I selected this engine for the first project because it is a home built engine built by the Dura-Wood Treating Company in Alexandria, Louisiana, USA and is composed of all flat pieces except for the roof. The photo to the right was taken in 1992. There will be three, four, or maybe more different engines in this project series. Each will be based on the Aristo-Craft motor block with Sierra Valley 7/8" scale replacement wheels.

The goal is to provide 7/8" scale modelers with an opportunity to build their own engine with basic shop tools for around $100. The engine will be powered by batteries and controlled by a simple switch hidden in the exhaust stack, which will provide a single speed for forward and reverse with a center off position. This engine can be built from plastic, thin model builder's plywood, or brass, depending on the skill level of the builder. Of course, the builder can add detail parts and gold plating to push up the cost, but that will be an individual decision.

To get started, we are going to work form the above photo. First, the entire hood over the engine is between the wheels. This lets us guess that the engine is standard gauge, which will put the width of the hood at around four feet. If we compare the wheelbase in the photo to the width of the track behind the engine it appears that the wheelbase is longer than the width of the track. The distance between the front pilot and the front wheel appears to be greater than the distance between the rear wheel and the rear pilot. But, since we are building a 2-foot gauge engine, is it realistic to have a hood that fits between 2-foot wheels? Yes, there are plenty of small automotive 4 and 6 cylinder engines that can be fit into this small space. So, since we are doing a "freelance" model of a "homebuilt" we can sketch up the side frames, which will fit onto the Aristo-Craft (Part No-#29351) drive as shown below.

This is where we start to use our modeler's "license" to make changes from the prototype as we build the model. In the photo above, it is clear that the side frames end above the axles but I have made ours deeper so that they extend below the axles enough to hide the motor block. You will need to make two of these from the 0.040 stock, which is flimsy, but needs to be thin to fit in the space between the motor block and the wheels.

The nice thing about working with sheet plastic is you can cut it to shape easily by scoring along a straight edge with the back of your Exacto Knife and then snapping the pieces apart. However, it is always best to clamp your straight edge down so that it doesn't slip out of place. I mark the thickness on each sheet as I remove it from its wrapper so I don't get confused as to which piece is what. I am going to be pretty basic with this series, assuming that many of you reading it have never scratch-built and engine before. So here is how I score plastic.

I started by marking the lines onto the plastic with a sharp pencil. Then I clamp a square on top of the plastic on the edge of my worktable. Note that I have modified my Exacto Knife by gluing a wooden ball onto the end. This makes it easier to grip and to apply pressure. I use the back of the blade and draw the knife along the edge of the square three times to score the plastic.

First I scored along the two lines for the side frames 1 ¼" wide. Then I marked the 8 5/8" length and set the square along the edge of the plastic and scored both pieces to length at one time. This helps to make sure the pieces are the same size. Then I bent and snapped the two long pieces off and then snapped each one to the correct length.

Then I mark the locations for the 5/16" holes on one piece. I place blue masking tape (less sticky & leaves no residue) behind the other piece. I line the two pieces up together on the workbench against a stop and tape them together tightly so I can drill both of them together. I mark the hole size in pencil and then take the piece downstairs to my shop to drill on the big drill press. (I have been known to get distracted and drill the wrong size) You don't need a drill press, a regular hand drill will do. Once the holes are drilled, cut the slot with your Exacto Knife, or a razor saw, or heavy scissors, or rail nippers and the side frames are done.

I used Testors Cement for Plastic Models. The real stuff with the harmful vapors, not the "safe for kids" stuff! I think that it works better. I keep a roll of wax paper in my work area and tear off a new piece to put down whenever I am gluing. It helps to avoid gluing things to my worktable.

Note: All of the dimensions and sizes are approximate. This is not rocket science. Nobody is going to check your work with a caliper. Cut the pieces to fit. Since we are scoring and snapping these pieces, keep them on the large size. Keep a piece of medium grit sandpaper handy and if they are too big, sand a bit off until they fit properly.

Cut a strip of 0.080" plastic 1 3/8" wide and cut off to match the length of the side frames of 7 5/8" to form the top of the frame. Glue the side frames to the edges of this piece and allow it to set over night.

Set the frame onto the motor block and turn it upside down on a flat surface on your workbench. Cut another strip of 0.080 plastic "about" 1 3/16" wide that when set against the inside of the side frames, is the same height. Cut three pieces 1 3/8" long. Glue two of them in the ends of the frame. Glue the third inside the frame against the back of the motor block. Cut two more pieces from the same strip 1 ¼" long and glue them against the inside of the side frames, as shown on the right below. Cut one last piece about 1 3/16" long and glue between the side frames leaving about 1/8" clearance from the shaft sticking out of the front end of the motor block. (I designated the end of the motor block that swivels as the front) Cut another strip of 0.080 plastic 1 ¼" wide and then cut two pieces from it 2 ½" long. Glue these pieces to the outside ends of the frame. Set the whole thing aside to dry (Testers says 2 hours)

Now remove the motor block from your frame and carefully take it apart. Use the proper size Phillips head screwdriver. The screws are in tight and the heads strip easily. There are 4 screws on the top and two on the bottom. Set the motor block next to the frame and remove the top. Put the top of the block into the frame and mark the four screw holes and the two rectangular openings with a pencil. Drill out the screw holes and then drill about 5/16" for the wires to come out and for the six air holes that will provide air circulation for the motor. Carefully put the top back onto the motor block and screw in the two bottom screws. Put the motor block into the frame and carefully screw in the four top screws and the frame is done.

In Part II, we will build the body and start with the details.