SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.


UBI Framebuilding Class - Day 2

5/12/2015 - Day 2

Fillet Brazing Demo

Dropout slot practice

Dropout Practice

Dropout Practice
  • Fillet Brazing Demo
    • Deburr & clean joint
    • A Feedback workstand is especially good for brazing because the clamp allows you to adjust the tension loosely and rotate the work around for 360° access
    • Heat warps tubes -- especially at the end of a tube
    • Position joint 15-20mm from the end of a tube
    • Scotchbrite the brass filler rod to clean it
    • Tack on obtuse angle at the centerline
    • Tinning seals up the seam
    • Heat the steel to just barely orange
    • Leverage gravity to get the brass to move where you want it to
  • Second Lug Practice
  • How to read vernier calipers
  • Dropout Connections
    • Types
      • Socket & Plug-style dropouts limit which seat- or chain-stay tubes you can use, since the diameters must match
      • Tab-style dropouts are much more flexible -- nearly any tube diameter can work
    • Demo
      • Deburr inside of tube
      • Tab for dropout should be 6-8mm deep
      • Measure the ID of the tube (11mm)
      • Measure width of dropout tab (14mm)
      • 14mm - 11mm = 3mm / 2 = 1.5mm needs to be removed from each side of the tab to fit inside the tube
      • Scribe with caliper to show width of tab
      • Scribe depth on tab with caliper
      • Measure thickness of tab metal and scribe onto tube (5mm)
      • Use hacksaw to cut slot in tube; cut to inside of your scribe marks
      • Break chunks out with needle-nose pliers
      • Use warding file to clean up the slot
      • Clean up and align tab to slot
      • Clean out inside of tube with emery cloth wrapped around a round file
      • Cut tab to fit with hacksaw
      • Use large file to adjust tab fit; round the sides to mate with the tube ID
      • Clean tab with emery cloth
      • Clamp practice joint in vise, with tab pointing up
    • Brazing
      • Use brass flux and filler
      • Use a full stick of brass for this practice -- half a stick per dropout joint
      • Heat the tab mainly, then "brush" the torch downward onto the tube
      • Tack at the corners to prevent/protect from overheating
      • Seal the joint by flowing brass between the corners and around the outside edges of the tab
      • Move torch around to heat tab evenly
      • Fill up the gap on sides of tab to create a brass plug -- watch for shrinking as brass cools and solidifies
      • Add a nice fillet at the top to cap the joint
  • Bike Design
    • Measurements of rider
      • Inseam (865mm)
      • Torso Length (590mm)
      • Arm Length - From crease at wrist to shoulder joint (585mm)
    • Frame Design Parameters
      • ERD
      • Tires
      • Wheel diameter / Tire Radius
      • BB Drop
      • Seat Tube Angle (STA)
      • Seat Tube Length (STL)
      • Top Tube Length (TTL)
      • Head Tube Angle (HTA)
      • Fork Offset
      • Trail
      • Chainstay Length
      • Front Tire Clearance
      • Bridge/Crown brake reach
      • Lower Headset Stack Height (default value is 13mm)
      • Fork Height (axle to crown)
    • Homework
      • Frame dimensions & angles worksheet
      • Fork design & headset dimensions worksheet
      • Wheel & Tire dimensions


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