7mm Mickoo's Commercial Workbench

simond

simond

Western Thunderer
mickoo said:
Actually, I was talking utter bollox, Whilst preparing to strip down I've had a closer look at the bogie wheels; these are not screw in stubs, the axles are actually machined with the stubs on and a tapered shaft for the wheels to fit on to, secure and locate.

It does mean you can still get the wheels off once the stubs are removed and trimmed flush with the hub.
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they're the older "MF" ones with push on wheels. I think the bogie & tender wheels simply had a hole in the plastic, the drivers for the outside cranks had a tapered brass bush and they were a bu**er to get off. (Buffer, obvs)

EDIT seeing the beast in the post below, it looks like they have brass hub bushes too?
 
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mickoo

mickoo

Western Thunderer
That's about as far as it goes before strip down. There's one or two nick nacks to do whilst away for paint or during strip down as well as some bits that can only be fitted after paint.

Next week is a mish mash week, last few bits on the JLTRT Crab tender, some 3D for the LNWR 2-4-2T tank, boiler, smokebox fitting then I can work out where the cylinder block fits.

A new project to start ramping up in the form of a JLTRT Castle, it should have started last week but real life....yadda....yadda....that'll run alongside the Crab for the next month or so.

In the spare time several models back from paint being reassembled to get them on their way to customers or weathering.

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cmax

cmax

Western Thunderer
Wow!!!, It seems a shame to paint it to be honest, but bet it looks fantastic when returned painted and presumably weathered.
 
Pencarrow

Pencarrow

Western Thunderer
mickoo said:
That's about as far as it goes before strip down. There's one or two nick nacks to do whilst away for paint or during strip down as well as some bits that can only be fitted after paint.

Next week is a mish mash week, last few bits on the JLTRT Crab tender, some 3D for the LNWR 2-4-2T tank, boiler, smokebox fitting then I can work out where the cylinder block fits.

A new project to start ramping up in the form of a JLTRT Castle, it should have started last week but real life....yadda....yadda....that'll run alongside the Crab for the next month or so.

In the spare time several models back from paint being reassembled to get them on their way to customers or weathering.

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I'm running out of things to say about this build. "Thing of beauty" keeps coming back to me...
 
F

Fitzroy

Active Member
simond said:
Do you have an ink monkey, or are they too new-fangled?

:))
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We are more modern than you realise. However, unfortunately as well as distilling the ink and preparing the cheese sandwiches the Ink Monkey had the job of leaping into the press at top dead centre and pulling out the parts at the start of the subsequent downstroke. An unfortunate lapse in concentration back in '03 resulted in an unscheduled downsizing...
 
mickoo

mickoo

Western Thunderer
A little more progress on the LNWR 2-4-2T (finally), I have a very bad habit on not forcing solutions and the front end was a little niggle to overcome.

The smokebox front drops down between the frames, nothing unusual there, but on the 2-4-2T there's no footplate so essentially it needed to be a part of the footplate, not quite sure where the fireman stood to empty the ash mind and as far as I know they retained this feature until scrapping.

The obvious choice was 3D but I wasn't quite there with settings, supports and design to get something that fitted, warp free and as artifact free as possible.

The first model is a form and fit venture with crude settings, much better to bin a 7 hr print than the production 13 hr print. The primary aim is to make sure it all fits, supports work and orientation doesn't generate warping or pressure waves. A quick sloppy coat of primer helps highlight any potential errors.

The little wrapper flares over the footplate are currently 0.6 mm thick but once the sacrificial edge goes should be down to 0.3 mm, I can live with that. There's also a little gap between the front and frames and the next (final hopefully) rendition resolves that.

The module is bolted to the footplate with two 10BA screws, massive overkill but it can't be allowed to move or the fixing fail, to make life easier two hexagonal recesses hold the nuts and they will be glued in on the final version; the central screw holds the footplate to the chassis.

The chimney is thin walled 3D and is supported internally with thin brass tube for strength, anchored inside the smokebox with a big profiled block and running to just below the top.

Ideally you want the smokebox door as part of the main module but then that limits you securing the boiler with the central screw and fitting the captive nuts, always a ying and a yang designing modules like this. The final rendition will also have the push pull gear features as bolt on parts.

Now this in place the rest can work around this, internal cylinder block (3D) and boiler (brass), once the cylinder block is in place then the slide bars and motion bracket can go in and then we're back on the yellow brick road joining the rest of the dots up.

