Chassis - Manufacturing Processes

Owned by Devon Copeland
Last updated: Sept 12, 2018 by Adam Marchand

Table of Contents

Circular Tube vs. Square

  • Round tubing is stiffer in torsion while square provides a stiffer beam 
  • Square tubing is easier to fabricate (no ‘fishmouth’ joints) but the tube distorts under load by ‘lozenging’ or ‘panting’.This adds to compliance and may lead to fatigue cracking.
  • Round tubing is best option, and does not need as much design justification. Harder to manufacture, but will lead to less design and strength issues 
  • May want to consider square tubing for horizontal frame members to simplify suspension mounting points and makes cutting planar joints easier
  • Triangulation/reinforcement in square tubing can greatly improve structural integrity

Design Notes:

  • To improve manufacturability: design chassis to be "self-jigging"
    • Constructed in separate parts which are then joined together

Choosing a Grade of Steel

Summary: Comes down to weight savings vs. cost and manufacturability. Chromoly provides more weight savings, but is more expensive and harder to fabricate 


4130 ChromolyCold Drawn Mild Steel (1018)
Weldability
  • Recommended to use TIG welding or nickel bronze welding (brazing)
  • Requires pre and post weld heat treatment to normalize the structure after any weld, or becomes very prone to fracturing
  • Can be problematic doing small attachments (brackets + other modifications) on the fly since every weld needs to be heat treated afterwards
  • Recommended to be welded professionally
  • Recommended to be TIG or nickel bronze welded, but MIG works as well
  • No heat treatment necessary post-welding
UTS (Ultimate Tensile Strength)
  • 590 MPA
  • 420 MPA
Elastic Modulus
  • Same
  • Same
Positives
  • Can use thinner walled sections in areas due to higher strength
  • Better strength to weight ratio
  • Less likely to be dented; higher structural integrity
  • Less expensive (by 50% approximately)
  • Easier to weld (more options) and no pre or post welding necessary
  • Better to use with a lack of welding experience
Other Teams
  • Principia

ASC Regulations

  • Battery enclosure must be secured to the chassis
  • Array needs to be attached to chassis with braided steel cable 
  • Safety belts need to be attached to chassis 
  • Needs to be designed to accommodate a minimum 5g load from all directions
  • Crush zone attached to the chassis on sides of the driver
  • Variety of other roll cage requirements

Welding Process

Safety Equipment:

  • Fire resistant jacket: 
  • Safety glasses:
  • Welding gloves:
  • Welding helmet (approved):

MIG Welding: 

  • Uses a thin wire as an electrode and filler fed by a wire feeder to the gun. Controlled by a DC power source 
  • Has gas (MIG) or gasses (Flux core) option 
  • Easier process to learn, but requires gas and wire feeder, making it less portable 
  • Cost of MIG welder (small, used) ~$500 

TIG Welding:

  • Very versatile and produces higher quality welds 
  • Uses a torch and tungsten electrode, with argon as a shielding gas 
  • Controlling the torch, wire feeding, movement and having the correct current makes it complicated 
  • Takes a lot of practice to learn properly 
  • Very precise, clean, and little clean-up required after. Grinding or smoothing not required 
  • Cost of TIG welder (small, portable, used) ~$1200 

Heating Treating 

  • Put into a furnace at a predetermined temperature and cooling rate 
  • Pre-heat the metal prior to welding 
  • Bring the welds up to 1100-1650  degrees and cool slowly to eliminate stresses and cracks 

Welding at UW

  • There are courses available at Waterloo and Conestoga if anyone is interested...
  • Anyone with equipment can weld in the welding room
  • Baja may be willing to lend their welder if we get gas for them from grand valley
  • Connor recommends to begin with a cheap MiG welder if we want to get one of our own
  • Grand Valley gives student teams free gas if we can go pick it up ourselves

Learn How to Weld:

  • Youtube
  • Conestoga Courses
  • Waterloo Courses
  • Practise

Important Notes from Other Student Teams


Good Resources

Relevant Youtube Videos