Ian_C's workbench - P4 and S7 allsorts

[Ian_C]

Here's a diversion. I'm trying to work out what plates the tender would have carried. The Wild Swan book says that 8142 was built with a 4,000 gallon Mk2 welded tender, number 9869. It still had a Mk2 welded tender when photographed in 1965. Goodness only knows if it's the same tender, there were lots of them and they got changed around often enough. But the chances of finding a clear photo of the rear of 48142's tender in its later life are about nil, so I'm just going to assume that it was still dragging around faithful 9869. So far so good, but now it gets more difficult. Here are some questions I can't answer...

• The loco had a build date of Feb 1942, but what build date did tender 9869 have? Could have been 1942, but not impossible for the tender to have been built at the end of 1941. I can't find any information relating LMS tender numbers to build dates.
• There seem to have been two variants of the LMS tender number plate that was fixed the the rear of the tender. Both the same size and shape and both carry the same information: LMS, number, year of manufacture. But one type has LMS in non-serif characters, the other in rather antique looking serif characters. They're all mixed up in terms of dates. There are early LMS tenders with non-serif and late LMS tenders with the serif characters. Was it determined by custom and practice at the works where they were built? So far I've not been able to work that out.
• Likewise there are two versions of the water capacity plate. An elliptical one (rather similar in size and shape to the typical LMS works plate on locos), and a rectangular one. Again I can't work out the reason behind tenders having one type or the other.
• All of the tenders have two plates on the back, number plate at the top and water capacity plate at the bottom. But some tenders also had a third plate that carried LMS, place of manufacture, year of manufacture. Elliptical in shape and similar to loco works plates. Again it seems random and I can't establish any pattern to which tenders had the maker's plate and which did not. Works specific again?

If anybody in WT land can answer the questions or point me in a useful direction then I'd be grateful.

The reason this has my attention is that I've decided to have a go at producing some artwork for photo etching. Something I've been meaning to do for years. Seemed like a set of plates for loco and tender would be an easy way to start. I'm planning to do for the loco:

• smokebox door plate
• works plate
• shed plate

...and for the tender...

• number plate
• water capacity plate
• water shut off valve plates x2
• water scoop in/out plate

Initial artwork after a day's research and a few assumptions looks like this...


Needless to say I'll get a lot of these on a single sheet of 0.25mm brass. I'm thinking I'll fill the sheet with a load of other 8F sets using info from the Wild Swan book. If you have any requests then do let me know - although I'm not promising any timeline and there's no guarantee that my first go at etching will produce useable results!

 

[Ian_C]

This is exactly the problem that I encountered. I do like your solution, sadly not having a lathe precludes me from following in your footsteps.

Well, once suitably equipped and (modestly) proficient it really doesn't take too long to make simple stuff. Soo0...Rob, and Scale7JB...if there were small machined items that would be a significant help to you then just PM me with a sketch. I'd be happy to make them next time I'm in the workshop.

 

[Ian_C]

Gubbins is important. As a kid, gubbins was one of the first things that made me realise not everything was right in the adult world. Dad had lots of railway books and I was allowed to look through them if I'd washed my hands. The text wasn't very interesting to a 10 year old but there were lots of pictures. I examined the pictures in minute detail and often went away to draw my own versions of LNER pacifics and J39s etc in my drawing book. All drawn from memory with pencils, crayons, no ruler and occasionally some useful round thing to help draw the wheels. The A3s were a favourite but they took a toll on my green colouring in crayons. I found one of the larger drawings recently when we were sorting out my late Mum's house. Not bad for a 10 year old, and the thing that struck me was that they weren't anything like the typical child's representation of a steam loco. All the gubbins was minutely drawn in as well: brakes and linkages, pipes, valve gear, steps, couplings, lettering & livery, the lot. Obviously I didn't have a clue what most of the gubbins was, but it was there in the photo so it was represented at various levels of fidelity in the drawing.

