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

[Bernhard]

Lawrence, this is really great work, and an interesting prototype. How did you recreate all those rivets?

Bernhard

[Lawrence@NZFinescale]

Thanks Bernhard

Rivets are a mix.  Most are just etched in, so drawn in the artwork and presto back come the parts all nicely riveted.  For various reasons that does not always work conveniently.  When that's the case I add an etched dimple on the BACK side of the piece and use a press to punch in the rivets using the dimples as guides.

I've enough experience with CAD and etching that I would probably do it this way even for a one off. After all, one needs to prepare working drawings to make a model, and turning those into etching artwork is not a huge extra step. However I never really do one offs as a) I usually have a short run kit in mind, and b) even if I didn't I have no doubt I could sell of sufficient etchings to cover the effort and costs.

The Wa class has much in common with the W that I did kits for some time ago.  Reworking the artwork to suit the Wa was not that big a job and since I want 2-3 Was  it is well worth doing.  The Wa is a viable kit subject as well and I have quite a bit of interest I can work on once the pilot model is done.

With this model I'm playing with a few ideas for my own loco building that likely won't be commercial, but 90+% of my build effort will go straight into the kit.

[1-32]

Hi Laurence.
love your posts,happy New Year from across the ditch.

[Lawrence@NZFinescale]

Something of a digression from the main topic here...

When building small locos the motion is always a trick and I'm always looking to make life a bit easier.  Illustrated below are castings for the cylinder ends, slidebars and motion bracket for a 1:64 NZR Ab class Pacific (second 2) and slide valve cylinder/slidebar/motion bracket for Wa217 discussed earlier in this thread (my justification for including these pics here).  Doing them in one piece is tricky, but makes assembly much easier.

The 'waxes' were 3D printed in two halves (left and right), joined with molten wax and sent to my contractor for casting into silicon bronze (generally referred to as 'brass').

All the holes will need clearing/opening up and the slidebars will need careful filing to clean up, but this will not be hard to do.  Casting this way involves very low shrinkage, so the parts will just clip in to the etched chassis/printed cylinders. They will form a super solid basis on which to assemble the valve gears.

These are pretty nice castings for the small scale.  The surfaces are not as nice as they can be from a true wax, but the detail level is way better than I could achieve with a hand made brass pattern.  Of course a hand made brass pattern would require a rubber mould - which would likely be impractical for these parts let alone the variable shrinkage that would need to be dealt with.  My understanding is that my caster just treats the printed 'waxes' the same way as he does regular wax.  Results would possibly be better if materials and procedures specific for printed resin were used.  Unfortunately my volumes are not enough to justify special conditions.

This has been a choke point so now I can get on to building the locos again.

[finescalerr]

They are sufficiently perfect that no imperfection will be evident when you paint them. Most satisfactory. -- Russ

[Barney]

Lovely stuff  - I wish some of the other casting people Could learn a bit and start supplying castings of quality
But keep the excellent work up
Barney

[Lawrence@NZFinescale]

Some more castings - this time for Wa217.

This is a quickly stacked image and there is a bit of 'glow' around the edges, but you'll get the idea.

Domes are just placed for the photo.  The sand domes are as received from the caster, other than removing the sprue and truing the bases to fit the boiler.  They need a bit of tidying up. The steam dome has been polished using diamond pastes and a felt wheel.  Safeties and whistle added as separate parts.

All domes are hollow with a wall thickness of 0.5mm or so.  This makes them easy to work with when drilling and adding detail.  The main bodies of the sand domes are just over 8mm diameter.

Also another pic of the real thing at the time I'm modelling.  Fresh from overhaul 1940 (SA Rockliffe photo, NZRLS collection)

[Bill Gill]

Lawrence, You even captured small dents in the steam dome that can be seen in the prototype photo!

[Lawrence@NZFinescale]

ahem, cough!  Yessss. It does look like that, but actually those are casting defects :-)

[Bernhard]

Excellent parts, Lawrence. It's fascinating how small and detailed parts can be cast.

Bernhard

[finescalerr]

I very much enjoy seeing what kind of mischief you get into. Please post a little more often. -- Russ

[Rail and Tie]

Brilliant work! Inspiring!

[Lawrence@NZFinescale]

A digression.

I'm currently on my 3rd and 4th 3D resin printers.  The first was a DLP that I have fond memories of, but it died and was prohibitive to fix. The second was a laser machine the less said about the better.  Fortunately consumer law here meant I got my money back, if not my time.  The current two are LCD machines with differing bed sizes and resolution.

Overall the LCD machines are the best of the bunch by some margin, but there are still some things that the DLP set up would do that the LCD has not been able to match. The DLP had a gentle release mechanism and I used a pretty rigid resin that allowed fine wires to print.

Lately LCD resins have improved a bit and I'm now close to what I could do over 5 years ago.

The grey primed wheel is today's print (35u resolution, 35u layer height).  Not exactly the same file as the others and I omitted the wheel nuts, but you get the idea.  These spokes are drawn at 0.15mm diameter and could possibly be finer.  0.1mm spokes did not reliably form, but did partly print, so finer might work.  You can see layering here, but not at any reasonable magnification. At these dimensions paint film thickness starts to be a significant factor too.

The other pics may have appeared here before.  The orange wheel was from the DLP.  Smoother, but that is probably due to a somewhat softer focus and a bit of over-exposure.

The last pic is just to provide a scale for the whole exercise.

I'm pretty happy.  Not being able to produce this style of print after years of it being routine has been a little frustrating, so it is nice to have this ability once again.

 

[finescalerr]

You are a master 3-D printer. -- Russ

[Ray Dunakin]

Such fine detail in something so small is astonishing to me!