MOK Standard 4 2-6-0 in S7

[Brian McKenzie]

Have you found anyone in the UK that would use these waxes?

Steve,
Although your parts are 'in production', they may only be at, or entering, the wax modelling stage. I'm based in New Zealand - where modellers generally use the firm Morris and Watson in Auckland. Any manufacturing jeweler casting rings etc should be able to manage your parts - so long as they are not too big for their casting flask. I know that Slaters could do them, but there must be quite a number of existing UK services used by the various ranges of model parts and kits.
In my travels I once wandered into the large multi-storied Jewelry Center in downtown Los Angeles and came across a guy in an upstairs office with two Solidscape printers. I had files available on a USB stick which he subsequently printed and had cast by another business in the same building. My items by Shapeways come from their New York site, where it has been suggested they job out the casting process - so your Netherlands experience may differ. Just recently I had another batch of castings done by Dave Sciacca (Valley Brass & Bronze) in Pinedale, Fresno, California using Shapeways waxes. His work is beyond reproach.

There is a model engineer in Auckland (Mike Jack) who has purchased the same '3D Systems' printer that Shapeways uses. Mike produces waxes for Cro Fittings (Crowborough) live steam items, and I'll try him in future. Alas, we were unaware of each others presence at last years Model Engineering Exhibition at Doncaster Racecourse!

Good night from downunder. Cheers, Brian

 

[Len Cattley]

Have you tried Laurie Griffen, he should know of someone who could cast for you?

 

[SteveB]

Although your parts are 'in production', they may only be at, or entering, the wax modelling stage.

Thanks Brian. I have sent them an email to see if I can change to brass. Thanks for all your comments. Regardless of the outcome with Shapeways, I will persevere with the process because it could open up so many possibilities.

Regards

Steve

 

[SteveB]

Have you tried Laurie Griffen, he should know of someone who could cast for you?

Hi Len

I did talk to Laurie sometime ago, but that was really about producing the masters. I'll email him to see if his contacts would work with 3D printed waxes. Thanks for the idea.

Regards

Steve

 

[SteveB]

Things have been a bit busy at work recently so I haven’t had as much time as I would like to work on the 76xxx. I have made some progress though.

Coupling rods are done. MOK supplies little rivets for the joint, which I personally don’t like the look of, so I’ve used some Alan Gibson 4mm crank pin bushes, which I think have an M1 thread, and just soldered on a 16BA nut. I’ve only got the nuts in brass rather than steel, but once they’re suitably weathered I think they’re look better.


I’ve changed the way the front end of the chassis is attached because I want to fit a speaker ‘up front’. The MOK design doesn’t allow for this. I forgot to take a photo of what its like before my modification, but if you that interested then you can have a look at Scanlons thread when he built his 76xxx.

All I’ve done is basically to leave out the screwed box assembly and replace it with ‘barbs’ on the top and front of the main chassis. That means I’ll be relying on the two screws under the cab to hold the entire boiler, smokebox, running board and cab assembly to the chassis. No claims on the originality of modification because that’s basically what MOK did on his 2-6-4T.



You can see the whole assembly so far. I haven’t soldered on the saddle yet, I thought it best to wait until the whole boiler assembly is ready to be fitted. You can see that the forward part of the frames, just overlap the main chassis by the thickness of the overlay etches.


I’ve just received an email from Shapeways telling me that my castings are on the way. If nothing else, their speed of manufacture is really good. I’ll post some photos when they arrive.

Regards

Steve

 

[SteveB]

I’ve just received my order from Shapeways and I have to say that its excellent! It couldn’t really have been much better. Visible layering from the print process is almost negligible. The only negative, is that the items are very slightly undersize (less than 0.1mm in all three planes), which is my fault really. I should have applied a shrinkage allowance, but following advice from Shapeways I didn’t apply it.

Their advice was not to apply a shrinkage allowance because it would be covered in their tolerances. I guess their tolerances are quite slack to cover any commercial guarantees.



Their service can best be described as excellent but not very flexible. The reason why I say its inflexible is twofold. Firstly, I tried to alter my material from bronze to brass less than 24 hrs after placing my order, but because the production process had supposedly started, then they wouldn’t allow me to do this. The second area is that I tried to get them not to rumble my castings but their system does not allow for this. The rumbling has rounded off the corners, but not by much and it can be easily compensated for by allowing a small increase in material thickness.

