What a frustrating week!

One of the good things about modelling LNER locomotives is the ready availability of reliable information. Who really needs more information than is available from the small grouping of:

RCTS Volumes –“Locomotives of the LNER”;

“Yeadon’s Register of LNER Locomotives”, and

Isinglass Drawings; ?

As far as I’m concerned, if it ain’t in one or other, or all of those, then you don’t need to know!!!!!

This week I’ve found out how very useful it is to have an Isinglass drawings, because they have not yet produced a drawing for the J10 and I’ve been working from one I drew myself a few years ago (2002 I think). For this I extrapolated dimensions from a photocopy of a works ‘pipe and rod’ drawing.

There are bound to be errors because even if the works drawing was correct, and that was not always so, then my photocopy may well have been made from another photo copy (ad lib) and even modern photo copiers are not renound for truly accurate reproduction. So the copy of the works drawing that I possess may well not be a true scale. Therefore any dimensions I have measured on that print may have been wrong on the drawing and I may have not measured accurately for every dimension I needed. Many sources of error with this approach!!!.

You can add a further error source because the print did not include a scale, meaning that I had to work one out using known dimensions like driving wheel diameter and calculating the ratio of the drawing measurement for the wheel against the known measurement.

My preparation for building the J10 started with this drawing and then I progressed to dimensioned sketches of the various parts of what I suppose we can call my ‘kit’. In the last few weeks some of those sketches have been used to mark-out nickel-silver sheet and I’ve fretted out quite a lot of the bits.

Only when I offered the newly rolled boiler-firebox-smoke box unit to the running plate did I begin to suspect an error. I was not certain that things were wrong until I started on making the smoke box saddle.

The intention is that this will be a block of tufnol, fly-cut in the miller to fit the smoke box and then screw-fixed to both smoke box and running plate. The other end – the firebox, will have a similar fixing to the spectacle plate. With every thing set up in the miller I began to suspect that the fly-cut seating for the smoke box was going to end up deeper than the thickness of the tufnol – not possible of course!!!

I have genuinely struggled to find where the error lay; It’s taken most of a week. Today I have proved that it was none of the errors that could have been expected and inferred above. I dropped an almighty clanger with that drawing in 2002. For some reason I drew the front view about 2mm too high. It was not projected from the side view because the A4 sheet would not allow that and some how I carried through the 2mm excess on to the cab. Accordingly my dimensioned sketches from which I mark up the sheet metal were incorrectly dimensioned and the cab parts, -two identical side sheets and the spectacle plate, - were all three, too long.

So I think that next week should see some progress towards some bits of bright nickle-silver beginning to look a bit like a steam locomotive.