The brass boxcars

Page #1 - Introduction

I was not satisfied with the Piko rebuilt boxcar. I contains too many compromises to be a "good enough" model. Thus I decided to scratch-build a boxcar from brass. Before starting, however, I made considerations about the most effective ways to build. After all I did not want to waste as many efforts for a boxcar as for a steam loco model!

Profiles

As the prototype cars were consctructed using many different steel profiles, mainly U- and C-profiles, but on some places L-profiles too. It was evident to do the same for the model. Brass profiles are common items in modeling shops. The vertical profiles on Hungarian freight cars were usually 80x80mm (3.2x3.2") U-profiles. The smallest available brass profile is 1.0x1.0mm (0.04x0.04"), a bit oversized but still acceptable. A more visible difference is the wall thickness, that is some 0.2mm for the model profile, 20% of the total width, while prototype profile material was only some 5.0mm, 7% of the profile width. This is an uncorrectable shortage.

The frame girder was made of C-profiles. The main rods were 240x100mm (9.5x4") at the early freight cars later on a stronger version was used with 265x120mm (10.5x4.8") cross section. First I used 3.0x1.0mm brass C-profile here, but the shape was not well visible due to the increased wall thickness thus I started to use 3.0x1.5mm (0.12x0.06") profiles. This is also a bit oversized but being below the model, the size is not annoying. The buffer beams were made from this material as well.

The longitudinal and slanted rods are rather thin on the prototype, usually made from 80x50mm (3.2x2") C-profile. For this the 1.0x0.5mm (0.04x0.02") brass profile was perfect. The cross girder members were usually 120x70mm (4.8x2.8") cross section parts, the models will have 1.5x1.0mm (0.06x0.04") brass here.

The slanted sidewall reinforcement rods were no C-profiles on the Hungarian boxcars but flat rolled steel bands. They show 3-3 rivets at the ends and 3 other rivets in along the section. Because the flat shape and the rivets I decided to make these by etching.

Bottom and Wall Sheets

Almost all Hungarian freight cars were constructed with wooden walls. The exceptions were only some coal cars and open cars with very low sides. It seems from the drawings that the usual planks were always 120mm wide for the walls. This is 1.35mm in H0 scale. I made long considerations how to model these wooden walls.

One solution would be to use real wood to model wood. Norteaster Wood offers thin wood sheets with different distances. I used this as footplate on my V40 electric model. Unfortunately there are sheets offered with 1.2mm and 1.6mm distance, nothing in between. A usual boxcar has 17 boards from top down to bottom. With 1.2mm wide slats the number would be 19, the 1.6mm ones only 14. I made drawings with both and the result was very annoying. Thus I dropped the idea to make the model car walls from wood.

When constructing the model from brass there are several ways. My first idea war to scrap lines into a brass sheet surface. This solution did not promise an easy job. The scrap lines should be parallel and deep enough. To make them deep it is necessary to scrap one line several times exactly at the same position in order to remove more material. If the lines are not perfectly parallel it is very visible, the human eyes are very sensitive on parallel lines.

I also considered photo etching. The layout is rather simple, just parallel lines on a black surface. But large sheets should be covered by photo resist varnish - just for a few parallel lines.

Thus I decided to make a try with the combination of both later technologies. I covered a brass sheet by a simple spray paint and scraped thin lines into the paint. These lines are not deep or wide, just remove the paint. The scraped sheet will be etched using the usual procedure. This way the etching liquid only attacks the brass in the scraped lines and deepens and widens those lines.

Construction Aids

Both the baseplate and the walls were made using this scraping-etching technology. To make the scraping job easier I made a simple tool that allows to scribe parallel lines on an easy way.

As a first step I programmed my small CNC machine to drill two series of 0.4mm (0.016") holes in a brass sheet exactly 1.3mm (0.051") apart. These were cut from the sheet and filed to form two appr. 2.5mm (0.1") wide strips. In the holes I soldered pieces of 0.4mm (0.0016" ) diameter brass wires. These were filed flat on one side and filed to erect some 0.5mm (0.02") from the sheet on the other side. These small "combs" were glued on the surface of a particle board. A " ruler" was also made from brass C-profile. Using this tool it is possible to scrap parallel lines into a painted surface. It is important to keep the scraping needle always in the same angle against the ruler and the sheet.

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