NZR A Class Loco Kitset

New Zealand Railways A Class

The Light of Day

NZR A Class Locomotive

Northyard 1:64 Kitset
9th December 2019 - 3rd June 2020

The Story
At the moment I seem to be mostly building kitsets that my father bought over the years, but never started. He was a great Dad and I feel that finishing these models is a way for me to celebrate his memory by finishing something he always wanted to. He spent endless hours with me when I was growing up, and it's time for these models to see the light of day in their turn.

The Northyard A Class kitset was, from memory, a real step-up for those modelling 1:64th scale New Zealand Railways. The kit appeared on our living room table, some time in the '80s. Every few years, Dad would take it down from the top shelf where it lived, and peer inside at all the bits and pieces. The box become tattered with its many openings-and-closings, but it was otherwise untouched.

Last year, I decided to make a start on it. I was lucky enough to be sent a treasure-trove of prototype photos, including a lot of detail shots of the frame, the valve gear, the brakes, and piping. This amazing resource made me think I should put in some extra effort, and add more detail.

The kit could be beautiful right out of the box, but the loco frame was just a simple one-piece casting, with fixed axle slots. It precisely located the drivers and added weight, but I thought traction over uneven ground might suffer, and the solid block wouldn't look as prototypical as a plate frame. I'd never scratch-built a frame before but, what the hell...

The Build

The kit went together no problem, because it had been very well thought-out. Due to my usual impatience, I didn't follow the instructions exactly but, instead, flitted between the tender body, the boiler, the loco frame and wondering how many more details I could add.

Knowing when to stop

"It became a case of, the more you look, the more you see."

The kit frame looked different to the prototype in places, so I followed the drawing instead. I noticed that the model firebox was a lot longer than on the prototype, and that the frame under the cab had been narrowed-down to give more clearance for the trailing truck. Some of the frame attachment points were slightly different to the prototype and some were missing completely. I spent a lot of time figuring out how it should all work.

Once I'd made the frame, I worked through the rest of the kit, adding all the bits and refining them as I went. The mechanism ran perfectly smooth, with almost no tweaking.

It was a joy to build, and became a case of, "the more you look, the more you see". For example, I noticed that some of the steam piping shown in the photos had been lagged, and so I wrapped very fine copper wire to simulate the asbestos rope used on the prototype. I had some extra pipework fittings and used them to add pipe unions for more detail.

The sequence of photos below will show progress on the model much more clearly than my ramblings. Each gallery of images is more or less chronological, not counting the odd re-build, due to dissatisfactions or mistakes.

First Steps

I followed the instructions for once, and the tender went together well. I didn't find the stainless top plate that easy to work with.

First Details

The hand rail mount would be very weak, so I added a brass shim base, with a brass top. At the time, I was quite happy with it, but that didn't last...

Piping Practise

Figuring out and then adding the tender brake piping, gave me some good practise on working with fiddly bits.

Missing?

There was no coupler plate for the tender. I don't know if there was one with the kit that got lost, but I took it as a challenge to scratch-build my own.

Nice enough for me

Making the coupler draft plate taught me a few things, and gave some satisfaction as well.

Fiddly

Here's one of NZ Finescale's tiny (0.4mm core) lighting conduit castings down on the rear beam, and my attempt to simulate a flexible conduit up to the rear lamp.

Almost Correct

Some of the prototype photos showed various pipe fittings and bits on the front of the tender. I made what I'd call an approximation of them, plus added an ash rake. The grab rails have been upgraded, too.

I originally planned to use Northyard bronze bearings in my new frame, but got talked into using roller bearings instead. That required a bit more work, but the end result was a much more smooth-rolling model. The front axle was sprung using NWSL Medium-weight springs and the two rear axles were equalised. To set the ride height, I made the equalising beams slightly over-height, and then carefully filed them down until the frame sat level.

It ended up running perfectly, and was worth the extra time spent figuring it all out.

Frame Upgrade

Scroll through the gallery below, to see the build sequence.

Figuring it all out

Here's the cast frame, with my new frame just cut out of 0.5mm brass, to see how it looked.

Use a Jig

I have found the value of making a jig for soldering. I used small scraps of pine that had been cut perfectly square on a table saw.

Weighty Decisions

Here's my clamping method: bits of wood, a flat file and a lead dive weight, giving an easy way to vary the clamping force.

Location, location

I added pins to the front bearing guides to locate them for soldering

Easy

After spending hours carefully gluing the jig together, the actual soldering took about two minutes.

Done

That turned out better than expected.

Upgrade

The first of my new roller bearing carriers.

I needed a way to hold the new bearings, so that they could be located in the frame. These carriers were the final result. The ones on the front axle had pins for locating coil springs. Filing each carrier to be a close slide fit in its matched guide was time-consuming, but worth it. All I needed to do next, was solder them in the right place.

It was a good system, but Lawrence from NZ Finescale has since made me a set of etched nickel-silver carriers based on my design which are much more accurate, locate the bearing better and don't take several hours for me to make...

Lining it all up

With the first set of bearing guides soldered in place, I put a steel dowel through them for a datum so I could locate the second and third axles.

Rolling

The time taken to get everything lined up, paid off.

Soggy

I'd heard of using wet tissue to absorb and control excess heat from soldering. I'd always dismissed it but, having tried it, now think it's the best thing since (soggy) sliced bread.

On her feet

Setting the ride height, so I can make the equalising beams for the rear axles.

Finding some resistance

It might have been due to its age, but the motor drew about 0.25A with no load. I pulled the motor apart, polished the bearings, and got it down to this.

Torque arm

This contraption locates the gearbox under load. The pins on the short brass tube sit in a yoke inside the frame, and slide on the main tube to allow for suspension movement.

