7mm Mickoo's Commercial Workbench

[mickoo]

Mike,

I forgot to say start forming the outer frames now as I seem to remember a problem with the fit with the steps and the inside frames. IIRC the inside bit was to wide to fit between the steps.

OzzyO.

Oh, so it is, that's a bit naughty isn't it.

Looks like I'll have to chop off the two droppers down the sides and move them in 2 mm or so to clear the kink in the step sheets. Of course then the weight shaft will need shortening and the bearings moving as well.

I've just been tipped that my brake cylinder tunnions are in the wrong place and I now have a decent drawing of the centre pedestal that supports the weight shaft so that'll all go in the printer shortly along with a revised hand brake lever, it's a single slotted arm, not dual like originally had.

 

[adrian]

The rest of the week was spent drawing up replacement white metal bits for 3D printing, the filler lid had an artifact on it which shew up once painted, so that needs addressing before fitting.

They look so much better, one quick question if I may.

I'm just about to draw out a leaf spring for my next project for 3D printing so any tips would be appreciated, what is the best way to approach it? Do you sketch out each leaf and assemble them into one part or do you sketch out the perimeter of the spring and then add grooves to simulate the individual leafs?

 

[simond]

Adrian,

I’ve just done some 3’6” RCH and 3’6” and 4’6” GW wagon springs, I can post them on here if they’d be of use, but the files are not small. An alternative is to do a file transfer.

I’m confident of the RCH dimensions, the GW ones may be a little “interpretive”.

pix on my workbench thread.

in answer to your question, the leaves are separated by grooves. I think the grooves need to be bigger than I modelled them (About 100u)

atb
Simon

 

[mickoo]

They look so much better, one quick question if I may.

I'm just about to draw out a leaf spring for my next project for 3D printing so any tips would be appreciated, what is the best way to approach it? Do you sketch out each leaf and assemble them into one part or do you sketch out the perimeter of the spring and then add grooves to simulate the individual leafs?

I draw out each leaf individually then chamfer the edges, the amount you chamfer depends completely on your printer and the resin you're using, you may find you have to over 'egg' the chamfer to get the print to finish how you want it.

Autocad is pretty good as once you've drawn one leaf and stacked them all up then you can select one end and just drag it to the right length, it'll auto adjust the position to match the curve of the leaf.

 

[SimonT]

Mick,
You could have got all the castings other than the brake cylinder and trunnions from F7. Yes, I know your mate Pat would have made you wait. However, nice work on the new prints. I'm not sure about the bracket either.

Adrian,
I do individual leafs for the spring and fillet them as that gives a better result when printed on a Form. A radius of 0.15mm ish gives a good result. Don't bother with the inside surface.
Print them 10-15degree out of horizontal across and 5degree out with the axlebox above the spring. Supports onto the edge of the spring works out well on the Form.
Simon

 

[mickoo]

Mick,
You could have got all the castings other than the brake cylinder and trunnions from F7. Yes, I know your mate Pat would have made you wait. However, nice work on the new prints. I'm not sure about the bracket either.

Adrian,
I do individual leafs for the spring and fillet them as that gives a better result when printed on a Form. A radius of 0.15mm ish gives a good result. Don't bother with the inside surface.
Print them 10-15degree out of horizontal across and 5degree out with the axlebox above the spring. Supports onto the edge of the spring works out well on the Form.
Simon

Yes I could, but then the client pays extra and I have quite a few big GWR engines coming up through the build order next year so it kind of made sense to 'roll' my own. If I know I'm doing five or six tenders from the same stable then I can offset the 3D dev work across the batch.

I've done some digging around, Kings class only, and all have the spring retention bracket so that stays in, interestingly they seem to change axle box covers, some have the top up bowl in the middle of the box, others (more later?) have a smaller top up bowl lower down at the leading edge on the RH side....not checked to see if it's trailing on the LH yet, that'd make sense if it were a common axle box cover.....but we're dealing with the GWR here.

I've modeled the lower one and both types of axle box are common in BR days, the clients loco sported both types at some point in BR days so probably a tender swap at some point. I'll try and define exact dates and if I can find a good photo to match will fit the required cover.

 

[Arun Sharma]

Whilst it costs more, I tend to use 3D prints as masters for lost wax castings. It is those brass castings that act as the mould masters for the white metal final items. The reason is simple - The compression forces and heat inevitably generated in the making of white metal moulds can distort or destroy a 3D printed master but have no discerable effect on a brass master.

Yes, it will cost more but spread through a run of 10-15 kits, it matters little.

 

[LarryG]

Whilst it costs more, I tend to use 3D prints as masters for lost wax castings. It is those brass castings that act as the mould masters for the white metal final items. The reason is simple - The compression forces and heat inevitably generated in the making of white metal moulds can distort or destroy a 3D printed master but have no discerable effect on a brass master.

Yes, it will cost more but spread through a run of 10-15 kits, it matters little.

I suppose there must be a concern about how large to draw the 3D master to allow for shrinkage of the lost wax master and then the whitemetal product. When a jeweller in Brummy was casting my bus radiators, the shrinkage was minimal even on a large item like a 1.50th scale bus roof. He obviously knew his business whereas modelling manufacturers were making moulds and whatnot on a hit and miss basis.