Fast forward to my first model railway christmas present. Some sectional track, a second hand Dublo 8F, a hand full of wagons (a very mixed freight) and a brake van. Very happy little boy. Except... the 8F didn't have any gubbins. Almost all of the details I'd got used to examining and drawing as a kid weren't present on the model. I quickly came to realise that this was the norm. Commercially available models lacked gubbins in those days (early 70's by then). Even Dad's models only had a sprinkling of gubbins. Gubbins seemed to be invisible to adults, and its absence didn't bother them. As I pursued the hobby I made attempts to add brake gear made from bits of plasticard and wire and araldite, pipe work from odds of wire and paperclips. Didn't always work out too well, but did fill some of the bigger gubbins gaps and made them look a bit more like steam locos. When Santa brought me a first railway book of my own one Christmas (London Midland Steam in the North West - Bradford Barton, I still have it) I was able to survey the gubbins on an 8F in detail for the first time. For some reason unremembered I never did go back and add any detail the Dublo 8F.

So, gubbins is important to me, and you really need most of the gubbins to be present for a model to have any chance of capturing the look of the prototype. There's plenty of gubbins on an 8F and most of it can be modelled well at 7mm scale. It's now time to make amends and add all the gubbins to the empty bits of the 8F chassis. Having the Wild Swan books on the 8F is a massive aid to understanding the huge amount of stuff going on in the grime and murk below the footplate. A lot of it won't be seen clearly on the model but you'd miss it if it wasn't there.

With that in mind, I've been taking a look at the brake linkage. The kit provides some brass castings for the brake yokes and some nicely cast brass clevises to connect the yokes to the pull rods back to the brake cylinder. The instructions show the clevises attached directly to the yokes. Plausible maybe, but incorrect. The prototype has a kind of swivelling link around the yokes, and the clevises are attached to that and not to the yokes. There's nothing in the kit to represent the swivelling links. The link was easy to model up roughly from the Wild Swan drawings, but it's a difficult little part to make from scratch.


I opted instead to make a representation of the links built directly onto the yokes. Much easier, and the following pics should clarify.

Cast yokes, some small brass turned bosses, some lugs cut from 0.9mm N/S scrap. All soldered together on the yoke casting. Tidied up after soldering and a length of 1mm brass wire added to represent the connecting pin.


Soldering was done on a scrap of tufnol using a 1mm drill to hold it all together.

The drill was coated in graphite (pencil lead dust) to resist the solder. The lugs were carefuliy made to be a tight fit on the yoke castings to stop them moving around when the heat was applied. After nadgering all the parts into alignment the assembly was fluxed and heated up until the solder flowed. A little extra solder was added to fill some gaps for cleaning up later. Easy in the end.

The cast clevises were added to the lugs, drilled through 0.8mm and added pins from brass wire. The front yoke is simpler and connected to its pull rod without a separate clevis. When I have the brake hangers mounted and adjusted to the wheels I'll cut lengths of 0.9mm wire to fit between the clevises. Incidentally, the diameter of the brake pull rods decreased between each yoke as the force required to be transmitted reduced. I'm not going to bother with that and I'll take 0.9mm wire as a close match for the 'average' pull rod.

A passable representation of the real thing and enough detail to tick the gubbins box. One day, when I take the Colin Gifford shot, against the light at near ground level some of this will be seen in black silhouette for sure!

LG miniatures has a decent cast representation of these assemblies, but I didn't fancy spending another £20 ,and that's only for a six coupled loco!

 

[Stevesopwith]

Brilliant!

 

[Lancastrian]

Ian,

Excellent. I'll definitely be following in your footsteps as it were as I was planning to replicate the links too.

Ian

 

[Rob Pulham]

Ian,

Excellent. I'll definitely be following in your footsteps as it were as I was planning to replicate the links too.

Ian

I wasn't, but after Ian's kind offer to make turned parts how can I not follow his lead on this too.

 

[Ian_C]

Some more important gubbins, the sanding gear. The kit has some rather nice cast sand boxes and...well..nothing else. Back to the Wild Swan book, measure and scale, and sketch up some parts that approximate to the real thing. Some of the detail is tiny and I'm not going to attempt it, even in 7mm. A decent representation will have to do.

If you're involved in mechanical engineering you'll know that 50% of all the things that get designed are brackets of some sort or another. The end of the sand pipes and the nozzles on the prototype are held in position by the mother of all brackets. It looks to me as if the originals are blacksmithed from 2" steel angle with another brackety plate bolted or riveted to the end, through which the sanding nozzle is connected to the valve (?) that combines the steam and the sand. There's no way around this other than making a lot of very small parts. Here they are...

