SimonD’s workbench

[simond]

And on the plate this evening…



Locomotive springs and their J brackets - a common issue with white metal ones is they break at the suspension pins. I thought I’d avoid that by 3DP the springs and brackets and epoxying a metal pin to join them

Looked great on the CAD but with the bits in my hands I started wondering how to assemble them - I have far too few hands to hold the parts in alignment, and it’s boring waiting for 5-minute epoxy to set hard

A jig!

3DP is brilliant for that kind of thing and we use the Bambu FDM printers at work quite a bit for jigs and fixtures - make one, try it, modify it, if it works, great, if it breaks, print another or copy it in ally or brass - fantastic time saver and cheap too.

Anyway we have a resin-print jig and we have springs and brackets and wire and epoxy…

 

[simond]

Looks promising…



And it’s a yee-haaaar!



I had a brainwave, I think another thunderer suggested they using 3D Printer resin as an adhesive was viable approach to sticking something and so it proves.

I extracted the pin (0.7NS wire) from each joint, dipped it in the resin and re-introduced it into the assembly.

Once each joint was made, I put the jig and assemblies into the curing chamber for 30 minutes, et viola! Or something, I’m sure I heard music…

Quite pleased with that, will do the other 4 tomorrow.

Then brakes…

 

[Giles]

I bought a little UV torch to do the job in about 30 seconds or so. It's a useful thing to have in the armoury.

 

[simond]

I bought a little UV torch to do the job in about 30 seconds or so. It's a useful thing to have in the armoury.

Yes, there’s a little uv flashlight supplied with the Elegoo curing chamber. I pondered using that, but it's on a wire that plugs into a socket the chamber so not super portable. Obviously I could rig up a socket on the workbench, but dinner was nearly ready, it’s in a jig, just leave it in the chamber!

Was it you who posted the idea of using resin as adhesive? Good call!

It seems to have worked well, a weak point has been well reinforced, and once they are epoxied to the frames, they’ll not be vulnerable at all. I do wonder how strong the bond to the metal will be, after all, it’s possible to unstick prints from the build plate. Not an issue here, but would be good to know the limits.

S

 

[simond]

That seems to have worked well.

time to clear the workbench and strip the chassis. The weather is a balmy 15 degrees and sunny-ish so it would be good to get a coat of primer on an assembled chassis. Strike whilst the iron is hot!!!

 

[simond]

wait for the Araldite Rapid…

Now, put the spray can in a pan of warm water.

 

[simond]

Mission accomplished…



I’m going to have to reprint the bushes for the pickups, I’ll do that overnight tonight all being well, and by tomorrow the U-POL will have dried hard, and I can then give it a waft of something reddish between the frames and dirty greyish on the outside, and then it can start going back together.

It’s been a fun project, but it’s good to be on the finishing straight.

 

[simond]

I had already fitted the pickups to the Manor, but had to remove them to fit the springs and the brake hangers. I had printed the bushes as it’s quicker and more repeatable than turning by hand, but it is an easy lathe job of course.

The pickup design is based on sketches given to me by David LO Smith, who was a talented model engineer (and talented real engineer too!)

These pick-ups are easy to insert and remove without disturbing the wheels or motion, and are "floating" in that they react the contact pressure of one wheel on it's mate rather than on the chassis.

I say printing is “more repeatable” but for some reason the all the smaller bushes were tight in the springs, and prevented the springs working as they should, so having it all in bits means doing it right this time! Along with a set of back-to-back jigs for assembling split axles, some brake bits, and an ashpan, I printed new bushes last night, and as people ask, I thought having some photos all in one place would be good:

The actual pickups are 11mm lengths of brass rod with the ends cleaned but not domed or chamfered. One end has a small hole a couple of mm deep as a solder pocket, and the wires are soldered in. I use “Hochflexibles Kabel” that came from ESU via one of the DCC suppliers. It’s very thin, and as the name suggests, highly flexible. The OD over the insulation is 0.5mm.

The smaller bushes insulate the pickups from the spring, and the larger bushes are secured in the frames with epoxy or cyano.

The springs are Premier Components 3-link coupling springs - there are plenty left over from my own wagon projects which use Peco type transverse wire springs for coupling and buffers.



The tags of wire are where I cut the old wires off. I shall remove them and solder in new wires.



The frame bush and spring bush.


Drawings - the pick-up itself



Spring Bush



Frame Bush





spring bushes, pickups and wires assembled.

the great advantage of this design is that the pickups can be removed without disturbing the wheels & motion.



rear pickups inserted in frame bushes (wrong way round, red on the right when the frames are the right way up!)



And the other two pairs.

I’m going to take them out again whilst I paint the chassis, but you can see how easy it is.

 

[Ian@StEnochs]

Neat, but for those without either a 3D printer or a lathe this is my version of the single spring ‘ toilet roll holder’ plunger pickups which I have used for many years. Fabricated with stock brass and styrene tubes, brass wire and fret waste. I use springs from Slaters buffers and are inside the brass tube.

