I'm joining this thread a bit late (I only just discovered it) but thought interested parties may like to know I have been building a 70' Railmotor to Dia R for my P4 model of Tettenhall station on the Oxley - Kingswinford branch (Wombourn line). Railmotors worked on the line during the brief period of passenger operation (1925 - 1932). Published records and other evidence show that Nos 93, 95 and 99 worked the line and were based at Stourbridge shed. Therefore a 70' railmotor is the signature train for this line.
The motivation for the model was that the real Tettenhall Station was at the bottom of my parent's garden. My father (railway enthusiast and local author the late Geoff Bannister) made a comprehensive photographic and cine film record of the line in the 1950s which has been the main inspiration. I have also obtained many of the official GWR plans for the buildings and civil engineering works from the National Archive. Baseboards for the station area are complete and track for this part now constructed as separate components on the workbench. Track laying and wiring is now work in progress and I hope to have this complete by the end of the year. I will post some photos of layout progress and further historical details in due course. It is 19 feet long so far and will extend another 10 feet or so to show the lineside south of the station, which will include a fine Warren Truss girder bridge over the Staffordshire and Worcestershire canal.
I will post some photos of progress of the railmotor as well when I can find a moment to get my camera out. So far I have built the main body work and non-powered bogie. The latter is a good representation of the 9' American GWR bogie but is supplied as a rigid item. I have built it as such but will probably alter it to a sprung type using Masokits components. The under frame is now complete except for the truss rods and water tank and I still have to tackle those external steps...... but at least David's comments are quite helpful and give a good insight into the challenges which await me. No particular issues have been experienced so far with the body, although the body shell itself was supplied already folded but without the tumblehome on the body sides formed. I decided it would be easier to return it to the flat for form these (done by the brass rod and computer mouse mat method). There is no interior detail supplied in the kit other than the partitions, but having made a David Geen Dia L auto trailer, there are many bits he can supply to complete the interior. However the "walkover" seats used in the real ones may require some further thought.
Not having any experience of building outside valve gear and recognising the considerable work needed to make the power bogie a runner in P4, I decided to subcontract the construction of the power bogie to my friend (and professional model maker) John James. He made many modifications to the original Blacksmith design which include making it split frame / split axle (his normal standard). The bogie is compensated on the front axle using High Level horn blocks and a horizontal pin which the upper face of the axle rotates up and down against. It is powered by a Portescap 1219 motor and runs very smoothly.
Andrew Bannister, Aberdeenshire