Chassis kits for CSB

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proto87stores

Chassis kits for CSB

Postby proto87stores » Sun Aug 11, 2019 3:53 pm

Just a few basic already proven fact checks:

There is no need for a fixed axle on any steam locomotive wheel arrangement using either springing or full equalization. Even for 0-4-0's . See the 4 point wagon suspension test video posted earlier for confirmation.

Any form of wheel springing suspension statically and dynamically alters the weight carried on the wheel when going over uneven, bumpy or twisted track. (Hooke's Law). Correctly designed wheel equalizing suspension does not. Nadal's formula relies on wheel carrying weight always being greater than the minimum value. Hence wheel springing in the absence of excess of the necessary minimum wheel carrying weight is a higher derailment risk than equalization at the same weight.

The actual and perceived "smoother running" of a "sprung" vehicle can easily be achieved by soft springing the body to chassis mounting, regardless of (as well as instead of) soft springing the wheel suspension system. See Ralph Nader - "Unsafe any speed" report on USA automobile safety.

Since the CSB wires must slide/rotate continuously through the mounting clips to operate at all, they are as much a partial longitudinal equalization wheel suspension system (AKA compensation) as they are a wheel springing system. At least for the 0-4-0 and 0-6-0 wheel arrangements. Other CSB fitted driving wheel arrangements,e.g. x-8-x and greater, however cannot provide correct equalization movement and direction.

Generally, CSB suspension (one continuous wire) implementation is only practical for fixed frame driving wheels of multi-wheel arrangements. Additional traditional methods are still needed for suspending bogie and pony truck wheels, for even the simplest and shortest driving wheel arrangements.

Andy

Dave Franks
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Joined: Tue Apr 16, 2019 9:02 am

Re: Chassis kits for CSB

Postby Dave Franks » Sun Aug 11, 2019 9:34 pm

Quote <Other CSB fitted driving wheel arrangements,e.g. x-8-x and greater, however cannot provide correct equalization movement and direction.>

Sorry but once again it has to be pointed out to you that many of us find CSB's work very well and that includes locos with 8 driving wheels as commented on by a number of my friends on seeing an 8F 'gliding' along with 60 wagons.

Dave Franks.

proto87stores

Re: Chassis kits for CSB

Postby proto87stores » Mon Aug 12, 2019 3:29 am

<Other CSB fitted driving wheel arrangements,e.g. x-8-x and greater, however cannot provide correct equalization movement and direction.>

Sorry but once again it has to be pointed out to you that many of us find CSB's work very well and that includes locos with 8 driving wheels as commented on by a number of my friends on seeing an 8F 'gliding' along with 60 wagons.

Dave Franks.


The somewhat simplified description of CSB stands for Continuous, Springy, Beam. Since it is supported by a fixed pivot point between each horn block , it has to be considered as several springy beams joined end to end. And beams that pivot on a fulcrum are the close equivalent of see-saws. Push one end down, the other end MUST go up. If the beam is springy, and the riders are heavy, then the see saw bends under load FIRST until the see saw supports both riders statically closer to the ground. But it still works as the same see-saw and if one rider pushes up, the other rider will go lower, just as before, and by the same difference. Find some spare children and try it in your garden with planks of different (but adequate) strengths ;)

The portions of CSB at each support are springy beam sections that act like springy upside down see-saws with their fulcrum at the support. So the effect of pushing up one wheel on a bump pushes the adjacent wheel(s) down harder on the track. Which is good :) It's a crude form of equalization. But, because the sections are flexibly joined to the next, the equalizing effect is more complex and is reduced as it passes further on to the wheel after the immediately adjacent wheel, and so on. But it is obvious that coupling multiple see-saws end to end means that the riders at the alternate couplings are going to be moving in OPPOSITE directions. Rider 1 up, rider 2 down, rider 3 up, etc.

And when you use a CSB on a model locomotive, the alternate, opposite movement occurs on that too.

I have included some simplified diagrams below of an 0-8-0 arrangement to make that movement effect, and it's negative consequence more obvious. And to be positive, have finally provided a simple solution to make it work almost perfectly.

Image

Here we see the normal static position of an 8 coupled CSB on flat track. I've approximated the curves of the wire to save my drawing and calculation time.

