M&K Junction Railroad

M&K Junction Railroad
Another train of eastbound coal crosses the Cheat River

Wednesday, June 1, 2011

This 'n That

It been a while since my last post; 3 of the 4 weekends in May were taken up with activities away from home that kept model railroad progress to a minimum. That is not to say that I got nothing accomplished. Here are photos of a scratch built 62"/48" curved turnout that I started in May and, technically, finished in June. The paper template for the turnout is laid upon the back of a 2' x 4' ceiling tile. Why a ceiling tile? My last scratch turnout was laid down on a piece of plywood and each spike hole had to be pre-drilled - a real pain. The spikes (actually "Perfect" brand track nails) push into the ceiling tile easily and hold well enough to solder the turnout; when the turnout is finished the spikes can be removed and reused. The ceiling tile is, in turn, supported by plywood as it would bend and break otherwise.

Here's the frog laid down:

And a close-up of the frog:

Stock rails in place:

One Closure rail in place:

The Completed turnout:

Close-up of the frog-wing-guard rails:

This latter picture shows the frog before the excess solder was cleaned up by filing and sanding.

The Fast Tracks frog/point form and stock-aid tools were used to aid construction. I have to say that I enjoy hand laying turnouts; I just wish that I was more adept at it as it still takes me far too long. However getting a smooth running turnout that is an exact fit for the location is nice. For instance, the 62" outer radius exactly fits the curve where this turnout will be located and the turnout was made with the code 156 rail found in the old (1970's) Atlas flex track as the hidden trackage is the old Atlas flex.

Another May project: I did some mold making. A couple of months back, I saw some "Ultimate, Make-A-Mold Master Castings" rock castings by Ultimate Scenery Center (www.ultimatescenery.com) on a vendor's table at a train show. It was love at first sight with these castings; unfortunately, I had expended all of the money that I wanted to spend that day. I recently found some of these castings at Mainline Hobbies in Blue Ridge Summit, PA (BTW an excellent train store) and snapped up a couple.

These are highly detailed, urethane foam castings that the manufacturer actually intends to be used as masters for the purchaser to use to make his own molds. I like this concept, no longer do you have to be in a gray area of legality or morality by making a mold from someone else's casting.

I started with #123 "Pennsylvania Shale", a large (13" x 9 ") casting exhibiting both stratified and 'blocky' rock in the same casting. It is a good match for the rock formations found along the rights-of-way that I model. Here's a photo:

Here's a detail picture:

Click on either photo to get a full-size view.

I was going to use the technique that I used in my O Scale Trains article to make an open-face mold, but the manufacturer included detailed instructions for making a reinforced latex 'glove' type mold, so I decided to follow their instructions.

Here's a photo just before starting the process. I used the same 'Mold Builder' latex mold compound that I bought at Michael's and used for the OST article.

Mold Builder is not the manufacturer's recommended mold making compound, but I had it on hand. I don't know if the substitution effected the outcome. The surface that I am building this mold upon is a 18" x 18" ceramic floor tile obtained from Home Depot. I chose the smoothest 18" x 18" tile that I could find, although this was a floor tile and not a glazed wall tile like I build smaller molds on. To make the tile's matte surface smoother, I coated it with clear gloss spray from a spray can. A smooth surface will prevent the latex from adhering and facilitate removal of the finished mold.

And here's the first coat of latex applied.

The latex is brushed on. The first coat of latex must be applied thin and without bubbles - unless you want bubbles to be a permanent part of the mold and of each subsequent casting; so watch your brush strokes. I extended the latex beyond the sides of the master casting to form a lip on the finished mold about 3/8" wide.

Here's a pic of the mold after a couple of coats of latex have been applied and dried.

Ultimate Scenery instructs to apply four coats of latex before the next step. Being a 'belt and suspenders' type, I applied five.

Next you are instructed to apply a coat of latex and wait for it to get 'tacky' then layer the entire thing with gauze. The gauge is supposed to be forced into all of the cracks. Even though I cut my gauze into 3" long strips for ease of manipulation, this master casting has so many small cracks that I could not get the gauze down into all of them; it would lift out and/or bridge over the detail. Maybe the latex that I used was not tacky enough.

After the gauze is applied, you're supposed to add another coat of latex before - as I read the instructions - the latex/gauze coat has had time to dry. I did this and it lead to further lifting of the gauze from the master. Here's a picture of the mold after adding this overcoat of latex:

After the latex/gauze/latex coat as dried; four additional coats are to be added before the mold is done. Just to be sure, I added six.

Here's what the finished mold looks like ready to be peeled from the master casting:

And here's a video of removing the mold from the master casting:

Making the mold took a lot of latex, the lion's share of the jar was consumed in the 14 layers of latex that I applied.

So now it was off to make a casting from my new mold. I mixed up a batch of plaster in an empty Cool-Whip container and I thought that I might need two of these to fill the mold. Mixed the second batch and it was just about enough to cover the face of the mold, but not fill the body. I switched to a larger mixing bowl and two additional large batches later the mold was filled. Here's what it looked like:

The chocolate pudding color of the plaster came from a failed attempt to color the plaster with the craft store acrylics that you see peeking out in the upper right of the picture. Actual rock samples and photos taken from the area I'm interested in are a chocolate type brown, but darker than the color I got with the acrylics.

Filling the mold took a LOT of plaster - the majority of a 5 lb. container is in that casting. Next one I may only fill the face and not the entire mold. After 24 hours to let a casting of this size dry and solidify, I took it out of the mold. Here's what it looks like:

The casting is not bad, if you can look past the weird color (which will be fixed by spray paint). The details seems to reproduced well, however there are a few bubbles that will need to be fixed, probably the result of my pouring technique.

A final observation: If you look at the pictures of the mold, you will see that some gauze extended beyond the latex rubber. I cut most of this away, but did not seal the ends of the gauze with additional rubber. During casting the gauze absorbed water and wicked it into the mold between the layers of rubber. This made the mold slimy and it took on a milky color. Now two days after demolding the mold is beginning to dry out and return to it's normal state. It's possible that this is responsible for the chalky white deposits that you see in the close-up. I find it hard to believe that water between the layers of latex made the mold slimy, but it did. Next time I'll try sealing the gauze completely.

No comments:

Post a Comment