Sunday, January 27, 2008

preskit matt's bike in progress / what's up with seattube sleeves??

well, got a great start on matt's bike yesterday. i got the design drawn and, all the small parts fab'ed up and polihed and shiny, and inspected all the tubing for blemishes and measured the butting profiles and checked for bowing in the tubes. it's gonna be a 29er onespeed built around a rockshox reba. now, matt's not a small boy.......and the tubing choice reflects that. it's a custom blend {like all my bikes} but almost every tube comes from a different manufactuer to achive the ride quality i'm looking for. the headtube is cut from a chunk of 37mm O.D. true temper, then faced and chased to square the ends and insure that it sits straight in the jig. the bottom bracket and stainless steel slider dropouts are from paragon machine works. the toptube is 1.25" x .035 4130 custom bent for me by curtis inglis at retrotec. the seattube is a 1.25" heavymettle made by reynolds in england and designed and sold by kirk pacenti. the s-bend chainstays are dedacciai, from italy. i'm going to handbend the seatstays out of 5/8" x .035 4130. finally, the down tube is true temper verus heattreat 1.5" x .9/.6/.9. good stuff! sooooooo...... i said over at mtbr that i'd cover seattube sleeves. they reinforce the seattube against the bending forces exerted by the rider's weight "flagpoling" the seattube. if no sleeve is used, the distortion created by the joining methods must be reamed out, weakening it and opening the way to a possible future frame failure. i could probally get away without one, lots of builders do, but i like the extra insurance, and, i think they look cool! so, in order of pics: first, i'm coping the end of a 4' stick of cromoly to make the "fishmouth." then, i cut it to length, deburr it, and smooth the edges so they are not deathly sharp {bad}. in the picture with the ping marks i have marked the hole for the seattube slot, the top of the toptube, and the toptube vent hole. next, all fluxed up and ready to go! the flux tells you what temperature the metal is at, and facilitates the flowing of the metal into the tiny gaps in betwen the two pieces. i have also drilled the vent hole partway to let gasses escape, otherwise the heated gasses will spew the heated metal back at you as you braze {bad}. next, the flux has been soaked off in hot water and wire brushed, giving you a view of the completed silver braze. and finally, the completed seattube assembly complete with seattube sleeve, slot, venthole, waterbottle bosses, and bottombracket miter. ready to go into the jig. sweet! steve.

1 comment:

Anonymous said...

Wow, plenty of work goes in to your builds! The owner of this one is sure to be a happy camper.

Preksit Matt