Steam Locomotive Cab Simulator
aka: My Ultimate Toy Train (MUTT)
Part 1 of 2 – Development
By Doug Johnson
Although the term “toy” is not the design intent, any simulation is in fact “let’s pretend” in that it is a facsimile of the real world. A perfect simulation would in effect be the prototype and all the inherent advantages of a simulation would be lost (leaving the many disadvantages of a prototype). Certain aspects of a simulation that do not exactly match the prototype should be “forgiven” for reasons of practicality in construction and/or operation. With that said, what follows is a summary of the design and construction of MUTT.
The initial spark of life for MUTT was started by my purchase of Microsoft Train Simulator (MSTS) a few years ago. Options that I found particularly intriguing were operation as if inside the cab and construction of custom routes.
The next piece of fuel for MUTT was the release of RailDriver Desktop Train Controller, a product by RailDriver, which is a division of PI Engineering (PIE). The controller is a small console that connects with a Personal Computer (PC) via Universal Serial Bus (USB) and audio interfaces. The console provides levers, switches, pushbuttons, speed display, and low frequency vibration to simulate locomotive cab controls. Their software was designed to support the original TrainMaster, MSTS and Trainz by Auran. RailDriver had also announced its intent to offer additional prototypical controls, gauges, and interface electronics for those interested in building full-scale simulators. As part of their strategic business plan they subsequently acquired the original TrainMaster simulator (now at version 4.3) and are redeveloping it into a new product called TrainMaster Train Simulator (TMTS) and communicated their intent to develop it into a MSTS-compatible software package complete with an Application Program Interface (API), similar to what is built into Microsoft Flight Simulator software but absent in MSTS. RailDriver also announced their intent to enter the commercial railroad training market by applying these products (which unfortunately, because of their success, led to suspension of TMTS development in the face of higher priority commercial workload).
Immediately after my initial use of a RailDriver console to operate MSTS and Trainz, the next logical step was clear – a full size cab simulator with prototypical controls and gauges. Upon searching the Internet for comparable simulators, it was discovered that although a few diesel cabs had been constructed, no steam locomotive cabs were found. At that point the challenge was “to go where no man had gone before” (at least no known man) and MUTT was born.
Initial research focused on learning more about prototype steam locomotives, both functionally as well as dimensionally. This was accomplished by using the Internet, reference books, and a Compact Disk (CD) of Locomotive Cyclopedia of American Practice, 1922 offered by the RailDriver folks. The latter was particularly useful in that it covers all aspects of locomotive construction and operation, and provided detailed scale drawings of virtually all components.
Another resource used was photographs on RailDriver’s website of a Ten-Wheeler No. 2 currently operating on the Huckleberry Railroad in Michigan that includes close-up views of the backhead. They also offer freeware models of the cab interior of this engine that can be installed in MSTS or Trainz. As MUTT evolved, it was patterned after this locomotive as its “parent”.
The next step was to make sketches followed by detailed drawings of the physical cab structure and component placement. The footprint of the physical cab structure was constrained by the room dimensions where it was to be ultimately located. This quickly led to the following three major decisions:
These three major decisions were primary drivers throughout all subsequent design.
- The engineer’s station and about ¾ of the backhead (including the firebox door) could be accommodated. Essential fireman’s functions would be provided, but not the fireman’s station.
- Relative to display of the external world through the windows, a 72” diagonal screen could be accommodated (4:3 aspect ratio) but would require a short-focus projector and mirror to reduce the distance required for imaging. Also, the screen would be placed at an angle to maximize the side window view while filling the forward window. To validate the window display arrangement, a scale model was constructed and attached to the screen of a PC running MSTS.
- The simulator must consist of modules for disassembly and moving.
The overall structure drawings were done using Microsoft PowerPoint as a drawing tool. Three view scale drawings were done of the cab structure and its elements. The engineer’s station followed prototypical dimensions to ensure realistic seating, control reach, and gauge/window viewing relationships. The backhead was foreshortened (a technique familiar to scale model railroaders) to achieve a practical depth of 12”. Next, placement of controls and gauges was determined using various prototype images as guidelines. Decisions were made to provide the following controls and gauges based upon consideration of which were most essential for prototypical operation and which were implemented in existing MSTS software:
Gauges (aka Gages)
- Regulator/Throttle (analog, notched)
- Reverser/Johnson Bar (analog, notched)
- Locomotive Brake (analog, notched)
- Train Brake (analog, notched)
- Injector Steam Activation (on/off)
- Injector Water Flow (analog)
- Cylinder Drain Valve (on/off)
- Sander (on/off)
- Damper (analog)
- Blower (analog)
- Fire Box Door (open/closed)
- Whistle (on/off)
- Bell (on/off)
- Headlight (on/off)
- Turnout (left/right, forward and rear)
- Cab View (forward/rear)
Several iterations were made on these layouts as practical construction and material factors were considered. Also, the envisioned “logical” operation in the cab influenced the placement of elements to some degree. For example, a key decision was made to place the reverser lever at the right hand side of the engineer’s seat to eliminate conflicts (physically and operationally) with other elements at the right side of the backhead (engineer’s left hand).
Next, detailed design of each control and display began. The primary tool used was Deneba’s Canvas (version 5), which provides control of scale factors and detailed dimensioning and object manipulation. During this phase an email dialog with RailDriver was established to determine details of the interface requirements. Controls utilize linear 10K ohm potentiometers for analog parameters and lever micro switches for discrete two-state parameters. Gauges are driven with servo motors typically used in remote controlled models and robotics. To support design of all of these, a family of low price plastic gears was found in a local hobby shop that permitted a range of ratios and physical size. Each cab element detailed design used these components as basic building blocks. [Continue]
- Boiler Pressure
- Cylinder Pressure
- Brake Main Reservoir Pressure
- Brake Equalizing Reservoir Pressure
- Brake Cylinder Pressure
- Brake Pipe Pressure
- Boiler Water Level, illuminated
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©2007 Doug Johnson. All rights reserved.