LTM 51 in HO

Detailing of the drive units - Above the footplate

Prepping the engine cover

Detailing work started with filling the gaps that where visible on the top edges of the engine cover. In the original etch there were slots etched and I partially filled them up with solder but did not manage to get rid of them entirely.

The engine cover as I found it on the etch The black lines clearly signals the etched through surface.

Even when filled the seam is still visible

I filled them with JB Weld.

The etched recesses at the back of the engine cover (left) were also filled. This side was etched as if it had hinging doors like the front side but on close inspection no doors could have existed at that location, just plain metal sheet.

After sanding I gave the superstructure a quick primer to reveal the spots I had missed during filling and filing. After a few minor adjustments I was happy and removed the primer again.

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Lubricators

At the front of the engine cover there are sets of three lubricators. Well actually two and a kind of junction in the lubricator pipes. I decided to mimic them as three lubricators. I am now at the edge of what I can still do. In fact before I started I was more or less convinced I was over that edge: simply too tiny. But I did not want to leave these details away without trying. So I tried. Judge the result yourself.

L-profile: legs 1.3 mm by 1.3 mm and 0.2 mm thick!

Drilled and cut to length.

The lubricators were mounted on a bracket. First I milled an L-profile from a piece of rail profile that I soldered to a sacrificial piece of brass. Legs 1.3 mm by 1.3 mm and 0.2 mm thick! After milling I drilled the holes on their appropriate places and cut the profile in lengths of 5 mm.

One hole was mis-drilled. The other vary a bit because you can't pre-drill a 0.5 mm hole, so the drill point wanders a bit before settling in the material.

Note: in the mean time I have bought drills and learned techniques that combined reduce the amount of wandering of drills. So if I were to do this again I would achieve a better result. well, you live and learn. Remember that this is hugely enlarged. In the end it is extremely hard to see.

I turned the lubricators from 1.2 mm brass rod. Dimension: 1.2 mm high, 0.8 mm wide and the stem is 0.5 mm wide.

They were soldered on the brackets in trios.

And the bracket on its turn was soldered on the engine cover.

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Lubricator pumps

The lubricator is a tiny thing, the height being just 4.2 mm and the diameter at the rings 2.3 mm. Yet I managed to turn a decent representation from 3 mm brass rod.

I drilled the body to 0.7 mm followed by a 1.2 mm drill. Then the the forward facing part was soldered in place (240 C) . The small seam on the right hand photo below is only visible on the photo.

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Tube from the lubricator pump

Not much to it actually. Drill a hole, solder 0.5 mm bras rod, and solder it on the other end as well.

The place tends to accumulate dirt of all kinds. I will clean that out later.

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Sandbox covers

There are two somewhat nondescript rectangles on the front of the running board on either side of the engine cover. These turned out to be the access hatches to the sandboxes that are located on front of the leading axle.

Construction is simple. Rectangles are cut from brass strip.

Sheet	Thickness	Length	Width
Top	0.2 mm	5.7 mm	2.3 mm
Bottom	0.4 mm	5.4 mm	2.0 mm

The difference in size creates an overhang of 0.15 mm to all sides.

It all sounds easy but getting a small part like this perfectly square and true and accurately to size is a work of filing with great care and patience.

I laminated the two layers together with 240 C solder.

Four of them, the left correctly positioned, the two on the right upside down to show the 0.15 mm overhang.

All four were sweated in place with 140C solder

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Watertank hatches

The hatches as provided in the etches were not to my liking. They needed all round cleaning up of the etch cusps, a job I was hardly looking forward to, and then soldering together before accurate positioning on the running board without a clear centre point. And even then I would be stuck with hatches that showed a small recess instead of the bulbous raised centre of the original.

So before going in to that I decided to have a go at making these hatches myself on the lathe. And my word, they came out pretty easily!

I miscalculated the height (left) but on a second attempt (right) a hatch emerged that was hardly any higher than the sandbox covers, 0.7 mm total height!. With the locating pin of 1.0 mm it should be possible to locate the hatch accurately on the running board. and solder it from the inside.

I drilled out the holes and soldered the hatches from the inside. The spigots made for easy positioning and soldering.

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Headlamps

The headlamps caused me a headache. Previous builds had shown me they are incredibly difficult to position correctly. First, they have no less than five dimensions of freedom, as shown in the pictures below.

