Atlantic's works: Portable layout - Scenic details next

[Atlantic 3279]

this months Model Rail

Guilty as charged m'lud.

I had a bit of bother with motivation yesterday, but eventually got on to some of the final tidying-up tasks on the bogie wagon master. I've concluded that I can't do much that's of use to add cast-in detail to the bogie mounting positions as it would get in the way of post-casting fitting of the cantilevers. I have however added some diagonal braces behind the headstocks and one or two additional attachment points for basic wire brake rigging. I've also pencil-marked areas where the rivets need restoration or enhancement, probably by means of tiny dots of PVA.

I'm sure that before I try to make the mould I'm going to have to seal the structure of the master and "fill" any wafer-thin, currently invisible "undercuts" with something more than grey primer - perhaps a coat of proper shiny paint or some clear lacquer. Those small, thin plastic parts that are attached directly to the brass will, I fear, be pulled off as soon as I try to get the master out of the mould if I don't do SOMETHING. Any good ideas on offer at this stage will be gratefully considered.

[Atlantic 3279]

Final additions to the underbody as mentioned above, diagonal braces for headstocks and some inboard drillable lugs for brake cross-shaft support etc. Some evidence of gap-filling having been done can also be seen.
Since taking this picture I've gone dotty, applying PVA to rectify as many as possible of the fair number of defective or missing rivets, and have given everything another good coat of primer, almost as much as I dare without swamping details or getting solvent attack on the plastic. This has helped considerably towards the business of sealing edge gaps and eliminating my fears of having silicone rubber creeping underneath ready to pull details off on removal from the mould. I'll still have to do a little more preparation, but the auspicious moment approaches.

[Dave]

Pva is a good and cheap dodge, I've also used Games Workshop "Green Stuff" which I applied with a brush and a bit of water, expensive when compared to pva but it works very well. Anyone else used it.

[S.A.C. Martin]

Yes, the "green stuff" I find is excellent for filling in holes or scuffs in locomotive bodies. Works well for me when combined with the Humbrol plastic filler. Both sand down easily too.

[45609]

If you haven't tried them before this type of liquid filler are very good for filling minor surface imperfections. Various grades are available.....

http://www.relishmodels.co.uk/gunze-san ... r-500.html

....and here is a review of it's application and use.

http://www.swannysmodels.com/Surfacer.html

It sounds like it is essentially the same as the old tub of cellulose car body filler (otherwise known as stopper or knifing putty) that I use. I'm not sure that cellulose stopper is available anymore because I've had my tub for years. Occasionally a few drops of cellulose thinner is required to revive it.

[Atlantic 3279]

Thanks for those ideas. I had already wondered about brushing on a dilute wash of PVA, anticipating that surface tension would lead to it collecting preferentialy in any cracks and crevices, both filling thse and having at least some bonding effect. An application of not-so-dilute PVA followed by a wipe-off with a damp cloth or moist brush is something else that I might try.

[2002EarlMarischal]

Forgive me Graeme if I have lost my way a little, but is it your intention to create a single resin mould for the entire wagon (excluding bogies)? Would that be the largest moulding you have attempted? My mind is getting carried away with thoughts of loco and tender bodies..........

[Atlantic 3279]

The plan, unless it proves to be just too ambitious, is to cast the whole of the basic body in one, but the trussing & brake hangers will have to be separate resin add-ons with bogies, underbody cantilevers, brake rigging, buffers and couplings coming from other sources / materials.

I hope I will succeed owing to the facts that the wagon body appears to be capable of being created using just one outer mould plus one "core" mould that plugs into the top, and is free of significant undercuts that would cause difficulty in pulling it from the mould. The idea of trying a full loco body still strikes me as prohibitively difficult if a high quality result is wanted. There would be lots of undercuts, loads of scope for mould distortion, and probably a need for multiple sections of mould to allow for release - and those would all have to fit together perfectly even as the mould material ages. I can't see how it would work at all well.

[Atlantic 3279]

In order to try to make the mould as durable as possible, I'm making a couple of changes to the master to avoid creating thin areas in the silicone rubber, as these soon distort and/or tear when castings are repeatedly pulled free. I have therefore largely filled the triangular voids behind those diagonal headstock braces and will remove the vacuum cylinders for separate casting.

[Horsetan]

.....The idea of trying a full loco body still strikes me as prohibitively difficult if a high quality result is wanted. There would be lots of undercuts, loads of scope for mould distortion, and probably a need for multiple sections of mould to allow for release - and those would all have to fit together perfectly even as the mould material ages. I can't see how it would work at all well.

