By Joe Atkinson
More information on the prototype IAIS 604

IAIS GP38 604, the "Al Roberts", is ex-HATX 110, xx-CSX 2073, xxx-C&O 3873, a phase 2a GP38 built in 11/67. 604 has a 3600 gallon fuel tank, which Atlas supplies with its GP38. Remove the forward portion of the skirt and relocate the fill pipe as described in my previous message regarding IAIS GP38AC 627.

This unit was delivered to C&O with an oil-bath filter, but according to D. Scott Chatfield, Chessie replaced it with an AAF paper air filter in the early 80's, at which time the front of the DB blister was notched to clear the new filter. The Atlas '38, however, comes with the shorter (later) style of DB blister. To represent the modifications made to 604, you can either add extensions to the GP38 DB hatch or modify the hatch from the Atlas GP40 (which has the longer blisters, but will require rooftop changes). I chose the former. If you do the same, first separate the paper air filter from the rest of the DB hatch. Remove the front tapers of the Atlas blisters, just forward of the DB grills, and replace them with 31" extensions made from the blisters of a second Atlas GP38 DB hatch. Before attaching, fill the DB grills on the donor blister with CA and file smooth when dry. The extensions should terminate at right angles to the long hood immediately aft of the just-removed paper air filter.

Chessie's replacement AAF filter box is the angled type rather than the squared variety represented on the Atlas model. Before rejoining the DB hatch to the paper air filter, file the Atlas filter box down to represent the angled AAF filter. Remove the access door on the left side, filing it smooth with the hood, and angle the upper corners of the filter box to match the angles found on the inertial hatch immediately in front of it. Care must be taken at this point not to file all the way through the thickness of the plastic. I found that by the time I'd achieved the proper angle, the plastic at the corner was paper-thin. To reinforce it, lay a bead of CA down each side of the filter box from the inside. Finish things off by wet sanding the filter box.

Once all filing and sanding is complete, fashion a new 24"x20" access door out of sheet styrene. Scribe a corner-to-corner "X" shape in the back, and fold gently inward on the scribe lines to simulate the prototype door’s appearance. Add a hood-mounted bell on the left side, just behind the DB blister, approximately 11" forward from the rear of the DB hatch. You can either use one of the commercially-available parts to do so, or fashion a styrene bracket and use the bell that Atlas provides.

A good representation of 604's horn can be achieved by modifying the Atlas horn provided in the kit. Remove the diaphragm heads from all three trumpets, then trim off the rear-facing trumpet, turn it around, and mount it facing forward at the same location on the bracket. Fill the cab roof hole that Atlas provided and drill a new hole for the horn 9" aft of it. Mount a firecracker radio antenna just to the right of it and drill a hole for the strobe flasher (Details West RB-126, modified as described in previous message) just aft, centered front-to-back on the cab roof. However, don't add the flasher until after painting. Install the Atlas wipers, then add a thin wire or plastic brace extending horizontally between the two center windshield wiper arms in front, about 4" down from the top.

604 carries a rooftop appliance I don't recognize: A small can-shaped object, about 3" in diameter and about 4" tall, mounted just to the left of the horn above the left numberboard. I represented it using a small bit of plastic sprue. 604's EOT antenna is about 2/3 of the way back on the roof, just to the right of center.

604 makes use of Cannon & Company #1704 radiator fans and #1853 dynamic brake fans.

Trim 9" square notches in all four upper pilot corners, then add the Atlas coupler cut bars. Fashion wire extensions for each corner with an angled loop at the ends (see photo above). The vertical portion of the extensions should be about 22' long, with only the upper 12" extending above the cut bar. I originally attached the extensions to the cut bars as on the prototype, but found that arrangement to be pretty fragile once on the layout. I now drill holes in the pilot behind the point where the cut bars turn 90-degrees, and the bottom portion of the extensions are glued into the pilot. Other pilot modifications (MU hose pockets, etc.) can be made exactly as described in my last message regarding IAIS 627.