Tasha Oates updated January 10, 2011


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  • Weathering EMD 'Tunnel Motor' Diesels


    Steve Orth described how to kit-convert an EMD SD45T-2 diesel from Athearn and Cannon parts in the October 2001 issue of "The Journal." The real "Tunnel Motor" diesels (including the prototypes for Athearn's SD40T-2) often display some severe weathering patterns. Here's how to duplicate that burned paint and rust effect in any scale. There are more photos of SD45T-2 locomotives in D. Scott Chatfield's article, also in the October 2001 issue. There's an index of all previous articles on modeling diesels on our website at www.railmodeljournal.com.
    Railmodel Journal - November 2001 - Page 38 Railmodel Journal - November 2001 - Page 39


    Diesel Weathering

    Last month I described the construction details involved in building a model of a Southern Pacific SD45T-2. The SP locomotives commonly see some severe service in their careers, and their external appearance typically exhibits that service. Particularly brutal are the continuous grades in mountainous territory, including long tunnels and snowsheds. This results in heavy coatings of oily exhaust soot on the hood sides. The long grades also require extended applications of sand, which result in heavy dusting of the trucks and fuel tanks. It is not uncommon to see an SP locomotive with a nearly black superstructure and a light tan undercarriage.

    Conversely, the downhill grades deal their effects on the SP fleet as well. The long down-grades encountered on the railroad require long-term application of dynamic braking to control train speed. On Southern Pacific and Rio Grande six axle locomotives, this dynamic braking results in very high temperatures in the dynamic brake resistor grids, which eventually scorches the paint on the top of the hood doors, directly under the dynamic brake blisters. The paint can eventually be burnt completely off, leaving unprotected steel that rusts. Below this burnt paint and rust, the heat has been known to cause the vinyl lettering to peel off SP locomotives, taking the grey paint with it, revealing the red primer under the grey. On some locomotives, this peeling is so complete that it appears that the lettering is actually done in red paint.

    I wanted to capture all of these effects on my model. It was not my goal to turn out a model that was "pretty," but rather one that was realistic. I began experimenting with different methods while I was building the model, using surplus shells. John Welter's article in the 1988 issue of Railroad Model Craftsman on using Microscale decals in both red and white to obtain the peeling paint effect provided some inspiration. John used an eraser to rub away some of the white decals prior to applying them over the red. I decided to use John's idea of stacking the decals, but developed my own method of removing paint using a small sandblaster.

    Painting and Decaling

    I began the painting process by spraying the hood doors with Floquil Rust as primer. I selected this color so that after removing top coats, I would be left with a rust color. I had originally tried to paint the rust over the grey and the lettering, but I ended up with what looked like rust colored paint on top of grey, which was not the desired effect. I also experimented with Floquil and Polly Scale paints. Both worked well, but the flat finish of Floquil gave me slightly better results. After painting the rust paint and allowing it to dry, I overcoated it with two coats of Testors GlossCote to protect it. This was allowed to dry for 24 hours.

    While the rust paint was drying, I disassembled the trucks and painted the truck gearboxes flat black. The wheelsets were pain ted with Grimy Black, and misted with rust. Locomotive wheels will not be a consistent rust color unless they are new, having collected road grime, lubricants, dust and other grime in the course of use. The dynamic brake fan insert was also painted flat black, and the fans were painted a dull aluminum. The prototype fans and hub are a one-piece aluminum casting and are left unfinished.

    After the rust paint and overcoat had dried, I painted the scarlet on the nose and long hood end. This was set aside to dry, and masks for the wings were prepared. To make a mask, I took Microscale decals and traced the wing pattern onto a piece of drafting Mylar. This pattern was then traced onto white paper for a test fit. The decal wings were incorrectly sized for the SD4ST-2 nose, so adjustments were made. When I had a pattern on the Mylar that was correct, I placed masking tape over it and cut the pattern out on the masking tape. The tape will not lose its adhesion qualities on the Mylar, and Mylar is easy to draw and trace with. This method works very well when I am attempting to make a mask to match a decal, such as an ATSF warbon net scheme.

    The tape was then placed on the model, and the remaining portions of both ends were masked. The SP Dark Lark Grey was then sprayed. To get a smooth finish, I mixed 5% Retarder, 20% Glaze, 50% Floquil paint, and 25% lacquer thinner. The grey was sprayed, and the mask removed as soon as possible. Removing the mask early helps prevent aline where the mask was. The hood sides were then given a light gloss coat. The model was set aside to dry for 24 hours.

    After the grey and gloss coat had dried for 24 hours, the red "SOUTHERN PACIFIC" lettering was applied. The decals were set with Microscale Microset and allowed to dry. They were then gloss coated, and the model was given 24 hours to dry again. I discovered earlier experiments that it is important to allow the gloss coat to dry completely before applying more decals over it, which in this case will be the white let ters. To get the white letters aligned over the red, the decals must slide easily.

    When the gloss coat had dried, the white decals were applied. A t this same time, I applied the remaining decals on the model. When the decals had set and dried, I painted the window gaskets and fuel filler caps. A brush was used to paint the vertical portions of the handrai ls white. The interior wall s of the cab were painted with a brush, even though a cabin terior was not installed. The nose grabirons were reinstalled and glued with CA.

