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RS-3 narrow gauge conversion

Started by Ray Dunakin, October 01, 2010, 11:43:05 PM

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Ray Dunakin

#15
I finished making a master for the brake cylinders. Here it is with a coat of primer; just needs to be touched up on a couple places. I need eight cylinders, and I really don't want to make them all by hand, so I'll make a silicone mold from this one and cast duplicates.




The grill over the radiator fan isn't totally accurate but it looks pretty good, so I want to keep it. Unfortunately the holes are much narrower on the back then on the outside, in fact they're barely open. So I'm carving them out, one by one, with the tip of an X-acto knife. Very tedious, so I can only stand to do a little of it at a time. I'm halfway finished so far:



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lab-dad

A jewelers reamer might make quicker work of that!
I have a set and find them indispensable!
-Marty

Ray Dunakin

I used the knife blade instead of a drill bit because I wanted to have a tapered hole, wider on the underside, to improve the "see-through" quality without altering the square grid effect too much. At least, that's my theory.

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Malachi Constant

Ray --

Um ... what Marty said ... get a set of jeweler's reamers, you'll be glad to have them on hand.

And, well, sorry to say ... they ARE tapered ... but maybe not quite as much as you want, so we'll let you slide this time!  ;D

Cheers,
Dallas
-- Dallas Mallerich  (Just a freakin' newbie who stumbled into the place)
Email me on the "Contact Us" page at www.BoulderValleyModels.com

Ray Dunakin

Visit my website to see pics of the rugged and rocky In-ko-pah Railroad!

Ray Dunakin's World

Ray Dunakin

Today I made a mold of the brake cylinder master. Because of the complexity of the shape, a two-part mold was needed. I built a form out of styrene, and filled half of it with sulfur-free modeling clay. Then I pushed the master into the clay, and worked the clay in around it to make as clean an edge as possible. I pressed a few dimples into the clay to make "keys" that will keep the two halves aligned:



Next I poured in some silicone rubber mold compound. I use Smooth-On brand "Oomoo 30" because it's easy to use and doesn't require a precision scale. It mixes by volume, not weight, and is pretty/ forgiving. When this set, I pulled off the bottom of the form and removed the clay. Leaving the master in place, I then coated the face of the first layer of silicone with a very thin coat of vaseline as a release agent. I also used a spray on release from Michael's:




I poured in some more silicone, let it set, then removed the form and pulled the two halves apart. Then I started casting. The initial casting came out rough, which is typical. The rest came out better. I had also made a simple one-piece mold of another part that will be used on the side frames, and cast that too. Here's how they look after cleaning up the flash:




And here's one of the brake cylinder castings after being painted with a coat of primer. It's a little bit rough but not bad:





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Ray Dunakin

A little more progress...

I finished casting all the brake cylinders and install four of them on the rear truck. 

The brake shoes on the original model are removable plastic pieces, and include a curved shape that is supposed to represent the sand line. As-is, these brakes look pretty anemic. So I reworked them, adding on new styrene bits to make the brake shoes a little larger and thicker, and also made the hardware stouter and more accurately shaped. (In silhouette, anyway. As on the original model, a lot of liberties have to be taken in this area.)

I cut off the original sand lines and built new ones that are much more realistic looking. Here's a shot of two remodeled brake shoe assemblies next to one of the unmodified parts:




Here's a couple shots of the modified parts temporarily installed on the truck. You can also see how the brake cylinder castings fit into place:






I still have to make four more brake shoes pieces, for the loco's front truck.

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Ray Dunakin

Doh!

Rather than making the four remaining brake shoe assemblies individually, I wanted to try molding and casting them.

I spent a considerable amount of time figuring out a way to make a two-piece mold of the brake shoe assemblies. This was not an easy task, because they are a fairly complex shape. Got the first half of the mold cast. Added some stuff to form the fill channels, then poured the second half of the mold. All of this was done piecemeal, between numerous interruptions, which also meant a lot of it was done in a rush. (You can probably guess where this is heading...)

Pulled the mold out of the form this evening and discovered the Big Mistake. I had forgotten to apply any kind of mold release between the two halves of the mold. So now I have one big block of (expensive) silicone rubber with two master brake assemblies buried somewhere in the middle. 

< sigh >
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Malachi Constant

Oh man, that really sucks!  I'll make some suggestions ... pretty much the obvious stuff here ...

