Inspired by the vast catalog of industrial parts at McMaster-Carr, and fueled by a passion for railroading, I embarked on a unique project: building my own pedal-powered train. As a volunteer at the Los Angeles Live Steamers Railroad Museum, I was eager to create a personal locomotive to navigate the museum’s extensive 1.5-mile track within Griffith Park. Instead of replicating a traditional locomotive, I opted for a “pedal car” design, enhanced with modern engineering and readily available components.
My vision was to minimize complex machining by adopting a modular construction approach. I chose 1.5” square extruded aluminum, commonly known as “80/20”, for the frame. To augment human power, I integrated a Bafang BBS02 750W mid-drive motor kit, typically used for electric bikes. This motor offers both pedal assist and full electric drive, promising to simplify the build process compared to traditional pedal cars or electric speeders. This reliance on Commercial-Off-The-Shelf (COTS) parts led me to christen my creation the McMaster-Car, a nod to the industrial supplier that made this approach feasible.
Before detailing the build, I was fortunate enough to have Lisa from Lisa K Entertainment experience the McMaster-Car firsthand during a visit to LALS. She captured the train in action in a fantastic video, alongside other content showcasing the museum and its public train rides.
Suspension System: Waterjet Precision
The suspension system was one area where custom fabrication was unavoidable. However, I streamlined the process by utilizing the Caltech Jim Hall design lab’s Flow Mach 2B waterjet cutter to produce key components.
Alt text: High-angle view inside a waterjet cutter as it precisely cuts steel plates, shaping components for the McMaster-Car train suspension system.
After the waterjet process, minimal machining was required. I finished the parallel flat surfaces and chamfered the posts that align the springs. The bearing blocks, however, demanded more manual machining, primarily using a Bridgeport mill equipped with a ProtoTRAK conversational CNC controller to create the bearing pockets.
Alt text: Close-up of partially assembled McMaster-Car train suspension components showcasing the waterjet-cut plates, machined bearing blocks, and springs.
Wheels and Axles: Meeting Industry Standards
For the wheels, I again leveraged a ProtoTRAK-equipped lathe to machine the 4” diameter wheels to meet the International Brotherhood of Live Steamers (IBLS) specifications. A keyway was broached into each wheel to ensure secure indexing on the locomotive’s two 1” axles.
Alt text: Four silver train wheels, machined to IBLS standards, arranged to display their size and keyway, essential components for the McMaster-Car project.
Frame Construction: Modular Aluminum Extrusion
With the suspension and wheels complete, the frame assembly could begin. Instead of fabricating complex interconnecting plates, I again opted for efficiency by waterjet cutting them from scrap aluminum, utilizing readily available CAD drawings found online for standard aluminum extrusion joinery.
Alt text: The foundational frame of the McMaster-Car train, built with 80/20 aluminum extrusion and various waterjet-cut adapter plates, showcasing the modular design.
Braking and Powertrain: Integrating a Geared Hub
Implementing a braking system presented a unique challenge due to the sprung axles and their inherent play. The solution was to locate the brake within the powertrain, between the axles and the motor. A suggestion from a fellow enthusiast led to the adoption of an internally geared hub, some of which are designed to accommodate a brake rotor. I selected a Shimano Nexus SG-3D55 3-speed hub. In the setup, the e-bike motor’s input sprocket is on the left, and the ANSI 40 chain output to the front axle is on the right.
Alt text: A Shimano Nexus SG-3D55 3-speed geared hub centrally mounted on the McMaster-Car, showing the input sprocket from the motor and the chain output to the axle.
To transmit torque from the hub’s output to the chain, a custom sprocket was needed. I machined the center out of a larger flat sprocket using another conversational CNC mill, then drilled and tapped holes to match the bicycle wheel spoke flange on the hub.
Alt text: Detailed view of the custom sprocket mounted to the geared hub’s output, highlighting the machining and integration within the McMaster-Car’s drive system.
The sprocket tooth counts were carefully selected to prioritize torque:
- Motor output: 44 (Bicycle single speed chain)
- Hub input: 16 (Bicycle single speed chain)
- Hub output: 24 (ANSI 40 chain)
- Axle input: 17 (ANSI 40 chain)
- Axle to axle link: 12 (ANSI 40 chain)
Motor Mounting and Electrical System: E-bike Simplicity
The Bafang BBS02 motor was mounted in an inverted orientation compared to its typical e-bike configuration. This was achieved using waterjet-cut plates and a welded tube, creating a robust and adaptable mount. This assembly, pictured on a short extrusion piece, also includes an “18W” (actually 12W) off-road spotlight intended as a headlight.
Alt text: The motor mount for the McMaster-Car, constructed from waterjet plates and welded tubing, with a mock-up headlight attached, demonstrating the motor integration.
With the motor mount in place, the McMaster-Car began to take its final form. To optimize ergonomics, I switched to aftermarket 140mm crank arms, shorter than the stock 152mm, to better suit the motor and seat positioning.
Alt text: The almost complete McMaster-Car train, showcasing the assembled frame, motor, wheels, and suspension, ready for electrical and finishing touches.
The Bafang BBS02 motor’s integrated electronics simplified wiring. It draws 48V directly from a 15Ah 13S3P 21700 Li-ion battery pack. A secondary 48V feed powers a DC/DC converter, generating 12V for accessories. An enclosure at the frame’s end houses 12V fusing, switching, and distribution for components like the headlight, a small motorcycle horn, a phone charger, and the FRED (Flashing Rear End Device). The FRED, often required for nighttime scale train operation, is implemented using a motorcycle brake light and a digital PWM generator module.
Alt text: The rear enclosure of the McMaster-Car, showing the illuminated FRED (Flashing Rear End Device), a safety feature for nighttime operation, and electrical components.
Test Run and Future Enhancements
With zip ties and a boat seat added, the McMaster-Car was ready for its maiden voyage!
Alt text: The author seated on the McMaster-Car, ready for a test run, showcasing the completed pedal train and its boat seat.
Riding the McMaster-Car around the LALS track is a truly exhilarating experience. Future updates are planned, including adding a coupler and airbrake system for compatibility with riding cars, and refinements like cup holders and more ergonomic handles.
Alt text: Front view of the McMaster-Car train on the tracks at LALS, highlighting its unique design and construction, ready for another run.
For a firsthand look at the McMaster-Car in action, here’s nearly 10 minutes of unedited track footage, perfect to accompany a reread of this build log.
