With the basic chassis made, it is essential to fit the nuts to secure the body to the chassis as both of these will be concealed with later work. So a quick test fit looks like this and we can get onto the next bit, the coupling rods.
As is not uncommon, these are made from a pair of layers of brass laminated together. You can see that the outer layer is half etched for much of its length, with the full depth only being present at the bosses. I have also sought to make it easier to build these by including them in a folding jig – the folding is underway in the bottom portion of the view. The logic of the jig, indeed the whole kit, is to make a really smoothly running chassis much easier to make. Modern CAD and computer operated phototool creation techniques by the etchers means that it is possible to easily draw and then etch such that each dimension is faithfully repeated on the product. Thus, it is possible to be confident that the wheelbase will be repeated exactly on each side of the frames and also on the coupling rods. However, this accuracy is completely lost if the user has to laminate the two parts together by hand; it is not possible to get them superimposed on each other exactly or repetitively so the spacings of the crankpin holes will change. The jig overcomes this as the fold line is so long that there can not be any twist as it folds, so the two parts will meet consistently and accurately.
It is true that there remain two areas of variability. The first is that the degree of etching will not be exact on every occasion so the holes will be slightly bigger or smaller on each occasion. This can be easily overcome by making all critical holes a tiny bit too small and then opening the holes up with a ream (not a file, reams will open up a hole consistently). The second problem is that a fold is not always consistent on a fold line so the jig can protect against twisting but might not necessarily put the two laminates directly on top of each other. However, the important point is is that they will be correct horizontally, any error can only crop up vertically. Thus, when the crankpin whole is opened up, it is possible that it will move vertically slightly but this will not change the dimension between the holes so the critical dimensions should be retained perfectly.
The above is all true in theory but in practise there was an almighty cock up in my artwork; so I was deprived of finding out. A total case of designer error and when this is yourself, there is no one else to blame……………….
………..I made one of the coupling rods no less than 8mm too long – doh! I have no idea how, but it needed chopping; so it was back to the old fashioned way of making coupling rods despite my high ideals! Fortunately, as they were laminated, it is possible to stagger the cut to make the splice – essentially the same technique as Alan Gibson’s variable length coupling rods. Anyway, after the cutting and splicing, I did get a sweetly running chassis and this is what it looks like. The unusually large wheels for a shunting loco are already making their presence felt!
The chassis is created around CSB’s; continuous springy beams. A spring wire is anchored to the chassis at four points per side (for an 0-6-0) and at the centre of each hornblock. Thus each hornblock is supported on either side and can “bounce” on the spring. However, the clever thing about CSBs is that when a hornblock is depressed, not only does the spring wire flex a bit as suspension, but it also rocks on the anchors so the adjacent wheels push downwards a bit to equalise out some of the deflection. It produces a really smooth chassis and, if it is conceived at the design stage, I think is actually rather easier to both design and build than traditional compensation. This is a close up of a pair of hornblocks and a pair of the anchor points (the other is hiding behind the frame spacer on the right). Also worthy of note is the colour coding of the hornblocks; to enable them to be reinstated in the same hornguide each time. This is probably unnecessary with modern (and therefore consistent) hornblocks and the accuracy of the etching I have noted but old habits die hard!
Putting aside the body for a while, to take a look at the chassis because it is necessary to mount the two together and it is not possible to close up some of the element of the body until this is sorted out.
As with the body, I am trying to take a moderately fresh approach to the chassis to make this a little easier to build than certainly most of the kits I am used to. In this regard, most of the kits for the Highland are quite traditional in their design and I readily admit that all but two of my ideas has been either all out pinched from other designers or at least significantly inspired by them. All I am trying to do is use more of these neat ideas in a single kit to make the life of the builder easier. I am, however, finding that it makes my life more difficult, as there are a lot more moving parts to most components, so more places for the tolerances to be catered for; so as John Price has already said, the list of little tweeks and amendments to make is growing! At least, no one can say this particular kit designer has not built their own model.
Anyway, this is what the chassis looks like in the flat; note that it is a fold up design – this is inspired by the Mousa Models chassis, so a pinched idea!
And this is what it looks like with the basic folds made up. What it achieves is really neat, as it is instantly sufficiently stiff to work as a chassis; by the time a couple of further cross braces have been installed the basic chassis is more than robust enough for its life.
