Rail 3D Stock design - How to build a T3
You can find a couple of tutorials on the use of the stock editor in the User Guide: these are restricted to very simple cases. On these pages, I will take a real design project, and follow it through the development process, illustrating a number of more advanced techniques.
I'm not going to repeat things that are already explained in the User Guide: this should be seen as a "case history" rather than a tutorial: if you're puzzled, please go to back to the examples in the User Guide.
Before starting, it's important to point out that there is no single best way to build a Rail3D model: everyone does it slightly differently, and different approaches work for different models, of course. This example illustrates my techniques, for steam engines, and is based on the current state of the software (Rail3D117, February 2003).
I've broken the project up into seven major phases. For each, except the first, there's a downloadable stock file: I recommend that you look at these in the stock editor while reading these notes.
Step 1: The prototype
As in any modelling project, the first step is to find out as much as you can about the thing you want to model.
I decided to build a Prussian T3 (BR89.70-75), a small six-coupled branch line tank engine built between 1881 and 1906 for the KPEV and DRG, which will be very familiar to anyone who has ever owned a Minitrix starter set. My starting point for the model was a set of drawings that originally appeared in MIBA in October 1959 (Re-issued in the collection "MIBA Reprint 1" in 1984).
A quick search on the web revealed a number of pages with further technical information and photos of the T3. A couple seemed especially useful, so I took care to bookmark them:
(On the Ostheide site are some drawings, which would be a reasonable starting point if you didn't have the MIBA drawings.)
This gives me the basic information to start putting together a Rail3D model:
Name KPEV_T3 Description Prussian T3 with dome Number 1 897%3d Metric Length 859 Wheelbase 300 Power 213 kW #290 PS Max 40 TE 56 kN #calculated Weight 36 tonnes #max service wt Brakerate 3
From the internet data, we don't know the TE, but there is enough information to work it out: the boiler pressure is 12 kgf/cm2, the cylinders are 350mm diameter, so the piston force is 113 kN. Divide this by the ratio of wheel diameter (1100mm) to piston stroke (550mm), and you get the nominal TE: 56kN.
Step 2: Preparing the drawings
My usual practice is to use a CAD program (I have an old version of TurboCAD on my machine) to help read the dimensions off the drawings. First I scan the drawing into a bitmap file, taking care that it is oriented with the baseline exactly horizontal, then I import the bitmap into my CAD program, and scale it so that 1 mm in the bitmap is equal to 1 mm in CAD space. Then I set the unit display in the CAD program to whole centimeters (in Rail3D we don't care about the figures after tha decimal point).
The next step, once the scale is right, is to add construction lines to the drawing to identify the reference points we shall need. The most important are rail level (H=0); the buffer extremities in the plan and top view (L=0 and 859); and the centreline in the top and end views (W=0). By snapping to these reference points, we can always be sure we are measuring from the same place. It is also useful to identify the wheel centres at this point.
In this case, it is very easy, as I shall only be using the MIBA drawing, and the four views were already nicely lined up. If you are combining drawings from different sources, you have to follow these steps for each drawing.