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:

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.

The Blog is 10

Just to show you all I'm not dead yet (thanks modern medicinal chemistry).

So the Blog is 10. I even managed to miss this. I see I've managed to make 2 posts in the last 12 months, with this being the second.in that time ive don very little NZ120 modeling, or even model railway modeling. I have slotted in a fair bit of wargaming trrain making (and gaming) along with the obligatory gardening and indoor renovations. I'm now getting to the end of these....I think.

One thing I do have to report is somewhat of a surprise.
Ocasionally I'll have a look on Trademe to see what is for sale. A few months back I came across a bit of a surprise listsing, and was surpised to purchase the model reasonably cheaply without a bidding war, though I suspect that no one else knew what they were looking at, or wanted it (probably number 2).

The first NZ120 loco I ever built. A Farish J94/08 chassis provided the basis. The plastic top wasn't heavy enough so it was also my first (and so far only) ecursion into brass scratchbuilding. The funnel and air pump were turned with a file (the only one I owned) on a hand drill. The brass was all soldered together which was an exercise in juggling new hot bits of metal into position while keeping the older bits in the right positions. It did work in the end. The way I've built it means that the top will not some off, and I think/know it's impossible to adapt to DCC.
So, its a remined of how far (or short) that my modeling skills have come since 1990, and nice to have it back in the collection

What can it be?

I arrived home tonight to a package.

 I wonder whats inside?

'Ooooooooo'

We had been discussing some modifications with Peter in the last couple of weeks and these have paid off.The funnel really looks the part now.
( Its still quite oily and smells of almonds. Is the oil normal? Has anyone else suffered from this?)

Ab IV

Looking at yesterdays photo I noticed that the running boards were a bit high. The inner finescaler demanded satisfaction, and it was too early to drink.

I then added the running boards back in using plasticard.

That looks a bit better.
Then, while looking for something else, I came across some brass angle that was perfect for the tender underframe.

Camera close ups indicate that there will be a bit of work required to get everything back to square. Then again, I've seen plenty of prototype photos that would get a 'please' try again' if replicated in model form.

Ab III

A little bit more work this afternoon.

The tender had the front headstock removed to shorten it a bit, and 1mm (or near offer) removed from the bogie pivots to lower it. Its now looking a bit better to my eye.

Unfortunetly the ladder on one side perished (I'm just so rough) and so both were removed. I have some old etched ladders from somewhere so these will replace the RP ones.

Next onto the loco I'll add in a cab and some details, and also the tender footplate will get some attention.

Ab II

I managed to spend a little bit of time in the Man-sion today despite being roped in to chopping down several trees outside. will this cursed fine weather never end? Maybe I should start building an outdoor railway?
Anyway, its was a chance to do some more on the Ab. Primarily to get the wheels fitted. A hunt through a collection of boxes (and under at least one wagon) turned up 4 spoked peco wheelsets for the tender and a couple of Parkside Dundas wheelsets for the loco bogie. The tender bogie had immediate problems.

'Oh, and I broke the printed bogie pin too'

Printing a model designed for 1:120 up to 1:105 and still want it to sit on N gauge track is a bit short sighted. I drilled some holes in some plastic sheet and cut them out to use as spacers. Fortunately the loco isn't required to move. This makes things much easier.

'Oh, and I broke the other printed bogie pin too'

The wheels for the loco bogie were a bit easier. I removed the wheels and then filed the pinpoints back to flat to suit the inside frames. the photo shows that I will probably have to fabricate a new front bogie with a wheelbase that's a tad longer. Oh and larger cylinders as well.

Then I put it all together to see how it looks.

One end is the correct height, and the other isn't. I'll have to do some plan checking to determine which one is the odd man out. My gut is telling me that the tender looks too high all round, especially the trailing headstock. Other than that, Its a good place to start. I like that its square, something normally beyond me.

Ab's away

Tonight I got a chance to have a go at the first layer of paint on the Ab. Sandpaper and a knife were the order of the evening. From the photo you can see how it went. I think I need to get some more grades of sandpaper.

I'm not sure how to attack the boiler, but that can wait as I'm planning to work on the tender first. This will be split into work below the footplate and the footplate itself.

A First

I arrived home tonight to a parcel from Europe (via Wellington).
Inside we find this item. Its an Ab from Kiwi Trains scaled specially for the Summit model at the Fell museum.

Its my first chance to see a Shape ways model up close. Well, its sparkly. The resin seems to be rather brittle (though I have yet to attack it with a knife or file). There are striations from the printing process on most of the surfaces. I'll give it a coat of paint which should give me a better idea on a plan of attack to get it onto the layout.

So it was off out to the Man-sion and time to grab what seems to be a useful article from the local rag.

'Tally Ho chaps'