Monday, 24 December 2007

Sleeper/chair combinations

I bought a sample set of ply sleepers and crossing timbers from Exactoscale recently and thought I'd compare them to the C&L plastic ones I'm already familiar with. Appearance-wise I think the ply sleepers are far superior (despite what I've heard some people say to the contrary - the wood grain may not be perfectly to scale, but then it's sometimes illusion not exact scale that is the key to things looking right in model form). However, in terms of the strength of the bond between sleepers and the C&L platsic chairs, the C&L platsic sleepers are hands down winners. I did a little test with a plastic sleeper, untreated ply sleeper, and a ply sleeper that had been pre-coloured using a wash of thinned Enamel paints, using Butanone to atach two chairs to each. After 12 hours or so I attacked each one with a pair of tweezers, to see how much pressure was needed before each gave way. The chairs attached to the coloured ply sleepers gave way first, with fairly little pressure required to seperate the chairs cleanly from the sleeper. The untreated ply was next, with a little more pressure required to acheive the same result. The platsic sleeper was the clear winner - no amount of pressure could seperate the chair and sleeper - in the end the chair itself broke.

Now obviously this is a fairly limited test. I haven't tried other types of solvent/glue and I haven't taken into account what sort of forces are ever actually likely to be exerted on track in the normal operational life of a model. However, it does highlight the fact that the bond between ply sleepers and platsic chairs is not all that great, and this concerns me. I'm now not sure what to do. I'd be much happier with the strength of the plastic sleepers, but much prefer the appearance of the ply ones. Any advice anyone??


  1. Matt,
    There's an article in a back issue of the MRJ where someone did some fairly rigorous testing with different solvents etc. I will see if I have it (my MRJ collection starts at issue 113 and it might have been before this.)

  2. Matt - a better bond to timber will be made if the timber is impregnated beforehand with polypipe. Polypipe is PVC-based stuff commonly used by plumbers. A better impregnation is likely to be made with polypipe diluted with thinner, but I'm not aware of any optimum dilution. (Polypiping is best done after timber dyeing.)

  3. I managed to get hold of a tub of Polypipe. It definitely does increase the strength of the bond - to something matching that using plastic sleepers. I haven't tried it diluted with thinner yet. The one problem is that the Polypipe basically makes the ply look like plastic (or at least, like plastic-coated ply!) which kind of defeats the point of using ply in the first place for it's more realistic effect. The 'Polypiped' sleepers have a definite sheen to them when the light hits them at a certain angle, and the very pleasing pale weathered look I had managed to acheive is darkened considerably. The only way I can find of reducing this is to lightly sand the sleepers after the chairs have been stuck down, to remove the polyurethane(?) coating, but this is time-consuming. Maybe thinning the Polypipe would reduce this surface coating a bit? I'll have to give that a try. Failing all, I may have to resort to the old-fashioned rivets and solder approach....

  4. Here's the information on that MRJ article:

    MRJ 131, p311, 'Pointwork Components' by J. Douglas Smith