    When all of the final brush painting was complete, I airbrushed a coat of DullCote on the model.


    Railmodel Journal - November 2001 - Page 43

    I let the model set for 24 hours to allow the layers of paint and decals to dry completely. The model was then placed in my sandblasting booth to begin the weathering process. To prevent damaging the paint on the dynamic brake intake grilles, I removed the dynamic brake section of the hood.

    Using a Badger Air Eraser operating with air at 40 psi, I began to remove paint below the dynamic brake intake grilles . Using this lower pressure, controlling the amount of paint being removed was remarkably easy. I eroded the grey paint, revealing the rust-colored primer coat. At this point, I moved down to the decals revealing the red letters underneath. Once again, removal of material was easily controlled. I used several photos in books and magazines to guide me to a realistic "peeled paint" look. I finished up by blending the eroded decals and paint together with just a small amount of sandblasting over the entire area. In some places, all the paint was removed, including the rust. This ended up adding yet another color of grey to the weathering, making it look like residual primer, which added to the effect. I feel that the final result is very realistic, since paint was actually peeled off by the sand blasting.

    The weathering continued with dry brushing rust paint over the dynamic brake intake grilles and the sandblasted area. The brush was moved in a vertical motion on the hood sides and horizontally over the grilles. White paint was dry brushed under the battery boxes to simulate acid spills, and some black streaks were dry brushed onto the hood sides to look like washed-down soot.

    Highlighting with Drybrushing

    Railmodel Journal - November 2001 - Page 44

    When a prototype object is viewed, take notice of how edges and corners of the subject appear lighter colored. This is the result of light glaring off of them, which we see as a brighter color. On a model, this also happens, but to a much smaller degree. So much smaller that it is very difficult for our eyes to detect. To emphasize or highlight these edges on the model, I drybrush the entire model with a lightened shade of the base paint. I mix some white paint into the base color on a piece of paper, and dry brushed this on the model with a brush that has long, soft, even-length bristles. The brush is first touched in the paint, which is preferably fairly dry. I work the brush on the paper to remove almost all of the paint, and then lightly brush over the mode. Be patient and continue to drybrush until the desired highlighting is achieved.

    When drybrushing is complete, I mist a light coat of flat black on the top of the locomotive for exhaust soot. I used a very thin, high-gloss black paint and allowed it to run down the fuel tank under the fillers. This paint was too glossy, and the spills looked like they were about 10 seconds old. To soften the spills and to weather the fuel tank and trucks, they were misted with thinned Grime and Dust paint to simulate dust from the sanders. A mist of Grime was also added to remainder of the model. I finished this misting process by applying a final coat of DullCote to blend it all together.

    The windshield wipers and cab size windows were painted silver. Glazing was installed in the cab and the wipers installed in the cab and the wipers installed in the holes that were drilled earlier. I drilled the class lights on the rear with a number 54 drill and installed MV 300 lenses in all four locations. The MU hoses were installed and painted flat black. I have installed these earlier on models, but the weathering collects on them, making them appear to be a light grey, so I now wait to install them. The Detail Associates MU hoses can be made to have a realistic droop by holding the tip of a soldering iron close to them and bending them. This heat-induced curve will remain in them forever.

    The handrails were installed and fastened to the shell with CA. I wait to install the handrails until after weathering for the same reason as the MU hoses. The weathering builds up on the handrails, making them too prominent. A very light misting of Grime was applied to the white ends to soften them. Finally, the safety chains were installed by cutting the railing and installing the chains over the wires with a drop of CA to retain them.

    DCC Decoder Installation

    Railmodel Journal - November 2001 - Page 45

    A Digitrax DN140 DCC decoder was used to provide control and lighting for the locomotive. Lights were installed, using clear 1.2 mm diameter, 1.5 V. 15 mA bulbs in headlight, rearlight, and Gyralight locations. A red 1.2mm, 1.5 V 30 mA bulb was used for the emergency Gyralight. By experimentation, I determined what resistors to use for each bulb to get the desired brightness. The front and rear headlights had 380 ohm resistor added in series with the bulbs. The front Gyralight, between the number board, had a 342 ohm resistor added. Finally, the emergency Gyralight had a 330 ohm resistor added. These values gave me lighting that was pleasing to my eye, and did not subject the bulbs to overvoltage, which would reduce their life.

    I carefully installed the decoder, wires, and reistors under the dynamic brake hatch. I did not permanently fasten the hatch down to allow access to the resistors and decoder. It was more of a challenge finding space for the resistors than the decoder. This made me wish the output voltage for lighting effects was programmable on the decoder. This would certainly simplify installation.

    When all the electronic installation was complete, the model was placed on a programming track and programmed. Operating the model revealed additional interference between the sanding lines and chassis. The interference was eliminated by bending the sanding lines. After I filed the mold parting line off the couplers, they were painted a rusty brown and installed in standard Kadee number 5 coupler boxes.

    With the model complete, I placed it on the rails of the layout for service. I think it realistically projects the rough use that its prototype encountered, and certainly looks like it could use a bath and a trip to the paint shop, just like the prototype. This is what "Modeling from the Prototype" is all about!

    Article Details

    • Original Author Steve Orth
    • Source Railmodel Journal
    • Publication Date November 2001

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