I giving the caboose projects a rest for a week or so. I am trying a diversion in starting a new build on a boxcar project. The subject of the build is a rather unique car design. It is a fifty-foot double sheathed wood automobile car. It has an inverse Dreadnaught end and a Murphy radial roof.
The Denver & Rio Grande Western purchased 500 of these cars in two different lots. The first lot of 200 was built in 1920. They were door and a half with reverse Murphy ends. The second lot was built in 1927 with double doors and inverse Dreadnaught.
The earlier lot was offered as kit by Rails Unlimited. It has been out of production for some time. Protocraft recently produced a fine decal set for these kits. I intend to adapt the set to the my project.
I decided to start with the Murphy radial roof. Construction is similar to the method used on the two caboose builds ongoing. The basic technique is to laminate thin sheets of styrene to create a solid sheet not unlike plywood. The bonding agent is CA for the most of the surface area. However, you do start with liquid styrene adhesive around the edges of the sheets. I attach the first sheet to double-sided Scotch Tape applied to the fixture. The idea is to keep the outer edges firmly attached to the jig. The liquid cement is applied to the long edge of one side as you mount the second and subsequent sheets. Carefully apply a little CA in the center of the two sheets and press down firmly. Use your fingers to work the CA around under the second sheet. If it runs out, quickly blot up the excess with a paper towel.
The roof was made from 4 sheets of .010″ laminated over the wood form. The last sheet was not applied to the roof form right away.
The next step is to trim the length and width to the correct size. The last sheet should be measured to fit with minimal overhang. This sheet will be used to lay out the location of the ribs on the Murphy roof. Once that is done, you can add it to the previous lamination.
The roof lamination is attached to a sheet of .040″ styrene with a center post to support the arch. The sheet needs a .040″ overhang on either side.
If you study the Murphy ribs, you can see the bottom layer is about .188″ wide with the next layer being about .135″ and the last being a rib of .080″ wide. I used .005″ sheet styrene to create the .188″ strip of the first layer. Cutting thin material like this has been a challenge for me. I try to do accurate cuts over a four or five inch edge but invariably it ends up with different widths at either end.
I thought about building a simple cutting fixture to facilitate the job. The 6″ steel rule is only .015″ thick. I spaced the ruler out from the backstop with a strip of .188″ styrene. I added small pads of .005″ under the ends of the ruler to keep if level across the cutting surface. You just slide the sheet .005″ in and run a sharp single-edge blade across using the ruler as the guide.
The strips are applied to the roof surface. The second layer is .010″ x .138″ stripe (HO 1″ x 12″).
I will finish up the roof in the next posting…….