OK, after two weeks holiday and a three-week "welcome home" dose of 'flu its back to work on the Wyvern. I did do a bit of shopping in Tokyo, places like this tool stall in Akihabara are hard to resist:
The other places worth a visit are a chain of stores called "Tokyu Hands", high quality small tools (a very fine file; replacement tips for soft-jaw pliers; packets of carborundum powder; really sharp, but reasonably cheap, taps and dies all came home with me).
Ah, yes, Wyvern - the next bits are the conrod and bearings. The rod could be carved from the solid but I chose to have a go at fabricating it. The shaft was found inside a part of the hoard:
The shallow taper was turned by offsetting the tailstock - the first time I've tried doing this - and this worked well. The little end and flange for the big end were from odds-and-ends. The brain fog induced by the 'flu had two effects firstly I forgot to take pictures and, more importantly I failed to think about how I was going to hold the finished taper shank for the rest of the machining. Starting again was probably the easy way but instead I tried 3D printing a fixture in ABS and the final version looked like:
Each half of the hole up the middle is tapered to match the measured shaft. The first attempt left a gap between the two halves into which the jaws of the four-jaw SCC slipped (that brain fog again) so when I came to use the fixture I had to pack it with metal strips. Here the big end flange is being cleaned up after silver soldering:
and the other end being scalloped before attaching the little end:
The oil hole drilled (should have left this until the bronze bush had been fitted):
then it was time to dig out the GM casting for the big end:
this was milled to length then thickness:
hacksawed in two (there was a lot of spare metal so this wasn't stressful) and milled to thickness:
The halves were fixed together with superglue and the crankpin hole drilled and reamed. If you look too closely at this picture you can see that I didn't even up the milling and the sides won't clean up to circular - still learning about dealing with castings:
More superglue (with screws for safety) stuck the part to a 1/2" mandrel and the sides cleaned up to width:
The new version of the ABS fixture held the shaft to drill and ream the little end for the bush:
and the flange milled to width:
The final use for the fixture was drilling the stud holes in the flange:
Two made-to-measure 4BA studs, plus a bit of polishing, finished off the job:
The 3D printed fixture did what was asked of it but I wouldn't use the method for any task requiring precision. An improvement would be to use a harder material than ABS (e.g. polycarbonate) as I could feel distortion when clamping up. The superglue worked well as an alternative to soft solder for holding the bearing halves together but I did make a point of leaving it overnight to cure fully.
David