Only showing 5 out of 6 sets because the first trial set is already fitted. The angle brackets are made from 1mm x 1mm milled brass angle, bent and filed to a slight taper on one leg.

The flat parts that look like the end of hockey sticks were marked on some scrap 0.5mm etch fret and cut out by piercing saw (see, I don't do it all by machine tool!). They're thicker than prototype but we need a bit of robustness in the model here.

The longer turned parts are the nozzles, and, yes there is a hole in the end. Not that it'll be noticeable on the model, but it keeps me amused.

The smaller turned parts are the body of the combining valve thingy. In reality it's a more complex shape than this because it brings the steam pipe into the sanding pipe at an acute angle, but I couldn't figure out how to make it easily. As you'll see in the assembled sanding gear a certain amount of cheating goes on.

The angle bracket is fixed inside the main chassis plate below the spring hanger. The small space for this on the prototype is mercifully also present on the model.



To assemble and solder together tiny parts like this you really need them to fit together mechanically. There's no chance of holding them in position accurately while the soldering iron is applied if they just touch end to end. So the spigot on the back of the nozzle fits through the hole in the hockey stick and into a hole in the combining valve. The 0.9mm wire sand pipe fits into a hole in the combining valve and a hole in the sand trap casting. and the sand trap casting is spigotted into a hole in the underside of the sand box. Makes a difficult job...slightly less difficult.

Once the angle bracket is soldered to the chassis and the hockey stick, nozzle and combining valve soldered together there follows a whole lot of bending and tweaking to get the nozzle exactly where it should be between wheels and track. There's no alternative to putting the wheels back in and sitting the chassis on track to check the nozzle position, then taking the wheels out to bend the bracket, then wheels back in and so on.

The nozzle has to be positioned so that it does not contact tyre or rail at practical suspension positions, and the bracket has to be sufficiently clear of the inside of the tyre not to contact at maximum side play. Eventually it all comes good. The steam pipe is 0.4mm copper wire simply soldered to the back of the combining valve, not quite prototypical but in practice you can't see that on the model.

Sand trap castings are not provided in the kit. That's bit of a surprise because other equally tiny cast parts are provided. Only the rear most sand boxes are outside the frames so it's only on those two sand boxes that you can see the sand traps. Bit of a head scratcher how to make these small and complex parts. I was ordering a few bits and bobs from Ragstone Models Ragstone Models and just asked if he knew of any castings for these parts because they're not in his catalogue (or anybody else's so far as I can tell). Magically when my order arrived what should fall out of the jiffy bag but a little packet containing 4 sand trap castings, and I hadn't even ordered them! Which reminds me, I owe Mr Ragstone £2-00 for them, which seems a very small amount to pay to save a lot of work. Ragstone be praised!

You'll notice the missing brake blocks (won't you?). I've chosen to model up some for Mr Modelu to print. That way I can have them close to the tyres without an electrical short if they happen to touch. Some day they'll turn up along with the crew.

Here it is all gloomy and arty in the Gifford style. Can't wait to get to the painting and weathering down here in the crud and the murk.


I've just got five more to do now, and that'll keep me out of mischief for another week.

 

[Ian_C]

For years I've done small work in the jaws of a toolmaker's clamp held in the jaws of a small bench vice. That works pretty well, but the scope for positioning the work is limited, and some times you just can't get it to a convenient angle. I remember reading about instrument maker's vices in MRJ, Barry Norman I think. You see the odd one on eBay, usually made by Eclipse. I finally got around to making one of my own. It's based on a set of drawings and a casting from Hemingway Kits but modified to take my faithful and familiar toolmaker's clamp. It's a lathe and milling machine job but with a few changes you could make it on a lathe only I guess. Nothing too difficult. Here are the parts all machined from the iron casting and bar stock...


And here's the finished article with all the bright work chemically blacked and the casting filled and painted. ..


By loosening the big hand grippy knob the stem can be extended or retracted and rotated in two planes to position the toolmaker's clamp. Tightening the knob locks it all in position. Not shown, there's a clamp to clamp it to the edge of the workbench. That wasn't part of the Hemingway kit, just made up from odds and ends plus the clamp screw and swivel from a poundshop G clamp. I have it in mind to make alternative ends for the stem for different jobs.