As long as you allow for their production methods, everything would appear to be okay. The only change I will make to future orders will be to allow for shrinkage and to get the material right first time. Having said that, the bronze looks good. I think I might also combine the 2 off Brake Brackets into a 1 off sprue of 6 just to see what happens to the price.

To give you an idea of prices, this is what they cost me. Prices are in Euros and exclude VAT. Shipping is free on your first order.

Brake Brackets E25.50 for two off

Cylinder E45.91 each

Inj Bracket E11.86 each

Motion Bkt E12.87 each

Weighshaft Bkt RH E11.14 each

Weighshaft Bkt LH E11.67 each

As you can see, the cylinders were expensive, especially considering that they were relatively easy to alter but the others are relatively cheap, certainly in comparison to the work involved in making the originals suitable.

I still need to make sure that the bits fit as intended. If they don’t, then the majority of the fault will probably be my initial design. Without getting too excited, for me at least, this is a great step forward. Once proven, all I’ll need to do is email the relevant files to anyone who wants them.

Regards

Steve

 

[mickoo]

Steve, you don't have to email the files, Shapeways allows others to buy your items so they only need a link to the items on Shapeways site, click, pay, buy, receive

Having said that, sending the file from each new person would count as a new order 'for them' and thus free postage

MD

 

[Brian McKenzie]

Steve,

I'm wondering if your castings may have been buffed before rumbling? The coarse finish inside the cylinders (not that it matters) is a puzzle. One imagines that the manufacturing process involved would provide the same finish inside as out.

My experience with 'shrinkage' at Shapeways is as they advise - no allowance is necessary. At first I added 3% - and received oversized castings. I continued cautiously, gradually reducing the percentage added for subsequent items. Most purchases are spoked wheel centres and now with no allowance added they arrive within a thou or three of file size (in the size region of 1 inch dia). Two batches were one thou over and all are remarkably concentric - which I wasn't getting with waxes popped out of vulcanised moulds by workers on piece rates.

(An allowance for shrinkage is necessary when the Shapeways item is to be used as a pattern for 'silicon tooling'. I don't take this route as shrinkage can be as high as 8% or more, and variable when casting businesses chop and change between brands of RTV without informing the customer.)

-Brian

 

[SteveB]

Steve,

I'm wondering if your castings may have been buffed before rumbling? The coarse finish inside the cylinders (not that it matters) is a puzzle. One imagines that the manufacturing process involved would provide the same finish inside as out.

-Brian

Hi Brian

You could well be right. I certainly didn't ask for the castings to be polished. Both surfaces inside and outside of the cylinder are equally shiny but as you say, the texture outside is quite smooth. My limited experience of rumbling suggests that you may get a smoother texture on the outside depending on the size of media used. Interestingly, the shrinkage is about the same inside of the casting to the outside, so that would suggest it hasn't been eroded by buffing.

I can't think why I would get shrinkage and you don't. Its not much, around 1.5% where I can measure it.

Regards

Steve

 

[Brian McKenzie]

Steve,

I wonder if Shapeways use an automated algorithm to compensate for any possible shrinkage, when they at first validate your file for printing?

My Shapeways service is ex the New York site - where they were happy to print the left hand motion bracket below, but rejected the right hand version - when it was merely a mirror image of the other.

-Brian

 

[SteveB]

Hi Brian

That's a bit bizarre. Did you ask them why? I've only sent and received a few emails from them, but all of them suggest they've been copied from a list of company approved statements. Perhaps I'm just being cynical?

Regards

Steve

 

[Brian McKenzie]

Steve,

The left and right hand motion brackets ended up as two separate brass orders (when racing to upload multiple files to meet a 20% discount deadline).
The orders were processed by different people, one man was happy, the other said no. He wanted more wall thickness. Later, Shapeways made both as waxes and I had them cast by another party. Shapeways and bizarre are not unknown to each other.

-Brian

 

[SteveB]

A bit of progress with the chassis. Rolls freely, which is always a bonus. With hindsight, I wish I had made the frames a bit wider. I went for 28mm between frames which is what Dave provided for the S7 version of his 8F and Std 4 Tank. The gap between the frames and the back of the wheel still looks massive. Its only 0.35mm (0.014”) wider than it should be, which sounds negligible, but you can see for yourself what it looks like.




