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

On to Day 9