Fitting W irons

billbedford
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Re: Fitting W irons

Postby billbedford » Fri Nov 08, 2013 3:48 pm

Flymo748 wrote:I don't know what research Bill did in devising his sprung w-iron system.

However, in connection with something that I'm designing for 5522, I've been poring over a number of detailed LNWR wagon diagrams. These seem to be consistent in showing:

Buffer height 3' 5 1/2" or 13.83 mm in 4mm scale


Is that loaded or empty?

Underneath of wagon/van floor 3' 10 1/2" or or 15.50 mm in 4mm scale

Except that models of wooden framed wagons are not constructed the same way as the real thing. On the prototype the floor planks sit on top of the solebars and there is a covering board bolted to the outside of the solebars that covers the ends of the floor planks. On most models the bottom of the floor is made level with the bottom of the covering board and the solebars are stuck onto the bottom of the floor. So the height to the bottom of the floor is going to be less than that on the prototype.
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Re: Fitting W irons

Postby billbedford » Fri Nov 08, 2013 3:52 pm

Tim V wrote:We are back to my comment about publishing a set of standards for 4mm models(in another thread). Buffer height/distance apart is specified on the real thing so why cannot manufacturers get it right?


Are you really telling use that an empty eight ton tare wagon has the same buffer height as when it is loaded with sixteen tons of coal?

'cos if you are I'll put your name forward for a Noble Prize for inventing a new sort of physics.
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Re: Fitting W irons

Postby Paul Willis » Fri Nov 08, 2013 4:07 pm

guyrixon wrote:
Flymo748 wrote:[
However, in connection with something that I'm designing for 5522, I've been poring over a number of detailed LNWR wagon diagrams. These seem to be consistent in showing:

Buffer height 3' 5 1/2" or 13.83 mm in 4mm scale

Underneath of wagon/van floor 3' 10 1/2" or or 15.50 mm in 4mm scale

Therefore I'm working on the observation that the dimension "x" under discussion is near as damn it 1.7 mm.


I thought that Russ asked for the height difference between buffer centre height and the top of the tabs on the BB axleguards when the wagon is set up correctly (presumably for some nominal wheel size and axle-weight, as per Justin's post). That might be 1.7 mm too but we don't know yet. Bill implied that the axleguards accommodate low floors in RTR vehicles, so maybe x < 1.7 mm.

He did :-)

I was just giving a reference point on what I had found it to be, working from the (?certain?) prototypes...

guyrixon wrote:BTW, I never bend up the sides of the BB axleguards, preferring to pack from the flat base of the unit rather than the upstanding tabs. Am I doing it wrong?

No... As far as I can see, it would make naff all difference, and you have a larger surface area to affix the w-iron to the wagon floor.

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Re: Fitting W irons

Postby Paul Willis » Fri Nov 08, 2013 4:12 pm

billbedford wrote:
Flymo748 wrote:I don't know what research Bill did in devising his sprung w-iron system.

However, in connection with something that I'm designing for 5522, I've been poring over a number of detailed LNWR wagon diagrams. These seem to be consistent in showing:

Buffer height 3' 5 1/2" or 13.83 mm in 4mm scale


Is that loaded or empty?

As it's from an LNWR diagram, then I am assuming that it is empty.

As I believe that you have already said, contemporary diagrams didn't specifically note these things.

Flymo748 wrote:Underneath of wagon/van floor 3' 10 1/2" or or 15.50 mm in 4mm scale

billbedford wrote:Except that models of wooden framed wagons are not constructed the same way as the real thing. On the prototype the floor planks sit on top of the solebars and there is a covering board bolted to the outside of the solebars that covers the ends of the floor planks. On most models the bottom of the floor is made level with the bottom of the covering board and the solebars are stuck onto the bottom of the floor. So the height to the bottom of the floor is going to be less than that on the prototype.


Quite. But that wasn't what I said, and it wasn't the question that I was looking for the answer to.

However it didn't stop me sharing information that I'd found with other members of the Forum, in case they found it useful.

