MOK Standard 4 2-6-0 in S7

[SteveB]

I’ve been looking forward to starting this build for quite some time. I can’t explain why but the Std 4 2-6-0 is one of my favourite designs. I think it’s just that, to my eye, it all looks in proportion and business like. It’s a good job we’re all different! I can’t specifically remember seeing them in my youth, so I don’t think it’s a nostalgia trip.

I came across ‘Scanlons’ posts on this forum the other day, about the same loco, so his notes will certainly be helpful. Coincidentally, I’ve chosen exactly the same loco 76026. I’m a fan of S&DJR and this particular engine featured very regularly on the line, although none of the class were ever allocated to it.

I’ll be building it to S7 and I’ll be making quite a few alterations to give me a bit more room inside for smoke units, forward/reverse servo and I also want to fit a speaker, somewhere ‘up front’.

This will be my third loco build and the first time I’ve attempted to go it alone, as my previous two builds (Std 4 2-6-4 tank and 8F) all came with S7 etches and in the case of the Tank, castings. Both locos also had quite extensive build notes on this forum and Adrians own website. I’m hoping that I’ll get some help, support and guidance from people on this forum. I think I’ll need it.

Assuming it all works out; I will make all my dxf and 3D files available to anyone else who wants to do the same type of conversion. I’ll no doubt alter a few of the frame stretchers to suit my own needs, but I’ll also draw them as direct replacements for those that want them. I haven’t asked them yet, but I guess the best way of making them available would be through the S7 Group.

The quality of etches, castings and instructions in the Kit appear to be up to the normally high MOK standards.

This is what I’m setting out to do:

Specification

Build to S7 standards.

28mm between frames, 29.35mm outside. As supplied it’s around 25.7mm between frames.

Split Axles, collecting current from 2 loco axles (not motor) and 3 tender axles.

CSB suspension on loco and tender.

DCC sound decoder fitted, with servo operating weighshaft and lifting arms. Speaker in Loco and Tender.

ABC Mini S motor/gearbox will be used. This is quite a low profile combination which gives more room in the firebox. It does mean however that some of the un-seen ashpan is carved away for the motor.

Issues and possible solutions

Frame spacers, loco hornblocks and tender chassis will be sorted by doing a new etch of replacement parts.

Cylinders will be modified from supplied castings.


Slidebar Brackets, are in two parts, the bracket itself should be quite straight forward to modify, however the second part which includes some form of wheel or splash guard are a bit more difficult. I may well try Shapeways.


The above photo also shows the nasty Injector Bracket. It could be modified but may not look too good. I could well end up trying Shapeways.

Weighshaft brackets, are not that easy to modify, may try Shapeways.

LH Weighshaft Bracket

RH Weighshaft Bracket

Brake brackets are quite easy to modify (they're the same as used on the Std4 Tank) but being lazy I may try Shapeways.


Firebox. Bottom needs to splay out by about 1.2mm each side. I'm not that experienced with Whitemetal. It may be able to encourage it to go wider at the bottom but if not then I’ll replace the section under the running boards with nickel silver.


Axleboxes and horn cheeks. I’ll make my own axleboxes from Acetal. This gives me the flexibility to adjust the ride height if I get the CSB position wrong, which is quite likely! The CSB will just rest on the top of the axlebox rather than going through an attached loop. It also means that I can put the tender CSB on the outside of the chassis, resting on slightly thicker axleboxes. The CSB height on the tender can also be positioned to hopefully miss the brake assembly.

My first bit of help please

I’ve seen quite a few posts where people have used Shapeways for 3D printing and it all looks quite positive. Has anyone used them to produce actual castings? I’ve enquired with a couple of UK based lost wax casters and neither of them seem to like going from a 3D prints straight to castings even when special resins have been used. This obviously adds another stage to the process which also adds considerably to the cost especially for very low volume items.

I have very little experience dealing with Whitemetal. I’m thinking here of the firebox. I would suspect that in cast form it’s quite brittle, what do you think about me being able to bend the bottom of the firebox out. It’s only about 1.2mm each side, so not a lot really. Would it be beneficial to heat it up to make it a bit more forgiving?

Regards

Steve

 

[SteadyRed]

Are any of the parts from the S7 standard 4 tank of use rather than manufacturing / modifying parts which Dave Sharp may already be able to supply?

Dave

 

[SteveB]

Hi Dave

Only really the pony truck which I've already bought from Dave Sharp. I think the Brake Brackets were just missed, but if I do get some cast then they would be good for both locos.

Regards

Steve

 

[Dog Star]

I’ll be building it to S7 and I’ll be making quite a few alterations...

Modellers who are thinking about adopting S7 often ask about what needs to be done and why - if you can describe what you do to "build (this kit) to S7" and why that is necessary then you shall be doing a great service.

Specification Build to S7 standards.

Issues Cylinders will be modified from supplied castings.

