If you need some inspiration, there are pictures of a cracking example built by Graham Larrington in the archive here.
gauge | 2 1/2 inch |
length/inches | 24 + 12 |
width/inches | 5 |
height/inches | 9 |
wheel material | cast iron |
axlebox type | plain bearing |
cylinder material | 3 x gunmetal |
valve type | slide |
valve gear | Gresley-Holcroft conjugated |
reverser type | pole |