Image

Now I've raised wheel # 1 as though it has ridden up onto a bump. I've simplified the wire beam shape even more as linked straight lines, as I just want to show that the beam sections pivot to take up the wheel (see-saw and rider like) movement. But now the problem with wheel # 3 and #4 becomes apparent. What works for an 0-6-0 for wheel # 3 as the reverse of wheel #2, goes wrong for wheel #4 in a an 0-8-0, because wheel #3 is trying to lift up from the track between wheel # 2 and wheel # 4. Obviously sufficient weight of the loco will force all the wheels down on to the flat portion of the track, by forcefully bending the wire against its alternating tendency. But that means the individual wheel weights will be increased or reduced incorrectly for optimum track holding.

Image

Here I've tilted the chassis to compensate for the bump so that the natural position of the wheels #1, #2 and #4 rest on the track as they would normally. But it is clear now if the loco weight was very light, that wheel #3 would actually being lifted by the reverse equalization, instead of beng placed firmly down between wheels # 2 and #4

Image

And here is the simple and completely effective solution. All that is needed is to break the CSB into two completely separate CSB's. The the equalization and weighting happens correctly between wheels #1 ands #2, followed by separate correct equalization between wheels #3 and #4. In fact this would become the correct construction for any of dual CSB's, dual springy beams, or dual rigid beams.

Andy




.

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Will L
Posts: 1634
Joined: Sun Jul 20, 2008 3:54 pm

Re: Chassis kits for CSB

Postby Will L » Mon Aug 12, 2019 11:20 am

proto87stores wrote:... Generally, CSB suspension (one continuous wire) implementation is only practical for fixed frame driving wheels of multi-wheel arrangements. Additional traditional methods are still needed for suspending bogie and pony truck wheels, for even the simplest and shortest driving wheel arrangements.


Generally I agree with that, though I am slowly working my way through a F6 (2-4-2T) with all 8 wheels on the CSB, with a weight distribution of 60% on the drivers and 40% on the carrying wheels (Ok yes only when static Andy). We'll see how I get on.

I'm with Dave by the way, I started by CSB career with a 2-8-0 which guides along a treat, nobody seems to have told it it has theoretical performance problems.

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grovenor-2685
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Re: Chassis kits for CSB

Postby grovenor-2685 » Mon Aug 12, 2019 11:32 am

Obviously sufficient weight of the loco will force all the wheels down on to the flat portion of the track, by forcefully bending the wire against its alternating tendency. But that means the individual wheel weights will be increased or reduced incorrectly for optimum track holding.

Andy, do you really want to rehash all this yet again when those of us using CSBs find that it works just fine. And sufficient weight is a prerequisite for any springing system to work. The size of track irregularitie we are working with is small so the wheel unloading is not enough to cause a problem, Nadal is happy!
Regards

bobwallison
Posts: 22
Joined: Mon Jul 12, 2010 9:42 pm

Re: Chassis kits for CSB

Postby bobwallison » Mon Aug 12, 2019 12:31 pm

proto87stores wrote:Any form of wheel springing suspension statically and dynamically alters the weight carried on the wheel when going over uneven, bumpy or twisted track. (Hooke's Law). Correctly designed wheel equalizing suspension does not.


Completely agree in the case of a vehicle at rest on uneven track, but what about the dynamic case - for example a vehicle moving on level track as it encounters a local dip? With a compensated vehicle, for all the wheels to remain in contact with the rail the whole mass of the vehicle has to move downwards to push the wheel into the dip whereas, like all moving objects, it really wants to keep going at constant velocity in a straight line. Earth's gravitational pull will accelerate the vehicle downwards, but it won't happen instantaneously and the distribution of loads in the meantime is uncertain. In contrast, if all the wheels are individually sprung, it is only one wheel (and a proportion of the axle weight) that needs to be pushed into the dip and because the inertia is low, that will happen relatively quickly and with minimal impact on the path and velocity of the vehicle as a whole.

One could dust off one's A-level physics and do the sums, but really, what is the point? We have all seen compensated vehicles performing really well; ditto CSB vehicles and those with individual springing. An individual's preferences will be determined partly by the quality of their track and partly by their own perception of movement. What we should be wary of, though, is applying the rules of static equilibrium to a very dynamic condition in an attempt to promote one suspension system over the others.

Bob


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