The material I used for the rocker pivots was purchased from McMaster-Carr. I chose some 3/32″ precision ground 316 stainless shafting, P/N 1263K37, that was 0.0002″ undersize. Two 36″ pieces should be enough to make the pivot pins and all of the pushrods.
I had some 10mm diameter 416 Stainless heat treated to HRC35 left over from a previous job. Even though most of the time was spent converting it from round to square, overall it was not very hard. However, don’t underestimate the added complexity such small parts can add to fixturing.
One of the biggest problems with trying to do something like the Hodgson Radial here in China is finding quality materials. I’ve been lucky with my aluminum products since there is a big Alcoa plant in Kunshan not far from where I live that supplies materials for both the China and worldwide aerospace market. Unfortunately I’ve not been as lucky finding a supplier of quality ferrous materials, and the purported 12L14 material I procured for my cylinders is a case in point. While I was assured this material was “equivalent” to 12L14, it was very gummy to machine and did not act at all like a free-machining leaded steel.
The valve spring cups began life as a length of 10mm 416 stainless steel heat treated to HRC32-35. These parts get beat on by the valve spring retainer many times a second and I didn’t want any deformation occurring. Besides, heat treated material machines to a beautiful surface finish.
Once again, the problem of obtaining high quality materials here in China made for a little more work in creating the valves. To obtain the necessary material, I used heat-treated stainless bolts sourced from McMaster-Carr in the US as my base material.
Well, it would have been nice if I could have found some soft 1000-series aluminum here in China so I could just turn and part off these rings from some round stock, but that turned out to be impossible. I ended up purchasing some 0.032″ 1100 aluminum sheet. 1100 alloy is essentially pure aluminum and the 12″ x 12″ sheet I ordered from McMaster (p/n 2471T11) was in the “0” (Annealed) condition – perfect for a head gasket.
The Hodgson plans call for the valve seats to be made from Alloy 954 Aluminum Bronze (here in China this is called QAL 9-4 bronze or C63000 nickel aluminum bronze). These valve seats are retained in the head only by a 0.002″ interference press fit. Retention by only a press fit between components subject to heating and cooling cycles between two materials having different coefficients of thermal expansion is a problem waiting to happen in my opinion. I wanted a Continue reading
This page is one of the longest in the Hodgson Radial log and probably reflects that this is one of the most complex parts. I chose Aluminum 7075-T651 for the head material and made a few changes to the process plan and the design of the head – most notably the method of retaining the valve seats. Follow along on this lengthy build log as I start construction of 11 heads.