DIY Photo-Etch Help?

[cbroughton67]

Does anyone photo-etch their own parts at home? Is the kit offered by Micro-Mark worthwhile?


Here's why I ask - I have an Oriental Limited N-scale PRR S1 6-4-4-6 with a broken part. I believe it's called the "gear connecting rod," and can be seen in the photo below. Since spare parts for these locomotives are non-existent, I'll have to come up with a stand-in component from another locomotive, or fabricate my own. Photo-etching a new part seems like the best solution, but it's something I've never done before.


So, any advice? Better yet, would anyone be willing to etch this tiny part for me for a reasonable fee?


TIA,
Chris


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[ChristianJDavis1]

Does anyone photo-etch their own parts at home? Is the kit offered by Micro-Mark worthwhile?


Here's why I ask - I have an Oriental Limited N-scale PRR S1 6-4-4-6 with a broken part. I believe it's called the "gear connecting rod," and can be seen in the photo below. Since spare parts for these locomotives are non-existent, I'll have to come up with a stand-in component from another locomotive, or fabricate my own. Photo-etching a new part seems like the best solution, but it's something I've never done before.


So, any advice? Better yet, would anyone be willing to etch this tiny part for me for a reasonable fee?


TIA,
Chris


(Attachment Link)

While I can't help with etching, I would like to warn you to be careful when trying to remove it or repair it, because the valve gear on those engines is decidedly fragile; riddled with cold solder joints. I've fixed mine twice now, and the guy I bought it from has fixed his before as well; all different problems, but all related to the rods and valve-gear. I wish you luck in your quest for parts, because now I'm questioning what mine looks like now or in the near future.

[Chris333]

If you can do some sort of drawing with measurements I can give it a try.

[peteski]

I have been doing DIY etching for decades. I started with etching my own electronic circuit boards (PC Boards), but I have etched some brass and nickel silver parts too (even double-etched which was a pain).  I don't use any kits - just roll my own.

The part in question (I believe it is called "expansion link") looks to be nickel silver.  But it is also rather thick and double-etched.  It is probably around 0.015" thick. All my home etched parts were either 0.005" or 0.010" sheets. The thicker the metal, the more difficult it becomes to etch at home.  Best would be to get it done professionally (or try to find a spare part for that loco).

Looks like Chris might be able to help. IIRC, he has his etchings done professionally (after supplying them with artwork).  That, IMO would be the best route to take.

[Chris333]

I used to do it myself and yes mostly .005" brass, but I still have all the stuff.

[mmagliaro]

Unless you are a die-hard purist... you could solder the broken one back together and then add a small bit of brass or nickel strip across the break to reenforce it.  It won't show much if the splice is behind the piece.

The hardest part will be getting the old one out.   Both pivots (the one in the center of the broken part and the one that goes to the rod) are probably a pin that is flared out to keep the part on.  It might take some crafty filing and prying to get the part off without breaking anything else. 

But once you get it out, soldering it back together isn't as bad as it looks.  Just tape it all down to a flat wood block so it won't move around.  After that, a dot of flux and a hit from the soldering iron should fix it.   This part just rocks on a pin for show.  It doesn't experience any real pushing forces.  I'm rather surprised it broke in the first place.

[woodone]

I am betting that this part is held to the loco with a small plastic pin that is part of the pivot bracket in front of this broken link? If you can release the part from the pin the next problem will be how to free up the link at the rivet points.
If you can get the parts off with the link.
Then you could solder the part back together. I would use silver bearing solder for this has it is a bit stronger.

[mmagliaro]

I am betting that this part is held to the loco with a small plastic pin that is part of the pivot bracket in front of this broken link? If you can release the part from the pin the next problem will be how to free up the link at the rivet points.
If you can get the parts off with the link.
Then you could solder the part back together. I would use silver bearing solder for this has it is a bit stronger.

A plastic pin?  On a brass loco?  Really?  I have never seen anything but metal parts holding all the links and pivots on brass steam.  I would bet that pivot bracket is brass or nickel silver with a metal pin in the back of it for the expansion link to pivot on. 

I had an S1 for a while, and fixed one for somebody, but none of my photos show this part enough to tell, unfortunately.

Now that you mention this... Assuming it's a metal pin, it should be easy to drill through from the front of that support bracket, drilling the pin right out the back as you go through, to release the expansion link.  Then, a new piece of brass wire could be pushed in when it comes time to put it all back together.  A drop of epoxy and some black paint will cover up the hole in front and make a neat repair.

[Chris333]

Since either way the part has to come out, I'd do that first. If you can't fix the part put it in a scanner and send me the pic.

[cbroughton67]

Since either way the part has to come out, I'd do that first. If you can't fix the part put it in a scanner and send me the pic.

Thanks, Chris. I already have the part out. The eccentric crank had come loose, which I believe is how the part broke - it allowed it to get pinched between the drive rod and the boiler. I'll try soldering it back together. If that fails, I'll send a scan to you. I really appreciate the help!
Chris

[randgust]

If you have Chris' offer to help, take it.    Max is right too on ways to repair the existing part.

I had a damaged crosshead guide on my Jamco 4-6-2 and made a new one out of K&S brass, but it was a white-knuckle adventure.   Lucky it worked.

Now in general terms, I consider home photo-etching one of the more difficult things I've ever done.  I had the Micro-Mark set, it actually worked, but was an extremely difficult and 'dirty' process with ferric chloride.   The aquarium bubbler system they supply to stir the etchant is borderline useless, and the etchant tends to embrittle and destroy everything over time including plastics.  I made an etchant stirrer out of plastic K'nex and Lego parts that worked quite well (Lego propeller on a Knex driveshaft)  I got to where I could make parts, but I wanted lots of a few parts, and the time to make a 2x3 inch max sheet wasn't 'production level' technology. 

Chris taught me how to do it and led me through it, he really knows his stuff.   But in the end I gave it up and hired out my parts to a contractor.  When you find yourself working under darkroom conditions, in toxic chemicals, with protective clothing, goggles, ventilation running, it starts looking like 'Breaking Bad' without the lucrative economic payoff at the end.

I certainly can't recommend launching into home photoetching on this one repair issue; it's like swatting flies with a very expensive brick.

[Iain]

The part in question (I believe it is called "expansion link")

As an aside, the precise term depends on which valve gear you are using.  If it's Walschaerts of Baker, it is expansion link, for Stephenson, Stephenson Link.


Also, something to note, but, your eccentric crank should be closer to 100 degrees rather than 90 degrees. 

[CRL]

There’s always the option of using a jewelers saw and files.

[metalworkertom]

There’s always the option of using a jewelers saw and files.

As thick as it is stated above this is exactly how I would do it.

[mmagliaro]

There’s always the option of using a jewelers saw and files.

I was going to suggest this too, but I figured it would scare people off.  I made one of these expansion links for some valve gear once.

It's really not as bad as it seems.  Just start with some .010" thick brass strip, eyeball it into its approximate "boomerang" shape with some files, and then drill a bunch of little holes in it with a #80 or #79 drill, and use a #11 Xacto knife to pick away at the holes until you open up a nice slot in the middle of the part.  Files are way too thick to make that slot.  But a #11 blade will do the trick.

CORRECTION: You probably want to do all the drilling and picking BEFORE you cut the part out of the brass strip and start shaping it.  Much easier to work on it that way.

The circled part on the right in the photo below shows the part before I finished the slot.

Be not afraid! 
You can probably make one of these parts in a couple of hours or less, and then it will be one solid piece with no joints or soldering.