7mm Mickoo's Commercial Workbench

[mickoo]

Fantastic work, I know it’s a pain in the A**E for you but I do like to see how you overcome poor kits with ingenuity and new tech.

It's not overly bad, despite my oft mumbling and dummy spitting, in many cases it's often faster and thus cheaper to make new 3D or sheet metal work than fight what's in the box. I do stress to anyone who asks me to build stuff, cheap kits are not cheap to build, quite the opposite by a significant margin.

The trick is to spot the bad bits before you get waist deep in the mire, not even attempt to make them fit function or form and build new, that only comes with experience I'm afraid.

 

[Big Train James]

Thanks for the info Mick. I already knew about the spigots and loops for securing printed parts to etched metal. My current concern is more about securing resin parts to other resin parts.

I'm doing hood doors that are to fit in a carcass. I'm limited on depth so adding bits for mechanical fastening isn't going to work.

I'm also limited by my method for executing the doors. I have a panel with a narrow rebate around the edges, so that the "sheet metal" door will overlap the corresponding opening in the carcass. I want to limit the width of the rebate so that I have a very minimal area of very thin (.13mm thin) printed material. Meanwhile maintain full thickness elsewhere in an attempt to improve durability and prevent warping. Opportunities to introduce interlocking keys or pins is limited.


Oh how I wish this material could be solvent welded like typical styrene. Just wick some solvent around the back and let it set.

Anyway, I'll go pick up some epoxy, I'll end up using it to fit parts to the diecast frame as well. Except in that case I will have a chance to make mechanical connections, which I'll set with the epoxy.

Jim

 

[mickoo]

Jim, you're not thinking far enough out of the box

If my hood skin was brass then I would add spigots to the rear of your door assembly (red circles), then I would print a flat bar with corresponding holes (green outline box, only top one shown).

To assemble, place door into space in hood, add adhesive to spigots place bars over spigots and clamp, go make coffee. If you wanted something stronger then use brass bars with holes drilled in to suit the spigots.



There are more eloquent solutions I'm sure, but this one triggered in my mind right away. For example (hard to explain this but I'll try) you could print a long slotted plate as part of the door section on the inside, along one edge top or bottom, that when slid in traps and grips the frame work, bit like the green bit but the same width as the opening, then the other end only have two spigots to add the bar to.

However, you're trying to bond two resin parts and have missed the little secret hidden away in most user groups

The resin you printed with is also an adhesive, place door panel into structure, using a small brush add liquid resin to the joint, if your fit is tight I'd add some to the surfaces before placing together, then zap the resin with a 405 nm UV curing pen UV LASER PEN + UV CURED RESIN LITE "THE BUG THAT BONDS" (BATTERIES INCLUDED) 5699849179258 | eBay , it'll bond the two parts together like concrete.

This Br 110 cab was bonded to the front section of the body as a test, I've not tested it to destruction but with quite firm twisting and pulling it hasn't split.



Nice doors by the way, really do need to get on with the complete printed cab tests........

 

[Big Train James]

Shoot, completely forgot about the idea of using the resin as the adhesive. It does seem counter-intuitive to me though, in that I wasn't sure that it would bond to parts that were already cured. But yes, I need to get a UV flashlight and give that a go.

The issue with the spigots and bars is simply that I have very little space inside the shell, exacerbated by my stubborn determination to fit a Tang Band 1931s in there. But even the Loksound decoder is nearly full width. I am gaining something by virtue of reducing the wall thickness from the Atlas armor plate, but I am leery to go too thin as I suspect I will end up with warping problems then.

The carcass will go in the printer in the next day or two. It will take the full height of the Mars 3 to accommodate it. I'm looking at something like a 20 hour print for that, even at .5mm slicing, since I have extra rest time added per cycle as discussed elsewhere. I'm anxious to see how everything looks once that's done printing.

 

[mickoo]

I'm running 4 second rest, I've run 6 and it didn't seem to add much and 2 seconds does give worse results. I'm just running a test on the tender tool box to try and minimize warping and get smoother surfaces.

I've read on the Elegoo site that these new printers will reach up to 180 microns into the previously printed model and over cue what's cured before and cause deformities, just for giggles I'm doing the new tool boxes at 80 microns to see what happens.

The biggest problem i'm finding is that whilst the raw prints look really smooth, an application of paint shows up a lot of surface issues and thus a new regime of post processing is required.

