I've been bevelling my test peice and will do that with the chassis.. I didnt think to pre-heat the chassis prior to the root pass.. but playing around tonight I think I've finally managed to dial my welder in for the uphill run. Yes I flap disked the inside of the chassis rail prior to pulling the two sections together.My .02 would be to “v” that seam and run a nice root pass with a pre-heat. Not sure if you cleaned the inside perimeters of the seams with an abrasive wheel, but that would help eliminate pulling contaminates into the weld.
Understood and I agree. I had queried the weld through holes with my engineer but am yet to receive a response. seems best to avoid it without his professional advice.After that, I would go with the fishplate design you made, with a couple exceptions. Put the weld-through holes on either side of the seam by a couple inches (several centimeters). That way there’s ample support on either side and the full meat of the plate covering the seam.
I had not intended welding the vertical edges of the fish plate but rounding the ends of the fish plate will mean I can weld the entire way around..And if possible, angle or round the ends to avoid 90 degree vertical welds.
I don't have any acetone so I'll try and source some (I'm sure the wife wont appreciate me putting a dent in her stash).I would also suggest scrubbing the seam with acetone before and after sanding the paint off prior to welding.
I had tried to weld over the weld through primer and struggled to get a good ground so I'll spend more time removing all the paint when welding the chassis.. I did think to prime and paint under the fish plate and keep the weld area bare metal but weld through primer seems to be a safer long term solution.as well as all around the perimeter (twice in one post) of where the fishplates will be welded. If you use any kind of weld-through primers (I’m sure you’re familiar with what you use) sand it back at least a 1/2” from the edge. I found some stuff recently that works way better than advertised weld-through primers, but if you’re not planning on using anything, that’s probably fine too