Learning from this project; drilling hard things. One advantage of using a decent quality toolmaker's clamp is that it will have hardened jaws. My old clamp was bought from RS Components a long time ago, it's 'Made in England' for heaven's sake, and the jaws are super hard. Pretty much file and saw proof. I needed to drill through part of it for the two mounting screws. I'd assumed that a HSS drill bit would find its way through with a bit of encouragement. No chance! The clamp is way harder than any HSS tool. Totally rounded drill bit and hardly a dimple in the clamp. That was a surprise. Some head scratching before I remembered I had a solid carbide stub drill. Thought I'd risk it, though it would be a shame to ruin the carbide drill. It drilled through the hardened clamp body with no problem, and no sign of wear on the drill cutting edges. Remarkable. Rock, paper, scissors etc...but tungsten carbide beats all.

Maybe I can get back to building the 8F now?

 

[Ian_C]

What's on the workbench ? Glorious clutter as usual. It's been worse. However much space I make I'll always end up working in about a 6 inch square near the edge. Entropy - "lack of order or predictability; gradual decline into disorder."


The sanding gear below the footplate is complete. A satisfying addition of authentic looking gubbins.

The sanding nozzles are now the lowest part of the chassis when the wheels are not fitted. Have to take more care when handling the chassis now. The combination of brackets soldered to chassis and 0.9mm brass wire for the sand pipes soldered to the sand boxes makes them reasonably robust. There are no sandbox location hints in the kit so that had to be scaled from drawings in the ever present Wild Swan book.



The front sand pipes were a curse to form and fit. I made a pattern first from soft copper wire before I copied it in brass wire. The routing was a bit of a fudge too. The drawings show a nice neat route under the leading brake cross beam and sloping more or less continuously up to the outlet of the sand box. Couldn't replicate that on the model as one of the frame stretchers was in the way of the obvious route. I'm guessing that in reality the fitters at Crewe improvised a little to arrive at a practical routing, Anyway, you can't see much of it after it disappears behind the frames. The steam pipes just follow a prototypical routing (and there's a lot of variation if you examine photos) and terminate when they get out of sight.



Injectors are the next piece of gubbins to be tackled.

 

[Ian_C]

Exhaust steam injector, and starting to fill in the empty looking areas of the chassis. There were two types of exhaust steam injector fitted to 8F's, Gresham and Craven Class H and later Class J (although at some points in the text Wild Swan seems to get Davies & Metcalfe and Gresham & Craven mixed up, not sure which is correct but I'm thinking they're G&C injectors, surely somebody out there in WT land will know - see update at the bottom). The MOK kit comes with a brass casting for a Class J injector, and since the change to Class J was made starting with 8126 at Crewe, mercifully that's correct for 8142. It's quite a nice casting when cleaned up. There's not much to go on in the instructions apart from a decent photo. With the help of the pipe drawings in the Wild Swan book and a few more photos I worked out more or less how it all went together. In passing, when looking for good shots of the RH side of the loco I realised just how many photos were taken of the LH side of locos.



The flange on the large exhaust steam feed pipe as it exits from behind the rear driving wheel is very noticeable, and although it's not present in the kit I wanted to model it. Half an hour on lathe and mill to make the flange to slip over the pipe.

The front of the injector is supported off the underside of the cab by a vertical steel plate that bolts to two of the steam pipe flange bolts. Clearly seen in photos and not in the kit either, but easy to make from scrap etch.

The auxiliary steam feed, water feed and boiler delivery pipes were made from odd lengths of copper wire saved from electrical wiring and matched as closely as possible to the prototype pipe diameters. Bend, fit , curse, repeat...etc.

The injector casting had no ports for water inlet or overflow so the positions were estimated from photos and some guesswork based on the Class H pipe drawings. I suspect the overflow pipe was a cast part on the prototype but I managed to torture a length of copper wire to approximately the right shape and soldered it on in approximately the right position. Although you can see 'something there' beneath the step in photos you don't see much of it so a little inexactitude will go un-noticed. Drilled a hole up the end of the overflow because a solid one would look daft, and obviously the water wouldn't come out.

