Building CP Rail NSC 3-Unit 48ft Well cars

[CP9302]

Its been a long time since I posted anything, but I thought it was about time to share some of what I've been working on again, so here goes. Hope you all enjoy.

As a modeller of Canadian Pacific in the 1990's and a lover of intermodal trains, I was confronted with a lack of accurate well cars to build my trains. While CP was an early adopter of Intermodal freight, they were slow to adopt the 'double-stack' car that is now common place. CP relied mainly of flat cars to carry their container traffic. In 1986 they took delivery of their first double-stack well car, a 3 unit, draw bar connected set numbered 524000/524001/524002 (yes, each car was individually numbered) It wasn't until 1993 that they would take delivery of their first group of cars from National Steel Car (NSC), and they were on lease! This experiment went well and CP ordered their own cars in 1995, again from NSC. This thread will follow my attempt at modeling these two batches of cars. The 1993 group will be referred to as the 'Early car' and the 1995 group as the 'Late car'. Both groups are very similar in design and construction. The Early car has angled sides around the trucks while the Late car has the rounded edge common to today's NSC cars. The Late car is also characterized by inspection 'port holes' in the car sides.

This is a photo of one of my first completed Late style cars. Note the curved side near the wheel and the round 'port hole' inspection openings in the side.

For additional information on building these cars and scale drawings, please see the November 2001 issue of Model Railroader. My efforts here are based heavily on the article by Jonny Barnstorf and the scale plans by Jonny and Rick Johnson.

Since no model of either of the cars is currently on the market, I was left with no choice but to build my own. Since the cars operate in 3 unit draw bar connected sets, to build one car I had to build three. And one set would just not be enough. I decided to make a mold and cast the cars in resin. Since I've only done one sided molds, I broke the car down into pieces that I could cast in flat, one sided molds and glue together after to complete the car. In the end I broke the car down into 7 pieces, 2 sides, two bolster/walkway ends, two well ends and the well bottom. I built masters of these parts using styrene and the plans referenced above. Take your time building masters, any errors, goofs or close enoughs will be faithfully reproduced in every part you cast.

To create the molds, I glued the masters to a sheet a styrene and built a wall around the masters using styrene strips. Make sure the walls are taller than your master so the mold compound can cover it completely. Also make sure and the joints are sealed, on the walls and your master part. I then mixed the mold compound as per the instructions and poured it into the mold. You can start by pouring a small amount into the mold and use a brush to paint it over the fine details. Use a pin or toothpick to release any trapped air bubbles. Pour in the rest of the mold compound until the mold is full. It is best to pour in the open areas of the mold, not directly onto the master, and allow the compound to flow over and around the master. This will help reduce the number of trapped air bubbles. Leave the mold to set on a flat level surface. If you have a vibration table, it would be good to let the mold set on their to help shake out any air bubbles. I let mine set on the dryer while running to shake the air bubbles out

This is the master for the sides and well end plates of the Early car. The pink in the lower right is some overflow from the mold compound.

Once the compound has set, you can peel the mold off the master and you're ready to start casting parts!

I used Mold Max 20 from Sculpture Supply Canada to make the molds for this project. I found it very easy to work with. It produces very durable molds and de-gases well. The molds have a very high tear strength, so they are good for many castings. It has a 10 to 1 mixture ratio, so some measuring and math is needed
http://www.sculpturesupply.com/list.php?sf=subcategory&vl=Mold+Max+20&cat=Rubber+Silicones

I've also used Micro Mark mold compound in the past. It is also easy to work with. The 1 to 1 mix ratio is easy, but the molds are not as durable and tend to tear/split easier.
http://www.micromark.com/one-to-one-and-rapid-mold-rubber-32-fl-oz,7883.html

Next up, casting parts...

 

[CP9302]

Part two: Casting

Now that the molds are done, we can start casting parts. I cast a full set of three cars as a test to see how well they would work as actual operating models. Luckily, my basic design worked well, but the resin cars were very light and could not be operated empty. A container with weight was needed to bring the cars up to operating standards. I'm a big fan of using steel shot to add weight to cars, as it can be poured into the smallest, oddest places, but these cars have nowhere to add any weight. I could try casting the cars in metal, but that would involve making a new mold that could withstand the high temperatures involved. And the thought of melting and pouring metal just did not appeal to me. I decided to try adding the steel shot into the liquid resin.

