History of Scale Drawings - 1:55 Series
I am often asked about the scale of the 1:55 drawings. The scale is 16.2 pixels per foot, an obscure number that can be traced back to the evolution of the drawing scales over previous years.
The common ancestor of all 1:55 drawings is a 1:880 GP40-2W. After being doubled in size four times and receiving several corrections to dimensions, the end result in 2000 was a 1:55 GP40 that was 959 pixels between the coupler pulling faces, which worked out to 16.21 pixels per foot.
Some time after establishing a round figure of 1:55, I looked into figuring out the exact scale of the drawings. Other drawings of the time were commonly scaled using a 72 DPI resolution as a base. This would make the exact scale of the series 1:53.33, since 72 DPI * 12 inches per foot / 16.2 pixels per foot = 53.33. However, I realized years later that my drawings are at 96 DPI by default, which translates into a scale of 1:71.11. I did not change the scale as listed, however, because it depends on printer and image program settings anyway.
Gradual detail progress
When I started the first 1:55 drawings, the overall length was often the only dimension I worked from. Truck centers, frame height, pilot-to-pilot distance and other dimensions were roughly estimated from models, other drawings or photos. As a result, there were many dimensional and detail inaccuracies that were started in the early drawings and were carried through to future drawings. One of the most obvious was the frame height. In 2001, for instance, all EMD units from the GP7 to the SD70 had exactly the same frame height, when in fact there's a significant difference between the models.
From the start, second-generation EMD units were divided into phases and Dash-2 units incorporated a few correct production variations that were not present in the early official railroad drawings. Other units, however, did not have phase details as I was not aware of them at the time.
As early as a month into the 1:55 series (November 2000) I included different horn types, one of the first railroad-specific details to be added to the drawings. By 2002, when the ALCO Century series was first introduced, a bit more detail was being added--brake chains, for instance. It was also in 2002 that I started including maintenance stickers in painted locomotive drawings.
2003 marked the beginning of right-side views, as well as more in-depth phase distinctions between models. It was at that time, for instance, that I discovered the many different combinations of frame length/truck centers in 4-axle GE U-boats and Dash-7s. It was also in 2003 that I first became aware of some very large dimensional inaccuracies in second-generation EMD locomotives such as the GP40 and SD45. I decided against correcting them at the time, simply because the task was daunting, although I did make some minor corrections to headlights, numberboard placement and fan size on the GP30 through SD60 series.
By late 2004, the inadequacies of the earliest drawings were becoming more and more apparent. This was when I first drew an SD70ACe, and clear photos led me to include much of the model's underframe cables and piping. However, doing so only highlighted just how much upgrading the old drawings needed. This led to the start of the long-term drawing update in 2005.
Long-term Drawing Update
By early 2005, I had received contributions from a number of people that were either original drawings far superior to mine, or my own drawings with a number of corrections highlighted. I finally decided to upgrade the oldest drawings at least somewhat. In April 2005, I started experimenting with upgrading an SD40-2 with accurate dimensions and a higher level of detail. As I progressed, an incredible number of detail inaccuracies began to surface, and I eventually decided to go all-out and correct them all.
The revised drawings were also the first to receive a blue background, which had been requested and which I began to view as necessary. It illustrates the see-through areas and adds depth to the drawing.
The first revision of the SD40-2 involved correcting many of the major dimensions (such as truck centers and frame height) but not much detail was added. Within the following days, as I began revising similar units (such as the GP40-2W) I began to add more underframe and pilot detail. I also started to improve various generic parts such as couplers and door latches, and added simulated screen to corrugated intakes. Many minor dimensions, such as battery box height and radiator intake size, were also corrected. In early 2006, all 1:55 horns (in the "Drawing parts" section) were redrawn.
Above: This shows what the first revised drawings looked like, starting with the SD38-2 and SD40-2. The SD38-2 above includes corrections made to major dimensions, but very little additional detail had been added at that point and there were still many smaller dimensions that would be corrected later.
Shortly after the start of the long-term drawing update, I found a couple of places where my drawings were being used without my permission and with no credit given. Realizing that my copyright notice was very obscure (at the bottom of the main drawings page only) I started adding copyright notices on all the drawings.
I was so satisfied with the revised locomotives done throughout 2005 that the update, initially aimed solely at the oldest and least accurate drawings, became a huge endeavor involving in-depth corrections to every drawing done prior to that time.
In December 2006, a second phase of revisions went underway. The SD50 and SD60 series were still in their original form dating from 2001. Thanks to many detail photos, the new SD50 and SD60 drawings incorporated many improvements over revisions from 2005 and earlier in 2006. The biggest changes were in the underframe detail. In earlier revisions, many underframe details were still roughly represented (even when I had good photos to work from). With the SD50-SD60 series, almost every visible pipe joint, valve, wire connection and cable was represented, within the limits of what the pixels would allow. This was also the first series where even minor dimensions--things like hinge width and cable/piping locations--were derived from photos and not just estimated.
The revisions from 2005 and early 2006 had many parts that were carried over from the old drawings, such as couplers, brake shoes and wheel bearings. However, with the SD50-SD60 series, many of these carry-overs were upgraded or redrawn. Following the introduction of those units, GP40-2W's and members of the SD40-2 and SD45 series were updated to a similar level of detail. It was also at this time that I started marking the exact date of the last revision (instead of just the year) on the fuel tank.
February 2007 marked the first time a drawing received a second major revision. The SD70M's (originally from 2001) had been redrawn in 2005, but I started work on them again. It started with the goal of making them similar to the SD50-SD60 series, but ended (thanks to some great reference material) by becoming the new detail standard for future drawings. More carry-overs (such as couplers, brake gear and handrail stanchions) were redrawn. Shortly afterwards, some of the AC4400CW series received the same treatment, with the last carry-overs being eliminated (solid black air hoses were replaced with outlines). The result was that these new drawings had not a single part in common with pre-2005 drawings, except for the outline of the wheels.
Throughout 2007, a few very minor additional upgrades were made to subsequent locomotive series, such as the inclusion of bolts on the handrail ends. A technical change is that there are a lot of 2-pixel solid black lines in newer drawings, illustrating things like thin ridges or two closely spaced seams. In previous years I avoided 2-pixel solid black lines like the plague.
2007-era drawings can be told from earlier revisions by a deeper sky blue background (instead of cyan). These more detailed drawings spread to several models before a new level of detail could be achieved with the introduction of the 1:36 series.
Back in 2003, when I first wrote a history of the drawings, I had said: "Various small details at first not included are gradually being added to the point where they're now as accurate as I can make them." Looking back at what I did in 2003, that was hardly the case! However, I can say that the drawings from late 2007 leading up to the 1:36 series indeed included every detail reference photos would reveal.