LP Valve Chest: Part 3c

  1. Cover Studs: Colin Sims (another SBA Leak builder) reminded me of this one – The LP Valve Chest Cover is attached to the Chest by 12 studs; and the chest is attached to the cylinder by 8 (EIGHT)…. the two at the top and bottom cannot be attached as the studs clash with the ports. So as I wrote at the time “It may be that my Technical Drawing A-level from the ’70s was to a different standard but only 8 of the 12 holes for the valve chest cover mounting holes should be drilled through. The 8 down each side do carry through to the block, but the 4 at the top and the bottom, should be blind – as they “clash” with the port pockets.“…. Moreover this also means that the stepped studs shown in the drawings should only be used on the sides (the top and bottom are plain studs as the larger ones would (do) clash with the stuffing box and tail rod)… Lastly in the BOOK (at least) only the four right hand holes are shown threaded – in fact the left hand ones need to be too (to take the aforementioned stepped-studs).
  2. The Lap: The ports as shown in the BOOK, have an undimensioned dimension indicating where the “LAP” is/can be measured? There is no indication of what this should be…but see below….Update: I found the lap and lead dimensions at the end of the Book in the valve setting section, Lap is given as 3/16″ and the Lead as 1/32″, but still not sure of the implications of the LP port height issue noted below.
  3. The Port Height: This is dimensioned in two places as two different sizes! I have only just realised this. I noted that the ports on my valve chest were 3/8″ high, and that this did not match the 5/16″ dimension shown on page 10 (of the BOOK) I thought this was just a blunder on my part. But tonight as I am writing this page, I realised I cut them this size because they are shown as 3/8″ high (on page 7 of the BOOK). Lord knows which is right, perhaps they are meant to be tapered! This will mess with the LAP, I guess I am going to find out when I time and steam the engine!
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