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Class 782 Cylinder Details

Posted: Thu Apr 04, 2019 12:19 am
by JimG
I'm in the process of drawing up the cylinder block for a 1:32 scale Class 782. I'm using the drawing of the Drummond block in Fig.24 in the Jumbo book. I was about to draw up all the jointing flannges and bolts on the underside when I noticed what looks like a thin sheet covering the underside of the cylinder. Could I confirm that this is the case?

I'm actually experimenting with using 3D prints for the frame spacers with nickel silver for the frames. I normally use split axle insulation so resin spacers will certainly suit that method.

Jim.

Re: Class 782 Cylinder Details

Posted: Thu Apr 04, 2019 4:55 pm
by Alan K
Hi Jim
I assume you mean the line on the front elevation at the top right of Fig 24 (which shows two cross sections)? But is that not just the outline of the casting at some point on its length? The bottom lines up with the base of the casting shown on the side elevation on the top left. The only photo which shows any detail underneath that I can find is Plate 20 which shows the drain cocks and the curvature of the cylinder casting. But the part of the casting which corresponds to the 'line' needn't necessarily be at the front and so wouldn't be seen there.
When I did Technical Drawing at school we were always told to mark where the sections were taken, but all the CR drawings that I've seen never show that. Maybe they thought it was self-evident - or maybe it was another way for the drawing office to keep information exclusive!

Alan

Re: Class 782 Cylinder Details

Posted: Thu Apr 04, 2019 7:06 pm
by JimG
Alan,

Yes, that's the line - or more accurately - the pair of lines. It was only after working with that drawing for a while and assuming that the bottom of the cylinder castings was open, that I noted the double lines which were shown in a similar way to those denoting the metal covers for the cylinder ends. I then started thinking that if they covered the cylinder ends, presumably to prevent rust and muck on the nuts and studs, then the same could apply to the underside of the cylinders with all the nuts and bolts there. I thought there might be an inspection pit picture in the 828 book to see what the situation is on that locomotive but I can't find the book at the moment, and a trawl around the Internet hasn't brought up any suitable pictures.

the lack of section information is notable on these Caledonian drawings - maybe you were just supposed to "use yer heid". :D I reckon the left section on the top right drawing is close to the cylinder ends with no exhaust channel, and the right section is through the centre with the exhaust channel.

Jim G.

Re: Class 782 Cylinder Details

Posted: Thu Apr 04, 2019 8:16 pm
by Alan K
Jim

The left-hand section (Fig 24) shows the 'cover' pierced by a drain cock, and both drain cocks for the left cylinder in plate 20 are visible and I can't see anything resembling a cover plate there.
Conversely, have a look at p 158 - specification for cylinders says 'cylinders to be lagged with wood then covered with sheet iron'. Is that a reference to your cover? Not sure where the wood goes though!


Alan