Atlantic's works: Portable layout - Scenic details next

[Atlantic 3279]

First attempts at filling the new mould with resin have proved to be less successful than I hoped / expected. The smooth shape of it made me imagine that with it held together in a suitable way, on end, nose up, then a steady and continuous injection of resin into the lowest point and the provision of air escape routes through the extended buffer stocks and the position of the central coupling hook should lead to the whole thing filling nicely without air bubbles, especially if a modest excess of resin was pushed through. It hasn't quite worked out like that. I have a suspicion that in finding a method that held the two parts of the mould very tightly together, with no scope for any temporary bulging of the sides or escape of resin in all directions, I created too few opportunities for the air to escape. One of the first two casting attempts has certainly ended up with air bubbles in places that normally ought to present no problem. The very tight and effective constraints that I've used on the mould during filling have also led to a couple of parts of the casting finishing up rather thin! It is not by any means hopeless however, but "could be better".

The next couple of days may be too busy for any further attempts at casting, but next time around I'll give the mould a little more freedom to find its own comfortable shape and to leak resin out through the joints as well as through the escape passages in the nose. That approach certainly worked with the Earl Marischal body front mould, which includes more awkward shapes. I suppose I should have expected that the ostensibly "easier" streamlined shape would actually be the one to catch me out....

[MorfieldCentral]

Hello Graeme, some great work on here i must say!.. I'm unable to pm just yet, so ill be brief. ive seen on facebook a great looking W1 somebody has built with resin parts and they said you make several conversion kits that you sell? Do you have a list of these items? Cheers, Lee

[Atlantic 3279]

Hello Lee,

Thanks for your interest. There is a list, badly overdue for a proper update owing to a chronic and on-going shortage of time. For the same reason, many items on the list are not actually in stock at present but are things that I can produce as and when time allows. If you are thinking about a loco conversion, as opposed to something more basic such as a change of chimney, dome or other fittings, then the W1 is probably the easiest one to start with, there being no changes to valve gear to tackle. The only simple way to get a list to you is by e-mail, and as it is clearly not wise to put your e-mail address on a public forum, the best plan I can suggest is for you to hang on until your number of posts on here opens up your PM facility, then send me an e-mail address.

That gives you a good opportunity to post some pictures of your modelling achievements so far....

Graeme

[MorfieldCentral]

No worries Greame, thanks for the quick reply. I'm in no rush, so ill 'hang around' and try and get some pictures up of what ive been up to thus far. The W1 did look a bit simpler than some of the others ive seen on here... ive seen many of micks nrm conversions, so I might have a go at some of them too. The loco lining is my biggest worry atm... I had a go last year at painting and lining a non corridor tender just before Hornby brought out book law with limited success.. painting was easy for me but the lining was a pain and its still not straight!
Lee

[Atlantic 3279]

Some relatively simple, carefully thought out alterations to the mould and to the technique for introducing the resin seem to have produced a virtually defect-free P2 Bugatti-front casting from my one attempt today. I'm moderately hopeful of being able to repeat the process now with all defects eliminated, or easily rectified after casting.

[Atlantic 3279]

Nine perfect or near-perfect castings so far have confirmed my belief that the modified mould would be good.

As I originally had it, only the extended buffer sockets and coupling hook position provided an outlet for air and resin at the apex of the mould when placed on end, the resin being injected through the port visible at the bottom of first picture. The offcuts of aluminium angle around the top edges of the mould and a good application of rubber bands were holding the two parts of the mould tightly in what I believed to be their "true" relative positions:

After finding the first casting to be so hopelessly riddled with air bubbles and unwanted thin areas, I used a combination of knife cuts and sneaky use of piece of brass tubing (with one end sharpened all round to a cutting edge) twisted through the rubber to create some more escape routes from the mould, around the lower edges / turn-under of the streamlined fairings. I also "loosened up" the grip on the mould, using just one rubber band to hold the base of it together and one bridging piece to stop the sides from bulging excessively amidships. A protectively gloved hand now does the rest of what is necessary to keep the mould together against the weight and pressure of the rising level of resin within. Once it is absolutely full and overflowing, the mould is tipped onto its back so that any remaining air bubbles have chance to rise into the slim gap (between the two mould parts) in the area that will simply be "flash" around the lower edges of the final casting. Gentle finger pressure is then used to ensure that the core seats fully inside the outer mould, expelling a little more resin (and air). Any excessive bulging of the sides in the unsupported areas can also be nudged back into line at this final stage too.

[Atlantic 3279]

I'll try to do a proper update soon, but time continues to vanish without trace. More Bugatti nose castings have completed what I regards as an initial batch, estimated to cover expected needs. With a mould of that sort, requiring a strict filling procedure, I consider it much easier to cast a batch than to try to produce individual pieces as demand arises. I've also produced a double chimney mould to suit 2003 and 2006 as built, along with the re-nosed versions of 2001 and 2002. "Specials" for 2004 and 2004 will have to be a matter for later consideration, if at all.

I think I've envisaged a viable de-gassing technique for small quantities of moulding rubber too, perhaps 30 or 40cc at a time, using a piece of equipment that has to be part of my toolkit anyway, i.e. without making or purchasing a vacuum chamber and suitable pump. That should prove very handy for the making of small moulds where surface detail has to be free of holes or bubble-witness marks and where it is awkward to orient the master in such a way that all bubbles in the rubber mix rise away from the surfaces of the master. More anon....

