I picked up a nice chunk of 5083 ali about 2" x 2-1/2" x 8" and spent what felt like 2 hours hand hacksawing a lump off it. Then I squared it up on the mill and faced it to just oversize, to allow for my any errors I was sure to make
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I used my boring head on the mill to bore it, but it turns out I don't have a long enough cutter to bore as deep as I needed to, so I had to come in from both sides. I was concerned about doing that but it worked for me this time. Once I had the bore and both end steps machined, I hogged out most of the pocket with drills, then milled the pocket to shape. After that I cheated and used transfer punches to mark, drill and tap the bolt circle from the head to the hopper. It was at this point that I discovered the off centre counterbore on the head :fan:. Once I'd finished my tantrum, jammed most of my hair back into my scalp and had a good think about the problem, I came to the conclusion that I may still be able to use the head as-is, but I won't be blending the water hopper to suit, in case I have to make another head in the future. I MAY make another head anyway, even if this one does work, but not just yet.
Another slog with the dreaded hacksaw yielded a blank for the hopper lid and a square blank for the rear water hopper retainer. The lid was a fairly straightforward piece of machining (once I worked out how to hold the piece at the correct angle) and I got that done quickly. The square blank for the retainer I drilled and mounted on a mandrel in the lathe. I'm used to interrupted cuts from my experiments with a wood lathe years ago and it was an easy job to turn it round. Then it was on to the mill to open out the bore. Again I used transfer punches to mark the bolt circle and finish the retainer by drilling and countersinking the bolt circle. Then I drilled and tapped the hopper (transfer punches again) and everything bolts together nicely.
Turning back to the cylinder head, I drilled the ports and drilled and tapped the mountings for the carby and exhaust. The only thing left to do on it is the 3 holes for the rocker arm mount to bolt to. as you are no doubt aware by now, I need to use transfer punches wherever possible to have a hope of bolt holes matching up, so I needed the rocker arm mount at this point.
I needed a piece of mild steel 5/16" x 3/4" x 1-3/4" and I came up with a length of keysteel that was big enough. It was 1/2" thick but I milled it down to size. What I first thought was a simple little bracket turned out to have a 17 degree angle through half of it and really tested both my drawing reading ability and my machining capabilities. Don't get me wrong, the design and drawing are perfect, I just haven't had much experience with such technical items. Possibly the best part of this project so far has been how much I'm learning and extending my abilities.
Anyway, I spent a good chunk of today (fathers day here in Australia) out in my shed carefully extracting a complex rocker arm mount out of a lump of old keysteel. Happily, it turned out well, although maybe slightly different to the plan.
Next up I have to fit the rocker mount to the head, then it'll be onto either the push rod guide or the sides and base. Included in the photos below is the piston complete with cast iron rings, and the only half of the conrod that I want you to see
. Fingers crossed my next update won't take as long as this one has. Thanks for looking!
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