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Re: Fitting W irons

Postby LesGros » Fri Nov 08, 2013 4:21 pm

billbedford
... Measuring the height of the buffer centre above the floor is really quite difficult on a built wagon.
Until the wagon is built you have no idea where the axles will be in the w-iron, because of the springs.[/list]
So it seems to me that building the wagon, resting it on the assembled w-irons, and checking the height of the buffers against a know marker, e.g. a buffer height gauge, is a lot more practical than trying to work out a lot of arcane dimensions...
Bill,
But this is not about a particularly arcane dimension. The request for this particular dimension arose from an enquiry about whether or not to remove the tabs from one of your etches. Nor is it about the height of the buffer above the floor either.
As you well know, your etches are located against the underside of the floor of the waggon, so it is all about a user knowing the relationship between the top of your etches and expected buffer height in advance of purchase/build of your etches. It answers such questions as whether surgery or packing will be needed to get a suitable buffer height for a particular model waggon, before it is built.
Not arcane at all, just a dimension desirable for careful work, and a bit less trial and error.

It is to Flymo's credit that he has produced a working figure for his design without apparent difficulty.
Last edited by LesGros on Fri Nov 08, 2013 4:25 pm, edited 1 time in total.
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Re: Fitting W irons

Postby Paul Willis » Fri Nov 08, 2013 4:23 pm

Tim V wrote:We are back to my comment about publishing a set of standards for 4mm models(in another thread). Buffer height/distance apart is specified on the real thing so why cannot manufacturers get it right? Anyone got any ABS wagons? Checked the buffer centres recently?

Is it any wonder beginners are put off?

With my Committee hat on, I can say that I have been through the dimensions given in Ray Hammond's hand-written notes from the 1970's and transcribed those that are still relevant. By that, I mean that (for example) commercial practice has determined that rolling stock axles are 2mm diameter, not the 1.8mm noted by Ray. To reverse 40 years of established practice would be a mighty windmill to tilt against.

I've also been through the 2FS standards as well, looking at what they prescribe and the types of dimensions measured.

I haven't yet finished a paper for the Committee on it, but it's not far off.

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Re: Fitting W irons

Postby jjnewitt » Fri Nov 08, 2013 4:47 pm

billbedford wrote:Until the wagon is built you have no idea where the axles will be in the w-iron, because of the springs.[/list]
So it seems to me that building the wagon, resting it on the assembled w-irons, and checking the height of the buffers against a know marker, e.g. a buffer height gauge, is a lot more practical than trying to work out a lot of arcane dimensions.


Sorry Bill but you should know exactly where the axle will be in the W-Iron under a certain set of conditions. I know exactly where mine will be under the conditions around which it was designed. This takes us back to theory. Behind pratical modelling there lies good theory. There are equations that will give you spring deflections as I'm sure you're aware. This is all simply about information. It doesn't matter if you agree that buffer heights should be consistent but the information should be there to allow those who do to set their wagons up as they wish. Indeed if you want to model your empty and full 16T minerals with differing buffer heights you still need to know how to get to where you want to be.

Justin

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Re: Fitting W irons

Postby Natalie Graham » Fri Nov 08, 2013 4:56 pm

Flymo748 wrote:As it's from an LNWR diagram, then I am assuming that it is empty.

As I believe that you have already said, contemporary diagrams didn't specifically note these things.


Some did. There is a general arrangement of a 7 ton mineral wagon reproduced in Caledonian Railway Wagons and Non Passenger Coaching Stock which shows a measurement of 3' 5" along with the annotation "To centre of drawgear when wagon is new and unloaded" In any case I think it is evident that a GA drawing intended to be used by the workmen in the wagon shop would carry the dimensions they would need. While the mechanical engineer who drew up the design would have been capable of calculating the likely spring deflection under load I think it unrealistic to believe that the wagon shop foreman would have been expected to estimate this and allow for it when building the wagon. Additionally the springs and axleboxes are generally drawn in unloaded positions.

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Re: Fitting W irons

Postby Crepello » Fri Nov 08, 2013 9:30 pm

billbedford wrote:The prototype buffer height dimension was nominal only. There was a 3 inch (1mm in 4mm scale) allowance for loads, weak springs etc. In addition, while the buffer height is marked on many drawings, we don't know the convention behind the drawing. Does the figure on the drawing represent the unloaded or loaded height or something in between? It is tempting to assume that it is the unloaded height, because that would be the easiest dimension to measure in the works, but I have never seen this expressed in any contemporary document.


