Detailing the boiler - Piping and handrails

Technically speaking, pipes and handrails are very different things with very different functions. In model building, they are usually made from the same materials (usually brass wire of various thicknesses). They are also made more or less simultaneously because there are dependencies in the geometry: you cannot install certain handrails until all the pipes behind them are ready, and sometimes pipes also have to be bent around the handrails. Reason enough to cover this in a single chapter.

Steam pipes under the boiler cradle

The thick steam pipes under the boiler cradle serve two purposes:

• supplying fresh steam from the valves to the cylinders (yellow in the diagram below)
• and carrying spent steam from the cylinders to the exhaust (red).

Because spent steam has a larger volume due to expansion in the cylinders, the latter pipe is thicker than the former. The course of the pipes is not immediately clear from the drawings. In the diagram below, I have projected part of the cross-sectional drawing onto the side view to clarify things a little.

Click on the drawing to enlarge.

Notes:

• The diagram also shows that the pipes under the boiler cradle are positioned next to each other and run above each other in the approach to the drive units. Bending those pipes will therefore be a challenge.
• The fresh steam pipe to the rear drive unit is not fully drawn at the height of the shut-off valve (right), probably to clearly show the course of the other pipe to the chimney.
• In practice, only the pipes to the rear drive unit are visible under the locomotive. In the diagram below, I have made a fuss about a lot of things that you don't actually see. If I had to do it again, I would limit the course of the pipes to what is immediately visible from the side. But hey, in the heat of the moment, you don't always realise that.
• Strictly speaking, the steam pipes are also visible at the pivot in the transition to the drive unit, but I decided not to model them. It's fiddly to get those holes right, and the steam pipes might collide with the underside of the boiler cradle. Once everything is painted, it will be dark there anyway and the absence of those pipes will not be very noticeable.

Let's get started. I calculated that the fresh steam pipe had to be 1.3 mm thick and the steam pipe for the spent steam 1.7 mm. This time, I opted for copper instead of brass, partly because I had those sizes available and partly because such thick copper is easier to bend than brass.

I knew from experience that bending complex pipes almost never works in one go. So I consider the first attempt to be exploratory work: where are the problems, what is possible and what is not?

Above you can see the result of the first round. I learned a lot from that.

• I tried to bend the tubes to the rear drive unit from start to finish in one piece. It turned out to be difficult to get so many bends in one piece. One irrecoverable mistake and you have to start all over again. If the tube is divided into two or more parts, you only have to redo one part.
• I now knew for sure that I would not be able to get the tubes through the mounting brackets. One more reason to divide them into two pieces.
• I now also knew where the difficult bends were and how to approach them to get them reasonably right.
• While working, I discovered that the thin tube did not run forward but to the shut-off valve.

All in all, it was a useful exercise. These ones went into the bin. Next time, I will cut the pipes to the rear drive unit into two pieces. The separation will then have to be in an inconspicuous place.

As shown in the drawing, there are several rings around the tubes. I wondered if I could replicate them. Based on the drawing, I concluded that the rings could only be 0.2 mm thicker than the tubes themselves. So for the 1.3 mm tube, I had to turn rings with an outer diameter of 1.5 mm and an inner diameter of 1.3 mm. The remaining wall thickness of the brass would therefore only be 0.1 mm. That's quite a challenge!

Several attempts failed because the tool pressure simply tore the thin wall to pieces.

A future ring in the chuck.

After some further experimentation, I arrived at the following method, which did work.

• First, turn the outside to 1.5 mm
• Then drill out the inside to 1.1 mm
• Then change the drill bit and drill out to 1.3 mm

By drilling in two steps, I only had to remove a minimal amount of material during the final operation and the tool pressure was low enough.

For cutting, I ground a separate parting balde that was only 0.5 mm wide. You have to be very careful to catch the ring, because once it falls between the chips under the chuck, it is immediately lost.

Absolutely tiny.

Where is it? (Click the picture to enlarge).

The 1.9 mm rings were made in a similar way. A difficult issue was deburring the rings after parting them. In the end, I did this with a round diamond needle file.

The next components are the various brackets. I first drilled two sets of holes in 0.7 mm brass plate. Then it was just a matter of sawing and filing.

Top left: a bracket for the firebox (pipes next to each other). I later made a second one. The two small brackets are located at the transition to the drive units (pipes above each other).

Top right: my thumb again serves as an illustration of the dimensions.

On the left, another freestanding bracket.

Now I can finally start assembling everything. First, the two brackets that need to go on the firebox. Those two will determine how the pipes look. Under the cradle, the pipes need to run perfectly straight, otherwise it will be immediately noticeable.

Neatly in the middle.

Note that I used a marker to write where the thick (dik) and thin (dun) pipes should go. Working upside down on the boiler cradle caused a knot in my brain every time.

