Scratch Building a Gas Mechanical Critter Part 2

In the first installment of this series, I discussed how I built the brass underframe for my "critter" to serve as a base for the engine frame and the decking.  The cab, motor housing and other details will be constructed from styrene and will rest on the deck.

With the brass underframe complete, my next task was to build up the side frames and end beams from styrene sheet, channel, angle and other styrene strips.   The parts were cut to fit around the underframe and test fit before gluing the assembly together with Plastruct cement.

Clearly the frame needed more detail to resemble the prototype model I found on the internet.  A quick glance at the photo I was using for inspiration reveals some interesting journal boxes, an access door of some kind, coupler pockets and ladders.

For journal boxes, I chose Grandt Line C&S caboose boxes and lids.  They were as close as I could come to the ones in the photo.  After allowing for the height and location of the Stanton Drive wheels, I cemented the journal boxes in place.  Almost immediately, the frame began to look more interesting.

For the end beam, I cut holes for the couplers in the styrene, and used tin snips to cut out the brass underframe where the couplers would go. The coupler pockets and the front and rear pilot steps were constructed from Evergreen angle stock in various sizes.  I used Evergreen V Groove .100" sheet for the decking, and painted it with Rust-Oleum weathered wood brown to see how it would look.

To my delight, it was beginning to look like a locomotive frame!  To get an idea how the finished locomotive might look, I cut up an old industrial diesel shell I from my junk box, and placed it on the deck.  The proportions were about what I was looking for.

The photo I was working from had an access hatch on the side frame between the journal boxes.  I cut a rectangle of styrene to fit, then added NBW castings and thin strips of styrene to suggest hinges.  A service ladder was added at the front.  Then I added strips of 5/8" scale rivet decals from Archer along the front and rear steps, around the coupler pockets and elsewhere.  I cannibalised stanchions from an old plastic locomotive and used piano wire to form the coupler lift bars.  Here are pictures of the finished beam and side frame after spraying the frame with Tamiya TS-63 NATO Black.

With the engine frame complete (minus couplers) I then turned my attention to the superstructure.  I drew up plans for the cab, motor housing, and the battery box on the back of the deck.  Dimensions for the cab were based roughly on the cut up industrial switcher cab.

Working from the plans, I cut out the walls of the cab from Evergreen V Groove .080 sheet and placed them on the drawing for comparison.  I made windows to approximate those in the photo using Grandt Line 6 light single sash (#5280) which I cut and sanded to make double windows without sills.

The cab was assembled with Plastruct cement.   The motor housing was built the same way, with additional detail (ladders, stack, access panel).  A radiator grill will be added in front after painting made from Scale Scenics aluminum micro-mesh.

 

Thin styrene sheet was cut to size and pre-bent to the curved shape of the roof by rolling it around a fat pencil.  The battery box and lid on the rear deck was cut from .080" V Groove sheet.  Bolts were added strategically using small NBW castings.  Cal Scale PRR style brass headlights (190-477) were installed on the cab roof.  By now the critter was beginning to take shape.

At this point, the realization dawned on me that with the roof glued in place, I had no idea how I was going to secure the cab on the deck so that it could be easily removed to reach the decoder.  A few days of mulling the problem over led to a solution.  I built up an open box from styrene that would be glued to the deck and sit over the motor.  The cab and motor housing would slip snugly over the box for operation, but they could be removed when necessary.  Here you can see the box mounted on the deck. 

There are still a few details needed at this point, such as the air tanks on the roof, the rear railing and various grab irons.  But the structure is finished enough to see how it might look on the layout, pulling a reefer on my Altoona Brewery spur.

This concludes part 2 of my series on scratch building a critter for the AP certificate in motive power. In the third and last installment I will discuss replacing the styrene deck with lead sheet for weight, installing the roof detail, railings, lights and decoder, painting and test operations on the layout.