I have various English Electric diesel GAs which state a 3' 5 1/2" buffer height, and one in particular mentions a service weight of 72 tons, with empty weight of 69 tons. That order of difference is not going to change the buffer height by much. But additionally, the height over roof hatches is given, presumably because it is of interest in establishing route availability. So this ought to be a maximum?.

I've just remembered I've got some Metro-Cammell wagon detail drawings for a 1963 design. Hang on a mo...

Right, I have in front of me, an arrangement drawing of a 4-wheel wagon spring, under a 10" solebar.
Marked dimension rail to underside of solebar:
Tare: 3' 0 1/4" *
Loaded: 2' 9 3/4"

The related underframe arrangement shows:
Rail to underside of solebar 3' 0 3/4"
Solebar 10"
Rail to Buffer Centres (light vehicle) 3' 5 3/4"

The GA also states the 3' 5 3/4" value.

* I think the 1/4" must be a drafting error for 3/4"

So we can say for this wagon, buffer height is 3' 5 3/4" light, 3' 2 3/4" laden.

jayell

Re: Fitting W irons

Postby jayell » Sat Nov 09, 2013 10:02 am

As a newcomer to building models I am puzzled by much of what has been written in this thread. I have assumed that having bought w-iron etches, for example I got some etches for the Ratio 4 wheel coaches at scaleforum, they would fit the underframe without me having to worry about things like ride-height etc. It looks like I may have to re-think this assumption and maybe not attempt to use those Bedford etches but get complete underfame kits, there are two possible sets available

Another thing that struck me was that if Bill doesn't have any views about setting a standard for buffer heights why does he produce a buffer height jig?
https://www.eileensemporium.com/index.p ... t&Itemid=9

"Confused of Yeovil"

P.S. I'll not be around answer any responses until this evening as we are about to go to Salisbury to visit my wife's cousin who is in hospital with spinal problems.

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Re: Fitting W irons

Postby grovenor-2685 » Sat Nov 09, 2013 10:36 am

Despite all the talk of 1/4" differences above there really is no rocket science to this. A buffer height gauge is certainly a help, but you can equally manage with a steel rule.
As Bill hinted, W-irons need to allow for different thicknesses/designs of floor, hence you usually need to fit some packing between top of W-iron and bottom of floor. So assemble your pair of W-irons complete with wheelsets and springs, take your body and a bit of weight to bring it up to whatever weight you want it to be in service, maybe 40 - 50 grammes for your average 4 wheel wagon. Sit the body on the W-irons and check the buffer height, usually its to low and you add packing to bring it up. Sometimes its to high, in wgich case yopu will need to remove those fold up tags if you have already folded them up, or you mak have to file away obstructions on the floor, or even rethink the floor design, but the latter is a rare event.
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Re: Fitting W irons

Postby Will L » Sat Nov 09, 2013 11:21 am

johnlewis wrote:Another thing that struck me was that if Bill doesn't have any views about setting a standard for buffer heights why does he produce a buffer height jig?


To be fair, as Bills approach is very much suck it and see (or more politely fit, check and correct as described by Keith). I really don't think he's suggesting you use random buffer heights, the point at issue being how accurately you can predict in advance what the buffer hight of a given vehicle build will be. To follow Bills approach some sort of buffer hight gauge is de rigueur. Russ and Justin may use such a thing but only to check if they've got it right in the first place.

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Re: Fitting W irons

Postby dal-t » Sat Nov 09, 2013 9:35 pm

This discussion seems to illustrate the dilemma at the heart of fine scale modelling - how far to go? The point is, once you deviate from the prototype in any particular there will be consequences. In this case, hanging model suspension off the floor rather than the solebars generates the issue over buffer height, but there is a closely related problem with getting sprung buffers to function if either the floor is fixed at the wrong height, (which, as Bill has indicated, often seems to be ‘designed in’), or if the solebars are too thick/too close together, another endemic problem with some kits. At one time it seemed around 50% of the wagons I built failed to allow working buffers to be fitted without some major modification - happily, things are rather better in more modern designs.