I’ve made a start with the smokebox, boiler etc. I’ll probably leave the chassis as it is for a while and concentrate on this because I dare say I’ll be marrying up the two quite a bit and I don’t want to cause any unnecessary damage to fragile chassis components.


Regards

Steve

 

[Ian@StEnochs]

A bit of progress with the chassis. Rolls freely, which is always a bonus. With hindsight, I wish I had made the frames a bit wider. I went for 28mm between frames which is what Dave provided for the S7 version of his 8F and Std 4 Tank. The gap between the frames and the back of the wheel still looks massive. Its only 0.35mm (0.014”) wider than it should be, which sounds negligible, but you can see for yourself what it looks like.

View attachment 65207


Steve

Steve,

I remember being close up and personal with one of the standard class 3 moguls which were common around here. My particular memory is of putting my hand between the wheel and the frames, my then 13 year old fingers just slipped behind the flange! The loco was out of steam at the time, a Sunday she'd bash, but that experience has stuck with me. Some locos you can get away with narrow frames but the Standard Moguls perhaps not!

Ian.

 

[SteveB]

Hi Ian

I don't suppose you had little fat fingers when you were 13?

It might not look quite so bad once its painted. Another lesson learnt.

Regards

Steve

 

[Ian@StEnochs]

Hi Ian

I don't suppose you had little fat fingers when you were 13?

It might not look quite so bad once its painted. Another lesson learnt.

Regards

Steve

No and my fingers are quite thin still.

Ian.

 

[SteveB]

I’ve just pi**ed myself off quite badly. If you look at my earlier post, you’ll see the gap between the outside of the frames and the inside of the wheel. I thought I would console myself by working out the difference between my S7 version and a normal FS one. Well, the gap on my S7 version is 0.001” thinner compared to what it would have been with FS.

Admittedly, the S7 flanges and the wheel thickness make a visible difference but when you consider I’ve spent a fair amount of time doing special etches and castings to save 0.001” I’m sure you can understand how I feel.

It’s no one’s fault other than my own. It was me that chose the 28mm distance between the frames. I partly chose the 28mm based on the conversion etches that MOK supply for other models and when I initially looked at the full size frame GA I saw that the between frame dimension was 4’ 1 ½”. I basically ignored the 1 ½” because I thought “well that’s not going to make a lot of difference in 7mm scale” well it does, 0.875mm to be precise.

My initial thought was to chuck the whole lot in the bin and take up jigsaw puzzles as a hobby. I’ve calmed down a bit now. I’ll put up with it, but I’ll know what to do next time, 28.9mm between the frames!

I also forgot to mention in my earlier post was that my wheels were expertly re-profiled by Eastsidepilot. A great job done very quickly and at a very reasonable price.

Regards

Steve

 

[Dog Star]

... I thought I would console myself by working out the difference between my S7 version and a normal FS one. Well, the gap on my S7 version is 0.001” thinner compared to what it would have been with FS.

Not sure that I follow this completely:- you have measured the gap for S7 wheels in S7 frames, I shall assume that as I doubt that FS wheels fit in S7 frames; you have measured the gap with FS... could that be FS wheels in FS frames or maybe S7 wheels in FS frames? If you measured FS wheels in FS frames then consider what the gap might be with S7 wheels in FS frames and compare that with what you have achieved. Irrespective, your work is very inspirational.

As to where you are with the model, just thinking...

What is the minimum radius curve for the prototype?
What radius curve do you expect your model to negotiate?
What sideplay is required for your intended curves?

Does your S7 wheels in S7 frames have the necessary sideplay?

regards, Graham

 

[richard carr]

Come Steve, we need the answer, or are you just as confused as I am.

Great post Graham

Richard

 

[daifly]

Steve
I'm no engineer but I'm puzzled as to why you keep referencing the distance between frames when I would have expected the critical dimension, particularly in S7, to be the width over the outside of the frames.
In your very first posting in this thread you specified "28mm between frames, 29.35mm outside. As supplied it’s around 25.7mm between frames."
As I see it, unless your frame material is very thick, even after applying overlays, the 28mm dimension will produce narrower frames than you are looking for. Slater's S7 axles will give a B2B of about 31.25mm if the wheels have been turned flat on the rear as yours appear to be. The hornblocks/bearings will presumably protrude outside the frames and need to be accommodated within the 'B2B minus outside frame dimension'.
I suspect that it is the 28mm dimension that is flawed. Over to the experts to put me right!
Dave