TLC (in model engineering terms this means – take light cuts)
Now there should be a batch of photographs showing some detail work on the motion plate (milling slide bar lugs), soldering the base of the cylinder into position, etc. ( following my experience I urge you NOT to solder and go for a good snug press fit bonded with a thin covering of Loctite). Anyway as a result of a flat battery camera I didn’t get any pics but it was all relatively straightforward so you should have few problems (yes I know, famous last words !).
Today, with my battery recharged, my attention turned to making the eccentric strap. A tricky piece of machining on both the mill and the lathe. The secret, like most model engineering activities, is take your time and take light cuts – oh and measure a lot, then measure again.
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- A length of 1″ brass bar provided the material for the eccentric strap and was marked up.
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- A start was made in rough cutting the strap to shape in the mill not quite up to the scribed lines.
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- The eccentric strap for Opus Proximum takes shape after removal of surplus material on the mill.
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- Holes are drilled for the straps fixing bolts. Drill thro with tapping size drill (1.6mm in my case)
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- Now that the holes have been drilled the strap is separated into two using a slitting saw for a controlled cut.
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- Bolt holes are tapped 2mm in the lower section and clearance holes opened up in the top piece.
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- The strap is mounted in the 4 jaw chuck for boring. Note pencil circle scribed on workpiece as guide to centre.
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- After progressively opening up the hole with increasingly larger drill bits the boring bar is employed for the final sizing.
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- The strap fresh from the lathe ready for the drilling and tapping required to take the threaded valve rod.
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- The strap now completed was given a quick tidy up with a needle file then a shine on the polisher.
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- The eccentric was turned from stainless steel using the parting tool to form the groove for the eccentric strap.
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- The turned eccentric still attached to backing piece was transferred to the milling machine to drill the offset hole for the crankshaft.