Since the ‘nuclear’ option of staying true to the prototype in every last detail remains unattainable, usually scuppered by the things that don’t scale - like gravity, or the properties of readily available materials - we all have to choose compromises. If 4mm/ft leaf springs behaved as predictably as 12”/ft ones, we could all fit our ‘W’ irons in the way the original wagon makers would recognise (and our suspension would be helped by open spoke wheels having some ‘give’ in them, our wooden-body stock would twist across diagonals, our axles would drag on cold mornings when the grease in the boxes was thicker, und so weiter). But this doesn’t happen, so in my case, as long as buffer heads meet without the risk of riding over each other, I care not a jot whether they are 0.037mm too high or too low*, either in loaded or unloaded state. But I do like my wheels to stay on the track, and Bill’s suspension units seem to achieve that for me, with a lot less huffing and puffing than some other systems. So I’m happy to follow Keith and Will's advice, and suck it and see (sorry, ‘check and correct’).

*Just measured a pair of LNWR D1s built straight from BB’s 3D printed kits, and buffer height on one is 13.4mm, on the other 14.1mm. They couple up and propel each other without a glitch. Fortunately, more by luck than expert packing, it’s the ‘loaded’ that’s lower and the ‘empty’ that’s higher, so I’ve attained unintended realism - perhaps because their UAWs are 33gms and 24gms respectively, despite all my (non-prototypical) efforts to cram as much underfloor ballasting as possible into the “empty” …
David L-T

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Re: Fitting W irons

Postby jayell » Sun Nov 10, 2013 10:09 am

I was about to make a longish posting here but decided it was more appropariate elsewhere so it now appears in 'Jayell's Thread' instead.

(a not so puzzled now) John

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Re: Fitting W irons

Postby Natalie Graham » Sun Nov 10, 2013 12:46 pm

johnlewis wrote:I was about to make a longish posting here but decided it was more appropariate elsewhere so it now appears in 'Jayell's Thread' instead.

Having read your comment I have been thinking the same thing, that the w-irons were securely bolted to the structure of the wagon at a fixed height. The dimension Russ queried should be constant for all vehicles using the same diameter of wheels regardless of loading, floor height, etc. Looking at a few wagon GA drawings it seems that, typically, the distance from the bottom of the solebar to the bottom of the w-iron was within fractions of an inch of two feet. I would have thought that this dimension was the reference for how much to pack the w-irons, not the buffer height. Surely any adjustment needed to attain the desired buffer height should be made to the moving part of the suspension not to what should be a fixed component.
Last edited by Natalie Graham on Sun Nov 10, 2013 1:35 pm, edited 1 time in total.

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Re: Fitting W irons

Postby Guy Rixon » Sun Nov 10, 2013 1:35 pm

dal-t wrote:…If 4mm/ft leaf springs behaved as predictably as 12”/ft ones, we could all fit our ‘W’ irons in the way the original wagon makers would recognise…


I don't see why a single leaf made from a metal of known properties would be any less predictable a spring than a length of guitar string. If one could get a reliable spring rate from that single leaf, the other leaves of the spring could be simulated with paper, adding nothing to the spring rate.

If a single leaf of metal is too stiff, perhaps one could embed a wire spring in a dummy spring of paper leaves.

If the spring works, then one needs a way of constraining the axlebox along the axis of the axle and then a way of fitting the bearing into the box that gets the end-float right. These things, of course, being solved or avoided already by the existing springing-systems.

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Re: Fitting W irons

Postby jjnewitt » Sun Nov 10, 2013 1:56 pm

dal-t wrote:Since the ‘nuclear’ option of staying true to the prototype in every last detail remains unattainable, usually scuppered by the things that don’t scale - like gravity, or the properties of readily available materials - we all have to choose compromises. If 4mm/ft leaf springs behaved as predictably as 12”/ft ones, we could all fit our ‘W’ irons in the way the original wagon makers would recognise.


But this is effectively what we do now. 4mm scale 'leaf' springs made from steel guitar wire behave very predictably but instead of fitting them on the outside of the W-Iron between journals and solebar we fit them on the inside behind the solebar. It's much the same system and they work in a manner that is comparible to the prototype. Instead of journals we have spring carriers and bearings, W-Irons restrain the axles in much the same way... You can even use parallel axles like the prototype if you wish.

