Building a Cambrian Seaham in 3mm/ft scale

[NCB]

My Cambrian interests go back a long, long way; in the 1970s I built a Cambrian Aston 4-4-0 in 4mm/ft (well, almost finished it) and odd bits of rolling stock. However, I drifted off into other scales, finally landing in 3mm/ft, where the major interest has been 1930's GWR. However, the Cambrian interest was still there, and over recent years I've built some 3mm/ft rolling stock, either scratch built, kit adaptions, or utilising Coast Line Models 3D printed wagon bodies. Time for an engine to pull them!

 

I started etching things nearly 10 years, and have done various chasses, for engines and for wagons. With my still not finished Rhymney Class M, having started scratch building I ended up etching some body parts, but had yet to do a complete body. The Cambrian Seaham 2-4-0T was top of my list to do, and last October set to and drew up the artwork for both body and chassis. With lockdown in place it seemed to be a good time to get stuck into the project. Hence this thread, started after I'd done enough to convince myself it wasn't going to be a complete disaster!

 

Background. The early Cambrian engines were mainly tender types, but in 1866 delivery was taken of three diminutive 2-4-0 tank locomotives, for short-haul work. Named the Seaham class after one of the locomotives, they were the first Cambrian engines to have a rudimentary form of overall cab. They seem to have done what was asked of them, and after 28 years in 1994 Aston rebulit them, with a new boiler, several enhancements such as steam sanding, and a totally new cab. The result was a very neat and capable locomotive. When the Tanat Valley Light Railway was built they were the ideal motive power. Come the Grouping in 1922, C. B. Collett took a look at them, realised their utility on the lightly layed lines the GWR had inherited, and promptly shipped them off to Swindon to be upgraded. The result looked radically different, with GWR fittings, and external bunker and Collett style cab. In this form they continued their humble existance. One was shipped away to the Culm Valley line, being withdrawn in 1932. The other two remained at Oswestry until withdrawal in 1948, thus just making British Railways.

 

The model depicts one of the Aston-rebuilt engines as running in the 1901-1910 period of the Cambrian. It is based on the 7mm/ft drawing in Mike Lloyd's Tanat Valley Light Railway book, which is said to be around 1904. The scale is 3mm/ft and the gauge 14.2mm.

Edited June 6, 2020 by NCB

[NCB]

Here's the etches for body and chassis:

 

The body is 0.3mm nickel silver, the chassis 0.4mm nickel silver; etching was done by PPD. I used Turbocad to draw up the artwork.

 

As I said earlier, this is the first complete body I've done, so it'll be "interesting" to see how many mistakes I've made! I've used slot and tab methods quite a lot, so one issue is to whether they're in the right place, also whether they'll fit.

 

Nigel

[NCB]

I'm starting with the body, specifically the footplate, which is formed from these two etches:

 

The detailed half-etched footplate proper on the right sits on top of the sub-footplate on the left. The latter folds up to provide a rigid platform onto which to attach the top. Also, the sides provide the basis for the footplate valances, and the ends the buffers. At the top of the etch is a bit of origami which folds up to provide the fairly thick front buffer beam. I've run a Stanley knife down the fold-lines to make folding a bit easier.

 

I've already noticed one mistake. The footplate top has slots to take the frames around which the tanks are built. The left hand tank has a couple of slots missing. Not too serious; I can remove the corresponding tabs with no real consequences.

Edited June 6, 2020 by NCB

[MarcD]

I like this little loco, a lot. I was part way through drawing it out in 7mm when I managed to loose the file along with a shed load of others. It's only to do list for next year.

Marc

[corneliuslundie]

I shall be following this with great interest.

Jonathan

[MartinWales]

1 hour ago, corneliuslundie said:

I shall be following this with great interest.

Jonathan

Same here! Plan to do one in EM, and also model in 14.2mm scale 3mm scale.

[NCB]

To work! Here's the sub-footplate folded up:

 

This went OK. The front buffer beam needed to be folded in the right order for it to work and needed some pressure to get the right shape, but I'm happy with it.

 

The bottom treads of the steps are fold up ones whereas the upper treads are separate bits fitting into slots. There are several fold-up bits on the top, namely outlines of the front springs and the reversing lever, also the single lamp bracket.

