A7 - Q7 ??

[7mm Mick]

Hi Everyone,

This topic is a little bit of a plea for help really. I'm looking at a O gauge model railway build of the NER Class Y, later A7. I have a GA, pipe and rod and some other detail drawings from the NRM which have been really useful. However I don't have any real detail dimensions around the inside and outside motion.

So the question is does anyone know a source for this information ( the Darlington list at the NRM has been searched already ). I thought maybe the Q7 would have similar components being a three cylinder, designed and built around the same time for a similar task? Can anyone confirm of deny this please. It this was the case it would make my life much easier as I could see/touch and measure the thing?

Any help would be greatly appreciated,

Many thanks Mick

[ArthurK]

Hello Mick

The full GA of the A7 is in the Darlington drawing list which is downloadable from the NRM. The drawing you need is 7702-D which has all the detail shown.

The Q7 is in the OPC list no. 10755. This is again a fully detailed GA.

The cylinder and valve-gear on these two locos is very similar (as is that of the B16) but there are subtle differences. One major difference was the inside slidebars. The Q7 had only one, the B16 two whereas the A7 had four.

Hope that helps

ArthurK

[7mm Mick]

Hi Arthur,

Thanks for responding. I have the drawing you mention already but not a paper copy. It has given the leading dimensions and the layout of the major components, however it doesn't give enough detail dimensions around the outside slide bar and crossheads, the marine big ends and some of the inside motion. I may have to clamber on the Q7 in the near future and obtain what I can and use that information, plus the GA to work something out?

Thanks again

Mick

[Robpulham]

Hi Mick,

Not that I can help at all but would like to ask is this for a personal project or is it likely to hurt my wallet at sometime in the future

[ArthurK]

Mick

Don't bother looking at the Q7 for inside crosshead detail. The inside crosshead of the A7 used four slide bars Whereas the Q7 has only one. The outside crosshead and connecting rods may well be similar.

I have a copy of the A7 drawing at 1/8th scale and use a 1/8th engineers scale to read off the dimensions directly. That is much easier than having a drawing at some bastard scale. The only downside is that the paper drawing is rather large!

ArthurK

[7mm Mick]

I think that may be the way to go in the future Arthur thank you.

Rob, it may well do. Come and have a chat at Reading if you're going

Cheers Mick

[Robpulham]

HI Mick,

Reading is a touch too far for us, we don't even venture to Kettering. Telford is as far as we go and then we make a weekend of it.