Atlantic's works: Portable layout - Scenic details next

[Atlantic 3279]

Regarding the green resin, the result of simply adding some green and some black powdered pigment to the liquid resin, I was hoping to produce a far better hue and density, but it isn't working so far, even with some trial additions of burnt sienna in mixtures that I've made up. The root of the problem is that the basic shades of green pigment powder that I've been able to get are neither dark enough nor rich enough. I've managed to get only two green powders, one of which, (Reeves Tempera green) in the dry state, looks as pale and "pastel" as basic copper carbonate (it may well be that). While it darkens vastly in the liquid resin, it returns almost fully to the pale state as the resin sets. The other powder I obtained is a bit more vividly green when dry, also darkening in the liquid resin, although it to returns to type when dry and still isn't vivid enough. I could only find it in small bags at relatively high cost, supposedly as a colouring agent for that plastic medium that can be kneaded into shapes to create ornaments and suchlike.
The snag in either case is that adding larger amounts of powder in order to try to enrich the colour creates far more chance of leaving islands of dry powder somewhere in the mixture, and the (presumably) less "continuous" structure of the bonds in the cured pigment-dosed resin seems to reduce the mechanical strength. I doubt that the pigment particles become a chemical part of the polymer structure, I suspect they just sit there with the polymer structure having to fit around each particle.

[Atso]

That casting looks really good Graeme, although the shade of green reminds me of the colour of some of my prints when I messed about with the resin - trying to get a denser pigment for better layer thicknesses. It didn't work as the resulting prints were too fragile for the same reasons as you suspect with your castings.

I'm hoping to actually be doing some resin casting this year and so I'll be brushing up on your methods and techniques.

[Mersey508138]

I would be interested to learn how the valve gear for 2002s chassis has been done please.

[Atlantic 3279]

Those pictures show a combination of valve gear parts from different sources, fitted to adapted Bachmann V2 cylinders. The con-rods, slidebars, crossheads and the return cranks are original Hornby P2. The drop links added to the crossheads, along with the union links and the combination levers (the front parts of the Walschaerts gear) are from a Comet V2 etch. The eccentric rods, radius rods, expansion links and the distinctive motion bracket come from an etch designed largely by Morgan Gilbert to aid conversion of Bachmann Peppercorn A2s into one of the Thompson versions. The long reversing rods are made up from nickel silver strip. Use of this mixture of parts demands a bit of work and ingenuity, but it results in valve gear that actually fits properly in the very limited space between the cylinders and the driving wheels. The motion bracket from the special etch doesn't fit directly onto the P2 chassis block, it has to be modified.

Apart from making up the joints between the different parts of the valve gear, some of which wasn't designed to go together, and folding/soldering up the motion bracket, the business of fitting the motion bracket to the P2 chassis involved cutting the whole motion bracket assembly into right and left halves, then re-joining those using some extra pieces of brass or nickel silver to create a stepped profile to the cross-piece that unites the two sides. If this isn't done, the assembly won't fit OVER the top of the chassis but UNDER the running plate on each side. It's a bit of a pain, but there you go!

[Atlantic 3279]

I might look at something other than pigment powder as a resin colourant. I only pursued that idea because I had some black powder paint, tried that, and found that it worked well. It seemed logical to try other colours, but it seems they are not so simple.;

This might be the way to go, if necessary:
http://www.easycomposites.co.uk/#!/resi ... resin.html

Although this sounds a cheap and easy idea to try out first:
http://brassgoggles.co.uk/forum/index.p ... #msg843749

[Atlantic 3279]

I did a couple of resin test mixes earlier this evening, one incorporating Humbrol satin dark green enamel, the other incorporating Railmatch Darlington Green. Little paint is required to give quite dense colour to the mixture, both appear to have cured well. There's no evidence of wet or sticky paint traces on handling the cured surfaces, or on either breaking or filing the stuff. I'm amazed it is so straightforward. I did not try previously to incorporate paint as a colouring medium, fearing that introduction of any oil, different monomer/polymer, or solvent might corrupt/poison the curing process.

[Tim Watson]

Interesting combination of valve gear components to make up Earl Marischal, Graeme - they work well. The valve gear is indeed very constrained on a P2. I tried and measured various etches for my 2mm Lord President, but ended up making the whole lot from scratch. It can be positioned in forward or reverse and is fully working (photo by Tony Wright).



Tim

[Atso]

The successful use of enamel paint is very interesting Graeme. A couple of questions if I may:

What ratio of paint to resin did you find worked?