My design uses the same slide in hornblocks as utilised by Comet and Brassmasters for their chassis. After a tiny bit of practise, it is possible to size the hole for the hornguides such that these are just too small when etched. This means that with a few strokes of a light cut file on each side, the hornblock becomes a tight sliding fit. Once all of the hornblocks are in, it is then possible to measure the distance between each on both sides of the chassis and also on the corresponding coupling rod. This is done with digital callipers and by the expediency of measuring the distance at its maximum with the callipers facing outwards and then repeating with them facing inwards the average being the actual distance between the centres. I reckon to be able to measure down to 2 or 3 hundredths of a mm, which is rather better than I can build to! Where there are inconsistences, this is dealt with by a few more strokes of the file on the side which needs to be adjusted to change the centre. This needs to be done anyway to turn the tight sliding fit to a snug but smooth fit for the hornblocks to work properly soif the centre does not need to be changed, the file strokes are undertaken equally on both sides of the hornguides.
This does need to be done after the coupling rods have been formed, of which we will see in the next posting. However, the chassis is also designed with a keeper plate to accommodate all of the cosmetic springing to the model and the ashpan sides. This is secured with a series of 12BA screws to enable it to be removed to allow the wheels/axles to be dropped out. A great boon as the model is built and painted.
To make the assembly of this element easier (in fact in this case a lot easier!) I have created a jig that holds the two layers of the laminate in exactly the right position. The jig is chunky enough to avoid distortion as it is folded up and it locates the parts perfectly. In this particular case, the soldering needs to be done with care as there are folds to make after the jig is cut away and it is important not to fill this with solder before hand.
And this is what the keeper plate looks like – it is pretty delicate until it is mounted but fine thereafter.
And the two components assembled look like this. The beginnings of the cylinders are also visible, this is a slide in module that can be removed for assembly and painting (although the scrap tanks were painted fairly simply, so this is not really relevant on this model).
I took the weekend off the other week and attended the Spring Railway Modeller’s Weekend at Missenden. It is great to spend two full days just modelling away from the distractions of life and amongst people who are all doing exactly the same. I find it a form of therapy and it is well worth going if you have been thinking about it (and even if you haven’t!).
I took with me the etches that I have had delivered by PPD for the Scrap Tank; with a view to doing a test build using them. The origins of this class are some of the earliest locomotives built for the line; the Raigmore class. In an attempt to increase the life of these new enlarged boilers were fitted to them. Unfortunately for the Highland Railway the boilers were too heavy for their frames and consequently these cracked. This left the Highland with a number of new boilers, wheels and many fittings but no locomotives! Ever the frugal, they recycled these parts into a series of three shunting locomotives which were designed by Peter Drummond and these inevitably quickly picked up the name of Scrap Tanks.
These were rather brutish looking locomotives for the time, characterised by surprisingly large wheels for a shunting locomotive – something compelled on the Highland due to them reusing these from the Raigmore class which were mainline passenger locomotives with 5′ 3″ wheels. For those of you who don’t know what these looked like, this is what we are aiming at:
And this is what we are starting with:
Whilst this may (well has!) got me into some trouble, I have sought to design the kit to be easier to build than the average etched brass kit and certainly easier than the Falcon Brass kits that are the staple in 4mm for many of the Highland’s locomotives. I have sought to do this in a number of ways and the first area tackled, the cab front/interior, illustrates one of these; the use of fold up assemblies to assist not only in creating the shapes but also the laminations. Many of the modern etch designers are using these (especially the 2mm boys/girls) but I have sought to do rather more than most (which has made the preciseness of the design rather more challenging, more of which anon).
The bulk of this assembly starts as a single piece, that is folded up to form the cab floor, splasher sides and the bulk of the cab front. To assist the lamination process, jigs either side of the cab front have been used. Wire rods are slipped through the small holes in these to ensure that they are registered on top of each other properly.
The view below shows the laminations now sweated together and illustrates the square cut outs behind the cab front which are to enable glass/Perspex to be slotted in to represent the sceptical glazing. The view also shows the boiler backhead which is made from three layers of etch (not with a folding jig – yet!). I am pretty pleased with this as this is only 13 * 15mm in size, so the wheels on the backhead are only 2mm in diameter.
To be continued…………(soon too!).
I am presently cracking on with a batch of NER hoppers for Benfieldside. Having acquired the layout, Tim and Julian have very little stock to run on it, so as part of the repayment for the use of their facilities and expertese on my boards, I thought I would help to correct this shortfall.