 

[Big Train James]

By new Elegoo printers, do you mean the newer iterations with the UV light arrays and fresnel lenses? That would be unfortunate, because I've just started thinking about throwing my hat in the ring for one of the newer Saturns. Then again, I just saw that the original Mars 3 is on sale for $209, I'm very tempted to get another just because it's so damn cheap. Frankly I'm happy enough with the results I get, I would love a tighter XY resolution but I can live with what I have. I just suddenly need more volume.

I appreciate the feedback on the rest time, I've been running 6 seconds lately, if I go to 4 for the carcass print it will shave about 2 hours off the time. Not that it really matters, it will get done when it gets done, and I'll almost certainly run it overnight. Although come to think of it, it's my first really big print, it might make sense to run it when I'm awake and can check on things periodically.

I haven't witnessed the wavy surface defects issue yet, but then I also haven't done primer on anything since the very early days when I first got the printer. Once these doors are done printing, I might waft some primer over a set and check the surface quality. I've also don't seem to have warping issues even after quite a bit of elapsed time, at least on the parts that I've cured. I had a print that was heading for the bin, I never post cured it, and it did curl after several days. Which makes me wonder if your parts are insufficiently post cured? Just riffing here, I have a hard time believing that, but I just haven't seen the same issues myself. Or maybe they are over-cured, done while printing subsequent layers, as you suggest above.

That has to be frustrating, it's hard enough to crack the code on printing variables already. Sometimes I feel like each print is like starting over again knowledge wise.

 

[mickoo]

Well the 80 micron test went straight in the bin

By new printers I also mean the Mars 3 and pretty much everything for the last few years, aka mono screens, it was just a simple comment on the Elegoo FB page somewhere, it didn't expand into a war of detailed research and debunking so I'm not taking much store by it. At the end its the finished result that counts and if you're happy with that then how or what goes on is irrelevant.

The warping is on the build plate, not even getting to the curing stage, parts tend to curl for the first 10-15% of the build and then straighten out, it happens to a lot of people, the cry is to add more supports, not always an answer.

The tool boxes printed reasonably square and warp free at 50 microns with slight wavy surface (more in a moment), yet the exact same supported model at 80 microns exhibited distinctly more warping during the build with exactly the same number of supports, ergo, supports are not the issue/solution.

Wavy surfaces, I should openly confess that if the surface is not mirror smooth then it's a failure in my eyes, my criteria for surface quality probably exceeds most peoples by a significant margin, I know this to be true as web pages and forums are full of happy people with their prints where I would not be. Thus, when I have an issue with surface quality, others should take that with a pinch of salt as their mileage 'will' differ

 

[michael mott]

Wow, on a Model railway forum a discussion about the infinitely small.

The tool boxes printed reasonably square and warp free at 50 microns with slight wavy surface (more in a moment), yet the exact same supported model at 80 microns exhibited distinctly more warping during the build with exactly the same number of supports, ergo, supports are not the issue/solution.

Tongue in cheek of course, and I thought 2mm fine-scale was pushing the limits.

I am truly amazed by the leaps and bounds that our hobby has made in the last couple of decades, which can only be of great benefit in the long run.

Michael

 

[Crimson Rambler]

Sorry to be a pain @mickoo but if your tender is destined for a 3F, which were right hand drive, the handbrake would be on the opposite side. If however the tender was fitted with water pick-up then a mirrored arrangement also appeared on the driver's side.


Crimson Rambler

 

[mickoo]

Sorry to be a pain @mickoo but if your tender is destined for a 3F, which were right hand drive, the handbrake would be on the opposite side. If however the tender was fitted with water pick-up then a mirrored arrangement also appeared on the driver's side.


Crimson Rambler

Especially as its all now finished with new front platform.......

Thanks for the heads up though, the strip down will now commence

 

[mickoo]

Hand brake stand now swapped over

Concerning the rest of the 3F tender, little visual progress but a fair bit of back and forth, unlike my usual fare these are warts and all work in progress shots.

Primarily it's almost finished and the photo's (as usual) have highlighted some extra areas for attention. I'm hoping the MR cast lamp irons from Laurie Griffin turn up tomorrow, that'll just leave some scratch built handles for the two water valves on the tender front and the brake weight shaft with cranks for pull rods and hand brake stand to complete.

The red oxide on the body is a witness coat to check for imperfections, only one or two small ones remain; eventually all of that paint will come off during that process.

 

[mickoo]

A little more progress on the Alan Gibson 3F, this is about as far as it goes out of the box sadly, even then I need a new wider buffer beam overlay and step adjustments. From this point it's all scratch built for the footplate upward (chassis next week with even more to scratch build).