Graeme:

Re: loco and tender bodies. I think this is a process where the modular approach you mention will work better, because you would be breaking everything down into small-ish sub-assemblies, i.e. one smokebox, one boiler, one firebox, one footplate etc.

What would put you off is the number of small moulds for one engine, but at least you would be able to control the moulding process a little better.

[Atlantic 3279]

Yes, I'm much more inclined towards the idea of sticking to modules comprising useful replacement sections of loco structure for the time being, although I might, in the not too distant future, try to produce a combined cab and firebox unit that would probably call for an outer mould with separate core-pieces for the cab and for the firebox.

[Atlantic 3279]

Bogie wagon again: I thought it might be useful to try to save the chore of bending up and fixing to every cast copy the brake pipe that runs along the central girder. I've therefore super-glued a piece of shaped plastic rod to the underside of the master, and have used filler, a brushed on bead of PVA, and a further squirt of primer to try to fill up the undercuts and gaps behind the pipe. I want the mould to form in such a way that I can remove the master again and get resin to go into the pipe-groove when I make a casting!
Here's the upturned body again, with pipe on and brake cylinders removed - after scribing around them to make the correct locations obvious on any castings.

I nearly ordered more wheels and buffers ready for the first cast copy today too. I say nearly as I couldn't get Gibson's on the phone for the spoked wheels, so I'm hoping for an e-mail response in due course. I also failed to order buffers from Wizard - I identified some that were reasonable value and that I wanted to order, more appropriate ones than my initial set of NB wagon buffers, but when I realised that postage would be £3.90 on goods costing only £2.40, I decided to wait until I can catch Andrew H at a show. My first cast wagon may therefore temporarily run with some simple turned brass carriage buffers and, if necessary, 10.5mm disc wheels from the local model shop.

In case anybody wants to know, a further search of the Wizard's catalogue revealed some alternative Spencer buffers, with the right size heads, at sub-luxury prices. So if you don't want to change heads on wagon buffers and don't want to pay for sprung ones (LNWC025) then have a look at either LNWC025B, with fixed steel heads, or dead-cheap all-cast LNWC025A - but in every case the shape of the base is still not ideal for the GC wagons.

[CVR1865]

Hi Graeme,
Another facinating adventure into a prototype I had not previously encountered. In their current primer livery they look very modern. If you put the bogies back on and left off the buffers but used Knuckle couplers you could place them behind a Class 60 Diesel and it would look all the world like an Ore train or additional Coal train. That is meant as a compliment to both your workmanship and the quality of the design.

I also noted more of your articles in the latest Model Rail, it is good to know you are being published, perhaps the Thompson next?

Thanks again and like everyone else I shall follow with interest.
Simonn

[Atlantic 3279]

Thanks Simon.

Here's a laugh at my expense - how I discovered that you should NEVER rely on double sided sticky tape to hold down a master part on the base of a moulding box unless the master is heavy/dense and the contact area large. So as to save any possible damage to the top edge of my bogie wagon that glue might cause (as I feared that even spots of glue might spoil it and thus spoil any resin duplicates too) I used three layers of tape to get a good seal and a reasonably resilient pad into which I could firmly press the rim of the upturned body. It seemed to be firmly attached, until I had measured patiently and accurately, then mixed and poured a quantity of rubber costing over £10. To my horror, after a little while the buoyant air-filled body slowly rose to the surface
I thought desperately to find a way to save the mixed rubber, avoid another delay, and avoid having a horrible mess all over the place. My only idea was to raise one end of the body clear of the rubber with a screwdriver, then quickly grip the liquid-covered item with gloved hands, flip it over, and put it back down in the rubber. I tried not to trap air under it, and was fairly relieved that by this stage most of the air bubbles seemed to have stopped rising from the rubber mixture. As the body floated much too high, I then had the idea of building the "bridges" seen in the image below to press the body down evenly to "brimming" level.

I am now praying that I don't find any awful bubble defects on the important areas of the mould for the underside of the wagon. In certain places I may be able to rectify a bubble defect in the mould once this pour has cured - if I drill or cut through the base of the mould to open out the bubble, put the master back in, turn it upside down as it was really meant to be and then pour in some more rubber from the top. Time will tell.

Okay, you can stop laughing now. That's enough.

[60800]

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