History of Scale Drawings - 1:24 and 1:18 Series
As with the 1:36 series, the 1:18 series is based on a simple pixel-to-inch scale of 4 pixels per scale inch, or double the size of the 1:36 series. The scale when printed can therefore be obtained by dividing the print resolution (in PPI) by 4 - in other words, the scale is 1:(PPI/4). The 1:24 series was drawn at an intermediate size of 3 pixels per scale inch.
1:24 Series: An Evolutionary Step
The 1:24 drawings are no longer online, but they represented much of my drawing work in the middle of 2012. At the end of 2012, I replaced them with the 1:18 series.
However, there were some additional steps and experiments prior to their introduction. Following the last 1:36 drawings on February 21, 2012, I experimented with creating vector drawings - something I had tried several times in the past. I made considerable progress on a vector image of an EMD GP40, more so than in any previous attempt at making vector drawings, and by March 2, 2012, I had completed the front truck and basic cab outline of the locomotive. However, there was one major caveat: that very partial drawing required four days of work, which was painfully slow.
As a result, on March 3, 2012, I started a GIF version of the same locomotive using my traditional drawing technique in MS Paint, but at the new scale of 3 pixels per inch—making the drawings similar in size to the 1:25 drawings of the Railroad Paintshop. I found I could complete the drawing about four times faster than the vector version, while achieving a comparable level of detail (albeit still pixelated). The 1:24 series therefore retained my traditional GIF drawing method while incorporating significantly finer detail than the 1:36 series, and the first drawings were uploaded on April 11, 2012.
The motivation for both the attempted vector drawing and the 1:24 series was similar to that for starting the 1:36 series in 2008—namely, requests for higher-resolution drawings and reaching detail limitations in 1:36. Since the 1:36 series was already detailed and generally accurate, the 1:24 series represented an evolutionary step forward with finer details and corrections to the last dimensional discrepancies. At 3 pixels per scale inch, the drawings were exactly 50% larger than the 1:36 series and were drawn in the same manner. For some parts in the 1:36 series that were already accurate, I simply enlarged and retraced them at higher resolution for the 1:24 series.
1:18 Series: Fine-tuned details
I worked with the 1:24 series for about nine months in 2012 and found it satisfying. However, the scale of 3 pixels per scale inch was awkward to use in a world of half- and quarter-inch dimensions, and I felt I could progress resolution one step further. As a result, starting in the first week of November 2012, I created 1:18 versions of all the 1:24 drawings I had done, largely derived from resized 1:24 drawings and using a new scale of 4 pixels per scale inch.
The first 1:18 drawings were uploaded on November 29, 2012. By this point, five drawing scales (1:110, 1:28, 1:55, 1:24 and 1:18) had made their debut with a generic B&O-style GP40, with the 1:36 series coming close with an RM-1 GP40 rebuild. With the 1:24 series still in its infancy at this point, I removed all of them from the site and replaced them with 1:18 versions, with the 1:18 drawings intended to replace (rather than supplement) the 1:24 versions.
Once again, I retained my traditional method of editing the drawings as GIF files in MS Paint. Since the 1:24 series was already very large, I discovered early on that I wasn't adding much additional detail—it was more a question of refining the lines.
The first drawings of the 1:18 series were made largely by tracing resized 1:24 drawings—hence the very short time delay for completing the initial batch. However, I did pay a price for doing so. Several of the traced components or dimensions were not precisely measured and re-scaled to reflect their exact dimensions in the new scale, and the result (many years later) was two massive batches of revisions correcting minor errors in EMD drawings in 2019 and again in late 2020 / early 2021, the latter case involving more than 1300 drawings.
The higher resolution of the 1:18 series presents a few additional challenges. More so than in previous scales, I measure everything—which often results in a lot of time devoted to creating accurate renditions of relatively minor components. The drawings initially didn't fit vertically into my working screen resolution, which made scrolling and editing the labels more of a challenge - although with a monitor upgrade in 2015 (from 1440x900 to 1920x1200) that's no longer an issue. They also take up 4 times as much memory as the 1:36 series. However, those are minor compromises when the scale allows a level of detail that I could never achieve before.
Upon starting the first painted 1:18 drawing in late 2012, I made one minor (but significant) change to my painting methods in MS Paint—after I discovered the beauty of PNG images. Previously, I converted undecorated drawings from GIF to 24-bit Bitmap images for editing, and I only re-saved them as GIF files (custom palette) when they were completed. However, the size of the 1:18 drawings made them huge and laggy for editing as 24-bit Bitmaps, so I now convert the undecorated drawings first to 24-bit Bitmaps, then immediately to PNG files. When complete, I use another program (IrfanView) to compress the images, as MS Paint does not offer full PNG compression. The resulting PNG files maintain the full colour palette of Bitmaps yet take up less memory than GIF images.
I can't predict the future with any certainty - but I do seem to have reached a plateau with the 1:18 series. Prior to 2000, each successive scale lasted less than a year. The 1:55 series lasted for 4 1/2 years before many were completely redrawn (sometimes twice); those lasted for less than 3 years before I started the 1:36 series; and those lasted for 4 years before I expanded into the 1:24 and 1:18 series. However, the 1:18 series is the longest-running drawing scale (now in its 10th year) and the earliest drawings from 2012 have the same level of detail and accuracy as my current drawings. So far, I have no plans for another new scale.