Pain in the Nethers - Chassis Frustrations 2 - Steamers

DB makes a few poorly researched observations:

We NZ120 diesel modellers are pretty lucky, having a host of N scale chassis offerings that are a good-enough fit for most of our diesel locos. After a few months of pondering this Wb, I'm thinking steam is another matter!

Issues include:

• Driver size and spacing 
• Wheel arrangement 
• Cylinder location/connecting rods.
• Motion
• N scale vs our 1:120
• Power pickups and decoders

Driver size and spacing was well covered by Premier Duff in several posts. 

wheel diameter real equivalent loco classes

7.5mm 3 F
8mm 3'2" W, Wa, Wb, Wd
9mm 3'6" B, Ba, Bb
9.5mm 3'9" Wf, X
10mm 4' Ww, Aa, Q, U, Ub, Uc
11mm 4'4" A, Ab, Wab, K, Ka, Kb, J, Ja, Jb 

12mm 4'9" G

More here  Put the Kettle on , Steam pt 2 , Steam Part 3

I've noticed that many overseas steam prototypes, and thus models, have a larger gap between the two rearmost drivers (presumably to fit the firebox) whereas most of ours have consistently spaced drivers. Even my Alco Wb chassis has this 'feature' although its not too noticeable.

Because of N's 1:160 to 1:148 scale, the large drivers of racehorse overseas locos become reasonable for us to use in 1:120 on NZ's plodders.

While in theory, leading and trailing pony trucks can be subtly altered, this is easier said than done. 

At the front this is hampered by the cylinder location, which can't really be moved because of the valve gear.  This is an obvious fact that I hadn't even considered, so you usually can't replace a pony truck with a leading bogie, because there isn't enough space between the cylinders and the drivers (and the rods aren't long enough). Many of the models I've looked at online don't have the sort of room between the cylinders and the drivers we need - most of our locos have quite long connecting rods. This is partially exacerbated because they are in N rather than 1:120.

My Wb needs the leading pony truck moved forward, and a trailing one added. The pony truck that came with the model is a larger diameter than it should be but I have another smaller one off a Japanese steamer I may use, or I might just keep this one.

As for motion, other than our early inside framed locos and some later appearances of Baker valve gear, we were primarily in the Walschaerts camp for the bulk of our designs. My Wb should have inside valve gear, which means removing everything other than the main connecting rod and the distinctive Baldwin bowtie crosshead that my chassis does not have. A risky and painful operation given it is reasonably nicely modelled. I could leave the motion there, as I wouldn't have noticed before I started staring at Wb pics recently. 

Ebb-Fettler has a 3d printed Ba loco top, needing a fairly narrow chassis, which made me dig out a pair of Japanese 2-8-0s that I was once going to turn into 2-foot six narrow gauge Chinese C2s with much larger scale tops. But these 'chassi' happen to have their connecting rods joined to the third rather than second driver! I'd never noticed this before last week. looking at the C2, that's how they are attached. So a fail for the Ba, but a win for the C2.

My Wb donor engine was a tender loco (a Bachman Alco consolidation). The tender has plenty of room for the supplied chunky hard-wired decoder, but that won't fit it into my little tank engine, so will have to be replaced with an ancient Digitrax Z scale decoder. The Pacific that I hope to turn into an Ab also has a big roomy tender which houses a long decoder board and a matching long speaker enclosure. Both of which will have to be shortened, as our tenders tend to be much, much shorter than American ones as our axle loadings restricted how much water/coal/oil we could carry. Shortening the tender without breaking too much will be a problem for another day. An A's square tender might be a better bet than the Vanderbilt one of the Ab.

The other issue with the need to remove the tender for the Wb... is that I'll be ditching 2/3rds of my power pickups, with the badly-laid-track-conforming tender bogies being sacrificed for a rigid six-coupled loco with traction tires on the front axle. Those rubber bands may have to be be removed. As for the possibility of picking up power from pony trucks. That would require engineering well above my pay grade.

So summing up the biggest challenge with steam in NZ120 for one without a CNC milling station and scanning electron microscope: With the 'modular' design of diesel models in the past, it was possible to swap out bogies from other loco types for different wheel arrangements, axle spacings and wheelbases, and even lengthening a chassis is possible. People have made custom chassis for NZ120 railcars for example. See also my DI with its reversed SD40-2 bogies in a GP30 frame. With steam, there seem fewer 'natural fits' for NZ prototypes, and modifying a loco chassis seems much harder, especially as they are 'advancing' with sound, miniaturised components and less user-serviceable designs.  Or maybe its just a mental block plus my lack of experience with tiny wheeled kettles and micro-engineering.

