Making Engine Valve Rockers -and Adding a Vice to a Rotary Table

摘要

When deciding on the construction of Internal Combustion engine models and a decision is made to make an overhead valve (OHV) version, sooner or later the time comes to make the rockers. The rockers may be operated by pushrods or direct from the camshaft as in the case of the Sealion engine designed by Edgar T Westbury, (ETW). In my younger days taking apart the full size versions was very usual; in particular the BMC A-Series engine found in the original Mini. Depending on the year of manufacture, the rockers in this engine came in three different forms. First, there were what appeared to be a nice forged rocker, but this was more than likely a cast steel item. The second was a fabricated version which was formed from sheet material and spot welded together. It carried an inserted pad that contacted the valve with a pressed in rocker pivot bush. The last that I came across was a Sintered Metal type used from about 1974 onwards that was altogether chunkier in appearance. The first version was not that dissimilar to those designed by ETW on his 1831 engine, but un-like ETW's, the BMC version had a tappet adjustment screw. The second pressed steel version was very similar to the fabricated versions produced by L C Mason (LCM) on his OHV engines. Those fitted to his diminutive 4-cylinder 4cc engine are a sight to behold. Most of LCM's versions used Silver Steel as the valve contact pad, where he used the curvature of the standard diameter silver steel bar as the valve contact face or pad. This had the added advantage that when he quenched the rocker assembly after the silver soldering operation the silver steel faces were left hard. Whilst the tappet screw bosses were also silver soldered onto the rocker in LCM's designs, this was something I considered to be just too fiddly for me.