If you can explain why the castings need to be modified... then I shall be grateful as a future build (here) may have similar issues.

 

[mickoo]

Motion bracket, I suspect David has made the shape (the important part) correct and simple extended the inner area to make up for the narrower frames, you could possible get away with trimming the inner edge to meet the wider frames.

Casting, pretty well what I've heard, you may have to resort to traditional pattern making in brass.

Whitemetal, it should bend easily enough that amount so long as you don't make the bends over a narrow area or too tight, you'll also have to split it up the front at the throat plate and widen to be authentic I suspect, then add a 2.4mm filler strip. Don't widen the boiler rear ring, actually it might be better to keep the middle section intact and make two slits up the outer corners and fill with 1.2mm strips on each side, that way the boiler rear ring will remain intact.

Good luck

 

[mickoo]

If you can explain why the castings need to be modified... then I shall be grateful as a future build (here) may have similar issues.

Because they are too wide, the mounting flange is too far away from the cylinder bore centre line to compensate for the under scale width frames.

With the kit frames the wrapper will be the correct width, add wider frames and the wrapper will stick out past the footplate valance by.....about 1.2mm each side

MD

 

[SteveB]

Thanks for your comments Mick.

You're quite right about the way some of the castings have been 'extended' to suit the narrower frames, its a shame that this extension is often on the inside next to a bolting face. I may well try Shapeways, just to see what the quality is like. The plastic items they've done generally look quite good and probably a lot better than my pattern making skills.

Regards

Steve

 

[mickoo]

Steve,

The 3D prints will be pretty good, there may still be some visible layering on the larger parts like the cylinders, but smaller parts might not show it as well.

The more expensive the material the smoother the finish on the whole.

3D is fine if you want to use the final product as is, but as you've probably found out by now, not much good if it's a transfer medium to brass or white metal casting.

The 76xxx is a nice little engine, there were a few kicking around on the GE for a short while, I've a photo of an unidentified one leaving Ipswich tunnel and was sure I had one or two storming up Brentwood bank, but for the life of me cannot find them now.

MD

 

[adrian]

Assuming it all works out; I will make all my dxf and 3D files available to anyone else who wants to do the same type of conversion.

Definitely very interested to see how you progress with this, more with a view to doing similar job with the Ivatt 4F as that's one I'd really love to have for my Tewkesbury project.

Brake brackets are quite easy to modify (they're the same as used on the Std4 Tank) but being lazy I may try Shapeways.

Again this would be another one nice to solve properly - how did you fix it on your Std 4 tanks? [ for info for other readers of this thread - the problem I had was with the wider S7 frames and narrower wheel treads means the gap between the frames and the rear of the coupling rods is smaller on the S7 model than the Finescale version thus the rear of the coupling rods would catch on the brake hanger brackets.]

I have very little experience dealing with Whitemetal. I’m thinking here of the firebox. I would suspect that in cast form it’s quite brittle, what do you think about me being able to bend the bottom of the firebox out. It’s only about 1.2mm each side, so not a lot really. Would it be beneficial to heat it up to make it a bit more forgiving?

Personally having scratch built locos in the past I would have no qualms in just ditching the whitemetal firebox and make a replacement in nickel-silver.

 

[SteveB]

Hi Adrian

I like the Ivatt 4F as well. They did have a stint on S & D but not for long and quite a few years before the period I'm concentrating on.

I modified the brackets whilst still on the sprue. I cut the outer face off, filed a bit off the remaining bracket (most was cut away with the saw, so not much extra had to come off. I then made sure that all three brackets were in line and then threaded some wire through all with the outer faces that were cut off. Easier to do than describe! Then, silver soldered the outer face back on. Keeping them on the sprue was the key because they all helped to support each other.

The whitemetal casting is quite nicely done. If I muck it up then I may well have to make it as you suggest.

Regards

Steve

 

[warren haywood]

There you go Steve

 

[richard carr]

Graham

You don't "need" to do any of this to build a model that will run on S7 track you just need to use S7 wheels the outer faces of which are only a fraction wider than finescale wheels. That's what I'm doing with my Ivatt 4 it won't look exactly right but it will be near enough for me.
I take my hat off to Steve as he is effectively fully S7 ing the kit as Dave Sharpe has done for the Standard 4 tank.
It's just a shame that so few S7 members bothered to buy that kit.

Steve if you do manage to get all these new castings made please let all the S7 members know as I can think of half a dozen who would be willing to buy some off you. Sadly I doubt there are more than that though.

Thankfully the 9f has very narrow frames so the kit works for S7 and finescale with only a few minor changes that Dave is covering in a separate S7 pack.


Richard

 

[SteveB]

There you go Steve

A thing a beauty Warren. I’ll be asking you to do mine as well please, although I will be asking for it to be bit dirtier. I’ve got to get the 8F finished first though.

