I am at the testing stage with the chassis construction. I have access to bending and laser-cutting and TIG welding equipment at work, so I shall take full advantage of that, especially as I can use all of those myself. The chassis rails are about 1200mm long and I want to weld up box sections, the outside folded around and a strip welded down the centre with lightening holes along the length. Since welding considerably distorts long sections, I am starting with a box-section of around 60mm x 40mm, 1.5mm thick. The actual measurements are a little different due to limitations when bending on our machine (size of Matriz and safety margin), so I have to change the bends for the next test!
Anyhow, this is generally how I originally intended t0 go on: WRONG!
After aligning and welding freehand the full length on both sides, some evidence of incorrect welding settings are visible here. Too much heat for a start at some points, which I could have avoided – but that is what a test is for! Material is stainless, by the way. I should have only welded in the solid areas, avoiding the thinner areas around the holes. That would have helped with minimising bending inwards and only affect the strength very little. As a result, the thinner areas are burned out and look ugly.
Look at the amount of bend on this short length (380mm). The chassis members will be four times as long, making the distortion 16mm from straight. I could, of course weld two strips the length of the other side to equalise the shrinkage, but that would not satisfy my idea of æsthetics for the job. That is not what I’m aiming at!
What a mess!
The plan now is to bend up two square C-Sections and weld them top and bottom the whole length, which will also avoid welding close to thin sections next to the holes. That should remove the bending problem and give a reasonable rigidity (despite the lightening holes on the INSIDE) and ‘look’ to the whole thing. The chassis will be powder coated gloss black, I think, so it really won’t matter that much as for a good length of the chassis, it is covered by the bodywork anyway.
And, of course, I will be using a decent steel instead of bendy stainless!