There - you'll have dire Seventies song lyrics buzzing around in your head for the next week... The reason for it is that I've finished the small project that I've been working on, and that I needed some brass countersunk screws for from Eileen's, which resulted in the spontaneous airbrush purchase at the St Albans exhibition.
As part of the Scalefour Society demonstration stand for exhibitions, we sometimes are asked about the need for suspension on models built to P4 standards. I'm not going to go into the reasons and circumstances why and where it may be necessary here, but there are three main options:
- rigid (i.e. drop-in wheelsets with no further work)
- compensated (the traditional method using a rocking axle)
- sprung (using steel wire to allow the individual axlebox to move up and down)
So I've built three wagon chassis, to illustrate each possibility:
As you'll clearly (sorry!) see, the "body" on which the suspension units are mounted are clear pieces of perspex, cut to the same size as a typical 10-ton wagon. This means that it is easier to see how the units are constructed, and also when used in practice on a demo piece of track.
The one on the left is sprung using Bill Bedford units, the one on the right has a Scalefour Society rocking unit, and the one at the rear is rigid, using Scalefour Society units but folded up to sit on the chassis without movement.
Of course, no matter what suspension method is used, it is critical that the axles are absolutely parallel with each other. That is why it is sitting in a Brassmasters chassis gauge, which sets the final adjustment into alignment at the chosen wheelbase. It's a tool that I certainly would not now be without in building reliably running wagons. It's usable for any 4mm gauge as well - not just P4. The final glueing of the suspension units with a spot of superglue to hold them on place is the reason why it is being used.
So there you have it. Hopefully something that will de-mystify P4 in one more aspect for those that are curious, and also a useful way of checking the reliability of my own track by watching the suspension work as the wagon is pushed along it.