So what chassis have other modellers used for NZ steamers, and what is your critical assessment of these in terms of fit, modifications needed, and performance? As with diesels, the limited runs that are produced these days probably make some of these old hens-teeth models real gems now. We could do with a steam loco chassis compendia like the diesel one referenced at the top of this...

Wb 2 - Bodywork and a pipe band

Db continues his Wibbledeebee:

Scalpel please, Nurse.

This might look a bit brutal, but was done for two reasons. Firstly, I didn't have much luck straightening out the warped side tanks. And second, I needed to make some space for a DCC decoder.

Below you might be able to see where I removed a fair bit of material on the underside of where the boiler and top of the side tanks join. There is also a lot more space inside the side tanks now.

Getting the band back together after a fall off the bench onto concrete separated the front end into four pieces (one still missing but replaced with styrene):

Part way through applying filler:

The body was then spray primed (nice) and brushpainted (yuck) with weathered black, which is a bit green for my liking. This was to ensure that there would be some paint on the parts that would be hard to get to after the pipes and things went on:

The distinctive Baldwin Wb 'curved gusset' between the top of the bunker and the cab was added, the air reservoirs under the cab, steps on the side of the rear bunker, and a toolbox. This 3D print has one on the front buffer beam, which I've only seen in one of these on a very old pic, but I quite like it. 

A mess of air pipes (the more the merrier!) handrails and some stays behind the cowcatchers completed things. The piping detail was done using this pic from the NZ Railway Observer as a guide, and a few other Wb pics stolen from the web.

And to close, a pic that illustrates my frustration with putting way too small coupler pockets into tough and brittle 3d prints. Its going to be a squeeze:

Elmer Lane 28 - Coal Bin

DB says:

Elmer Lane always seemed to have an old yellow La with coal on the stub tracks outside the Supervisor's office.

So mine does now too. This was one of a dozen La castings I got from someone (Rod Murgatroyd? Cross Creek?) that were the start of an undisclosed (and inelegant) Stone Train that I started putting together when I built the DI all those years ago. 

One of the wagons was de-limestoned (and what a surprise to find I'd buried a lead slug under there), its door was cut open, filled with coal and repainted. I suppose I expended about ten minutes on this. It's now permanently attached to Elmer Lane. 

Obviously needs more rust and fading, but that might look unprototypical...

Wb 1 - Wubbada Wubbada

In which DB contemplates his first steam loco model (this long-maturing blog entry was written in September 2024, had its genesis in late 2023, and is in mid-2025 almost ready to go...).

I have always been a diesel man, as that's what I've grew up with, but if there is one place I'd like to go back to in a time machine, it would be the West Coast in the late 1950s-1960s. A magnificent collection of ancient engines with jaunty little trains of four wheelers running through bush scenery and over rickety bridges to remote coal mines on wobbly branches to places with funny names like Blackball/Roa, Dunollie/Rapahoe/Rewanui, Conns Creek and so on.

When we decided to come back to NZ in 2015, I had visions of making a small Rewanui module to get back into NZ120. I bought a couple of Bachmann 2-6-0 locos in anticipation (underpinnings for a Wa and Ww maybe), and when we were in Wellington looking for a house, I started making a relatively awful Q hopper wagon on a Peco 10 foot chassis, but that was a very short-lived attempt to return to NZ120. After that, we were away for a while, and Swiss Z scale won my heart for a few years.

In October 2023, I came back to modelling after a few years off. Press-ganged into operating the massive 9mm layout at the Christchurch show, I spent the whole weekend running a small train around (and around and around) with a Wb. The loco was running backwards the whole time because only the headlight on the bunker end worked, and because it seemed to run better that way without derailing anyway. Both were handy excuses, because I secretly prefer the aesthetics of a tank loco or a Dsa running backwards. 

Delving further into the aesthetics of tank engines, I have always preferred the looks of the W, Wa and Ww, so have never paid much attention to Wb locos, but this big 9mm model won me over. The other train that was running for most of the time was an Ab with a couple of red wooden carriages and a matching car-van.

Elmer Lane 27 - Officer's Mess

 DB raises another building.

The last major building to be installed at the depot is labelled '32/33' at the bottom left of this previously-featured cropped image taken by Ian Coates from the Steam Inclined book. This was the loco crew's amenity block, with lunch room, lockers, lavs and showers. The building was extended over its life and survived into the 1980s.

The building was made using the methods previously detailed that have been employed with the others on the module, being an evergreen clapboard shell with chunky strips for eves, and (modified) brass etched Ratio British N scale windows, which are obviously a tad small. But the effect is OK I reckon.

