Honley Tank asks - CSB or Not CSB? That is the Question!
Entry posted by Dave at Honley Tank
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My excursion into construction of a continuous springy beam chassis (see previous posts about my J10) was useful but has resulted in quite definitely negative feelings about them.
It seems to me to be an excessively complicated system that demands a skill level that the majority of modellers are unlikely to have developed. At least that is so if the published technology is to be believed.
I have to admit that my predilection for split-axle current collection and models that can be handled by the ham-fisted and which are capable of day in and day out working on layouts without too much maintenance, quite definitely effects my opinion.
My J10 was completed and carried out many hours of work on both ‘Bowton’s Yard’ and ‘Birch Vale’, where it proved to be a worthwhile addition to the stud.
It is however performing no better than locos I built with beam compensation way back in the early 1970s, nor is it better than those I have built since, - guided by Sid Stubbs, Norman Whitnall and John Langan, (in future such chassis I shall call “SWL chassis”).
These last are split axle with tufnol block frame spacers and simple downward acting cantilever springs acting on the axleboxes.
The axleboxes can be simple ‘top-hat’ affairs turned up at home. The tufnol blocks make for a very strong chassis and because of screw-&-dowel-fixing, the mainframe assembly can easily be fully stripped in the future should this be necessary
The two outer axles normally ride at the top of their axle slots and fix the correct ride height, any inner axles have the top of their axle slots about 0.020” higher than the outer axle slots, and that value is not too critical!
It is possible to drop any axle independently simply by removing the axle retainer, normally screw fixed.
There is no need of any complicated calculation for the springing; - about 20mm cantilever of 27swg phosphor-bronze wire, again not critical! Adjust the pressure on the axlebox by bending the wire – just as we do with Alex Jackson couplings (edited 1/4/16 - or the scraper wires used with scraper electrical pick-up) – so that there is gentle pressure of the wheel on the track. It’s all so simple, just basic mechanical engineering principles and none of it over-critical.
Such a chassis can be built and tested before its body is completed (or even started!). Initial test running can be done with a temporary weight equivalent to approximate body weight and fixed round about chassis middle. No need to worry too much about correct weight distribution.
In comparison a CSB chassis needs a good bit of forward thinking and technical calculations. Granted that resort to a well-known web page can do those calculations for you but it seems that the ‘sums’, distances, and weights are all important.
You need to ensure a clear space for the spring, along the length of each mainframe, making frame spacer design quite critical. Designing frame spacers that also insulate the mainframes from each other (split-frame for split-axle), leave space for the springy beams and produce a rugged chassis is no sinecure either!
Removing an axle means removing both springs. Easy to say, not to difficult to do, but replacement means threading that wire through quite a lot of tiny holes, all this to be achieved in a very limited, difficult to illuminate space. I found this bit extremely frustrating.
Were my J10 a brilliant performer way beyond anything I had already managed then I would have to agree that CSB is worth all this extra effort – it isn’t!
I would now like to show how – “ it isn’t!” was proven!
What then about performance? First, perhaps “performance” needs a definition. For me, any loco should de-rail very rarely, and any derailment that is not down to poor driving, or inordinately poor track, should not occur. Just like the real thing!
A model loco should be capable of pulling a model load equivalent to the maximum load that the prototype class of loco was allowed, in this case 2F. The model should also be capable of smooth creep speed, preferably less than normal walking speed, but to achieve this feature, typical top speed should not be compromised.
I’m more than happy that locos I have built in the last twenty years have achieved those features and have also been of sufficiently robust construction as to not need ‘kid-glove’ handling. Perhaps my B1 and my K3 need careful driving techniques when asked to pull 10 coach trains on curving gradients, but that cannot occur on my own layouts and they rarely go visiting.
For the J10 pulling power test I set up a 33 wagon train on a gentle curve (about 12 foot radius) on ‘Bowton’s Yard’. This incidentally covered all of one fiddle yard and all but about three foot of the scenic section, so it was a train length well beyond any I could ever sensibly run! Is there really any point in having locos that could pull more?
The J10 started the train without problem, even with all couplings taught. So well done!
But my only other 2F classified loco, a J72, performed the task equally well, and that one was built over twenty years ago and has a SWL (Stubbs-Whitnall-Langan) chassis. There seemed little point in subjecting other models to this particular test. I know that my J11 (3F); J6 (3F); J94 (4F); J39 (5F) have all hauled similar loads in the past.
“Had my J10 proved to be a brilliant performer way beyond anything I had already managed, then I would agree that CSB is perhaps worth the effort” – it didn’t, so it isn’t!
I’m sorry you CSB proponents, at least those of you who have actually tried the system and achieved success. But was that success using comparison against previous attempts where “toy train” chassis design was applied? Or are you a modeller whose locos normally haul trains of un-prototypical length, on layouts with un-prototypical curves and/or gradients?
Because my layouts, (two with S4 track and DCC, and one with EM track and analogue control) are shunting planks, then I don’t have need of locos that can do better than their prototype, But who does?
For that reason, the B1 & the K3 referred to earlier have not had weight added over their driving wheels. None the less, their haulage limitation is comparable to the real thing.
Perhaps I’m lucky to have been introduced to a simple chassis design long ago. And perhaps the modesty of my heroes led to them not writing sufficient articles about their designs and because of that, others could not copy their ideas
Whatever the reasons, my experience is that their remarkably simple design of chassis is more than good enough to achieve what I need, and I believe that similar needs apply to the majority of you too.
Oh! - at the first call for heavy maintenance my J10 was fitted with a SWL chassis. It's performance is not changed but future maintenance will be quicker and easier.
Keep It Simple, Stupid !
Good modelling wished to all of you,
Dave
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