Cat-Sized LEGO Train: Turning Bricks Into a Ride Your Pets Can Actually Use

Inspired by the “Building a Cat-Sized Lego Train” video—an RC build with 3D-printed rails and wheels sturdy enough for two cats, Cookie and Muffin. 

Every now and then a LEGO project comes along that redefines what’s possible with plastic bricks. A recent video showcases exactly that: a remote-controlled, cat-sized LEGO train running on custom 3D-printed rails and wheels—robust enough to carry two very relaxed passengers named Cookie and Muffin. It’s not just adorable; it’s a masterclass in hybrid building, where standard LEGO geometry meets bespoke printed parts to overcome real-world constraints like weight, traction, and track tolerances. 

At the heart of the idea is scale. Traditional LEGO trains (even hefty 8-wide builds) are designed for minifigs, not mammals. The moment you scale a carriage to pet size, everything changes: wheel loads increase dramatically, curves demand gentler radii, axles and bogies need smoother rotation, and the chassis must resist torsion without becoming a brick-eating behemoth. The video’s solution is elegant—keep the “look and feel” of LEGO for the visible bodywork and interior, but offload the most demanding structural and mechanical loads to 3D-printed components. Custom rails provide consistent gauge and grip; printed wheelsets with proper flanges and bearings tame rolling resistance; and an RC drive system delivers smooth starts and stops that won’t spook feline riders. 

The result is a playful proof-of-concept for AFOLs: when your build crosses into “rideable” territory (for pets, plushies, or props), pure LEGO may struggle with shear forces, axle friction, and part availability. Hybridizing lets you keep the creativity and modularity we love about LEGO while leveraging printed parts where physics demands it—think wheel hubs with press-fit bearings, rail joiners that lock with LEGO studs for scenery, or underframes that hide steel rods. Crucially, the design still builds like LEGO: SNOT panels to shape the cars, tiles for a clean studless finish, bracketed interiors for padding, and click-hinges to dial in comfortable backrests for your VIP passengers.

Beyond the novelty, this project is a blueprint for experiential MOCs: displays that move, entertain, and invite interaction. Imagine this concept at a LUG show—kids guiding a “pet tram,” a treat-stop station, or a themed fairground loop with animated props. If you’ve ever wanted your layouts to do more than circle the tracks, this is your invitation. Start with the vibe of a classic LEGO build, then add the invisible muscle where it matters—drive, rails, and safety.

TL;DR: Use LEGO wherever the aesthetics and modularity shine; use 3D-printed parts for the high-load, high-precision bits. Your cats (and your bearings) will thank you. 

Tips: How to Use (and Adapt) This Technique

• Plan your scale & payload first. Weigh your passenger (cat, plush, camera rig) and size the car accordingly. Bigger cars need gentler curves (think large-radius track sections). 

• Hybrid rails & wheels. Keep the body LEGO; print the rails and wheelsets for strength, true gauge, and flange geometry. Press-fit bearings reduce drag and noise.

• Low center of gravity. Put batteries, motors, and any metal reinforcement as low as possible. Build seating on the chassis, not above a tall pedestal.

• Reinforce the underframe. Layer plates in alternating directions, use Technic bricks with axles/pins for torsional stiffness, and consider hidden rods or printed spine pieces.

• Gentle power delivery. Use RC control with smooth throttle curves. Start slow, test unmanned, then do short, supervised rides. 

• Track joins & alignment. Print rail joiners that key into each other (and optionally onto a LEGO-built ballast bed) to reduce kinks that could derail at low speeds.

• Comfort & safety. Add padded tiles or foam inserts, side walls high enough to prevent tipping, and a simple soft harness or removable bar if your pet is squirmy.

• Modular cars. Separate the drive unit (locomotive) from payload cars so you can swap bodies (open gondola, enclosed coach, themed tram) without redoing the drivetrain.

• Serviceability. Make the roof or floor removable with a few pins. Quick access to batteries, ESC, and receiver keeps the fun going.

• Aesthetics last. Tile over studs for a polished look and use SNOT brackets for curvature—after you’ve proven the chassis handles the weight.

Ideas: MOCs You Can Build With This Approach

• Pet Parade Tram: A low, open car with padded sides for cats or small pets; station platforms built from LEGO with printed rail beneath.

• Theme-Park Peoplemover (Display-Only): Oversized cars moving plush figures around a micro-park—perfect for LUG events.

• Treat-Stop Loop: A slow train that pauses at decorative stations; attendants hand out treats while the train idles (keep pets supervised).

• Maintenance-of-Way Speeder: A chunky work car with tool crates, signal arms, and a printed snowplow or brush head for outdoor demos.

• Mining Tram Diorama: Rockwork, tunnels, flickering “lantern” LEDs, and sturdy printed rails for reliability under load.

• Garden Express: Weather-tolerant printed track on a patio path; LEGO scenery modules (shrubs, fences) clip on and off for storage.

• Camera Car Rig: Stabilized platform for a lightweight action cam to film your LEGO city at “eye level.”

• Monorail-Style Shuttle: A single-beam printed track with LEGO cladding—sleek look, simplified guidance.

• Delivery Wagon for Shows: Move giveaways or parts bins between tables—great conversation piece at conventions.

• Holiday Coach: Re-skin the car for seasonal displays (Winter Village coach, Halloween ghost car, birthday party train).

Projects like the cat-sized LEGO train prove that when you blend LEGO’s creativity with custom engineering, you unlock experiences that delight both builders and audiences. Start small: prototype a robust chassis, print a short test section of track, and iterate until the ride is smooth and quiet—then dress it with the LEGO styling you love. Whether you’re building for a pet cameo, a show demo, or an interactive display at home, this technique turns a static model into a moving memory. If you want a spark to get going, watch the original video for inspiration—the RC train, 3D-printed rails and wheels, and those chill co-conductors Cookie and Muffin will have you sketching track plans in no time. 

Happy building—and safe travels to your tiniest passengers!

Disclaimer: This article was created with the assistance of AI. While efforts have been made to ensure accuracy and originality, the content may include automatically generated text and should be considered as informational only.