Edited June 7, 2020 by NCB

[NCB]

Now to attach the footplate top. First of all I lightly tinned the sub-footplate around both the outside and inside edges. For all my model construction I use Carr's 188 degree solder and Green Label flux; this combination flows beautifully around joints wherever it is needed, doesn't form blobs and spreads easily. I also use two Antex 25 watt soldering irons, one with the supplied bit which is fine for when I want to flood something with heat, and one with a much finer bit for more delicate work. For tinning I used the supplied bit. When soldering I cut small bits of solder off the stick and pick up with the iron just enough for the job in hand, and flood the area with flux; this helps to transmit the heat to the metal. So for tinning I ran some flux along the edges (picking up drops with a cocktail stick then dropping them on the work piece), picked up a small amount of solder with the iron then applied it. With this solder it's very easy to spread it along the surface.

 

The footplate and sub-footplate have matching holes to take 12 BA bolts for attaching body to chassis. These can be used to bolt the two pieces together before soldering, ensuring that everything is aligned correctly, as show below. The bolts are also useful for holding the body in a soft-jawed vice, for future work.

 

Before attaching the top, the lamp bracket was folded upwards so that it poked through the slot in the footplate. Once everything was aligned, I sloshed flux on the joins and ran the iron along them, with a bit more solder. In the above pic, the outer edges have been soldered, with the inner ones yet to do. A spot of solder has been added to the lamp bracket (just behind the front buffer beam).

 

Nigel

[NCB]

Once the two pieces had been soldered together, it was time to add half-etched overlays around the sides, for the valances and the buffer beams. The only detail on the valances are the flanges for the rear steps, both upper and lower. Before attaching the valance overlays I turned up and soldered the bottom treads on the steps. Here's the work in progress (apologies for the quality of the pic):

 

The side valances have been added, by tinning the sub-footplate sides then using a similar method to attaching the footplate top. An old screwdriver is used to ensure the bit I'm soldering is held firmly against the part underneath.

 

Mistake 2: one overlay was shallower than the other. I'd drawn the valance outlines simply by copying artwork from the sub-footplate. In one case I'd included (correctly) the area occupied by the sub-footplate fold line; in the other I didn't. Doh! In the event, I simply aligned the bottom of the thinner valance with the bottom of the sub-footplate side; the missing 0.3mm strip at the top was filled with solder and isn't really noticeable..

 

The only detail on the buffer beam overlays is a raised bit around the coupling hook hole. The holes to take the buffers were just the right size for 10 BA bolts, so I used a couple as seen in the pic to temporarily attach the overlays while I soldered them in place.

 

Mistake 3: For some reason I haven't accounted for, the rear buffer beam overlay was too deep, the excess being at the top. However, I managed to remove the excess with no trouble.

 

 

Nigel

Edited June 8, 2020 by NCB

[NCB]

Now to deal with what's above the footplate, starting with the front springs and reversing lever. After bending up the bits on the sub-footplate and extracting the overlays from the fret, this is what I have:

 

Of the two springs in the foreground, the right hand one is as it comes of the fret. The spring proper has 3 additional bits extending from the top which bend down over the front to provide additional detail, as seen in the spring on the left. Again, apologies for the quality of these pics.

 

Then it's a question of adding the springs to the vertical bits:

 

I've also added the reversing lever overlay, the top treads to the steps, and the small grab handles level with the front steps.

 

Nigel

Edited June 9, 2020 by NCB

[NCB]

Now to get on with the tanks and cab. Here's the cab bits:

 

The windows have frames which fit in half-etched grooves around the edge of the windows. I tinned the frames while still on the etch then removed them. To fit each one, I sloshed some flux around the edges of the window then held the frame in place with a screwdriver while I applied the iron, together with a tad more solder. The cab front and sides at the top of the pic have been done, although need a further bit of tidying up.

 

Mistake 4: This is the first serious one. The bottom piece is the cab rear together with the bunker sides and front. The fold lines between rear and bunker sides should line up with the edge of the top part. Instead, the fold lines have mysteriously drifted outwards, so there is excess metal there. Also, the tabs have drifted out with them so don't align with the slots in the footplate. One option, the cleanest, is to have this bit re-etched. However, I don't have a PPD order anywhere near ready. So I'm going to try a butchery job on the existing piece.

[NCB]

The interesting part coming up; building the superstructure, starting with the tanks. For these I etched a couple of frames which fold up to provide a structure for the tank. They also provide the tank top and rear, with the side and front added later with an etched overlay. Here's the structures in place:

 

Getting the distance between the tanks spot on is critical for being able to attach the cab correctly, so I soldered in first one frame, then used the cab front as a template to position the second frame properly before soldering that.

 

The two frames weren't quite as easy to get the right shape as I expected, but I managed it; I'll take another look at that to see if it can be improved.

