2) Frame Manufacture

Question 1

What are the 2 stages of Metallic frame manufacture?

Answer 1

2 stages - Tube manufacture and Joining of tubes

Question 2

What are the 2 types of tube manufacture?

Answer 2

Welded and seamless

Seamless is better.

Question 3

Describe the hot and cold working stages of seamless tube manufacture.

Answer 3

Hot working:
- Initial formation of shape

• Above recrystalisation temp
• Wall thickness to near final requirement

Cold working:
- Below recyrstalisation temp
- Final dimensions and finish
- Hardened but more brittle.

Question 4

What are the 4 heat treatment methods for seamless tube manufacture?

Answer 4

• Annealing (above recrystallisation temp, slow cool, softens material)
• Quenching (above recrystallisation temp, quick cool, hardens material)
• Tempering (below recrystallisation temp, reduce internal stress, used after quenching)
• Age/precipitation hardening (increase hardening over period of time after quenching)

Question 5

At what stage of manufacture would heat treatment occur?

Answer 5

After hot working, before and after cold working

Question 6

What are the two joining techniques used for bicycle manufacture?

Answer 6

Brazing and Welding.

Question 7

What are the key differences between brazing and welding?

Answer 7

Brazing melts a filler material to join tubes together, the tubes themselves are not melted.

Welding melts the filler material AND the tubes aswell.

Welding is stronger than brazing however requires more heat - more expensive.

Question 8

What is a method of making brazing cheaper? (lower skill and equipment cost)

Answer 8

Lugged brazing.

Question 9

Describe butted tubing.

Answer 9

The inner profile of tube is modified. (thicker at ends, thin in middle, reduces frame weight)

Question 10

What are the challenges of welding, and how are they mitigated?

Answer 10

• Contamination by oxidisation - use shield gas.
• The heat at joints can affect material structure - post heat treatment of entire frame

Question 11

What method may be used to improve the aero dynamics of a metal frame?

Answer 11

Hydroforming (tube placed in a die with high pressure fluid pumped through the inside of tube.

Question 12

Describe the components of carbon fibre.

Answer 12

Matrix - polymer

Reinforcement - carbon fibre

Question 13

What type of carbon fibre are bike frames made up of, and how is it created?

Answer 13

Carbon fibre sheets, woven from individual carbon fibres

Question 14

Describe the process of manufacturing a carbon fibre frame.

Answer 14

1. Carbon fibre sheets laid in heated moulds with internal inflatable bladders to support inside of frame.
2. Frame removed from mould and baked in oven to cure the resin - hardens frame, removes moisture.
3. Preformers removed, painted, seat stay and chain stay bonded on separately.