proto87stores wrote:However, I have a related question. Given the large number of P4 Steam Loco Builders in the Society, did anyone build a steam loco chassis with single independent sliding wire springs per wheel and do a running comparison with a similar model with the then new CSB's? Obviously the prototype does it that way, but I don't seem to see that subject, or a comparison, coming up here or elsewhere. And presumably Bill chose not to make his 4 wheel wagon wire continuous for more than just convenience reasons.
As Keith has pointed out, the nearest equivalent thing is the Dave Bradwell product, available from the Society stores, as well as in his kits. Like any individual sprung system, the real issue is knowing how closely the spring rate available meets the weight bearing requirements of your loco. Unlike other individual sprung systems (Brass masters, Alan Gibson etc.) the Bradwell units are adjustable, but that just begs the question of how you know what you should adjust them to?
The single individual spring system are allways, unless your are lucky, going on or near one end stop or the other. The springs in the brassmaster variant are said to be rated so as to suit the likely loco weight, but does anybody know what weight that is? All I know is that we don't all model locos of the same size.
We have spoken before of the difficulty of measuring the weight being carried by any one individual axle so any adjustable system is inevitably going to depend more on guesstimates and the niceity of the builders judgment.
A non adjustable two fulcrums and a wire system might prove simpler, as we can work out what weight each wire will carry, so working out what size wires we need to suit a given loco weight should be practable, but that will work out siginifanctly more complex than an equivalent CSB with more fulcrum point and even more wires to fit, so I see no advatages. Also, fitting a spring wire through 3 or more fulcrum points automatically straightens out any natural curvature in the wire, while just 2 fulcrum points won't, which may prove significant under an asymmetrical multi wheel chassis.
So I think CSB works out to be both simpler to set up and more closely adjusted to the locos actual weight than any other springing system.
Bill's wagon spring system can't use a single spring per side as the wheels are too far apart, but weight distribution on a 4 wheel chassis is less complex, and any subtle bowing of the wire will only has a marginal effect on final buffer heights.