Today (10-4) welding started in earnest. First step was tacking the main rail and the sub rail carefully from both sides. We marked the intended welds, staggered on both sides with some gaps and the tacked the two pieces carefully to keep them straight. Not paying attention to evenly spread the welds, and not too close in the beginning, might result in a banana shape. It is quite amazing when you see how this big beam can bend by just misplacing a couple of welds.
The main rail is 9″ high with a long section behind the suspension of 12 inches. The lower beam runs all the way out as the supports for the bumper bar. The 12 inches are also strong enough to support the deck without much deflection.
The image below shows the beam partially tacked. We finished one side completely with around 90 welds and tomorrow we will do the other rail. Next week we will put the frame together for the lower chassis. We have decided to do the lower chassis and the neck separately. We can finish the lower chassis with wheels and everything and the put the neck on, which will be manufactured separately. Both components separately are easier to handle.
I made some thermal images to see how far the heat of a full weld spreads into the upper parts of the big beams, which can cause problems. I mean I have seen people in the industry weld across the top of the main beam every 50cm and honestly believing that there is nothing wrong with it, and it was aluminium and not steel.
The image above shows how the heat spreads along the joint of the two beams where the material is thickest and less air around. This is where the heat spreads most and quickest. Above temperatures are harmless to the consistency of the aluminium.
Above is the image a of a full weld, around 70mm long, immediately after stopping. The image below shows the same section a minute after the weld was finished. The material cools down very quickly and that is due to the thick and long beams, which spread the heat well and the cooler weather. To the right of the image is the top side of the rail and at no point it got hot in any way.
This is the important bit to retain maximum strength of the structural aluminium. The spread of the the heat is quite local and this is due to the MIG welding process instead of TIG welding, which would be much hotter especially with this thickness of the material.
I will take a couple of pictures of the completed beams when we have finished the second one tomorrow.