MODELING: SMMW AAR 70-Ton Flat Car Kit

Quarter-inch scale modelers now can purchase a very nice kit from Smoky Mountain Model Works. They released a AAR 70-ton flat car kit. The prototype cars were 53’6″ long with an extended width deck. The kit is composed crisp resin castings, wire, weight and detail parts made out of resin and plastic. The prototype design was first offered near the end of WWII. It was purchased by major railroads like the New York Central, Baltimore and Ohio, Nickel Plate Road, Pere Marquette, Santa Fe, New Haven and others. The cars were equipped 5’8″ wheelbase 70-ton trucks. They also had a drop style handbrake that would not interfere with long loads.

I decided to build the car shown above. The Pere Marquette bought two lots of these cars. The road used two different hand brake systems Ureco (16500-16749) and Universal (16750-16849). I liked the group with the Ureco hand brake system. An interesting feature is that there was an additional lever that connected the brake cylinder to the hand brake.

The kit goes pretty fast with the exception of the stake pockets. All of the pockets are cast on a sheet of urethane. The pockets were designed using a 3D CAD program and were increased in height to allow for cutting the individual pockets from the substrate. I used a Zona razor saw. The pocket “ears” do need to be trimmed slightly to fit in the location. The alignment process is made easy with pins cast on the backside. I found that when properly trimmed the pocket will snap into place. Make sure you use a slow setting CA so fine tuning the position can be done.

The picture shows the stake pockets in position. The AB brake system was upgraded to San Juan Car Company parts. You can see the added brake lever I added in front of the cylinder. I decided to cast a new weight for the center sill. The kit comes with a steel bar for a weight. I decided to use Cerro Bend bismuth alloy to make the new weight. The metal melts at 158 degrees so it is easy to work with. I made the mold out of heavy card stock and some wood. I used a new CA (to me) to hold the weight in the center sill. The new CA is IC-2000 made by Bob Smith Industries.  It appears to have a rubber compound added to the CA.  It is popular for adding engineering plastic to models.

The new weight has added three ounces to the car. When I installed a pair of Protocraft 70-ton trucks the weight added up to 14 ounces. That should operate pretty well.

The car body is is essentially a single casting with some added details such as the crossbearer caps.

The deck is composed of four castings that have details like the steel plates for the bolster and centersill above the draft gear. I didn’t mount the deck to the body quite yet. After cleaning the castings up, I primed the them with Tamyia gray primer.

I decided to try a different weathering approach. After the primer set for several days, I used a wash of Vallejo black on the deck. After that dried I used a little Mean Green to remove some of the black. I used MIG Ammo Oil Brushers to add brown and gray tones to individual boards. It is a work in process so the jury is out on the effect. The steel deck parts really stand out with the black paint applied. They will be treated with rust pigments and other touches.


That is all for now. The next installment will address the hand brake construction, painting and weathering.



5 thoughts on “MODELING: SMMW AAR 70-Ton Flat Car Kit

  1. gene:
    did you run the piping through the center sill
    or just dead them?, i’ve just started on a “s”
    scale version, and the dead ending seemed
    awful fragile?

    • Mel
      I ran the pipes between the reservoir and control valve through the center sill and terminated them inside. So , no they don’t go through the center sill. The trainline was not run through the side of the center sill. I cut the wire at so it would be flush against the side.

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