[Atlantic 3279]

The de-gassing technique for small volumes of rubber mix appears viable. I pulled the piston or plunger out of one of the 60ml syringes that I buy from Squires for resin injection, put a cap over the nozzle, mixed about 25ml of rubber and poured it in to the syringe, reintroduced the piston (only just within the bore at first) and tipped the syringe "nozzle up" so that the liquid rubber drained down to the far end. Removing the nozzle cap I then pushed the plunger gently in until the rubber just reached the mouth of the nozzle, and replaced the cap. I then pulled firmly on the plunger and observed the appearance and expansion of numerous bubbles in the rubber mix. I maintained the "pulled" position of the plunger, with the nozzle uppermost for a short while, to give the air bubbles chance to rise in the rubber, then slowly released the pull. On removing the nozzle cap there was air space within the nozzle where there had previously been none. I again gently pushed the plunger to bring the rubber back up to the mouth of the nozzle, replaced the cap, and pulled again. I repeated the pulling process several times to try to expand as many air bubbles as possible out of the rubber, then used the syringe to pump the rubber into the moulding box for a set of P2 cylinders. Very few air bubbles rose from the mixture once it was in the box, suggesting that the removal technique was some sort of success...

Inspection of the lower face of the final mould will reveal more.

[Mersey508138]

How are the latest results coming along in casting the parts for the P2. I must say I am impressed with what you've created.

[Atlantic 3279]

Slowly but surely. I may manage to find time to post updated images and notes early next week.

[Atlantic 3279]

Coming soon, honestly it is.

[Atlantic 3279]

Care and patience with that mould for the Bugatti noses, when time away from work and other problems actually allowed me to TRY, certainly paid off. I now have a reasonable number of front-end body castings.

I've also produced a quantity of the necessary streamlined double chimneys (not the same as the A4 type) and several sets of cylinders that simply clip on to the Hornby P2 chassis in place of the originals. I'm afraid I have no pictures just yet. I haven't done a single chimney, nor a double with a by-pass orifice, so ingenuity and effort will be required if a model of Mons Meg or Thane of Fife is desired.

The valve crosshead guides on the rear of each cylinder casting are particularly vulnerable to being broken off, being connected to the main body of the valve chest by a very thin "neck" of resin. With this in mind, I've cast a supporting wire into each one, but this provides only a limited improvement in the resistance to breakage, SO ANYBODY CHOOSING TO USE THOSE CYLINDER CASTINGS WILL NEED TO BEAR IN MIND THE FRAGILITY DURING CONSTRUCTION AND TAKE CARE. Once they are on the loco with the valve gear installed, they are far less vulnerable.

I did consider producing two separate moulds for the cylinders, one to suit Earl Marischal with original styling, and one to produce slimline, rudimentary cylinders to fit inside the skirts of the other locos. In the end I decide not to do that at this stage. For small numbers of cylinders, it is simple enough for me to trim down a full-width set of Earl Marischal cylinders in order to provide the type needed for a streamlined front.

I'm stuck for the time being regarding the matter of the extra parts that will need to be etched for the valve gear, since the existing Thompson A2 conversion etch doesn't provide everything. I have patterns and dimensioned, hand-drawn figures for the parts that are required, but I've been unable to re-establish contact with my previous excellent provider of the necessary CAD drawings. A possible alternative provider is just about to move house so I don't want to ask him at present. There are one or two others I could ask, but not necessarily people to whom I would want to owe a favour.....
I've never done any CAD myself. Something will no doubt turn up.

On the subject of etch design, I recall that within the last few years MRJ published an article in which the author had produced a comprehensive table of figures to show the necessary size adjustments required for various shapes, in order to allow for the etching cusp, depending on the thickness of the material being etched. If anybody can direct me to the relevant issue of MRJ, I'd be much obliged.

[mick b]

Graeme
List of possible articles ? here

http://www.modelrailwayjournal.com/inde ... 0&x=51&y=7

[Daddyman]

Graeme,
I'm making the first steps to learn etching myself. I'd like to produce a sheet of various LNER valances and cab sides - the hardest part of scratchbuilding - for K4, J38, D49, and one or two others.

There was a recent article in Scalefour News by/about Mike Edge's etching process (May 2016). Judging by the screenshots he uses a programme called Turbocad Pro, the new version of which is £1000. However, the discussion here gives a few alternatives:

http://www.rmweb.co.uk/community/index. ... tcw-files/

The latest MRJ has some advice too, and gives the same list of etchers' names, who are apparently very ready to help. In the end I downloaded the free QCAD as it seems to be adequate for a modeller's needs. One would hope to be able to scan in a drawing and convert it to an etching-ready file, but it doesn't seem to be that simple. The programme also doesn't seem to be self-explanatory, but there are no doubt Youtube tutorials. You learnt casting; you can learn etching...


Re the P2, did you create a bulge around the cylinders? It's hard to see from the photos. And are you changing the cyclinders because of the thickness of the valances in plastic/resin, or did the later locos have smaller cylinders. I'm working on doing the bulge in brass: will I be able to use the original Hornby cylinders?

[S.A.C. Martin]

Brilliant work Graeme. Is there a waiting list, or can we just order from you as per normal?