They lie nicely flat!

The steam pipes to and from the front drive unit.

I halved the steam pipe for the discharge of spent steam with a file so that both pipes will fit into the hole at the bottom of the smoke box. In reality, there was a casting (the light blue part in the drawing) that connected to the blower (dark blue) which forced the smoke gases from the smoke box through the spark arrester and chimney to the outside. In this way, the smoke box created a vacuum and a draught was created on the fire.

The two long pipes to the rear drive unit were each made in two pieces.

The horizontal pipe is an aid for marking the pipe to be bent....

... which was then bent precisely.

Again, it is very important to check that the horizontal part is indeed flat.

The aforementioned separation between the two pipe halves ended up just behind the bracket at the front edge of the firebox. A ring needs to be placed there, and that ring will cover the gap nicely.

While removing some excess solder after securing the brackets, I accidentally pierced the bottom of the firebox. You can imagine that this resulted in some less than flattering comments. Repairing it from the inside was not possible, so I filled it with JB Weld, which I would later sand down.

All parts of the steam pipes ready for soldering. Number count: 23! (click on the image to enlarge)

The attentive reader will notice that there are 21 parts in the photo, but I am also counting the two brackets that were already attached to the firebox when the photo was taken.

Now that all the pipes have been bent into the correct curves and are the right length, they can finally be soldered.

Here is the attachment on the drive unit side (rear). It is nice to see how the pipes change from being next to each other to being on top of each other.

Rear end of the firebox.

Front end of the firebox.

Halfway between the firebox and the front drive unit

The placement of the various rings.

As mentioned, the rings at the front of the firebox (photo above right) conceal the transition between the two pipe halves. It is slightly visible because the rings are slightly raised. That is unfortunate, but I will not be doing anything about it. Once it has been sprayed black, you will not be able to see it anymore.

It all looks easy, but in reality it took me almost three months to figure it all out. I hope other LTM 51 builders will benefit from it.

The new steam pipes interfered with the existing posts taht were placed to limit the amount of turn-out of each bogie. So I quickly milled a suitable opening (left).

Handrails along the boiler and around the smokebox

Long handrails along the boiler often have tricky bends, but miraculously, this one went perfectly in one go.

I drew a bending template on brass, which I used to straighten the most difficult bends. Once that was done, the ends on both sides could be bent backwards at right angles.

Once it fit, it went into a box for the time being, as otherwise it would be too much in the way.

Steam pipe for the air pump

Strangely enough, this pipe runs along the right-hand side of the boiler all the way to the front and then over the top to the left-hand side, where the air pump is located. This may have been chosen because there were far fewer pipes on that side than on the left-hand side, which was already quite crowded.

Here too, it went well in one go, even though it is not an easy pipe. The two sections that run over the curve of the boiler require a lot of attention. In addition, the space in front of the chimney is very limited, so the right-angle bend that leads to it must be positioned very precisely.

What did bother me was that the pipe kept slipping out of place. I made two brackets from leftover handrail holders from a War Department locomotive (NS 5000). I turned off the collar and widened the hole.

Well-placed holes in the boiler ensured that the pipe remained more or less in place when fitted.

Guardrails ahead of the smokebox

Well, to a certain extent, this is a repeat of the guardrails on the front deck of the drive units (link).

Here, too, the centre-to-centre distance between the holes is measured as follows.

• Insert two identical drill bits into the holes.
• Place the calliper gauge on a drill bit and set it to zero.
• Measure the distance between the holes over the outside of the drill bits

and you will automatically have the correct value.

I made a sketch of the main dimensions and transferred it to paper using Fusion 360. I glued the paper onto a piece of aluminium and sawed and filed it into a bending jig. I made two notches in it where the lugs could hook into so that they could be soldered in the right place.

The lugs were turned, placed on the jig and soldered in place. That's now a piece of cake.

The only thing you might notice is that the feet stick out quite visibly through the footplate. But that's just the way it is.

Small bushes in the smoke box

The locomotive had stop bushings for airtight pipe passages into the smoke box. These are, of course, impossibly small.

Control pipes - preparations

Five thin control pipes run along the left side of the boiler. They are used to switch the various devices on the boiler on or off, such as a blower (in the smoke box), the steam bell, the air pump, and in one case as a connection for a spray device to clean the smoke box. These pipes run as a bundle from the cab to their respective equipment on the boiler cradle.

I chose to make the control pipes from 0.3 mm brass wire. That may be a little too thick, but otherwise it would all be very fragile.

First of all, a valve for the steam sprayer had to be installed on the boiler. The holes for the control pipes had to be drilled into it. To make sure that the pipes would fit through, I used a drill bit one size larger: 0.35 mm.

