(Translated part of the text from the hobbyist magazine ABC, where I have my reference pictures from): "In the period of the first Czechoslovak republic ( 1918-1938 ), the ČSD (Czechoslovak Railways) had over 20 locomotive series of Austrian and Hungarian origins. Mostly, these designs were obsolete and ineffective. This situation called for lowering the number of series, thus lowering the maintenance costs. Therefore, in 1920, the ministry of railways ordered a light and universal but powerful tender steam locomotive from the First Czecho-Moravian Machine Works (nowadays ČKD - Czechomoravian-Kolben-Daněk). The first 30 locomotives were ready in 1921 and 1922 receiving the serial numbers 423.001 through 423.030. [...] The series design changed seven times during their production. [...] They proved very useful on the Czech local railways. Because of their load, they gained an admiring nickname "bejček" (the Bully) or "velký bejček" (the Big Bully). [...] During the occupation of Czechoslovakia in 1939 till 1945, our railways had to surrender 52 423.0 locomotives to the German railways (DRB - Deutsche Reichsbahn) and 9 locomotives to the Hungarian railways (MÁV - Magyár államvasutak). Thus, after the liberation in 1945, the ČSD ordered the 423.0 series from the ČKD again, in order to quickly renew the fleet, decimated by the war. The order was for delivery of 120 more engines. [...] The last 423.0 locomotives were constructed in 1948. In 1946, the ČKD workers built one locomotive more and gave it to Slovakia, whose railways were in a desolate condition after the war. The 423.0 locomotive of the post-war series is depicted in the drawing on the previous page. [...] [...] The 423.0 series locomotive had a tractive effort of 128.5 kN and load of 750 HP (552 kW), pulling the trains of weight of 700 tons at a speed of 60 km/h (app. 38 mph) on a level track, 600 tons on a 10 per mille slope at 16 km/h (10 mph), at the same speed 300 tons on a 20 per mille slope and yet 200 tons on a 30 per mille slope at 14 km/h (9 mph). [...] The 423.001 locomotive is an exponate of the Prague National Technical Museum. The 423.0 series and derived 433.0 series locomotives were typical propulsive vehicles of the Czech railways from 1924 till the definite termination of steam traffic on ČSD in 1980." Well, that was a bit exhausting, but at least you got to learn a bit about our railways and the 423.0 series (I found that article very educating and interresting myself). I found this monography together with precise 5-view (the bottom view is not present ) drawing of the locomotive, which made me start thinking about making a paper model of the "Big Bully". I took a pen and paper and started sketching, then drew the parts in Inkscape (Linux program, similar to Corel Draw) on my computer, printed them out and started modelling. You can find the sketches of the model, some screenshots as well as photos in my gallery. The most demanding design job was thinking out the functions for the curves on the chimney and steam dome parts as well as corresponding curves on the boiler whereas the most demanding modelling job so far was putting the cab together, because it also has an interior. When I've finished the model, I will create simple instructions for putting the model together, and post the model somewhere on the internet for the others to freely download it. The only think I don't yet know how to achieve is coloring of the model. I could either export the model to raster format and paint it in a bitmap editor (Gimp rulez 8) ) or print it out in high quality on some thick paper, paint it manually with watercolors (which will be more work and is not guaranteed to be a success, but should look better, not too "computerish"). If you have any ideas or experience with the painting of your paper models, I will be glad to read a post or two from you. Yeah, of course: Also feel free to post feedback on the model and/or the techniques used in creating it and/or whatever else needs your feeding back . OK, in my gallery you can find pictures of the model, some screenshots and my conceptual drawings. Czestmyr's gallery P.S. I found out a formula of a function, that can be used to determine the shape of the bottom of an arbitrary-diametered cylinder, sitting on another cylynder of an arbitrary diameter. I think it can be useful to some of you. The formula states either: f1(x) = sin(acos(cos(x/r2)*r2/r1))*r1+hmin or: f2(x) = sin(acos(sin(x/r2)*r2/r1))*r1+hmin (the first one makes the seal of the smaller cylinder on the side, the second on the top of the bigger cylinder), where r1 is the diameter of the bigger cylinder, r2 the diameter of the smaller cylinder (the one, that is supposed to sit on the former), x the position on the circumferrence of the smaller cylinder and hmin is the minimal height of the second cylinder (that is, its height, measured from the peak of the first cylinder), f(x) then yields, for every point of the circumferrence at the position x, the height of the second cylinder. Thus, when you plot this function, scale the picture and trace it in a drawing program, you get exactly what you wanted: a rectangle with one side replaced by a strange-looking curve, which, when rolled and its oposing sides glued together, becomes a cylinder with a cut at one of its bases that exactly matches the curvature of the first cylinder.