Chrismas eve 2011

Well, we have reached a bit of a milestone I think – I have managed to erect the main castings (cylinder block, rear columns, base).

In the end I changed the order described in the manual, and mounted the rear columns first. Fitted the lower cylinder covers to the block (to ensure accurate positioning of the bolts, and then mounted the lower covers on the rear columns with a single bolt (as suggested) then remounted the block, spotting through the other mounting holes on to the column tops.

I came to this approach for two reasons:

1 -I did not manage the  machining the “spare bits” off the HP & LP covers accurately enough so there was about a 15thou gap between them. This meant that their angular position in the bores was not “totally” fixed.

2 – when I ran I trial erection, I discovered that very small lateral changes in the location of the block (displacing it along the line of the crank) produced very significant angular displacements of the covers – I am sure the geometry would  show this to be the case. So I concluded that it was better to settle the position of the covers (and their bolt holes) and manage the final alignment of the crank/slideways/cylinders  by control of the crank end-float.

Time will tell if I am right!

Next step is the front columns (a Boxing day job)! I am looking forward to this, although I have considerable concerns that the off-set turning jig to produce the offset footings will not result in a column that correctly matches the base and cylinder bolt holes without considerable “fettling”!

Drawing Errors

I tripped over a couple of problems –

1 – LP steamchest cover mounting bolts. 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 the “clash” with the port pockets.

2 – The bottom (and top) cover mounting bolts. The location of these is not well defined on the drawings,  and care needs to be taken to ensure that they miss the ports in the cylinders (I wound up needing to redrill two on the LP side, as it became clear this was to be a problem.

3 – The bottom cylinder cover-to-column mounting holes. Again the location of these are not well defined on the drawings, and in the end  I wound up re-drilling these to ensure their correct location.

A Whole New Section on Drawing errors…

I have added a section to this site to log all the drawing errors I and others have noted… You are welcome to contribute too! Please see here.

2 thoughts on “Chrismas eve 2011

  1. Nick

    Are you really catching all these problems before youi have drilled through? not possible to get replacements I guess.

    1. sybefur Post author

      Yes I am catching them, but only by going slowly and thinking hard (lessons learnt the hard way) – I can get replacements, but at £2,500 a set I would prefer not to have to buy any!


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