This is a small industrial diesel tractor locomotive. These types of locomotives were built using a farm tractor as the mechanical and motive power, and then modified /built into frames/chassis to function on railroad tracks. 

Construction

The "tractor" portion of the loco was constructed using heavily modified and reshaped parts from a 1/48 scale Bandai SdKfz.-11 half-track kit, as were the rear transmission and "tractor frame". The firewall was made from sheet styrene, and an HO boxcar brake ratchet mechanism enclosure. The transmission ia part of a Grandt Line O-scale caboose stove, and the floor plate is from an HO  Jordan truck kit. The gusset plates came from a Grandt Line Koppel ore car kit.

 The loco frame was modified from a Grandt-Line "Battery Mine Loco" 

All parts were painted using a Paasche 'VL' double-action, internal mix airbrush, with a #1 tip. Brush painting was only employed for filters, weathering and some minor areas of touch-up. The exception was the Primer coat of Gunze "Mr. Surfacer 1000, which was applied from a spray can.

The painting & weathering  process was broken down into the following steps:

Primer Coat

Pre Shading

Color Coat & Panel Shading

Filters & Washes

Chipping

Rust

Pre-Dusting

Dust & Dirt

Oil Stains

Final Pick-up & Touch-up

Pre-Shading, Color & Panel Shading 

After primer, pre-shading was done using Tamiya “Nato Black”. (an example of pre-shading can be seen HERE on another project).

The color coat was applied in 3 layers, the first consisting of Tamiya, “JN Grey” (XF-12)  lightened to about 90%. with "Flat White" (XF-2), and then thinned to a ratio of 60% paint to 40% thinner. Each of the following layers was lightened an additional 10-15%. and sprayed working inward toward the panel centers (panel shading), on surfaces/areas that would have bleaching from the sun and elements, and to add some shape, and depth.

Once the color coat was dry for a day, the filters were applied. The the filters were made up of Windsor Newton artists oils, mixed to a ratio of approx. 5% paint to 95% Grumbacher "Pre Tested Odorless Thinner". The filters were evenly applied with a a 1/4" wide soft flat brush, that was only "damp" with the color. The first filter color was "Prussian Blue", to accentuate and give some depth to the blue base color. After about 2 hours of drying time a second filter color was applied, Burnt Sienna; this was used to age the blue base color, to try and give the feel of "yellowing/dulling" that often happens with old paint.

Following this filters were added using Windsor Newton artists oils:  Prussian Blue (#33), Sap Green (#37), and Naples Yellow (#29)

When dry, it was given light washes of Paynes Grey (#32), and Black (with just a smidge of Burnt Umber).

The washes consisted of various mixtures of Windsor Newton artists oils, "Black" and "Burnt Sienna", thinned with Odorless thinner, and applied in multiple thin layers. The ratio of Black to Raw Umber depended on the area being washed, and the effect that was trying to be achieved. Door lines and panel lines for instance, received a mix with more black to both darken the line, and to represent collected "grime", whereas the areas along fender edges were done with almost pure Raw Umber, to represent collected rust, as well as areas that had started to rust through the paint, or discolor from subsurface rusting. These Washes were done using an 0/18 brush.

The roof and hood surfaces were washed in preparation for the next step, and to represent general streaking of rust and grime off these surfaces, making sure the brush direction followed the direction that water would flow.  This effect was also carried onto/accentuated on some of the vertical surfaces. A small soft flat brush was used for this

(These photos were taken outside and it is interesting to see how the change in light brought out the underlying blue color and filter tone in some areas.)

 The chips and scratches were painted with Vallejo acrylic paint For the chipping I used a mix of Vallejo Acrylics "German Camo Black Brown" (#822) and "Black Grey" (#862), using a 0/18 brush. The wear on the horizontal surface was done using a small piece of fine foam, and the 0/18 brush. The chipping process took about 5 hours.  

Rust was done using using artists oils. Once the "chips" were dry, some had "pin washes" of a very thinned mixture of Burnt Sienna and/or Burnt Umber applied, while others received small dabs of Raw umber, which were then drawn/streaked vertically downward with a thinner dampened brush.

The rusting to this point took 6 hours. In the third photo below, one can see where I still have to do the rest of the side-frame at the rear of the left side, and the gas tank. (I was still  not quite sure how I wanted to approach the weathering on the tank, and/or whether I wanted to replace it with a different style.)

