Atlantic's works: Portable layout - Scenic details next

[Horsetan]

Ha. I know Graeme plays Sudoku now

[45609]

AcK! Hopefully that will be a good save there Graeme. It's just a shame that you were not recording a Youtube "how to" video. With so much Anglo-Saxon narration English subtitles would have been a necessity. Fingers crossed......

[Atlantic 3279]

You've made lego watertight? It's a bleedin miracle

Not quite, although I quite like the idea of divinity. The silicone mixture is a denser and much thicker liquid than water. The extra density of course aggravates any air-buoyancy problems with hollow masters - as I now realise. If you don't seal the inner face of the box with tape, and I don't bother with that now as it is fiddly and time consuming, then the rubber does creep into the brick joints, but never seems to get to the other side. As you see, I still put it on newspaper just in case, and often the tape that I use to hole a plain base on the box partly seals the outer face of the sides anyway.
Once cured, the thin rubber leaves between the bricks often tear away from the main block of the moukld as you remove the mould from the box. The trapped pieces peel away easily as the Lego is dismantled.
Another way to seal the inner face of the box is to apply a generous smear of Vaseline - so long as you don't get a clogging layer of that onto details of the master too.

Have never tried Sudoku - don't much enjoy crisis control either The puzzles in the paper are the work of my darling wife.

Anglo-Saxon? Well yes, I'd have expected to utter plenty of that, but perhaps because there was nobody around for me to swear to/at I remained oddly silent. I was of course doing a pretty convincing impression of Ethelred the Unready, and competing for incompetence with Alfred's cake-burning stunt.

After calming down, it was crystal clear to me that if I had simply cut a couple of little (say) wooden blocks, maybe even with padded edges, to fit tightly into the body, and then glued or even screwed these to the base of the box (and screws would make subsequent release of the base without disturbance of the body within the mould dead easy), then I might have had no trouble at all..........

Even when things had gone wrong, calm clear thought might have told me to pour off the rubber mix into a plastic bowl, clear as much as easily could off the box base, put four pinholes in that under the footprint of the wagon plus a hole in each of two of the inner wagon bulkheads, and tie the body back down on the base. I could probably have done that quickly and cleanly enough to save the slowly reacting rubber for a re-pour with little loss of volume. You just can't get the staff these days, can you?

It wasn't just the cost of the rubber I'd mixed that made me anxious not to waste it by the way. I reckon I've only just enough left in stock to do the core mould for the wagon and the mould for the underframe parts, if I'm careful. Getting more involves not just material cost, but either hefty postage or journey costs to collect, plus any delays that entails. Definitely fingers crossed!

[Atlantic 3279]

Following the debacle with the production of the outer mould for the wagon, I weighed up the pros and cons as I saw them of the various ways forward. I decided to go ahead with the production of the combined "matching" core and top, without disturbing the master from its place in the rubber or the rubber from its place in the moulding box. Nothing of this size and complexity every goes back in perfectly once it has been disturbed, so the production of properly matching parts tio the mould becomes impossible. In pressing ahead I was of course hoping that any defects later revealed in the outer mould would be either insignificant or capable of rectification!
In view of my low stock of rubber, and the cost of the stuff, I decided to try to save on volume for the production of the core by cutting up an old mould that had become useless and casting re-cycled chunks of this into the "dead spaces" in the new item:

You can probably see that I'd also tidied up the top face and edges of the lower mould, using knife and scissors to trim away rubber that had spilled over the edges and the rough areas where the lego bridges had been. I tried to trim back the rubber to expose most of the thickness of the top edges of the wagon sides and ends so that there wouldn't be an overhanging ledge in the rubber against which the master and all subsequent castings would snag on removal from the mould.

[Atlantic 3279]

The recycled chunks appear so far to have integrated nicely into the top/core mould. The only minor imperfection in the core I found on separating the cured moulds should only affect the floor of the wagon which will in any case be hidden under a coal load. The cause of the white patches on the master wagon floor in the picture below is very slow curing of the rubber when it is spread in very thin layers - hence the middle of the thin film under each recycled chunk hadn't gone off completely in the usual 24 hours that sees the rest of the mould well-cured. With luck, the chunks will be held in by the rest of new rubber well enough and the core mould will not fail unduly early. The inside faces of the wagon are all plain so I hope that there will be no dragging / snagging to fatigue the core mould each time it is removed from a casting.