Hi Richard

I appreciate that I don’t need to do all these modifications, but at the moment at least, its what I enjoy doing. It would be great if only one S7 modeller would have a go, so ‘half a dozen’ would be tremendous. I think it would be best to see how I get on first, but I’ll willingly let anyone have the files now if they want to take a risk!

Regards

Steve

 

[SteveB]

I’ve finished the ‘artwork’ for the etched items. Most of the items on the etch are actually for the tender on my 8F. This is a part welded mk1 and its the only variant thats not supplied with the MOK kit. I hadn’t realised at the time I chose my prototype that it had one of these, but even if I had, then I would probably have still gone with it.

I have already done the tender chassis on a previous etch when I changed the 8F tender chassis. I had some spare space on the etch which I just used up with the 2-6-0 tender.

Please don’t think that its only taken me a few hours to produce this artwork. I’ve been working on it for quite some time. I hate to think how many hours its actually taken. It has made me realise how much time and effort actually goes into producing a complete kit. It must be hundreds or perhaps even thousands of hours!

The black areas are what will actually be left after the etching process. The pictures below are just jpeg views of the artwork, the files will actually be sent to the etchers as dxf. This is a standard format developed by AutoCad for interpreting digital design files.

Front of etch.

Rear of etch.


I’ve altered the stretchers at the front of the std 4 so I can more easily fit a speaker but I used the original setup as starting point. This gives me a bit of confidence that (assuming this etch works) the wider standard version will also be okay for any other S7 builder who wants to have a go.

I came across some very useful information about etching.

www.hollywoodfoundry.com/HowToPapers.shtm

It may well have been from this forum. I just can’t remember, anyway, it’s quite good and covers areas not on the PPD website.

www.ppdltd.com

Regards


Steve

 

[mickoo]

Looks like you're getting the hang on etching

The hollywoodfoundary how to is handy but is not a mandatory regulation.

I've not read the document recently but they advise something like 1.5 or 2x material thickness for bend lines and such like, you can go much lower.

I work mostly in 0.375 (15 Thou) or 0.45 (18 Thou) nickel silver, in 0.375 I'll make my bend slots either 0.4 if I want a slightly rounded corner or 0.45 and scour with a scrawker for a knife like edge. My CAD grid and snap is 0.05 which suits both of those material thicknesses and I don't worry about the 0.025 fudge factor.

PPD do have guidelines and when I send my order in I write to say I take full responsibility for any art work outside of their guidelines, to date I've not had a single item fail to etch as I intended, even the GP40 stirrup handles and checker plate work came out fine.

If you're using PPD then try to keep within whole inches (accepting carrier edge), say 12" x 6" (which is their minimum size BTW), however, beware they add 10-15 mm around your artwork for a carrier edge so your real work area on a 12 x 6 (300 x 150) is 280 x 130 mm, 275 x 125 is better and makes them fidget less

If you make your artwork 280 x 140 mm you go into the next bracket which is 12" x 7" and you end up paying for scrap etch around the outside, they may cut the material back to leave the 15 mm border but will charge up to the next size. Not a problem for one etch but I've got six in process at the moment, two at roughly 16" x 11" and if you go over by 5 - 10 mm then that's a lot of waste your paying for.

Remember also that the photo tool also follows the same guidelines so you get hit twice on the first run and once for material only on following runs.

Try to tab parts on at least two sides, preferably three, it just reduces the risk of accidental damage or loss.

PPD ship items with one side hardboard the other cardboard, if your etch is valuable or important, ask them to ship in two pieces of hardboard, it's no extra and just protects your work from Mr Pat and his cat. Virtually every piece I've received, backed on one side by cardboard, has been damaged. I now insist on hard board both sides but then I do have a lot of etches going through them so may be getting preferable service.

MD

 

[SteveB]

Hi Mick

Thank you, that's very useful information. Incidentally, Hollywood are now saying 1.0 x material thickness for bend lines. The etch will be 0.45mm and I've allowed 0,50 for the bends, do you think that'll be okay?

I'll ask PPD for two pieces of hardboard as you suggest. The first one I got from them had the cardboard packing. It was okay thankfully, perhaps I just got lucky.

Regards

Steve

 

[mickoo]

Steve,

0.50 mm slots for bends in 0.45 material will be perfect.

MD

 

[SteveB]

Thank you Mick.

 

[mickoo]

Steve,

I've no idea what bits are what or how many you need, but some look like primary candidates for carpet hide and seek and hyper-sonic travel, you've plenty of spare space so it might pay to add a couple of spares of essential bits to those spaces.

There's nothing worse than making an etch with 12 tank brackets and loosing one, resulting a £50 re-order for one tank bracket

MD

 

[richard carr]

Steve

You are doing a great job here
And if you do get some castings made I for one would like a set too please and as I said I'm sure there are a few others who would too.

Have you used tab and slot construction on the new chassis etch.

Richard