. Have > > you tried, say with Sun rims, to identify these flat spots and hops > > before the building begins? I know you've posted about them at your > > webpage? Again, I'm asking whether you have tried to identify and > > quantify the out-of-roundnesses ahead of time. > > > Harry Travis > > Washington, DC > > > On Sep 30, 11:17 pm, Peter Jon White <[EMAIL PROTECTED]> wrote: > > > > If the out of roundness in a rim is small enough to have no effect on > > > the performance of the wheel, yes, you should ignore them and get the > > > spoke tension as even as possible. But you can be faced with a > > > difficult choice when the rim isn't quite round. If you're using an > > > inexpensive rim because you're just riding the bike a few miles back > > > and forth to work, you would be silly to start all over when you find > > > that the rim isn't perfect. You rarely find these flaws before you've > > > spent a lot of time lacing and tensioning the wheel, so do you want to > > > start all over with another rim which may be no better than the first? > > > > On the other hand, if you're building wheels for PBP, your standards > > > need to be quite a bit higher. > > > > On Sep 30, 9:23 pm, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> > > > wrote: > > > > > Jamie Swan offered this opinion to a first-time amateur wheel builder > > > > over at Classic Rendezvous (bikelist.org). He has trued over 400,000 > > > > wheels. > > > > > _____________________________ > > > > > The big issue is: are those hops and/or flat spots the true shape of > > > > the rim or did you put them there as you applied tension to the > > > > spokes? If those minor eccemtricites are the actual shape of the rim > > > > then you shouldn't try to change them. You should just support them > > > > with uniform spoke tension. > > > > > Jamie Swan > > > > Centerport Cycles Inc. > > > > Northport, New York, USA > > > > ___________________________________ > > > > > Any opinion here from other wheelbuilders? Is it feasible for amateurs > > > > to mark non-concentricities in rims against a perfectly drawn circle, > > > > and so not make mistakes in trying to correct them? Or are they too > > > > subtle to see? > > > > > Harry Travis > > > > Washington, DC USA --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Bicycle Lifestyle" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/bicyclelifestyle?hl=en -~----------~----~----~----~------~----~------~--~---
