SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.


UBI Framebuilding Class - Day 8

5/20/2015 - Day 8




  • Seat/Chainstay Bridges
    • Dimensions needed for mitering on the mill
      • angle
      • miter length at bottom,
      • tubing diameter
    • If caliper brakes: chainstay bridge height = BSD/2 - 6mm (for dummy axle) + 45mm (for brake reach)
    • For canti or disk brakes, position bridges similar to fork-crown clearance (365mm on my frame)
    • If using seat stay bridge reinforcements, subtract 3mm from miter length
    • Use 0.5-inch diameter tubing for seat stay bridge
    • Use 5/8-inch diameter tubing for chain stay bridge
    • Scribe center line to establish locations for any drilled holes
    • Rough cut - measure across bottom of brake bridge, add 1 seatstay diameter to length
    • Seat stay bridge dimensions
      • SS Angle: 11° or 5.5° bisected
      • Miter length along bottom: 65mm - 3mm (for reinforcements) = 62mm
      • SS Diameter: 16mm
      • Rough cut length: 62 + 16 = 78mm
    • Chain stay bridge dimensions
      • CS Angle: 19° or 9.5° bisected
      • Miter length along bottom: 45mm
      • CS Diameter: oval chainstays? - 30.7mm  (Dan uses 35mm? hole saw for oval stays)
      • Rough cut length: 46 + 16mm = 61mm
  • Water bottle bosses
    • Drilling bottle cage bosses
      • Two different jigs available
      • Use angle drill and 0.25-inch bit
      • CAUTION: Go easy -- don't punch through the other side of the frame tube!
      • Cage position: ~150mm up from BB shell for both ST and DT cages
      • Scribe a centerline on tubes -- use this to align drill holes and any reinforcement stars
    • Brazing bosses
      • Use silver filler
      • Heat the tube until the flux goes clear
      • Brush flame gently onto boss
      • Watch for stopped bubbling
      • Add silver filler
  • Frame Braze Ons
    • Decide which you need
      • Brake type -- rear cable
      • Rear derailleur cable stop
      • Downtube shifter bosses or cable stops
      • Dyno light wire guides
      • Cantilever brake bosses
    • BB Cable Guide
    • Use special braze-on clamps to fixture braze-ons to frame
  • Canti Brake Studs
    • Use Anvil jig
      • Set to 265mm for 650B
      • 75-85mm stud spread
      • Braze with silver filler


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