Saturday 29 January 2011

I can see clearly...

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.


  1. That looks a good practical demo. I like the last comment ".....a useful way of checking the reliability of my own track by watching the suspension work as the wagon is pushed along it." I think I'd send a good few moments just enjoying watching the suspension units operate, especially on my track.

    What about the weight of the wagon, does that not affect the sprung units operation?

  2. More on the track reliability in future posts. I had a little gadget turn up from Mr Masokits a few days ago and I must get around to putting it together...

    To answer your very legitimate question, yes, the weight of the wagon does affect the springing. All of these are substantially lighter than my usual standard of 25g per axle.

    Originally I tried the wire supplied in the Bill Bedford kit, and it seemed too rigid. So it was this morning that I swapped it out, easily done in a couple of minutes per axle, for some 11 gauge guitar string. This is the lightest that I have, and it seems much more responsive. No criticism intended of the stuff originally in the kit, as I'm sure that it is the best choice for normally weighted stock.