In the photo below we have the molds for the Early car. The top mold is the sides, as shown in the first part of this thread. Below is the well bottom, the black is the steel shot that I poured into the mold before pouring the resin. To the right of that is the bolster/walkway mold. I use the last two molds for both the Early and Late cars. Note the styrene rectangular tube in the bolster/walkway mold. The first castings I did, I poured the steel shot into the entire mold, this turned out to be a very bad idea, as I destroyed my drill bit trying to make screw holes into the steel shot to mount the trucks. The styrene tube keeps the steel shot out of the area I will need to drill later. Also note I have not poured the steel shot into the bolster mold yet, I found the shot was too thick and the resin didn't penetrate well enough so the casting didn't turn out. I pour the shot into the mold after pouring the resin.

Early car molds ready to pour resin.

I use Smoothcast 305 resin. It has a 1 to 1 mixture ratio and 15 minutes of working time with a 45 minute cure time. 15 minutes is just enough time to mix, pour, add steel shot and remove some bubbles. The resin is clear and pours like water. It drys to a solid white finish. This resin is a little particular about the mix ratio, so I use syringes for liquid medicine to accurately measure the two components for mixing. When adding the components together, pour down the side of the container to reduce the amount of air you trap in the mixture. When mixing the two components, stir thoroughly, but not vigorously, to help reduce the amount of trapped air.
http://www.sculpturesupply.com/list.php?sf=subcategory&vl=Smooth+Cast+305&cat=Liquid+Plastics

I pour the well bottom first while the resin is freshest and will seep into the steel shot the best. I pour the sides and bolster sections next. Try to pour in one place and let the resin flow out and over the mold, this will help reduce the amount of trapped air bubbles. As you move over the mold, keep pouring into an area that already has resin in it and let it flow out from there. Try not to over fill the molds, any excess will be flash you need to trim later. Once the resin is poured, I carefully pour the steel shot into the bolsters. Don't over fill them with shot as it is very difficult to sand flat later! I use wood skewers to tamp the shot flat and scrape excess resin off the mold. Ideally, the molds should be filled to the top, but not over. I go over the molds try to pop any bubbles using a toothpick. Experience with the mold will help point out where the bubbles like to form, but check the small details first and any undercuts in the mold. I check for bubbles continuously until the resin starts to thicken, like liquid honey, then it is time to stop and let the resin cure.

Here we find the resin poured and starting to cure. I've poured in the steel shot and popped all the bubbles I could, now it's time to wait.

Once cured, this resin turns white. These parts are ready to be de-molded.

Note that I place my molds on a pane of glass. I do this to have a flat surface to work on, but also because it is easier to clean excess resin off of. The resin flows and seeps just like water, so putting down news paper under the mold could result in gluing the paper to your work bench with resin. Cardboard underneath may prevent the resin seeping through, but you'll need to replace the cardboard often if you're sloppy like me But using the glass pane, you can scrape the excess resin off with a knife and keep on going.

And here we have the parts out of the mold. All that white joining the parts together is bad That is all flash that needs to be trimmed before assembly.

A note about resin: When resin cures it produces heat. The more resin, the more heat. So if you mixed too much resin and left some in the cup while poking out the air bubbles in your mold, the cup may be very warm now. I mix my resin in plastic cups and have the measurements pretty accurate of these cars now, so I don't waste much resin, but remember, while curing, it can get hot, so don't touch it!

Next up, Assembly

 

[CP9302]

Part 3: Assembly

The first step after demolding the parts is to trim the flash and repair/fill any details damaged by air bubbles. If the casting has heavy flash, a useful trick to make cleaning the flash easier is to sand the back side against a flat surface. This will thin the casting to its proper thickness and thin the joint between the good part and the flash to make trimming easier. This is also a good time to fill any holes caused by air bubbles with putty.