There is as it turns out some "bubble rash" on the top face of the lower mould which creates the underside of the wagon, but none of the large air pockets that I had feared, and nearly all of the bubbles are still skinned over with rubber. I hope that even if those skins break, I shall be able to fill the largest bubbles with extra rubber mix and simply ignore the smaller ones. If they create tiny resin pips on the bottom of the wagon castings I should be able to just scrape those off. As far as I can see, all of the necessary detail on the sides and base has been well captured. I have every reason to at least try this mould out for casting - probably tomorrow.

[Atlantic 3279]

My fears about the possibility of pulling all of the detailing strips off the master when making the moulds have not been realised. The layers of primer and PVA, plus filler in the larger surface gaps seem to have been sufficient. I've only got one patch of damage to the master and that is fully repairable with ease. This was actually caused when I was going around the top edge of the wagon with the knife, trimming back the rubber overspill as I explained above. I tried very hard NOT to get the knife to or down the outside face of the wagon as I knew that would wreck details, but here I managed to just split away the rivet strip:

[52D]

With painting you have instant weathering and corrosion built into your wagon.

[Atlantic 3279]

Now there's a thought!

[Atlantic 3279]

I've learned a bit from my first two attempts to cast in that bogie wagon mould and have high hopes for a third attempt! The first one wasn't right because I mixed all of the resin in one go, and due (presumably) to the warm day and possibly the larger-than-I've-previously-tried volume that I mixed, it started going off quite rapidly. By the time I'd ensured that I had got resin into all the awkward little nooks in the bottom of the mould I had to hurry to pour in the remainder and found that as I was trying to centralise and seat fully the top/core piece, the resin was already "thick" and wouldn't let me get the mould parts fully aligned. My second attempt, with a two-stage mix and pour gave me much more time to work, but revealed that I could probably do with a bit more mixture to ensure total filling of the mould and sufficient overflow to help to take air out of the mould. I got the mould top on easily with the resin still runny, then also discovered that putting weight on top of the mould, even if perfectly evenly spread on a flat plate, is not a good idea as this splays the tall sides of the mould (unless you brace those). Besides that, as I belatedly realised, if the resin is nice and runny the mould top sits down well enough under its owen weight.
Capture of surface detail however looks excellent, and those bubbles in the rubber mould have not yet wrought havoc.

[mick b]

Good luck , something I have never attempted !!.

[Atlantic 3279]

Going back a step, here's one of the parts of the underside of the top mould that lost a thin film of fresh rubber owing to the slow-curing. The recycled old rubber block is still well embedded - I've emphasized its outline in the image.

I thought a sensible prelude to casting would be the drilling of these breather holes above the reinforcing bulkheads. I suspected that their long flat top edges might otherwise fail to form due to trapped air.

[2002EarlMarischal]

Fascinating stuff! Good luck with the next stage.

[Atlantic 3279]

The third casting out of the mould is indeed usable, although it has minor defects that require rectification and I've not yet fully filed the flash from the top edges of the sides - until you get a first waft of gey primer on it is devilishly difficult to see whether everything is "just so" with the creamy coloured resin!
Casting No 4 ought to be even better. Top weight IS it seems after all handy in closely uniting the two moulds, and whilst I failed to make arrangements to key them together I've devised a simple way to stop the sides of the mould splaying when weight is applied - I've fitted a weight-spreading top plate with some edge rails to keep the sides of the mould "in gauge"!

Those bubbles in the rubber mould have caused slight, but unimportant (unless you want to model an up-turned wagon) "botty rash". Strangely enough these are indentations in the resin, rather than blebs where the resin has sunk into the unsupported bubbles. I can only assume that the heat evolved as the resin cures makes the bubbles in the rubber expand???

Casting No 4 is showing hardly any floor bubbles inside the wagon, unlike No 3 shown here. Maybe I didn't let the agitated resin components settle for long enough before pouring this one? You can still see the ragged step in the flash along the top edge of the wagon - it will all file flush without loss of the rivet line on the outside.

A section of the side - acceptable reproduction of detail for my purposes.

[2002EarlMarischal]

A section of the side - acceptable reproduction of detail for my purposes.

More than acceptable I would say. Any small blemishes would potentially enhance the look of a weathered, well used truck anyway.

[manna]

G'Day Gents

They've turned out well, you won't see any of the blemishes from 2 feet away, you'll soon have your 40 wagons done

manna