Launching Scale Model Roller Coasters with Linear Motors

Getting over the first hill

As anyone with coaster riding history would tell you, that first drop is one of the most important and thrilling aspects to the entire experience. The significance is not only found in the high level of excitement, but also the physics of how roller coasters operate. Due to the lack of extra kinetic energy being provided at any point except for the first hill, it must be the tallest point on the ride unless its train is set into motion with a launching mechanism such as a flywheel, linear induction motor, linear synchronous motor, or some other system.

Linear motors

Stemming from a lifelong love of roller coasters, YouTuber 3DprintedLife set out to build his own scaled-down version of a linear synchronous motor-based (LSM) coaster launch model. At its core, an LSM is just like any other DC motor in that it consists of coils of wire, a power source, and one or more permanent magnets, but unlike the more typical spinning variety, they push objects along a rail by utilizing a lineup of coils and precisely pulsing them on or off.

In his first attempt, 3DprintedLife had a couple custom PCBs fabricated that each contained 6 coils and positioned them about 1cm apart. He also created a high-power driver board that routes the incoming power supply across the coils and tightly controls their timing via a set of MOSFET driver ICs.

Building the coaster and track

For the coaster itself, 3DprintedLife drew heavily on existing coaster wheel assembly form-factors, meaning that his miniaturized version still had adjustable outer wheels, low-friction bearings, and a lightweight crossbar that connected the opposing sides together. The rails were created from malleable brass tubing for easier bending and joined using 3D-printed cross members.

A series of revisions

With his proof-of-concept working, a second set of PCBs were created that contain the coils as well as connection points for soldering a far more compact driver board underneath. This allows for multiple coil modules to be combined into a single, much larger launching mechanism while requiring a minimal amount of extra wiring. One problem 3DprintedLife encountered was a lack of real-time position feedback, as knowing what coils to energize and when is vital to achieving smooth accelerations, so a 1cm-accurate lidar module was added at the start of the launcher.

Launch

The last few steps of building this coaster launch project involved attaching additional train cars with ball-and-socket connections, reducing rolling friction even further thanks to new O-rings, and of course, introducing a pair of LED strips along the launcher's coils. To see more about how 3DprintedLife was able to construct an LSM-based launcher, you can watch his build log video here on YouTube.