May I ask you how you made the "tray" with the three holes for the air filter element
Yes - guess the photos don't show the actual process. Doh!!!
In the photos you can see that I cut the blank out of aluminium sheet with a 20mm perimeter, and clamped it between 2 medium density fibre (19mm MDF) board former patterns. Probably should have annealed the corners first to make the forming easier, but you live and learn!!
Then I clamped the formers and sheet in my 8" vice and used a nylon hammer to start beating the perimeter over onto the former. Moving the part in the vice as needed. The straight sides form easily and can be done without annealing. In the corners there is an excess of material that needs to thicken up and grow out if the corners are going to be smooth. The MDF is a bit too soft to really bash out the corner. So I removed the ally tray from the formers - annealed the corners with a propane torch - and then used some solid 63mm steal round as a former in the vice and a steal hammer to finish the corners.
When the flange is fully formed the flange edge is far from flat due to the corners growing, so I clamped it onto the mill table and cleaned it up to a flat surface.
Final process was to cut the 60mm holes for the carbi inlets. The 3 holes used to clamp the MDF formers together, were at the correct spacing so those holes were used to guide the hole saw in the mill.
All in, including making the former patterns there was about 2hrs work in making the tray and probably 5 hrs for the whole air cleaner as you see it.
The MDF former pattern is pretty much stuffed now, with a steal former pattern it would be much easier and quicker to form the aluminium, but much more work to make the patterns.
Definitely no welds.
Cheers
Tim