Rewanui - a 1940 West Coast NZ layout in 1:64

[Lawrence@NZFinescale]

Back on topic...

In 1878 New Zealand railways were very much a British colonial affair, but it was dawning on some luminaries at head office that some American practices would be more appropriate for our steeply graded, tightly curved, narrow gauge system.

So an order was placed with the Gilbert Bush Company of New York for some 'drawing roomed cars to be lined in plush velvet on the double bogie principle', passenger accommodations having hitherto been of the 4 or 6 wheel variety.  The cars were successful and became the pattern for subsequent locally made stock. A family resemblance was evident in wooden sheathed stock through to the end of steam, so this small batch of imported cars were historically significant.

The GB cars were constructed from American hardwoods, whilst the local versions ('Addington' cars) were in native, lower strength, timbers.  As a result, the US cars had 13, as opposed to 12, windows to a side and shallower underframe timbers.

By 1940 these premium cars were on their last legs having been downgraded significantly.  The three on the Rewanui service were all written off by the end of 1940.  I have yet to find a photo of a GB car at Rewanui, but there is one of a car leaving Greymouth Riverside on a Rewanui train.  The Gilbert Bush car is the second in the train behind one of the early local copies (with wood underframe) and ahead of a later variant (with steel underframe).

As a modelling prospect the GB cars are appealing for my needs. Relatively easy, as the basic method was proven on my 'Addington' cars. Etched windows were on hand and the bogies just needed to be stretched from 4' 4" to 4' 6".  On the downside the original drawings have not survived, but I was able to create a good side elevation by photoshopping the image of late survivor A230 at Dunedin.

My model of A256 is coming on so hopefully some pics in the next few days.

[Lawrence@NZFinescale]

As promised, here's the model.

1:64 on 16.5mm gauge track.

Basically a number of large 3D prints.  Added to this are 3D printed and cast brass details.  There are some etched parts in there too - notably the window frames (which slide open per the prototype), and the gates.

As always it's about integrating the various methods into something that blends smoothly into a model that well represents the prototype - that's the plan anyway.

This one has been a while coming as I seemed to fiddle endlessly with some of the details. I've upped my game a bit and as there are a few to do it was worth sorting some methods I can use for future cars.

[Barney]

Very Nice and a very clean bit of model engineering in miniature
Barney

[finescalerr]

Someone jealous of your skills could call the sliding windows overkill but, still, most satisfactory. -- Russ

[Ray Dunakin]

That looks great!!

[Stuart]

Beautiful!

[Lawrence@NZFinescale]

Another slight digression...

I've been working on wheels for Wa217, but for various reasons I've ended up completing a set for an Ab class pacific (which has no place at Rewanui) first.  Other than the fact they are a different wheel entirely, the method (and hopefully result) is similar.

I'm a self taught machinist with limited equipment so some of my techniques are pragmatic.

• Digital patterns incorporate the crankpins, chuck mounting flanges and alignment features
• Printed in a castable resin and investment cast into brass.  These castings are wickedly accurate and true.
• Castings are cosmetically cleaned up.  A bit of emery on the spokes to remove some minor 3D print layering is all that's needed.
• Tire blanks turned from free turning steel. (under bore, over diameter and over thick).  It's a heavy job done at a friend's place as my Unimat3 is not up to it.
• Castings faced at the back and the axle bore opened out to a press fit size on the 3mm axle with a 1:50 taper pin reamer.  The castings are very accurate and the cast axle hole is nominal 2.9mm bore, so it is not a lot of work. I have a little turned jig with 3 lands corresponding to too small, just right and too large. I want to use the bore as the datum as any errors should be evenly distributed and not obvious.  If I use the rim to drill the centre boss any lack of concentricity is very obvious.
• Stub axles are fitted. All subsequent operations/fixtures use these as the datum so the finished product is true.
• The crankpins are turned/drilled in a fixture and tapped M1.
• The centre is turned to the correct OD in a fixture
• Tire blanks are faced and accurately bored to a press fit on the centres.  Again I make a too small, just right and too large jig to easily get this right. The jig is made when I turn the centres.  Too large (ie the tire will be a sliding fit) is identical to the OD of the wheel centre, just right is 0.03mm smaller and too small another 0.03mm less than that.  If the tire sits snugly on the 'just right' land, but will not go onto the 'too big' land then they'll be a secure press fit. Obviously I'm using the lathe graduations to get this right too, but small ID holes are hard to measure accurately and the jigs remove the problem.
• Tires are press fitted so that they are flush with the wheel back
• Tire profile is machined.

All of these operations are done batch-wise so that the lathe set up is identical and each wheel uses the same settings. I've done a number of wheelsets now and refined the method as I've gone along.  It's still a bit laborious (particularly when you snap the tap), but went pretty smoothly this iteration.

[Ray Dunakin]

They look great!

[finescalerr]

Jewelry. -- Russ

[Bill Gill]

Lawrence, terrific!
Will the wheels be electrically insulated on one side of the locomotive? If so, what will be the insulation and how will its fit between the tire and the center gauged? (I'm just curious and impressed, this is far beyond anything I could atempt, but I enjoy following along.)

[Lawrence@NZFinescale]

Lawrence, terrific!
Will the wheels be electrically insulated on one side of the locomotive? If so, what will be the insulation and how will its fit between the tire and the center gauged? (I'm just curious and impressed, this is far beyond anything I could atempt, but I enjoy following along.)

Thanks Bill
I build my locos as 'split frame' (aka 'split axle') meaning that the loco frames are electrically isolated from one another.  So the wheels are live to the frame on each side.  Electrically simple and no pickups/wipers required, and you can have metal brake shoes/sand pipes nice and close.  However you do need to isolate the frames (simple with PC board spacers) and axle halves (not that hard to do. I'm using a commercial solution here, but there are other ways).

[Bill Gill]

Thanks, Lawrence.Sounds like a simple and reliable system. My Mantua 0-4-0 has a very thin insulating layer between the tires and centers of the drivers on one side. I've been told it's probably paper.

[Lawrence@NZFinescale]

Thanks, Lawrence.Sounds like a simple and reliable system. My Mantua 0-4-0 has a very thin insulating layer between the tires and centers of the drivers on one side. I've been told it's probably paper.

I'm aware.  In the remains of the british empire that's referred to as the 'American system'. :-)

[Lawrence@NZFinescale]

Continuing on the Ab pacific digression...

My locos have mostly been based on etched chassis from digital artwork.  So etched rods and etched frames mean that the centres are exact and identical as they need to be.  However, etched rods are not the best way to represent the large rod ends typical of NZR engines.

So this time around I'm trying something a little different.  Cast rods with separate brasses.  The brasses sit in elongated holes that allow adjustment in a jig to achieve the correct dimension. The centre driver is the datum and so doesn't need the extra fiddle.

The pic shows the castings more or less cleaned up with a sprue of 'brasses' to fit.  In 1:64 scale rods are a little flexible so I've added a strongback that should be invisible from normal viewing.  The pic reveals I have a little more cleaning up to do, but the castings should look a lot more convincing that a laminated etch.

My test run for this process suggests it will be quite feasible, so I'll be using the method on the Wa too.  The only wrinkle there is that the parts are somewhat smaller which will just add to the fun.

[finescalerr]

Absolutely gorgeous. Stick with castings. -- Russ