And second as the headlamps are subconsciously the eyes of the "face" of the locomotive. This is is a primary function of recognising other people so we are experts in spotting when "eyes" do not line up properly.

As supplied the headlamps had only rudimentary stems which varied in size and location. So I filed the bottoms flat. Yet, to reduce the free movement of the headlamps while soldering I wanted a stem to be there. So I drilled 0.7 mm holes in the exact centre of the bottom, inserted a piece of brass rod and soldered (240C) them in place.

I marked and punches the places to drilled an made 0.7 holes to accept the headlamp's stems

Only to find out the obvious collision of the headlamp's stem with the underlying stem of the buffer.

I carefully shortened the stem to 0.6 mm, the thickness of the running board (0.4 mm) and a bit of extra grip.

I used the cross table of my drill stand as a positioning device. I put the superstructure of the drive unit in the vice and slightly tightened it, just enough to hold the part without squeezing it. A pair of self-closing tweezers on a solid base gripped the headlamp at its top. I inserted the lamp in the predrilled hole. Then I first positioned this tweezers so the the headlamp rotated in the correct alignment. Then I used the X- and Y- feeds of the cross table to get the lamp sit perpendicular to the running board. A short touch of a hot soldering iron with a scrap of 140C solder fixed it in place.

The end result, I amm happy with it.

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Air hose vacuum brake

These parts from Weinert are stunningly beautiful. As I needed to add a protective plate before the vertical pipe, I carefully opened up the part with a jeweller's saw with the fined blade I have, a mere 0.12 mm wide (left).

Much to my dismay I also had to remove that wonderfully cast valve (right)

A 0.4 mm hole in a 0.7 mm wide brass, hmmmm

One done, one to go

The piping leading to the brake hose casting was too short so I drilled a 0.4 mm hole in the back (left) and inserted a 0.4 mm piece of brass rod. I then drilled a corresponding 0.4 mm hole in a piece of 0.7 brass rod and joined that rod to the back of casting. Then I soldered it all together with 240C solder (right)

And now comes a bit of micro-engineering work. Later photos of the loco clearly show a protective plate in front of the vertical vacuum tube. Earlier photos do not show this plate so I assume this is a later change, made around 1933. This plate offers two challenges: it is very small and is is trapezoidal shaped. See the photo at the right and the drawing below (circle on the left note).

Milling such a small part, especially the tapered sides was relatively new for me.

A set of "technical drawings" of the protective plate. Click on image to enlarge

So I set out measuring from different photos. This proved to be difficult so most of the measuring is guesstimation.

I guessed the flat top of the trapezium to be 3 times the width of the vertical vacuum pipe, giving an estimated width of 1.65 mm (arrow on the top right of the left note).
I also estimated the height of the plate to be two thirds of the height of the vertical pipe, 4.7 mm (arrow far left).
The estimated angle of 2.5 degrees determined all other dimensions (left circle on the right note).
I also decided to go for an overall material thickness of 0.3 mm, which is no doubt unprototypical but very practical in the sense that you get a thickness that is acceptable for an HO model, thinner than usual but strong enough for most purposes..
I had to polish up my trigonometry skills. What was it again, angles, opposite side, adjacent side, hypotenuse, tangent, sine, cosine? Brrr, all the things I thought I would never use in normal life when I was at school. Much to my shame I had to look it all up on the internet. After forty odd years the knowledge had become dusty. But I figured it out and for the first time in my life I used a tangent calculation for real.
I added 0.2 mm to each side of the base of the trapezium.

Now I could go to work.

I soldered two pieces of brass to a sacrificial base plate. I milled them to the rectangular size (2.05 by 4.7 mm). Then I miled them down to 1.4 mm thickness and next I dropped the cutter further down by another 1.1 mm leaving the bottom end of the L-shape standing free.

Now I had two rectangular L-shapes. I "unloosened" (thank you Joe Pieczynski) one clamp of the vise and tapped it until it matched the protractor which I had set to 2.5 degrees. I reclamped the vise.

I marked the sides with a permanent marker pen. This way I could see how far the cutter had milled the material away. After all I had to remove only 0.2 mm at the top end.

After milling one side of each part I "unloosened" the clamp again tapped the vise to 2.5 degrees in the other direction and milled the other side of the parts.

I unsoldered and cleaned the parts.

A coin for comparison

A test fit.

And soldered in place. Quite happy with the result although the plate looks a bit on the high side.

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