The roof going on below. This is the same ancient but lovely Fidelis N scale corrugated iron used on the yellower-coloured office block on the other side of the depot. This time I scored a midline and chopped this into skinnier verticals and glued the sections on, rather than using one solid sheet. I'm not sure even I can tell the difference.

A test fitting, yes, the building should be located on a different angle, but this was intended to partially hide the shadow sidings behind:

Despite the orangey look in the picture above, the door and windows are a similar shade to the roundhouse windows. The next morning, the crew block and the larger stores building beside it had some weathering applied:

Odd angles mainly due to the wide angle phone lens. The crew building has an open back and hides the Digitrax autoreverser module featured in a previous entry, so this building will probably be glued down, whereas the roundhouse, stores and railcar shed are still removable. The Stores shed may lose the unprototypical lean-to out the back, or at least its roof, for better access to the Kato turntable controller underneath it. 

Elmer Lane 26 - Autoreverser test

 DB plugs onwards.

A return was made to the basement to see if I could get the remaining bits of the module any closer to finished.

The 'shadow' storage tracks out the back were laid in a fairly ugly manner. I used up some old code 80 points and track here, and lazily did not power the frogs (relying on the electrofrog wipers). Seems OK so far.  All rails were extended towards the 'north (the station) and a piece of PC board applied under them and wired up. I've also decided to extend the depot track at the 'back' (closest to the red fence) towards the camera so that it can be accessed from the rest of the layout. Previously it was only accessible from the turntable, which meant you couldn't store pairs of diesels there easily.  Its yet to ballasted at this end until the point is located just this side of the next module.

A Digitrax AR1 autoreverser was added onto the balloon loop to deal with the unfortunate physics of the "red wire becoming the black wire" as you go around the loop and back in the direction from whence you came. 

This works by having an isolated section in the loop that is powered from this device, which is (seemingly unsophisticatedly) a relay that works like a reversing switch.  As a train enters or departs this from either end of the isolated bit,  if a short is detected it tries flipping the polarity. This seems to work, and gets good reviews online. I picked it up when Acorn models in Christchurch had a sale on a while back. 

My original plan had a one metre length of flex track on the Hoki line (in front of the railcar shed) that would be powered by the autoreverser, but I recently decided to isolate the entire lump between the points at the far end of the storage sidings through to the points at what will be the Greymouth Station. This should be long enough to take the longest train (about three metres), and avoid the tiny probability that both ends of a one metre section could be bridged by metal wheels at the front and back of the train at once. Very unlikely given that most of my wheels are plastic anyway, but having said that, most of my vans have metal wheels, as does the Tranz, and that is longer than a metre. 

So, with that installed, it was time for a test. Out with the Multimeter and... shorts everywhere. I took off the remaining locos, checked for exposed wires touching underneath, isolated the autoreverser... Nope. 

Finally I decided I'd have to snip some wires to isolate a few segments to track down the error. Either on the new shadow tracks, which look fine, or on the roundhouse roads, which also look fine, or on the small bit of Greymouth platform/loop, which looked OK, but was now covered in light ballast, so I couldn't really tell. Snip. Action stations! I'll have to re-feed those two tracks later. I knew I should have been testing this all along....

Anyway, the module works, the turntable still works, and you can spin a loco or drive one onto the powered roundhouse tracks.

Pain in the Nethers - Chassis Frustrations -1a - Atlas

DB follows up - 

FYI here are the three versions of the Atlas SD7/9/24/35/etc. 

The 1990s Atlas/Kato one  - they still run well, but the motor had to be isolated to add a DCC chip:

The early 2000s edition was 'DCC friendly' with an isolated motor, and you could unscrew the chassis halves a little to pop out the light board for a DCC replacement. The negative with models of this era was maintaining good electrical connection between the frame and the decoder board (often requiring slim brass shims wedged into the four corners), and between the board and the motor. These models have quite slow speed motors from memory, which was a pain when running them with other locos, which why most of my other diesels have been modified with DCC speed changes to they will run with these slow DC/DBR/DA chassis:

The new one. Black speaker box under the board at right whether you want one or not, little piggyback board under the main board at the left end, joined with an E24 connector (DC here, but these can be replaced with a DCC or DCC+sound one):

On the plus side, while the bogies look identical to the older models (complete with now-redundant sticky-up copper tabs), tiny wires are now used with micro connectors to bring the power up to the board, rather than the old brass strips along the sides. I think the motor is also linked to board with wires, so I may end up throwing away the supplied board and hardwiring an orange decoder into those wires. Of note, the chassis isn't split frame anymore,

With the tiny wires, connectors and components one wouldn't want to drop this on the floor...