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mickoo

mickoo

Western Thunderer
timbowales said:
“not quite sure where the fireman stood”.
Remember this was loooong before any idea of elf ‘n safety!
Tim T
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True, but even so that's still a bleedin great big 'ole to fall down and I suspect many a man has fallen down there over time.

I've just been back and taken a closer look at the photos, there's a small ledge between the frames attached to the front buffer beam, it closes the gap by about 50%, which makes more sense.
 
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adrian

adrian

Flying Squad
mickoo said:
The little wrapper flares over the footplate are currently 0.6 mm thick but once the sacrificial edge goes should be down to 0.3 mm, I can live with that. There's also a little gap between the front and frames and the next (final hopefully) rendition resolves that.
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That's a beautiful bit of work there, the "little gap" wasn't really noticeable until I read your text. Once it's all painted black do you not think this gap would disappear?

Back to the main reason for replying - I was going to say the fit of the smokebox flare to the footplate looked really clean and "tight" but then you confused me talking about the sacrificial edge. From the photo there is a line of rivets along the edge of the flare so you can't be reducing the width. Do you mean you've effective printed the flare with a "Gurney flap" underneath to file back to 0.3mm. Does it not get a little too thin and fragile at that point or will it be file and fix permanently?
 
mickoo

mickoo

Western Thunderer
adrian said:
That's a beautiful bit of work there, the "little gap" wasn't really noticeable until I read your text. Once it's all painted black do you not think this gap would disappear?

Back to the main reason for replying - I was going to say the fit of the smokebox flare to the footplate looked really clean and "tight" but then you confused me talking about the sacrificial edge. From the photo there is a line of rivets along the edge of the flare so you can't be reducing the width. Do you mean you've effective printed the flare with a "Gurney flap" underneath to file back to 0.3mm. Does it not get a little too thin and fragile at that point or will it be file and fix permanently?
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Cheers.

You could leave the gap as is and make it a working gap and yes it'll probably not be obvious once it's all black, but the gap was 0.5 mm (0.25mm per side) so I've made the part wider to leave only 0.1 each side, that I can live with.

The sacrificial edge is underneath, it's easier to see on a CAD render and is effectively a 'Gurney Flap' as you suggest, just a bit broader.

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I need that extra thickness to give the part/edge strength during the printing forces and prevent warping, once printed and cured you can then file it back to the desired thickness. Yes it can get fragile but knowing when to stop is the key....and accept that the lip might be slightly over scale when finished. The part orientation plays a part in how thick you make your sacrificial edge, the more parallel the base surface is to the build plate the thicker it has to be to withstand the compression and peel forces.

If you printed vertically as in the CAD render then you could effectively run with no sacrificial edge and print at the finished thickness. This is the chimney printed vertically, the lower lip (highest in the render is only 0.4 mm thick but the compression and peel forces are all vertical. That may have an affect on the final height, usually a bit short by say 0.1 - 01.5 mm depending on exposure settings and lift/retract speeds; personally I can live with that sort of error tolerance. But if you can't and it keeps you awake at night, then just draw it taller so it ends up the right height when printed.

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However, if you rotate the part then the forces are from a different axis and what tends to happen is that the end result is an oval shape.

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3D CAD for printing is a bit arse about face, ideally you need to start with a clear idea of what the part should end up like and most importantly, your areas where you're prepared to take a hit on fidelity, form or sacrifice (in the case of the smoke box I'll take a lip between 0.3 and 0.5 mm). Then you need to work out how you're going to orientate the part to achieve that, only then should you finally sit down and design the part to achieve the end result.

Normally I'd not go much below 0.6-0.5 mm for a thin edge, but being as this one is a tapering edge and the really thin part is only a small fraction of the overhang, I can probably push it a bit thinner; especially as it's fully supported below by the footplate.
 
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Overseer

Overseer

Western Thunderer
mickoo said:
True, but even so that's still a bleedin great big 'ole to fall down and I suspect many a man has fallen down there over time.

I've just been back and taken a closer look at the photos, there's a small ledge between the frames attached to the front buffer beam, it closes the gap by about 50%, which makes more sense.
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Many smaller locos didn't have space to stand in front of the smokebox, even if the footplate was continuous. The solution was a plank of wood laid across the buffers during servicing. A modern (more OH&S friendly) aluminium version is this -
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Apologies for introducing a pannier to the thread.
 
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