 

[mickoo]

Whilst it costs more, I tend to use 3D prints as masters for lost wax castings. It is those brass castings that act as the mould masters for the white metal final items. The reason is simple - The compression forces and heat inevitably generated in the making of white metal moulds can distort or destroy a 3D printed master but have no discerable effect on a brass master.

Yes, it will cost more but spread through a run of 10-15 kits, it matters little.

That's the difference, single client builds are well suited to using 3D as is, so long as it's used in the right context and the client is happy with it. As soon as you get into multiples and more importantly, other people using the bits, then metal castings become a more attractive way forward.

There are of course parts that cannot be cast cost effectively, in which case, 3D is the only practical and affordable way forward.

 

[Compton castle]

I can’t wait to see what you do with the Duke!

 

[mickoo]

I can’t wait to see what you do with the Duke!

There's quite a lot of info on the Duke's cylinders and gear boxes, we should be able to replicate them quite closely. I'm sure quite a bit of the Duke drawings are on fiche so I'll get the pipe & rod plus frame arrangement ordered, mostly for my own collection for possible future use. I'll tie that in with your build so I can reference them with any stuff we might need.

 

[3 LINK]

I can’t wait to see what you do with the Duke!

All we need then is a 5MT 4-6-0 and a class 2884 ….

 

[Compton castle]

All we need then is a 5MT 4-6-0 and a class 2884 ….

I agree the 5MT is a great looking loco, I'm
Quite dubious about spending the money DJH are asking with the questionable castings now being supplied in some of their kits.
I think the 38 is on the Finney to do list so fingers crossed for us both.

 

[3 LINK]

As you know I’d love a 38, but I know that it’s far down the F7 “ to do “ list, so don’t hold your breath. It looks like I will have to go for the Seven models kit and I expect to spend a lot more on some quality castings to finish her off to my liking.

As for the 5MT, I’m hoping MOK might be doing one next, fingers crossed.

No harm in dreaming

 

[mickoo]

Last update for 2022.

More bashing about on the King tender chassis, tipped off by Ozzy O the first task was to strip down the front end. The fold up etch that holds the weigh shaft trunnion bearings is too wide; out of the box it's 43.6 mm but needs to be 36.6 mm. The problem with the original width is that it will conflict with the front steps when you fold the turn in on the backing sheet.....that'll become more apparent later on.

Whilst doing that the last but one piece of white metal (vacuum brake lever) failed and fell off the shaft, in hindsight I should never have put it on in the first place.

Armed with works drawings graciously passed to me by a helpful modeler the rebuild could commence, the side sheets were moved in, weigh shaft shortened, a new centre bearing pedestal drawn up and fitted, new vacuum cylinder arm and new hand brake lever were also drawn up and fitted.

The final task was to draw up a new vacuum tank and fabricate some stretchers to hold it in place. I opted to make my compensation beam with double sets, this means that it passes over the top of the tank (just) and drops down to the axle. Some folks prefer a more swept arched beam like a long bow profile, in that case the beam will pass right through a lot of the tank. It's six of one and half a dozen of another, the long bow profile is easier to form and set up but a lot of work needed on the tank to clear it; the double set is harder to form but less work on the tank.

The floating axle top hat bearings bugged me, they just float in the slots with no means to stop them rotating, any grit or gummy oil later in life with seize them and the top hat will spin merrily in the inner chassis and wear the metal work.

I folded some 0.7 mm wire into a J shape and soldered it to the bearings, the long tail then passed through a 1 mm hole in the top of the stretchers. The bearings are free to rise and fall but will not rotate any more.

I still have the water scoop front end levers and cranks to sort.....but that'll be next year.

 

[mickoo]

That's better, just one final revision to the spring retention clip (lower by 0.5 mm) and I can sign the axle box CAD off. New fittings will pop out of the printer in a couple of hours and then fit along with steps and buffer housings.

Next week it's back to the BLP to push that along with cab and front end to finish, then check the casing side sheet fits before sending off the revised etches.

 

[mickoo]

Cab assembly - Check
Casing assembly - Check
Chassis - Check

Assembly interface - Checked:- Inspectors note, cab tilted down at rear by 0.2 mm. Action point:- check interface for perpendicular alignment and debris.

Proceed to next assembly bay.

 

[Tim Watson]

View attachment 177375

That looks wonderful. It does remind me a bit of a dovecote in its present form.

Tim

 

[mickoo]

Slow progress, few odds and ends at the front end done, most of the time was spent sorting out the new 3D smoke box module and getting a good fit, quite important as the chimney needs to align with the internal roof (folded brass not fitted yet) and fit into it.

Just noticed in the photo that one of the 3D lugs has snapped off (kind of sums up the past week really) probably from the tweezers fitting the steam feed pipe, so that whole module goes in the bin and a new one will be printed overnight, at least it all fits so won't take too much time to assemble and proceed.

First casing roof in the printer, still open court on 3D through out or 3D core and etched overlay. Metal skin has the kudos and bling, but will quadruple the build time for that component.

 

[david duxbury]

Amazing detail and fantastic quality again Mick, Bring on the Kudos and bling Please!