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Re: Fitting W irons

Postby grovenor-2685 » Sun Nov 10, 2013 1:59 pm

Having read your comment I have been thinking the same thing, that the w-irons were securely bolted to the structure of the wagon at a fixed height. The dimension Russ queried should be constant for all vehicles using the same diameter of wheels regardless of loading, floor height, etc

but on the real thing the W-irons as such have no influence at all on the buffer height, their sole purpose is to restrain the lateral and longitudinal movement of the axleboxes within acceptable limits (and stop the axles falling out if you lift the vehicle). The ride height is adjusted by the fittins supporting the centre of each spring on the top of the axlebox and the two spring ends on the solebars, by spring shoes, J hangers etc. Adjustments are made here to suit the spring depth and camber etc.
With the BB W-iron design the spring seats are fixed by the positions of the holes in the W-iron, the height from bearing to spring by the length of the bearing carrier, it is usually this latter that is modified to suit the different designs. However the adjustment available to the user is the packing between W-iron and floor, unlike the real thing the solebars are not involved.
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Re: Fitting W irons

Postby LesGros » Sun Nov 10, 2013 3:26 pm

Keith wrote:
... However the adjustment available to the user is the packing between W-iron and floor, unlike the real thing the solebars are not involved...

Which brings us neatly back to the dimension "x" information required by a user who wishes to calculate the thickness of the under-the-floor packing needed to set an appropriate buffer height. :)
Why is BB so reticent about this?
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Re: Fitting W irons

Postby Natalie Graham » Sun Nov 10, 2013 3:26 pm

grovenor-2685 wrote:but on the real thing the W-irons as such have no influence at all on the buffer height,


Exactly my point. The w-irons are fixed to the structure of the wagon and as the various components of that structure are equally securely fixed together the actual point of attachment is of no relevance, The floor does not move relative to the solebars any more than do the w-irons. My reference to the bottom of the solebars was as a convenient reference datum when locating the w-irons in position on the model but it equally pertains to the buffer centre line.

The relationship between the w-irons, the axleboxes and springs, and the solebars is quite important to the visual appearance of the wagon. If the w-irons are going to be moved up or down from their scale positions then that relationship will change. It might not be noticeable for very minute adjustments but, going from experience in other scales, unless we also adjust the vertical size of the axlebox/spring castings or whatever, it does not need much to make the appearance of the wagon look odd, especially if it results in reducing the distinctive gap below the axleboxes.

I don't have direct experience of the BB w-irons, although I note the wagon kits that I have to hand using the same system have no provision to change the height of the w-irons (they are part of the same etched component as the wagon sides.) and it may be that very little adjustment is needed. Speaking generally though I would think it preferable to put the w-irons where they should be and then adjust the moveable bit to get the axle centre in the right position. Assuming you have scale diameter wheels, if the relationships between the axles and the w-irons and between the w-irons and the wagon structure are correct the buffer height will follow.

Looking at the diagram in Russ's post earlier it would not take much effort to open the spring retaining holes to give vertical movement and place the packing under the spring ends rather than the w-irons if such is needed although I would have thought that just tweaking the shape of the spring wire, by bending it up or down as required, should do the job quite nicely

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Re: Fitting W irons

Postby billbedford » Mon Nov 11, 2013 4:21 pm

Russ Elliott wrote:Bill - I accept that floor heights vary (which was my main point), but if the geometry of the W-irons is constant, what is the following dimension for a 13.8mm buffer height?

w-iron-to-buffer.png



Nice one Russ,

You really got the know-nothings dancing around looking for solutions to non-problems.
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Re: Fitting W irons

Postby LesGros » Mon Nov 11, 2013 7:25 pm

Bill,
I visited your website recently, and was pleased to note that you are providing downloads to assist would-be builders of your kits; :thumb Oh good, I thought, Bill has paid attention to feedback about customer relations.

Then you wrote:
Nice one Russ,
You really got the know-nothings dancing around looking for solutions to non-problems

If you think that I am " a know-nothing ", fair enough, you are entitled to your opinion; but why the insult instead of the information that would help me be "a know-something" ? in this case, about the products that you want us to buy. (else why produce them)

This topic could have been an opportunity for you to share more of your expertise. :( Sadly, you have shown us that you are rather more willing to provide insults, than information.
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Re: Fitting W irons

Postby John McAleely » Mon Nov 11, 2013 7:30 pm

Thank you all for a spirited discussion. I'm calling time on this one now, since the discussion appears to have strayed from its course.


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