Mitering the chainstays for MC#5

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I welded up the front triangle and mitered the chainstays this weekend (note to self: no more 0.55mm at the end top tubes for MTBs…too light/thin).  For chainstays what I’ve learned is to dimple them first (if needed for tire clearance), miter second.  If you dimple after mitering you might end up changing the angle of the miter a little (which DOES happen, trust me…).

After dimpling/crimping at around 14.5″ up the chainstay from the rear axle, I hand-filed with the 10″ half-round file to get fit the dropouts.  I’m using hooded dropouts for this frame and the Paragon hoodys are rad. Solid, clean, simple, just awesome.  The removable aluminum hanger is…well, a good idea I guess, but I’m not one to always carry an extra hanger in my pack.  I think a steel hanger would do just fine.

After filing for the dropouts, I load them up in the Sputnik fixture and do my best not to over-cut the tubes in the mill. I swear, i spend as much (or more?) time setting up the fixture than I could spend just using a hacksaw and filing the damn chainstays to fit the bottom bracket!! But the Sputnik keeps the chainstays perfectly in phase if set up right, and the right length (if set up right), so I really like using it.  But I’m probably not saving much time…yet.

I went a bit lighter on tubing for this frame: I’m using a 28.6mm True Temper OX Platinum top tube, 35mm OX down tube, and S-bend OX chainstays for this frame. The tubing is LIGHT! If you don’t know what OX Platinum is, it’s a special blend of heat-treated steel tubing which makes it have a higher strength than non-heat treated tubing if the butt profile is the same (9/6/9 heat treated is lighter and stronger than non-heat treated tubing).  It is also supposed to be stronger at the weld than ‘normal’ 4130 Cromoly tubing (think Surly tubing).  Great for a great welder but i’ve already had some not-so-perfect welds on a couple of tubes so I may be keeping this one for myself (sorry Heyride!).  I’ll build you another before the CB100 race in September.

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