The other detail I added was the diagonal stay for the steps. I didn't notice this until I spotted it while looking for photos of injectors. There seem to have been two types. One type of stay, and the one shown in some of the Wild Swan drawings, is a goofy looking bracket made of curved angle iron fixed between the main frame plate and the inside of the steps. The other type is a simple round bar bolted or riveted to the frame plate at the upper end and the inside of the steps at the lower end. I've no idea which type would have been fitted to 8142, so for once I took the easy way out and made a round bar stay out of 0.5mm wire. Adds to the general look of busyness under the cab.

The injector water inlet operating shaft was made from 0.3mm wire.

All the pipes and the water inlet operating shaft were simply taken up to the space beneath the cab floor and soldered to a convenient bracket or chassis edge out of sight. they'll be further hidden when the valence is added to the footplate.

Bending the large copper wire to make the exhaust steam pipe to fit between the injector and the grease separator located between axles 1 and 2 was a bit of a game. It bends all over the shop to dive in behind the rear driver, pass beneath the ashpan, and eventually rise up to meet the grease separator casting. Lots of trial and adjustment and very pleased with myself to get it to fit nicely. But guess what? When I did a trial assembly of the chassis I found that it passes right through the bottom of the gearbox. So a chunk will have to be cut out for that. Could haven made it in two parts anyway. Duh!

----------
I have a few days of leave so I'm able to spend some time on the job for a change (between cutting grass and walking Mr Dog). Momentum builds. The exhaust steam injector was puzzled out and done in a day, which is warp speed compared with my usual pace. I've spent a lot of time focused on detail so I thought it would be fun to just assemble all the parts to see how much progress has been made. Here's the progress report.



The boiler, firebox, cab and footplate are just 'put together' as they are and dropped on the chassis. There's some fettling to be done before proper assembly can take place. The camera plays havoc with the verticals this close up so I'm trying not to start fretting about cab and firebox alignment. The brake linkage parts weren't fitted for this shot; they'll fill-in some more of the daylight between the wheels.

It's starting to get the look and feel of an 8F now, in a way that 4mm locomotives can never quite pull off. There's still a lot left to do, but it feels like progress.
----------
Update on the injectors - annotation on the LMS drawings reveals that the live steam injector was from Gresham & Craven and the exhaust steam injectors were from Davies & Metcalfe. The LMS piping drawing C32522 reproduced in the Wild Swan book carries the signature of a bloke called W.A.Stanier, probably an authority on the matter. You'd think Tom's chaps would have done a bit of drawing checking before presenting it to 'the man', so it's almost certainly correct.

 

[Ian_C]

Working through the list of chassis jobs now. Two jobs that I've been putting off, but I'm in the right frame of mind for now; damper control linkage and hopper ashpan operating gear.

There are some basic parts in the kit to represent the damper controls beneath the cab. You don't see much beneath the cab in that location but you do see something, so I felt the need to elaborate. The damper controls pass through the cab floor to cranks and shafts that are supported beneath the cab by a casting. There's some cryptic hidden detail outlining the arrangement in the Wild Swan drawings, but that's not easy to interpret. I've only found one decent photo of the casting and cranks - http://www.hall-royd-junction.co.uk/Hall_Royd_Trains/Stanier_8F_detail.html . If you take a cut from that photo and increase the brightness in photoshop you can see the details quite well. I'm not attempting to replicate all the prototype detail, but just enough to suggest all the right stuff is lurking beneath the footplate. An approximation of the support casting was made from bit & bobs. Cranks and links were from scrap etch. The whole lot is secured to the chassis by a plate that won't show when the cab's in position.


8142 was one of the few 8Fs fitted with a hopper ashpan to speed up disposal. It was operated from a lever bracketed off the chassis behind the rear LH driving wheel. It's not shown on any of the drawings in the Wild Swan book, but there's a good photo in the Pictorial Supplement. I estimated the dimensions from the photo and made up some tiny parts from scrap etch. Somewhat of a fiddle, used up the whole day's quota of patience, but it worked out OK.


The live steam injector and a load of pipework will fill in the gaping hole behind the step.

 

[Rob Pulham]

Superb Ian,

Should I .....

 

[Dog Star]

Should I .....

And just how many WTers do you know who shall be watching for such details to be added now that we know that the job can be done?

