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Sprague Motrice heading for the scrapyard

Paris Metro HO Electro etching 3d printing vinyl sides




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#1 L49

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Posted 04 August 2017 - 00:35

Good evening all,

 

It has been ages since I posted anything on RM web, largely because it has been ages since I have done any modelling worthy of posting. However, I thought my latest little project might be worthy...

 

So to begin with, what do you get when you mix a sheet of brass with a sheet of printed vinyl???

 

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The answer is, the basis for a little experiment in electro etching.

 

This is a technique which I found completely by accident being referred to here on RM web. I did a bit of digging, and Tommy and I decided that it was worth giving it a go. The principle is quite simple. Print out your etch artwork on self adhesive vinyl, then stick it to the brass, and cut out the white bits.

 

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The instructions I found online only showed the process being used for a single sided etch, but I decided that if I was going to give it a go, I'd got he whole hog and do a double sided, with half etching front and back.

 

The next part of the process involves tap water and quite a lot of table salt.

 

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Once the solution is mixed, place the vinyl covered brass sheet in the bowl. For this one, I soldered a length of wire to the corner of the sheet. If I do this again, I think I will solder the wire closer to the centre in future. The joint is covered with more vinyl. This wire should be connected to the positive terminal of the 12v DC outlet.

 

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Then you need to find something to use as another electrode. I found a fork in the study! Susie has just about forgiven me for the next bit; 'cos I wrapped the end of a piece of wire around it, clamped it on with a bulldog clip, and connected the whole lot up to the negative terminal on an old Mainline transformer.

 

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The instructions I found online told me that once power was applied, I'd see the metal I was etching start to bubble. It didn't, the fork did. So what did I do, I swapped the terminals over... Bad move! We sat and watched the bubbling sheet of brass for about four hours. It went all sorts of funny colours, but neither of us could perceive much etching going on.

 

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It was only when we got fed up and decided to give it all up as a bad job that I took the fork out of the saline bath. We hadn't etched any brass that day, but we'd done a pretty good job of stripping the plating off the fork, and even etching along the near edge of all the tines. It turns out that I had the terminals the right way round to start with, and that it is the anode which bubbles, not the cathode.

 

The following morning we got back to it, and it worked Ok, although it etched far deeper at the edges of the sheet than in the middle, which is why I might try changing the position of the connection next time, also I might try setting it up in a metal dish and using the whole dish as the anode, as it definitely seemed to etch faster on the side which was nearer the fork!

 

I'm afraid I didn't take any more progress shots at that point. I was so uncertain of the result, that I just got on with the model to see what might happen. As it was, with a bit of cleaning up, I had a passable one off etched brass kit, which I could solder up quite quickly.

 

The trouble was that the etching on the bodysides was not very deep, so I beefed it up with some microstrip. At this point I was wondering why I hadn't just used plasticard from the start. It came out Ok, and got a couple of coats of paint.

 

Then I was faced with a bit of a dilemma. These vehicles carried a quite ornate livery, which was rather unusually applied by enamelling the panels. I decided to go back to the vinyl again, this time printing the panels in colour complete with lining and II class insignia.

 

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As this car is for my Ceinture layout, it is only ever going to be dragged around, either being brought in from the SNCF, or being taken away for scrap. As such, I was going to go for a great dodge, and have the interior completely gutted. Unfortunately, I cannot find any reference for a Sprague car being gutted before being remove from the system. That mean I had to make seats, and lots of them.

 

I did this once before in card, and I really didn't fancy doing it again, as it is fiddly, and awkward. Instead, I decided to have a play with the 3d printer which I have on loan from Baby Deltic of this parish. I drew up some simple seats with just enough detail to look good, while being solid enough to print on the DaVinci junior.

 

I had also printed out some HO scale newspapers, which were then liberally strewn around the floor, as well as cracking a couple of the windows.

 

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Finally, this evening, I thought I'd have a go a printing the underfloor details. I had a bit of a play around with different ideas, and ways to make it strong but not use up too much material, and this is how it came out.

 

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I'm pretty happy with this at the moment. There are some bits which I would do differently, but as a guinea pig for lots of different techniques, I'm pretty proud of it! If anyone is around Bedford and Kempston on the 4th November, come along to the show at Kempston East Methodist church and hopefully you'll see it running!

 

 


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#2 Joseph_Pestell

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Posted 23 August 2017 - 14:24

Lovely. Surely you have to make the rest of the set and build a new Parisian layout for it to run on.














Also tagged with one or more of these keywords: Paris, Metro, HO, Electro etching, 3d printing, vinyl sides