That I know, but the intricacies and esoterica of converting chain sag to axle movement is beyond me (thanks Bill for the catenary curve formulae, but they are to abstruse for me -- who learned and forgot and had once again to learn and once again forgot the calculus).
At any rate, whatever the relationship, the factor is a huge one. Just to be on the safe side, today I took the files and wore away a bit more of the dropouts' rear parts. They now ought to be able to accommodate a chain for its full lifespan. On Sat, Dec 21, 2013 at 1:27 PM, Eric Daume <[email protected]> wrote: > Add one chain link = 1/2" of axle movement. > > Add one tooth = 1/8" of axle movement. > > See Sheldon, of course: > > http://sheldonbrown.com/fixed-conversion.html > > > On Fri, Dec 20, 2013 at 7:50 PM, Patrick Moore <[email protected]>wrote: > >> I've bitched and moaned on this list about the annoying position of the >> retrofit Campy 1010s on the '03 Curt (installed by local builder Dave >> Porter some 6-7 years ago), that, with my preferred ring-and-cog combos, >> leave the axle at the 1/2 or even the 3/5 point along the dropouts in the >> cruising cog, so that I am limited to another 2 teeth before I run out of >> dropout room. Since I lika-da-Dingle, this has limited me to a 17/19 >> instead of the 17/20. >> >> (Tho' I found after grudgingly installing the 17/19 that the 19/63" is >> the perfect chugging-along gear for extended hills and headwinds when I am >> carrying a heavy load.) >> >> I talked to other local builder Chauncey Matthews about re-positioning >> the dropouts, but he was reluctant to undertake the job, so after much >> fretting and internal anguish, today I took big and small rattails and a >> flat file to them and laboriously filed them back by a couple of mm. >> >> Lo and behold, a very little horizontal distance takes up a heckuvalotta >> chain slack. The axle is now within a mm of the back-end of the dropout in >> the 48/17, and there is ample room for, not only a 20, but, I daresay, even >> a 22 or 23. Not that my mighty quads need such piddling gears. >> >> I may have to file the dropouts back another mm or so to take up chain >> slack as the chain "stretches", but that should be no problem. The backend >> of the dropouts is noticeably thinner now, but there is ample metal to >> support the axle. >> >> I had to do the same thing to the '99 Joe gofast when I got it in '99, >> since I had -- thou fool! -- neglected to specify long dropouts and got >> Riv's then-current short horizontals. But the file did its work and the >> gofast can take a 5-tooth jump: I've installed a 20 t (or was it a 21?); >> the crusing 75" is a 46/15. >> >> All of this leading up to a couple of questions: >> >> 1. How much linear "stretch constitutes sufficient chain wear to require >> replacing the chain? (I use a Park tool, and I've found that, on the '99 >> Joe, when I just begin to notice that I cannot any longer take up >> sufficient slack, the tool measures close to 100% worn. So the dropouts >> make up a kind of on-bike chain check setup.) It can't be more than a very >> few mm. >> >> 2. Is it true, or is it false, that the lateral movement of the axle as >> you move it back and forth to accommodate smaller and bigger cogs, is 1/2 >> the distance that would be required if the chain were a mere single run, >> instead of being the double run it is? My head can't wrap around this one >> enough to picture the results of looping the chain versus a single line of >> chain. (That question makes sense to me, buddy.) >> >> 3. Is there a formula to convert linear axle movement to vertical chain >> deflection? That is: if I measure 1 3/4? of chain sag from the horizontal, >> then pull the axle back so that the chain is now horizontal (I know that >> this term is inexact), is there a formula that will tell me how much the >> axle will move laterally? >> >> (For Steve P.: Steve: it's *great* fun filing away energetically with >> crude hand tools at a $3,500 custom frame!) >> >> Patrick Moore, who would be at a total loss if he hadn't such trivial >> esoterica to fret about, in Burque, NM. >> -- >> *RESUMES THAT GET YOU NOTICED!* >> Certified Resume Writer >> http://resumespecialties.com/index.html >> [email protected] >> http://www.linkedin.com/in/patrickmooreresumespec/ >> >> Albuquerque, NM >> >> -- >> You received this message because you are subscribed to the Google Groups >> "RBW Owners Bunch" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at http://groups.google.com/group/rbw-owners-bunch. >> For more options, visit https://groups.google.com/groups/opt_out. >> > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/rbw-owners-bunch. > For more options, visit https://groups.google.com/groups/opt_out. > -- *FOR A RESUME THAT GETS YOU AN INTERVIEW, CONTACT:* http://resumespecialties.com/index.html [email protected] http://www.linkedin.com/in/patrickmooreresumespec/ Certified Resume Writer Albuquerque, NM -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. 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