 

Nigel

[NCB]

Next thing were the etched tank overlays, which also include the rather fancy and probably unnecessary extensions at the top (the GWR had no hesitation in chopping them off):

 

They were positioned by getting the rear in line with the tank rear and working from there. At some point I'll have work out how to do the rounded corner of the extensions between side and front; in the past I've worked something up in Milliput and will probably do this again.

 

Nigel

[NCB]

Now for the cab front/sides:

 

This folded up and fitted fine. So I got that one right

 

Before dealing with the back, there are internal splashers to the cab to fit:

 

The soldering isn't as messy as it looks. Honest!

 

Nigel

Edited June 12, 2020 by NCB

[ChrisN]

I have to admit I have a soft spot for 3mm but there is no way I have the ability to do what you have done.  It is enjoyable to watch though.

[NCB]

Chris, if I can solder, anybody can solder!

 

Now to the cab rear. As I mentioned, I decided to butcher the faulty etch. In fact, I managed to remove the excess metal without too much trouble, ending up with 4 bits; the cab rear, one bunker side with half of the bunker front, the other bunker side, and the other half of the bunker front. I filed off part of the cab rear tabs, until they fitted the slots in the footplate. And soldered them all up:

 

A fair enough outcome. One thing I was pleased about. The cab side extensions were exactly the right length, so the cab rear was dead vertical. Misshapen cabs are all too easy to do, so this was a plus.

 

Nigel

Edited June 13, 2020 by NCB

[NCB]

Final bit on the cab rear is to attach the overlays for the bunker, rear and sides:

 

These were sweated on with no problems. However when viewing the above pic I realised that the overlay for the tank side hadn't properly attached to the tank frame, so sloshed some flux on it and pressed it with a hot iron, which cured the problem.

 

Nigel

[NCB]

I prefer to fit the cab roof last of all, after all details have been completed, and after all painting thereof has been done. To assist in this, I've added a strip of 2mm nickel silver behind the cab front and rear, curved to match the roof contour, as below:

 

The completed roof can then be simply glued to these surfaces. They also strengthen the cab structure; you can't make things too strong!

 

The main thing remaining is the firebox/boiler/smokebox assembly. However, before that I want to get the chassis done, to test things like motor and gearbox fit.

 

Nigel

Edited June 16, 2020 by NCB

[NCB]

The main piece of the chassis is a single fold-up etch:

 

The sides are folded in at 90 degrees, after which the cross pieces in middle and both ends can also be folded in, and the seams soldered up to make a strong structure. The end pieces have an extra fold to form a platform fot the couplings (B&B). I'm a big fan of fold-up chasses; they are quick, very easy to do, and only need a bit of care to get everything square. Before folding anything, I ran a Stanley knife down the fold lines a couple of times to make folding easier. Here's the first stage:

 

I have folding bars, but because of their thickness they're not good at doing multiple folds like this U shape. So what I did was stick a couple a 12" metal rulers in the fold bars and gripped the chassis using those, after which the folds were done easily. It needs a bit of checking to make sure the correct 90 degree angles are obtained.

 

Nigel

Edited June 19, 2020 by NCB

[NCB]

The next stage was simple enough; fold up the middle and end pieces so that they're vertical and solder in place, thus creating a rigid chassis. See:

 

Some explanation of the screws/nuts is required! Each end piece has an additional fold which serves as a base for the couplings (B&B). The idea is to solder a nut behind the base, so that the couplings can be attached by screws. I usually do this by attaching the nut using a screw, screwed up tight so that (hopefully) any solder around the nut can't leak past the nut onto the screw thread and solder everything up. On this occasion I hit a problem. I was forced to use a new stock of 12BA cheesehead screws and found that with none of them did the thread continue right up to the head. Because of the thinness of the metal this means that things can't be screwed up tight.

 

While I thought of a long-term solution to this, as a short term fix to solder the nuts in place I fed another nut onto the screw and passed it through the hole to receive the main nut; by tightening the nuts I could get things tight enough.  The pic shows things set up ready for soldering.

 

The thing on the right is a tray to hold the pickup assembly and gets soldered to the frames between the drivers. It also needs a 12BA nut attached.

 

Re the problem. After much investigation and enquiring around, I've come to the conclusion that screws of the sort I want are no longer available. So for the immediate future I'll need to use washers. Longer term I may go metric.