First uplift is the cab tool boxes, both different in size and shape, the RH one has a notch cut for the reversing level quadrant and part of the bracket to hold said level is in place in the print, a brass quadrant will go on top of the pegs once the lever in in place.

Both boxes have glands for the injector drain handles (I presuming that's what they're for, the drawing is indiscriminate as to their purpose) so those will need fabricating or the fittings spares box raided for suitable handles.

 

[Simon]

Very clean work Mick, as ever.

Those toolboxes look humungously big set into that cab - were they really that size?

 

[mickoo]

Very clean work Mick, as ever.

Those toolboxes look humungously big set into that cab - were they really that size?

Appreciated,

That's a very good question which sent me scurrying for the books, according to the drawings in the very nice books you sent last week, then yes that are the correct size apart from the width.

The problem is O fine wheels which are too narrow and for scale width boxes, thus you have to make the boxes wider by about 1.5/2.0 mm to cover the wheels. The same problem occurs with the back head which waists down to fit between the frames, on O fine models you have to make the waist even more severe to fit between the wheels/tool boxes etc.

Not all 3F had these large boxes, depends on the year and boiler fitted, later 4F (earlier builds) had similar boxes but smaller on the LH side, later builds had even smaller RH and virtually no LH except the bit that covered the wheels.

I haven't set these in place yet as I need to run a few clearance checks, the rear axle will be fixed laterally as it's the driven axle then I will see exactly how much space I have between the inside of the wheel and the inner sides of the boxes, I think I can shave a good 1 mm off to make the floor space wider; even then it'll still be below scale width but may not look so crowded. It's much easier to trim back than to add material is my thought.

The small strap across the front of the cab base is just to support the boxes level whilst the 'eventual' adhesive sets.

 

[Dave Holt]

Mick,
More lovely work, as always.
The spindle glands on the top of the tool boxes are for the injector water feed valves.
According to the Terry Essery books about his footplate career at Saltley, 3Fs were well regarded by crews for the large size of the tool boxes as they provided a good place for a snooze on night shifts.
Dave.

 

[mickoo]

Mick,
More lovely work, as always.
The spindle glands on the top of the tool boxes are for the injector water feed valves.
According to the Terry Essery books about his footplate career at Saltley, 3Fs were well regarded by crews for the large size of the tool boxes as they provided a good place for a snooze on night shifts.
Dave.

Yeah I can imagine the big flat tops would be nice and cosy to snuggle up to on a cold winters eve.

After last nights dialogue I re did the tool boxes and squeezed another 0.8 mm off each side to give a wider platform between the two, any more is near impossible due to the restricted inside face wheel measurement for O fine. The side wall for the splasher section closest to the wheel is now 0.5 mm thick, about as thin as you can go for a thin wall like this, thicker than brass sheet but zero risk of shorting should the wheels tilt/rock on the compensation beams.

I realized as well that I can't limit all side play on the rear axle, you need a little to allow the axles to tilt on uneven track, if not they'll just jam in the horn guides.

 

[simond]

Mick,

you can always have one fixed (no vertical, side, or angular play) axle in any equalised model.

I don’t think it’s a good idea, because the body must then follow every lump and bump in the track, and I think it always looks better if the vehicle “glides” smoothly.

The other axles must, of course, be able to accommodate the vagaries of the track, in both vertical and horizontal axes, and twist, of course. Well strictly, two axles should have no side play, but all but one must have vertical play and twist.

If you spring the model, all axles would have vertical play and twist.

(granny, eggs, etc…)

atb
Simon

 

[mickoo]

Smacked gob time, just on a fancy I tried a 3D smokebox for the 3F to save hours cutting one out by hand. Other than a quick sand on the base it's just a rough and ready trial fit; I'm aware the piano front needs smoothing to remove the layers and a few more will likely turn up when the finished item gets a coat of paint.

I cant get my head around how square and smooth the new machine is with these new settings.

I know resin is not everyone's cup of tea but it took 20 minutes to draw up, ten minutes to clean, sand and test fit, saving at least four hours over a scratch built brass one.

The boiler and firebox are scratch built but then they are much simpler shapes to contend with.

 

[AJC]

If you can, and it looks as good as this? Excellent stuff.

Adam

 

[mickoo]

If you can, and it looks as good as this? Excellent stuff.

Adam

It's a leap from sand boxes and tool boxes, large surface areas and important to avoid warping or non 90° angles. Back head's I've done but they're mainly hidden away but this is pretty much the focal point. I'll need to see how it goes once the primer is on, that's the real acid test for surface quality; the shape I'm more than happy with.