 

[Ian_C]

The brake blocks have been missing for a long time but finally they're fitted. A huge gap between brake blocks and tyres is a bit of a give away, another of those little things that shouts 'model'. So I wanted to keep the blocks as close to the tyres as possible. Taking the side play on axles 2 and 3 and the small amount of suspension movement into account I knew I'd be pushing my luck with brass brake blocks. I decided to file the brass blocks off the hanger castings and replace them with some 3D printed blocks. The blocks were easy enough to model up from the drawings in the Wild Swan book.

I had the blocks printed by CW Railways , good service and good quality parts, I recommend them. I had a load of blocks printed, enough for 5 or 6 locos and tenders (well, I might live that long). Came out at about £0.36 per block, well worth the time saved making them from scratch. The tender brake blocks are slightly different from the loco blocks so I prepared separate files for them, however at 7mm scale I can't reliably tell them apart. One size would have fitted all!

The blocks are pinned to the hanger castings with 0.9mm brass wire and fixed with a drop of low viscosity cyano . The pins provide a mechanical fixing in case the adhesive doesn't survive a dip in the cleaning tank.

Another gap filled. You can make out the brake yokes and linkage (earlier post) behind the wheels in this shot. All the accumulating gubbins around the chassis is starting to create that sense of prototype.

Another detail job crossed off the list today; the cylinder drain cocks and pipes. The drain cocks and pipes are supplied as a brass casting. The castings are OK but the pipes are a bit plain. They don't project far enough below the cylinder, there's no representation of the pipe union where they are fitted to the valve and there's no clip holding the three pipes together forward of the cylinder. Also they look very tidy, like they were when fresh out of Crewe. These pipes got a bit of a bashing it seems and most of photos of 1960's 8Fs show the drain pipes looking knocked about. The cast pipes were snipped off, castings drilled to accept 0.5mm wire, some tiny unions turned on the lathe and the whole lot soldered together. A
pipe clip was added from brass shim. What's missing is the operating rod and crank under the rear of the cylinder - can't decide whether it's worth adding.

 

[Ian_C]

Superb Ian,

Should I .....

Hi Rob, I just came across your O6 build on a another site.

Should you? Unless you're unlucky you may not need to. Very few 8Fs had hopper ashpans. I chose to model 8142 before I'd discovered it had a hopper ashpan. But by then I was pretty much married to 8142, so felt obliged to model it. Details of fitment in the Wild Swan book.

 

[Rob Pulham]

Thanks Ian, I have the book so I shall have a study when I get back to it.

Are those brake blocks available from CW Railways for general sale by any chance?

 

[Ian_C]

Thanks Ian, I have the book so I shall have a study when I get back to it.

Are those brake blocks available from CW Railways for general sale by any chance?

Dunno Rob, probably not. PM me and I'll post you a set.

 

[Ian_C]

Not done much for a while because I've taken advantage of the weather to completely overhaul the workshop roof. That's nearly complete and fully waterproof now. Well, at least I think it's waterproof but until we get some rain that's speculation. Maybe it'll never rain again and I've wasted a month of spare time?

Anyway, 8Fs. This job's been in the 'difficult box' for a while so I thought I'd better get on with it. I've decided to make a new boiler backhead. The one supplied with the kit is a whitemetal casting and Im not confident that I can solder all the clutter to the casting without melting it at some point. Also it doesn't look to be quite the right shape and some of the detail lacks a bit of crispness. I did obtain a brass backhead casting from LG Miniatures a while ago. It's a Stanier style backhead but it's just too large to fit in the cab. I'm assuming it was intended for a Princess or Duchess. So, how to make a new backhead from brass from scratch?

It looks like quite a complex curvy thing at first but it's not so bad when you break it down into basic elements. There are enough dimensions scattered around the drawings in the Wild Swan profile to enable it to be modelled in CAD, and as usual modelling things in CAD helps me to get my head around how to make things. I had the impression that Stanier backheads and controls would be reasonably well standardised but it turns out that there are plenty of variations to think through and the cab detail castings supplied are a bit 'generic'. I've listed below the main ones that apply to 8142.