The origins of all of this present batch of hoppers all go back to the Slaters’ injection moulded kit, which is of diagram P7 wagon. There were around 17,500 of these wagons at the time of the grouping and the LNER carried on building them for some years thereafter with only subtle differences; so not unsurprisingly there were quite a lot of variants. Thus, I have been doing a lot of modifying!
In each case, I replaced the very clunky W irons with Bill Bedford replacements; even though these were to be to EM, I felt that they would improve their performance. The first examples were essentially built as the kit was intended with fairly traditional brake gear (which was to one side only). However, having built my first one, I decided to refine the brake gear by drawing an etch for replacement steps, V hangers, morton brake mechanisms and brake levers. This (along with a comparison with the plastic equivalent – the painted wagon), is below:
However, a significant proportion were modified with end levers that operated a crank that was connected to the Morton gear. At the ends, there was a much more chunky ratchet arrangement to retain the lever in position. Again, I drew this up on the etch, and the arrangement looks like this:
The NER undertook a number of experiments with these vehicles to attempt to reduce rolling resistance and this was the subject of my next modification. On the right (below), shows the provision of a second outside set of W irons. This was to add stiffening to the axles. There is a set of Bill Bedford W irons to cater for this, but I chose instead to create a fresh set on the etch. On the left is a further variant, where an anti-friction bearing was added in addition to the outer W irons. This was a wheel that ran on the top of the axle and I presume the idea was that as it rotated less, there would be less friction. I suspect that the introduction of an open bearing surface that would instantly get contaminated with coal and grot would actually have the exact opposite impact – as these were removed by the grouping era, I may well be right!
The final variation of construction that I have modelled was a slot cut into the ends, which appeared on some vehicles. The NER used these on vehicles that were hauled up rope inclines – of which they had many. A plank of wood was inserted into the hole and wedged such that it was secured behind the end posts to ensure that the haulage point was close to the centre of the wagon. They found without this that there was a tendency to pull the end posts loose due to the uneven point of pressure.
Next up will be the painting and lettering of these; where I have three eras to chose from that would have all been apparent immediately pre- first war, which is when Benfieldside will be set. More on this in a future post.
If there is a desire from anybody for the etches, I would be able to offer them; so drop me a note?
I had a delivery from PPD a week back, so I have been playing with some test builds of this:
This is a dia 25 cradle bolster; a type of vehicle that I have not seen on another railway. It has a square cradle that sits on the top of this, with four bolsters protruding from the corners of the cradle. They were used on pairs and the whole cradle rotated when the pair of vehicle went around curves. The intention, I presume, was to offer the load more support by offering more points of contact. Anyway, as no one else had tackled this vehicle before, I thought I would have a go!
As this is my first etched design for a vehicle, I have certainly encountered a number of problems. As the top photograph shows I produced this in both 4mm and 7mm; the latter has proved more successful due to the thickness of metal being greater. The main issue that I created for myself was to half etch the solebar overlays so that the rivets and the ironwork could be portrayed. However, rather than backing them on a further layer of etch (like the etched kits I have built – they evidently knew something……), I spanned it between supports. The intention had been to make the kit fold up more readily but in practise what has happened is that the half etched solebars have distorted (badly in the case of the 4mm one) due to the stresses introduced in the heat from soldering. Thus, whilst I have a working model (at least in 7mm), a rework is going to be required.
Both the 4mm and 7mm versions will have sprung axleboxes, using a varient of the guitar wire sprung version used by Bill Bedford and others. The 7mm chaps don’t seem to use it much and I guess the mass of their models helps. However, it does glide with the springing and is better as a result I reckon.
I have also done a 3-D design for the cradle, which I am proposing to use as a master for some resin castings (certainly in 7mm, I might go down the lost wax brass route in 4mm). A new process that I have not previously attempted. I need to find out where to get axleboxes and buffers from – Larrie Griffin I presume.
Also back from PPD, were some etches for something altogether more bold (which is a worry in the light of the problems I have encountered on a relatively simple wagon!). This is the chassis and body etch for a Drummond Scrap Tank. I have made a start on this and again, some reworking will be required but again there is a viable model in an amongst these parts; it just needs tweeking. More to follow once I have got further with it.
I will be making at least some of the items that I have been developing available for sale.
Therefore, I have set up a separate website entitled Miscellany Models that shows what is available, how to get them and (when I get some time to do it) will become a repository for prototype information that I have on the items I have made, construction/finished photographs and instructions.
You can find this website here. If you look hard, you will see some hints as to what other things I have been working on and are expected to be made available in due course.