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 Chromoly	Cold 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

http://robotics.ee.uwa.edu.au/theses/2011-REV-SAE-SpaceFrame-Waterman.pdf

Relevant Youtube Videos