-- First, if your frustration/aggravation level is high, let it sit for another day so you don't destroy your patterns trying to get them out ...
-- Try different lighting, magnifiers, etc. and see if you can find any evidence of the two different mold pours.  If the RTV was mixed by hand and you didn't use a super-precise scale, there may be some subtle difference in coloring on the two pours.  If that happens, then with the right lighting, you may be able to cut along that line.
-- If the shape of your mold is irregular ... eg, a rectangular block, you might be able to "imagine" where the parts are inside and their basic orientation.  If it's a perfect cube with the bits right in the middle ... well ...
-- RTV will close itself somewhat after being poked with pins ... so you might want to use some fine needles to see if you can locate the parts.  Then start cutting in very gently with a very sharp blade (for a clean cut) ... proceed gently until you just tap the pattern.  Then start lifting the opening a little to see what you might determine visually and work around the pattern, etc.
-- At the very least, you should be able to remove the pattern in reasonably good condition ... with a little luck, you may actually be able to separate the mold halves into useful pieces.
-- Re-read the first suggestion.

Good luck!
Dallas
-- Dallas Mallerich  (Just a freakin' newbie who stumbled into the place)
Email me on the "Contact Us" page at www.BoulderValleyModels.com

Ray Dunakin

I got the parts out of the rubber but could not salvage the mold. The shapes were just too irregular. I'm currently in the midst of a second attempt at molding the parts.
Visit my website to see pics of the rugged and rocky In-ko-pah Railroad!

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Ray Dunakin


Finally have another update on this project...
 
First, here's how I made the mold for the brake shoe assemblies:
 


 
I was concerned about the sand lines, which seem to be in a position where they are likely to get banged up a bit in use. So I inserted brass rods into the mold prior to casting:
 


 
Here's a shot of the masters (top) and the castings (bottom). As you can see the castings are slightly thicker and rougher, but should be acceptable:
 


 
I made the brake rods from brass:
 



I used short sections of rectangular brass tube to make the clevis on the brake rods. First I grind off one side of the tube, then cut off the short sections using a Dremel and cutoff wheel:
 


 
I also made castings for the brake lever and the sideframe extension that goes above it. Here's how the sideframes look with the brake cylinder, brake rod, lever and extension in place:
 


 


 
 
That's all for now, more later.
 
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Malachi Constant

Ray --

Glad you were able to rescue those patterns and go on despite the intermediate headache(s) ... all those nice little bits will add a ton of dimension and interest to the model, which seems to shaping up rather nicely!  ;)

Cheers,
Dallas
-- Dallas Mallerich  (Just a freakin' newbie who stumbled into the place)
Email me on the "Contact Us" page at www.BoulderValleyModels.com

Ray Dunakin

I've finished the trucks on the RS-3. First,  here's a "before" photo showing one of the stock trucks for comparison:



And now here is the finished truck:




And a couple detail close ups:






This truck has the cast brake shoe assemblies:




Prior to painting, I masked off the openings to the motor and gears. Then I used a q-tip to smear vaseline onto the tread and flange of the wheels. I applied a coat of gray primer, then a coat of Rustoleum gloss black.

To weather it, I began by mixing some Model Master "Gun Metal" and "Steel" paint together, and dry-brushed it onto the areas that seemed likely to become scraped or scratched. All the rest of the weathering was done using Apple Barrel flat craft acrylics. Next I added some rusty colors. Some of this rusty color was applied directly over the "metallic" colors, then rubbed partly off. When this had dried, I went over the whole thing with a wash of dusty gray-tan mix. When that dried, I added a mix of "apricot" yellow and black to a few areas, to represent grease. The final coat was a very thin wash of blue-black over the whole thing.

Once the final wash was dry, rubbed my fingers over various parts of the trucks, removing some of the thin layers of acrylic and letting some of the black undercoat show through. Then I sprayed a light dusting of Krylon UV matte finish over the whole thing.

The weathering is a bit understated, meant to look well-used but not overly grimy. It looks a little better in person than in the photos. I'm not sure if it's enough though, but I can always add more weathering to it later if necessary.

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finescalerr

The whole is greater than the sum of its parts. -- Russ

Ray Dunakin

This is one of those projects where one thing leads to another...

Having made the deck wider, I decided that the fuel tank needed to be wider as well, so I built a completely new fuel tank. This actually works out well though because I now have room to fit the speaker in the tank, eliminating the risk of moisture damage posed by the factory speaker location. And of course I also got to detail it out nicely too.

Here's the original fuel tank:



And here's the new one:

 


The areas that have been patched with putty look pretty ugly now but it'll look much nicer when it's painted:




In this photo you can see where I'll be mounting the speaker. I still need to drill a bunch of little holes to form a speaker grill:

 

 
The original air tanks weren't worth reusing, so I'm replacing them too. The new tanks will be wider and more detailed. Here a shot of the new tank next to the old one:

 

A closer view of the new tank (I still need to build the second air tank for the other side):

 

Here's how the fuel and air tank will fit together. I still have to add the plumbing, too:

 


I already had some domes, but I didn't have any styrene tubes in the correct size for the air tanks. So rather than order them online and have to wait to have them delivered, I found a pair of plastic knitting needles at Michael's that were exactly the right size!


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Visit my website to see pics of the rugged and rocky In-ko-pah Railroad!

Ray Dunakin's World