This photo shows all the main castings and both side variations. Late above with Early below.

I use CA (super glue) to assemble the parts. I built a couple fixtures to make assembly faster, easier and more accurate. The following photo show the two fixtures I use for the main assembly. The fixture at the bottom sits flush against the well bottom and aligns the sides on the bottom. I use a thick gel type CA applied to the edge of the well bottom and then use the fixture to position the sides. I assemble the cars on a pane of glass because the CA does not adhere well to the glass in case of excess glue seeping out. Its no fun to glue your project to the work bench!
The fixture above is used to position the bolster pieces in the car. It holds the bolsters level and at the correct height. This fixture required some careful measurements, but makes assembly a much simpler. I use a gap filling CA for gluing the bolsters in to help hide the seem between the bolsters and sides.

Assembly fixtures. Also note the green putty filled areas.

The final piece of the basic assembly is the well end plates. These fit into notches on the bolster and well bottom. A little trimming and sanding is required to get a nice snug fit. The same gap filling CA is used to attach these parts.

This Early style car is now ready for detailing.

Next up, adding the details

 

[CP9302]

Step 4: Adding the details

Its the smaller details that really make a model come alive. (that and some weathering for character )

The first step is to drill holes for the grab irons on the ends of the cars and for the stirrup steps on each side. I started each of the end grab iron holes on the master, so each cast part has marks for each of these holes. I didn't know the spacing of the stirrups when I made the mold, so I build a jig to aid in locating where to drill these holes.

Jig for drilling stirrup holes.

I use strips of styrene to build up the walkway platform mounts. The mounts are glued to the car using CA but I don't attach the walkways yet, as they are not painted with the car. All the brake components are glued on now as well as other small details appropriate to the car. Photo etched IBC boxes and lift tabs from Plano give a fine scale appearance to the car.

Each end of the car has stanchions made from angle iron shaped ABS plastic from Plastruct. I find the dark grey ABS plastic to be sturdier than the white styrene parts and hold up better to the occasional bump associated with transport and operations. I drilled holes in the stanchions and bent grab irons and railings to fit. I built another jig to aid in the drilling of holes in the stanchions. Everything is glued together with CA.

The Stanchion drilling jig. The dark grey 'L' shaped pieces are the already cut to length stanchions. The black lines scribed in the jig are where the holes need to be drilled. The jig is elevated by strips of styrene on the back, so the drill bit can pass through and not into the work surface.

Here is an Early style car completely detailed and ready for painting.

The next step will be painting and decals.

 

[CP9302]

First up, here is a side by side comparison shot of the early (bottom) and late (top) style cars completely detailed and ready for painting. The photo etched walkways are not on yet, as they don't need to be painted.

I wash the cars in warm water with dish soap to remove any grease and oil residue from handling during construction and let the cars air dry. Once dry I airbrushed the cars with Testors acrylic grey primer.

After the primer was dry, I airbrushed the cars with TrueLine Trains CP Action Red acrylic paint. After the red was dry, I airbrushed the cars with Future Floor polish to give them a nice gloss finish for decaling.

I decaled the cars using a production line approach. I put all three cars together and did the same decal on each car before moving on to the next one. This seemed to speed up the process. Once decaling was completed, I glued on all the photo etched walkways and put the couplers, draw bars and trucks on. These cars are brand new for my modeling era, so the weather will be minimal when I get around to it.

Here is the B-Unit of CP 524176 on one of the bridges on the WMRC layout.

The whole 3-unit set of CP 524176.

Another shot of the B-Unit of CP 524176 showing the photo etched walkways more.

I hope you enjoyed seeing this project completed as much as I do. Now to build a few more to fill out my fleet.

 

[Cjcrescent]

Fred,

OUTSTANDING! WOW! This was a very fine how to, one of the best I've seen in ages! At the 1987 Eugene National, Al Westerfield, bought the molds and masters of a similar set. The modeler who had the cars there, almost took the Gold Award for the top model there. He missed by 2 points, but did take the top in cars. I bet that if you entered the cars in the NMRA contests, you'd do just as well.