A bit of fun -

[silverfox]

Q18

Being a bit of a pedant B12/3 does not count as all were scrapped by 1961 except 61572 which was withdrawn in Sept 61 End of steam on GE was 1962

Now what bit of 'End of steam' do we use please, or am i reading it wrong?

[sturrock]

Good point siverfox, I should have said "towards the end of steam", maybe that would cover it, but as you say ---. Incidentally I missed the rebuilt W1 which was also pressed at 250 psi., although that brings us to the semantics of what is a design and what is a rebuild? The C7/2, B16/3, C9 and later Thompson's B3/3, B2, O1, K1, Pacifics and two cylinder conversions come to mind.
Anyhow, here's my answers Q13 to18 for my sins.
Q13. The J50 (and J51) and the J6 used Ivatt's later standard wheel spacing bringing it to 16ft3in seems to be the shortest, and unsurprisingly the P2 at 37ft11in. is the biggest.
Q14. The U1 Garratt at 56.5 sq.ft. The P2 (again) and the rebuilt W1 were next at 50 sq.ft.
Q15. As silverfox said, the B17. Doncaster failed to get their proposal short enough using Gresley's insistence on drive to the same axle -(what do you call that?) Goodness knows how the NBL drawing staff convinced him on divided drive! Probably practicality?
Q16. As Dave S. pointed out, the short lived Baldwin GNR H1 2-6-0.
Q17. I've done it again! I said six, but I can only think of four!
W1 4-6-2-2 (or if you prefer 4-6-4)
D47 4-4-0
N2 0-6-2T
B17 4-6-0
I had the J50 0-6-0T but forgot the rather obscure J51. Have I missed any?
Q18. I had in mind Robinson's O4, but as Belvoir pointed out they may be others, bearing in mind my modification to the question above!
Regards, Jon. (sturrock)

[Hatfield Shed]

17. Gresley designed and built six classes of locomotives which were the only ones of that wheel configuration.
I couldn't get beyond 5: B17 4-6-0, D49 4-4-0, N2 0-6-2T, U1 2-8-0+0-8-2T, W1 4-6-4.

18. Which constituent’s main line design was used continuously from 1911 to the end of steam?
Thought this one would cause trouble! As worded I believe the answer has to be either the J27 or J36, both very much in service in 1911, and going to have their last class members withdrawn from service in mid 1967, and leave the experts to wrangle over which was the very last. Had the question been 'oldest LNER constituent design lasting into the final year of steam operation', the J36 by some margin.

[sturrock]

Hatfield Shed, -of course - the Garratt - and I forgot about the J51 which cancels out the J50. That made the incorrect six D47 should read D49. my typographical error in Q17.
Agree, poorly worded and thought out Q18. -but it gives people some pleasure in discussing stuff.
Jon.