I wanted to get the chassis running as well as I could before starting on the boiler, but failed. I was too impatient. I wanted to see how the rest of the model would look when it was finished, so added domes, the chimney, running boards and pipes in between operations on the frame. It kept things interesting, but did mean I got ahead of myself at times.

These next photos show progress on the boiler, and hide the fact that I couldn't figure how the eccentric cranks should be fitted. I wasn't happy with the splash guards over the drivers, either. I did what any sensible person would do, and pretended they weren't there.

The Fun Stuff

With the basic frame finished, I could start adding details to the boiler. I had a bit of trouble knowing when to stop.

Oooops

The muffler for the Westinghouse brake pump was cast as part of the whitemetal boiler. A bit of carelessness with a soldering iron reduced it to slag, so I had to make a new one.

In place

Here's the new muffler. It turned out alright, but the drain tube thingy on the bottom is a bit bent. I left it as it was, rather than mess with it and ruin the whole thing. I later realised I'd put the muffler in the wrong spot, so had to move it and patch the boiler.

Wrapping

Here's my first attempt at adding lagging to the pipes. At the time I was happy with it, but ended up reworking this first part as I subsequently became better at wrapping wire. .

Piping

I got a real kick out of adding pipes. That first lagged pipe on the air pump was starting to bug me, though...

Time for Tee

I wanted to add the sanding valve steam line, and used this cast tee. It's actually too big but, was also the smallest one I had, and looked the part.

Drifting

Drifter pipes, sanding lines, and all sorts of bits to add to the picture. I had also noticed that the safety valves on the prototype were actually set into the boiler cladding, so I recessed them in to suit.

Forgetting Bits

One side-effect of ignoring bits that scare you off, is having to address them later when it's a lot harder to do.

With the boiler almost finished, and the cylinders and valve gear working well (apart from the eccentric cranks), I had to start doing the bits I'd not been able to figure out and had "left to do a bit later on". That meant adding the drawbar, splash guards, brakes and other such details at a point where I risked de-soldering much of my work. Not to mention making it harder to solder them on square and true. I managed it with a lot of messing about, and lumps of soggy loo paper...

Here, I'm adding a new tender drawbar. The whitemetal one in the kit seemed too thick. Ironically, now that it's finished, it's almost hidden anyway...

Chopping Up

The rear equalising beam bracket had been made narrow to fit the cast kit frame. I remade it to the prototypical width, and added extra bits to it as well.

Brakes

The brake hangers were supposed to just glue onto the top pivot points, but that'd make them very weak. I added brass wire braces at the bottom, and was planning to add rigging as well. Maybe in another life...

Splashing Out

The splashers that came with the kit were those simple laser-cut things by the track. I made new ones from scale thickness shim and brass wire beading.

Naked

Steam cocks weren't supplied, so I tried to make some using the photos I had.

Tiny

With no dimensions, I guessed at the sizes, using 1mm tube and a coil of copper wire inside to represent the spring. I've since found that they are oversize. What the hell, I like 'em.

Steam cocks in place

The valve bar has yet to be thinned down. I had extended it forward as well, hoping to model the actuating cylinder, but the lead truck would have fouled it on curves.

Closer

More messing about with the splashers.

Rework

The piping and valve for the Westinghouse pump had to get an upgrade. As I got better at wrapping pipe lagging, it really stuck out. The pump valve stem was also too short, so I replaced it with a longer one and recessed it into the boiler wrapping, like the safety valves.

I learned that the eccentric cranks were designed to be soldered to the con rod screw and therefore had to screw in exactly the same amount every time, to stay in alignment. I didn't like that idea, so I fixed threaded pins to the drivers instead. The eccentrics are soldered to threaded tube, which precisely screws onto the pins.

The final piece of piping to add was the lighting conduit. I used NZ Finescale junction boxes. The ends had to be drilled out 0.4mm, which made me sweat. The wire seated in the hole a lot better, once I filed a very slight taper to it. I also made a coiled flexible conduit up to the cab.

In a last-ditch fit of madness, I also made the brake levers and clevis links under the cab. I'm glad I did, as they just seem to finish the picture.

Beyond Me

I've now learned enough about scratch-building in brass, to know when to say, "enough" and use available technology. This one-piece printed backhead would have taken weeks to make in brass, and not been anywhere near as good.

Trailing Behind

After making a new equalising beam, I thought the additional links and rods for the trailing truck would be a good thing to add.

Eccentric

The assembly method on the eccentric cranks was one of the few points on the kit that really didn't make sense to me, so I replaced them with fixed pins and threaded tube.

Really, really tiny

Here's that conduit junction box and flexible conduit. I'm pretty sure that I'm the only one who will know they are there. I also made new cab windows while I was at it.

More Madness

I wanted to add the brake levers under the cab and had to figure the sizes from photos. The brake rod is sleeved with 0.8mm tube underneath, so the trailing truck can be removed.

The ugly truth

Here's the underside. The tubing that allows the brake rods to be separated is almost invisible, by the rear axle. The larger tubes further back are turnbuckles. I've tested the model on a 1m radius curve, but time will tell if I have enough clearance...

Six months on, and this has become the most satisfying model I've built. It runs very smoothly on DC power and only awaits a decoder, lighting, and a paint job. Taking the time to add those extra layers of detail have paid off both in modelling enjoyment, and as a final result.

It only occurred to me after I'd finished, that since I scratch-built the frame and a lot of the details too, I've learned enough to do something I've always wanted: make a locomotive in brass, by hand.

Thanks heaps to Peter for his encouragement and a stack of great photos, and to Lawrence at NZ Finescale for good advice, a set of roller bearings, and one of his fantastic one-piece backheads.

And to my Dad, who gave me pretty much everything.

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