Search for the valve in the vise!!

Well, there...

Without realizing it, I got myself into quite a mess when I soldered the cab together. I had drilled two holes for a pipe and a handrail, but hadn't noticed that three of the five control pipes ran into the cab here.

It is virtually inconceivable to drill three holes

• at an angle (the drill “runs away”)
• by hand (not stable enough and takes too long)
• with a 0.3 drill bit (breaks)
• at equal distances (you can't even see it)
• and in the same line

Drilling with the Proxxon drill is conceivable. That solves the first three arguments. But for the last two, I had to come up with something.

I decided to take advantage of the fact that there were already two holes where the other three had to go.

I drilled those two holes in a brass plate with the three holes to be drilled in between. I soldered two teeth into the outer holes.

Using those teeth, I placed the drill jig in the holes that had already been drilled in the front of the driver's cab.

I could now insert the drill bit into a hole. The drilling template ensures that the drill bit does not slip and that the holes are spaced correctly and in the right place.

The photo shows that there still was some deviation, but the result is again: good enough.

The next challenge was to figure out how to make the brackets to attach the control pipe bundle to the boiler. First, just for giggles, to see if it was possible, I tried to mill a bracket from solid material.

Long story short: yes, it is possible. Even with these small dimensions.

But it took me half a day to make just one, and I still had to make two more. Add to that the risk that I would lose one or mess up one or more while soldering. It was all too much work for me.

So I made a simple stamp and mold with which I could press the brackets from 0.5 mm wide strips. Slightly less attractive (opinions differ on that, by the way), but making the molds took me an hour and then I could press a bracket every minute.

Stamp and mold, and just in front of it is a bracket.

The difference. Top: pressed. Bottom: milled.

The excess length will be trimmed off in due course.

Control pipes - Installation

Now I could start bending each of the ten ends of the five pipes into the right shape. It was like trying to tame a bunch of fleas. It took me a few hours, but all in all I made good progress.

...and then disaster struck.

The pipe broke off and was then too short to reach the hole.

In real life, a damaged pipe is sometimes repaired by placing a sleeve over it. So that's what I tried. But honestly, no, you could still see it. Now what? Starting all over again wasn't an appealing idea either.

At night in bed, I came up with a simple method to tear the broken pipe out from between the other pipes. Just a piece of 2.0 mm brass rod. Not too thick, because otherwise the pulling force would not be distributed properly, and not too thin, because it had to be able to withstand the twisting motion and I also had to be able to drill a hole through it.

The broken pipe was inserted through the hole in the tool, and I began to roll slowly...

I could now put a new pipe in place of the old one and simply solder it back in.

The final result. (Click on the image to enlarge)

Feedwater pressure pipes

This bending job looks deceptively simple, but it does have a few tricky aspects:

• the offset in the pipe at the front of the firebox
• following the curvature of the boiler whilst ensuring the pipe runs exactly vertically
• ending in a sharp bend to connect to the water inlet valve on top of the boiler.

Due to the offset at the firebox and the precise positioning of the right-angle bend upwards, the length of the horizontal section of the pipe is fixed on both sides, which means you have to work with great precision. I must admit that it took me three attempts to achieve a satisfactory result.

Two lines drawn on a scrap of paper help to ensure that the offset in the pipe is of the correct depth and that it lies flat with both ends parallel.

A piece of aluminium is used as a wedge to hold the pipe in place whilst soldering.

Connection for the steam blower.

One of the control pipes ends at the front of the smoke box, and I assume there used to be a connection for a nozzle that could be used to blow out the smoke box and the flues. The control line itself is 0.3 mm thick, and I wanted to give the end a bit more substance.

So I drilled a 0.35 mm hole in a 2 mm brass rod and then turned the brass down to 0.5 mm.

The wall thickness is 0.075 mm! It didn't work out first time. I had to learn to carefully shave off the final 0.1 mm with minimal tool pressure. The first time, there was a beautifully shredded flake of brass around the tool tip 🤣.

The connection in its initial building phase.

Assembly. A sliver of BluTack holds everything in place and a small piece of aluminium controls the distance from the boiler.

Done!

Exhaust pipes from the steam bell and air pump

I had to drill two more 0.8 mm holes for those two pipes..

It wasn’t easy, but with a bit of luck I just managed to reach it. The left-hand hole was fitted with a plug with a 0.5 mm hole, and the right-hand hole with a three-way fitting that I made from a small brass casting by Philotrain.

Bending the pipe from the plug box through the three-way fitting to the steam bell was a particularly difficult job. It requires great precision to ensure that the vertical section of the pipe lies close against the pressure pipe. Here too, I only succeeded on the second attempt. Once that was in place, I was also able to make the exhaust pipe for the air pump.