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Tube-To-Tube-Bicycle-Framebuilding

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					  Tube-To-Tube Bicycle
Framebuilding Technique
               Agenda
• Tube to Tube Carbon • Joining Process
• Advanced Composites • Vacuum Bagging
  intro               • Braze ons
• Laminate Theory     • Finishing
• Design Validation   • Repairs
• Cutting/Machining   • Misc Q&A
• Bonding
Definition of Tube-To-Tube

• Based on standard frame building
    technique
•   Prefabricated individual frame tubes,
    mitered
•   Tacked in fixture
•   Fully joined with additional carbon
    wrapping
      Advanced Composites Intro
               Matrix
• Matrix                    • Forms continuous
    – Epoxy                     phase
•   Thermoset               •   Exceeds polyester
•   Binding                     –   Adhesion
•   Shape and structure         –   Shear
                                –   Fatigue
•   Cross linking present
                                –   Strength
•   Load transference           –   Stiffness
 Advanced Composites Intro cont.
          Carbon Fiber
• Types                       • Fiber properties
  – Rayon                       – Tensile strength
  – Polyacrylonitrile (PAN)     – Modulus
  – Pitch                       – Elongation at break
• PAN most common             • Forms
• Processed                     – Tow
  –   Into filaments, tow       – Uni
  –   Under tension             – PW, Twill and HS
  –   Up to 6000f                 weave
                                – Braid, 3D
Advanced Composites Intro cont.
       Fiber properties
   Fiber          Tensile        Modulus Msi   Elongation%
                  strength ksi
   Standard           600            33            1.6
   modulus
   Intermediate       880            42            2.1
   modulus
   High               550            55            1.0
   modulus
   Ultra high         500            64            .5
   modulus
Advanced Composites Intro cont.
     Common Fiber forms


     3k PW 5.7oz   3k twill 5.7oz
     .010”         .010”




                   Uni 150gsm .006”


   6k 5HS 10.9oz   Uni 300gsm .010”
   .016”
 Advanced Composites Intro cont.
           Composite
• Prepreg Carbon Fiber       • Wet resin
  – Carbon pre-                – Manual mix 2k resin
    impregnated with           – Manual wet-out of
    epoxy                        fibers
  – Suspended in low           – Room temp to
    temps                        elevated temp cure
  – Cures in elevated          – forgiving
    temps
  – Specific cure profiles
            Laminate Theory

• Metals
  – Isotropic, equal strength in all directions
• Fibers
  – Anisotropic, strength in axial direction
  – Quasi-isotropic through multi orientations
  – More strength/stiffness where needed
          Laminate Theory cont.
         Tube To Tube Design Considerations


• Tube walls .040”-        • Wrap material
    .065”+                    –   Cured ply thickness
•   Characteristics           –   Form characteristic
    –   Bending               –   Aesthetics
    –   Torsion               –   process
    –   Hoop
Design validation
           Cutting/Machining
           Cured composites
• Carbon/epoxy considered abrasive
• Abrade don’t cut
• Mitering
  – Diamond or Carbide grit hole saws
     • 1000rpm +
  – Abrasive belt, spindle 80grit
• Drill with diamond plated bits or points
                    Bonding

• Considerations          • Bonding
  – Secondary bonding       –   Acetone/MEK
  – Similar/ dissimilar     –   Abrade
    materials               –   Acetone/MEK
  – Galvanic corrosion      –   Wet both
• Thixotropic 2 part        –   Twist together
  toughened structural
  epoxy
          Joining Process

        Wet              Prepreg
• Vacuum bagging   • Vaccum bagging
• Winding          • Trapped rubber
• Wet layup
     Vacuum Bagging Theory

• Uses Atmospheric pressure to clamp
  laminates
• Vacuum in an airtight envelope
• Clamping method
  – Theoretically even pressure
• 29Hg theoretical 14.5 psi on the laminate
    Vacuum Bagging Schematic
                                        To vacuum Pump
                    Gauge
   Vacuum bag
                        Through bag

Sealant




                                                    Tool
             Perf Release
  Breather                  Peel Ply   Laminate
Vacuum Bagging Caveats
• Leaks
• Bridging
  – Pleats, low mod, high elong bag,
    cauls
• Blow through
  – Joints sealed
• Alignment
  – Service temp, fixture
             Braze ons
• Cable stops
  – Riveted
     • Rivet grip depth, pull strength
• Bottle bosses
  – Nutsert
     • Bonded
• Make your own in carbon
                    Finishing
•   Deflash, sand
•   Fill
•   Clearcoat
    – 400g, soap and water
    – Adhesion promoter
    – UV acrylic polyU, build and sand, topcoat
• Paint
    – 400g, soap and water
    – Adhesion promoter
    – Hi build primer, sealer, base and topcoat
              Repairs

• Identification of damage
  – Tap, squeeze, understand extent and
    cause
  – Patch or tube replacement
  – Impression patch
  – Scarf joint laminate patch
     • Tapered or stepped
• Follow best practices
Q&A

				
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posted:10/29/2012
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