Ian.

 

[Rob R]

Simon,
I may have missed it but what is your Smokey Grey resin?

 

[simond]

Hi Rob, it’s Elegoo Smokey black. Ordered in error, but actually very good. It’s just a bit weird having translucent brake levers and springs.

the detail might not be quite as good as FNG, but you’d be being picky, and it seems tougher. Certainly less brittle, and easier to drill.

 

[Rob R]

Thank you.
I am sure the transclucent stuff, of whatever brand, cures better 'cos the uv can get through to all of it.
I also have a theory (unproven) that transclucent resin is nearly all resin with a tad of colouring and the other stuff has a lot of (cheap) inert filler to bulk it out.

 

[simond]

That’s certainly possible. If you don’t shake the FNG, it separates, there’s a very dark layer and a milky gloop.

 

[Kev T]

Thanks for the pickup drawings Simon. They show that you use 2mm brass rod into a 2mm hole in the printed bush. Don't you need to put some clearance on this? And why the missing quadrant on the frame bush?
For super flexible heat resistant cable I use silicon insulated, readily available and so far excellent.
Kev

 

[simond]

Hi Kev,

Yes the spring bush will need a drill to open it slightly, you could print it with clearance but it wants to be snug, I think I used a number drill that was a midge’s over 2mm

The missing quadrant on the frame bush flange is to clear the J hangers of the loco suspension springs

Where was the silicone insulated cable from, please?

Cheers
Simon

 

[Kev T]

https://www.amazon.co.uk/DAOKAI-Silicone-Stranded-Electrical-Printer/dp/B09TK2NHN7/ref=sr_1_15?crid=1RI2NWVT0VP2W&dib=eyJ2IjoiMSJ9.W2qyxY085PrUEvZz4s3w1PZVnZlLdZo7XddGbCC3s5eQ8CgObyJjTYGFPob--aOisSPKGTUlbhIyixtnyoaDFou26K1y1cOz1WWmqQimMla9xbbPtNkiNypjXYcHgzUtjRe9npFqHflDrQbowvMdpECGJdXJOAnITLrnKSd8_sHJza7ugIanhTXWLuvmtbXfNIqIQGuVPelu18HzlOebbqQDH3BG_ol_elmBq5u-g-OSEYsqiVYOuJEzm7CuU1Y8r3tg0atCZI_dzR0LYSTK-TpqQl_uOxn-2mPP3vNoRYI.625C9_GA9D2fpKo0BxYwj73p1IwYIDN13ah5oUWmHcA&dib_tag=se&keywords=silicon+wire&qid=1762801777&sprefix=silicon+wire%2Caps%2C147&sr=8-15

pretty sure this is what bought last time.
Kev

 

[simond]

Well, another useful step forward. The chassis has been painted (5:3 Vallejo 950 black and Vallejo 994 Dark Grey) and the cylinders refitted. I painted the frames red inside, and considered printing some dummy motion but the chances of seeing it are slim to none, so I’ll not bother.

Thanks to Barry @lankytank the piston rods look rather better in NS than brass.

The snick has gone, I think one of the crossheads was a wee bit tight in the slidebars.

Ashpan fitted, as is the brake cylinder, though that’s pretty much invisible too. Nice though the body is, I think there’s rather more footplate than the prototype…


I’ve just got to finish the CAD for the stretcher beams and the adjusters and the brakes can be done.

It still needs injectors, vac pump, a backhead and cab floor, glazing, crew, lamps, tools and a water scoop for the tender.

And the missing cab step repairing, vac & steam heat at the front, heat at the rear, whistles, drain cocks, cylinder relief valves…

and I‘m sure there’s other details that could be added.

 

[simond]

It’s a little curious to see transparent brakes, but I’m very pleased with how it went together.



I suspect I’m going to regret not having painted at least some of this before assembly.

Happily, it all seems to run quite nicely, though I imagine there will be some brake drag until it’s done a few laps of the Folkestone club track. The brakes are pretty close, and don’t move and the wheels do with the suspension so I guess it’s inevitable that there will be some contact.



Next entertainment is going to be some visible undergubbins for the tender. Unfortunately, the water scoop downpipe (“uppipe”?) doesn’t quite fit, not sure where I went wrong there, but it’s not a big deal. I’ll cut the base, work out how it goes and reprint.



There’s a bit of arcane bodgery going on with an ex 3-rail Achilles 3031 class coming up soon…

 

[Osgood]

Thats a pretty amazing piece of design work - the pivot pins running right through is a neat design.

 

[simond]

Thanks Tony,

it seemed to me that they’d be a bit fragile if they weren’t reinforced. They’re probably a bit over scale thickness, but 1mm is just shy of 2” and the shackles keep the halves together. I was surprised and delighted that nothing broke as I was clearing the holes out.

the one that also surprised me was printing the guard plate for the water scoop. It’s well under 0.5mm thick, I really didn’t expect that to work!

cheers
Simon