Any chance of some pictures of the casting please?

Many thanks

Interesting combination of valve gear components to make up Earl Marischal, Graeme - they work well. The valve gear is indeed very constrained on a P2. I tried and measured various etches for my 2mm Lord President, but ended up making the whole lot from scratch. It can be positioned in forward or reverse and is fully working (photo by Tony Wright).



Tim

I keep meaning to say this on RMWeb but that is incredible Tim. I missed you at Stevenage but would love to see it at Ally Pally if that is possible. Your method of making the pin to the radius arm is fantastic and an idea I will shamelessly steal if I ever make my own valve gear! (if that's ok with you)

[Atlantic 3279]

No reasonable request ever refused, so, now in rich green and straight out of the mould this afternoon:

The match to the Hornby P2 factory livery isn't as close as the images may suggest (my monitors shows them to be quite similar), the resin actually looks closer in colour to the unpainted interior of the Hornby moulding. With the benefit of experience from the first use of the mould, I've improved the result giving a bubble-free area in front of the smokebox (although there's one tiny bubble in a lower corner of the buffer beam) and there's a fully formed mounting boss inside this casting. The boss didn't form in the first example, but I didn't reveal that....
There is, this time, as you may notice, a small bubble in the leading edge of the smokebox fairing on the side nearest the camera.

Don't take the figures as gospel but I estimate 2.5cc at most of paint (correction, later reassessment has shown the volume to probably be nearer 1.5cc) went into a 35cc final volume including the resin. The colour in this case was mostly Humbrol 195 with 6 to 9 drops of yellow. I don't think there's much chance of getting perfect match for the Hornby paint finish and probably no point in trying given that filler and paint will inevitably be need to hide the body joint and to conceal the positions in which the reverse rod for the Lenz gear was previously attached. The main functions of the green moulding will be to act as a "sympathetic" base colour for a top coat that need not be so thick as to clog up the surface details, and to help to conceal any minor breaks in the green paint caused by wear and tear.


Tim: I can only echo the well deserved compliments regarding the 2FS P2. Wonderful work. It's a good job its in the smaller scale as there would be queue of people trying to nick it if it were OO.......

[Nova]

Interesting combination of valve gear components to make up Earl Marischal, Graeme - they work well. The valve gear is indeed very constrained on a P2. I tried and measured various etches for my 2mm Lord President, but ended up making the whole lot from scratch. It can be positioned in forward or reverse and is fully working (photo by Tony Wright).



Tim

fully working!? please tell me there's a clip floating around on the internet, for it to actually be fully linked together and moving realistically is one thing, but to have a working cut-off scratch built in 2mm scale is practically artisan levels of skill.

how is it adjusted? Screw-wound reverser?

[Atso]

That is incredible Graeme! Did the resin take any longer to cure because of the paint? Would adding a little of darker colour help to balance out the naturally light colour of the resin?

fully working!? please tell me there's a clip floating around on the internet, for it to actually be fully linked together and moving realistically is one thing, but to have a working cut-off scratch built in 2mm scale is practically artisan levels of skill.

how is it adjusted? Screw-wound reverser?

Sorry if Tim is upset that I've beaten him to it but this is one of my favourite videos at the moment!

https://www.youtube.com/watch?v=fUTQ5Ibe1Bk

[Atlantic 3279]

Agreed, the greater bias towards the darker colour in the added paint mixture would probably improve the final resin tone. No noticeable extension of the curing time.

Note that I've amended the volume figure above, after doing a little test to establish how much paint was transferred from the tinlet with three dips of my drinking straw!

[john coffin]

Be careful not to take too long a swig on the straw Graeme!!!!!!!

I wonder whether acrylic paints might also work quite well, since they are technically water based, and should do little to
upset the chemical balance. Even the cheapo from places like Works might work well, let alone Rowneys.

Otherwise the casting looks good and a sensible starting point.

As for Tim's valve gear one can only weep at his skill.

Paul

[2002EarlMarischal]

The EM front end is amazing Graeme. If I have not already asked, please add my name to the list of potential customers (for all versions)!

I have especially noted the flange that should allow an easy joint between the two boiler halves. Was that there on the earlier moulding?

[Mercator II]

Cracking work there Graeme, must be something in the water near the Humber, the speed you go at when work comitments allow is amazing

Looking forward to seeing how it takes the paint and the match to the rest of the body

Keep up the good work, and I eagerly await the bugatti variant (but not so my wallet when it comes to my turn in the que and have to buy a donor or two to chop up!!)