 

Nigel

[NCB]

Having soldered the nuts in place, I removed the bolts, then folded down the end coupling platforms and soldered them. Then I added the pickup tray between the drivers. While it was easy enough to position this, I think in future I'd provide positive positioning tabs on the tray and corresponding cutouts on the sideframes, to make positioning even easier. Here's a pic:

 

 

When I came to look at this again, a thought struck me, and I checked that the gear on the leading axle would fit. As I feared, it fouled the pick-up tray. Doh! I wasn't inclined to try to unsolder the tray, so took a cutting disc and file to the front of the tray and removed enough for the gear to fit:

 

 

Nigel

Edited June 23, 2020 by NCB

[NCB]

Sharp Stewarts of this era seem to have had fairly low-slung cylinders, enough to be clearly visible below the buffer beams, so I'd included provision for these on the etch:

 

 

Here's the cylinder front and rear, together with half-etched circular pieces with bolt detail. The latter doesn't show up too well, and maybe I should have made the bolt-heads heavier, if over-scale. The circular bits had been tinned on the back before removing from the main etch. To fix each one, I just sloshed some flux onto the circles on the main bits, held the circular bits in place with an old screwdriver, then applied heat:

 

 

The inside of the chassis has half-etched guide lines (see previous chassis pic) where they go, and it was fairly easy to solder these in place, although I did have to file down the top of the front circles a bit where they came into contact with the coupling platform:

 

 

The cylinder bits are in place at the front of the chassis (right hand end). Note also that the rear of the cylinder has a hole, there is a corresponding hole in the middle chassis former, and a piece of 1mm nickel silver rod has been fed through both and soldered. This is a pivot bar so that the front axle, which runs in slots in the chassis sides, can waggle up and down.

 

Finally, there is a half-etched cover for the bottom of the cylinders. This is slightly oversize and needs to be filed down a bit to fit. Here it is in place:

 

 

It has a hole in it to allow access to the body-fixing bolt. There isn't really that much room for the front coupling, although I think it'll be OK, and there's not much I can do about it if I include the cylinders. Or rather, I've just thought of a method, providing a slot for the rear of the B&B coupling to slide inside the cylinder, but it's too late to do that now!

 

Nigel

Edited June 26, 2020 by NCB

[NCB]

On to the brakes! Eack brake consists ot two similar items each of a hanger and pad. One, the rear, is of full thickness metal and just has the outline; the other, the front, has half etched detail:

 

 

One the right, the front is at the top, the rear at the bottom; they need to be soldered together. Each has 3 0.6mm diameter holes, one each end for the brake support rods, and one in the middle for the bolt which holds them together. The rear one has had the surface tinned in the middle. They are assembled as seen on the left. Short bits of 0.6mm nickel silver rod pass through them and into holes drilled in the wood. Heat and a bit more solder is applied to the middle, soldering the lot together, but avoiding soldering the end rods in place. The whole assembly can be lifted off the end rods, and more solder applied round the edges. If the end holes have received some solder in this process, they are easily drilled out again. After cleaning up this is the final result:

 

 

To mount them on the body, 0.6mm nickel silver rods are for hanging the brakes and also locating the end of the brake pull rods are passed through holes in the chassis and soldered.

 

 

Nigel

 

[NCB]

Bit busy of late, but managed to shove in the odd half hour or so, and have got the brakes done. To make sure they're in the right place, I've temporarily added the drivers to the chassis. Normally these would sit in compensation beams, but for this purpose used the holes in the chassis:

 

 

The bearings are placed in the holes, and there's a washer or two added to the axles to control sideplay, although there's more than there'll be on the final chassis.At this stage I'm using discarded axles, to avoid them getting rusted up by flux; the wheels are slightly too easy a fit on them, which is useful for avoiding wearing in the wheel holes when taking them on and off.

 

Next thing is to loosely add the brakes and associated bits and pieces:

 

 

The brakes are hung from the top rods; cross rods go through the bottom of the brakes and the brake pull rods. This needs patience; it can fall apart very easily!

 

Each brake is then soldered to the top rod it's hung from, making sure it's the right distance from the chassis. The right distance is so that they won't project enough to catch on the connecting rods when fitted, but are far enough away from the wheel flanges not to make contact. The general positioning is such that that they keep clear of the wheel tread and moreover are just far enough away so that the wheels just squeeze past them when taking them on and off.

 

Once the brakes are soldered in position the bottom cross rods can be soldered to them as well. Here's the state after wheels and brake pull rods have been removed and the top rods trimmed:

 

 

As I said, a lot of patience needed! The tricky bit is getting each brake to stay in position while soldering it to the top rod.

 

Nigel

 

Edited July 7, 2020 by NCB

[MarcD]

It's coming along very nicely. 

Marc