1. Brakes. 8Fs had a mixture of different brake arrangements fitted at various points in their life. 8142 had both vacuum and steam brakes but was one of the locos fitted with a combined brake valve AND an independent steam brake valve. And so far as I can work out it kept that arrangement. There's a decent combined brake valve casting in the kit, but no independent steam brake valve. I can't find an appropriate steam brake valve casting in the LG or Ragstone lists so it'll have to be made from scratch.
2. Sand gun. Many 8Fs were built with a sand gun and fittings in the cab for cleaning the tubes. They were later removed. Both the Wild Swan pipe drawings show the valve and steam plumbing on the backhead for this. At this stage in its career 48142 will just have a blanking plate where the valve was in the backhead. The plate will have to be made from scratch.
3. I'm sure 8142 would have had a continuous blowdown valve but there's no casting in the kit for this. It's a simple enough little thing to make.
4. The steam manifold casting supplied is nice enough but it has some fittings on that don't belong to an 8F so there'll be some modification before it's fitted.
5. Gauge glasses. I have both MOK supplied and LG Miniatures gauge glass castings. The MOK ones seems a bit long and thin and the LG ones are short and fat. Something in between would be ideal! Of the two the LG castings are the better so they'll be used.
6. There's AWS kit to be fitted in the cab. Obviously that's not shown on the LMS drawings so that'll have to be worked out from photos, and I'm keeping my fingers crossed that it was in the same location in service as it is fitted to preserved locos today.

The backhead models up easily enough, and having decided which castings to use for each part I measured the spigot diameter of each and plotted their locations on the backhead. Having those holes pre-drilled to the right diameter should make the assembly easier. I elected to simplify some of the shape, for example the backhead clothing tapers out slightly towards the cab front. That's barely visible and not (to me) worth the complication involved. What's not shown in the CAD are the washout plug positions lower down on the radiussed edges, I marked them out and added them by hand towards the end.


An offcut of 5/8" brass bar is the starting point. It's a bit thicker than needed but that's easily milled to size.


The basic profile is cut first, the angled section done by tiling the vice to the appropriate angle.


It's quite a heavy lump and there's probably enough weight over the rear axles already with the hefty firebox casting. The some material was milled out of the back to reduce the weight.


Taking the centre of the lower edge as 0,0 the coordinates of the holes are calculated...


...and drilled.


The CAD model is used to print a paper template of the profile. There's a bit of messing around with scales to get the benighted printer (my advice never buy an HP printer) to print exactly the right size. The template is glued to the brass blank taking care to align the coordinate origin and the holes correctly.


The some milling and much filing removes the unwanted material and makes the basic profile. It's just like sculpture - file off all the bits that don't look like an 8F backhead and, logically, you end up with an 8F backhead. Small rebates were milled on the lower sides to clear the dummy frames in the cab floor. It's starting to look like something.


The next step is to add the radius around the edges. Lots of filing and easy to mess it up, but there's a way of doing it in stages that improves the odds of success. First of all a 45 degree chamfer is filed around the edges. The size of the chamfer is calculated so that the middle of the chamfer face is tangent to the final radius. That takes off most of the material. Then the edges are rounded off working back to the end of the radius and blending to the middle of the chamfer (the arrow in the sketch below) from both sides. To make this easy the backhead is blacked up with marker pen and lines are scribed around the edges offset by the distances that define the edges of the chamfer and the edges of the radius. Hopefully a sketch and a photo make this clear.




Let the filing commence...


Eventually the chamfer is filed to the lines all the way around. No need for a super fine finish at this point, just get the material off efficiently. Big files from the engineering toolbox, no point wasting your finest Vallorbes on this!


The radius is added next, taking care not to remove any material at the middle of the chamfer and blending the tangent edges together smoothly. Voila!


All that's left to do is mark and drill the remaining washout plug holes in the radius and clean it up with emery, wet & dry and Garryflex to remove the machining and file marks. You'll see a little band of solder running across above the four washout plug holes. That's because the two milled surfaces on the blank didn't quite align and there was a small undercut where they meet. Plus the prototype would not have a sharp corner here anyway. A seam of solder was run along the line and blended in. Altogether about a day's work.


Just for comparison here are the MOK whitemetal casting and the LG brass casting.

 

[Scale7JB]

Very impressive bit of fabrication!

JB.

 

[Rob Pulham]

Gob well and truly smacked Ian