Dust/Dirt

The next step was adding Rain Marks, and dust/dirt. The Rain marks were done using thinned Tamiya "Deck Tan" (XF-55). Dust/dirt was done by airbrushing a mixture of 50/50 mixture of Tamiya "Deck Tan" (XF-55) and "Buff" (XF-57)., this was then thinned to a ratio of 80% thinner to 20%paint, and applied in multiple layers at the lower edge of the side and end frames, on horizontal surfaces, and in corners where dust would collect. When dry some the side frames were given a very light, highly diluted pin wash of a Life-Color brown. Lastly  a light dusting with mix of "Dust Bowl Brown" and "Ash" Bragdon's powders was applied to various areas and corners.

The tractor seat assembly was made using a modified McKenzie Iron & Steel White metal seat casting, formed and drilled brass strip, and Tichy .020 Rivets. The seat was colored using Floquil "Roof Brown" (from a spray can), when dry, the seating surface was rubbed with MIG "Gun Metal" (#P231) pigment.

Display Base

In order to elevate the loco for better viewing, and to give a hint of context for the model I decided to build a display base. The base is built out of .080 sheet styrene, and some assorted strips, from Evergreen. Once built and sanded the top of the styrene was shaped to mach my proposed ground contour. A Piece of 1" thick  insulation foam was then cut and inserted into the base, and shaped to match the styrene edge contour.

Fabrication time to this point about 6 hours. Cost about $2.50.

I ended up making them out of .003 paper, so they scale out more prototypically…..I was going to try and vacuum form them, or emboss them in sheet brass, but neither of those proved a workable solution……so I did the same method I did with the OOB 38t corrugated…I soaked the paper piece in diluted matte medium, and then press embossed it into a two part styrene “form”.  When dry, they were removed and trimmed, then sealed with a brush coat of Dullcoat. For stiffness under the rails a short (34” scale) piece of inverted .100 styrene channel was  ACC glued to the underside.  I still need to make the small bolt fasteners o hold the rail to the sleepers.

The ties are each a scale 5-1/2” x 2”.

Coloring was done using using the new Life Color weathering set/washes, Bragdons weathering powders, and artists oils

These photos were taken after I had to remove all the rock and dirt scenery around them and on the base, because I did not like the way it came out. The orange rust are some areas where  I used a wash of  Bragdons powders to color some damage from and remnants of the scenery. These will be better blended in the final finish. It was actually not bad, the damage left texture that looks like built up/crusty dirt and rust along the bottom edge of the ties….just like prototypical ones I have seen. 

The white strip that can be seen under each sleeper is just a spacer I added to lift the sleeper to fit with the eventual scenery/grade.

For the material I used Arizona Rock Company's "River Bottom" material/gravel. 

To apply the gravel, a thin coat of the tinted modeling paste was brushed onto the base, which was then sprinkled with the gravel material. the base was then tapped to level/distribute/remove the excess. A pair of tweezers, and my finger were then used to prod and remove the gravel till I achieved the desired appearance. A 60/40 solution of water and Liquitex matte medium were then dripped evenly onto the material using a syringe, and allowed to "wick" through the gravel material till it was all damp.

Once dry the gravel was given a base wash of thinned Tamiya "Medium Grey" (XF-20), this was then followed multiple thinned washes and thinned surface brushing (sim in concept to "dry brushing") of various mixed shades of Tamiya "Deck Tan" (XF-55), and "Buff" (XF-57).

Once dry the area was given a spot dusting of Bragdons "Dust Bowl Tan" powder.

Originally I had thought that due to different steel types and manufacture, the steel rail would weather to a different rust color/hue than the pressed steel ties/sleepers, but upon careful research of prototype photos, they all showed the rails and sleepers the same color. 

The rail was sprayed with Floquil "Roof Brown" (from a spray can). While the paint was still wet, the sides were sprinkled with varied hues of rust toned pigments. The rail pieces were allowed to dry and the excess pigments brushed and blown off. The pigment that remained adhered to the paint, provided a nice subtle texture. 

Once the rails were fastened a graphite pencil wes run along the tops to give a worn steel color. Lastly the rails were dusted with some Bragdons "Dust Bowl Tan" pigment.

Materials List:

Tamiya:

 Putty ( Basic Type)

XF-63

X-20A Thinner

Mr. Hobby:

"Mr. Surfacer 2000"  Spray Can

"Mr. Surfacer 500"  Jar

Vallejo/Model Color

#822 German Camo Black Brown

#862 Black Grey

Humbrol:

Enamel Thinner

Grumbacher:

Turpentine

Pre-Tested Odorless Thinner

Windsor-Newton:

#2 Burnt Sienna

#24 Ivory Black

MIG Productions:

Bragdon's Enterprises:

"Rust" Weathering Powders Set

 Water

90% Denatured Alcohol

Marc Reusser

Nov. 2007