Cats are naturally curious and energetic creatures, but indoor living can sometimes limit their opportunities for exercise. While commercially available cat exercise wheels exist, they often fall short in terms of design, durability, or simply not fitting specific needs. Driven by this, and a desire to create something unique, I embarked on a journey to build a custom treadmill for my cats. This project wasn’t just about providing physical activity; it was a fascinating exploration in design, 3D printing, and problem-solving. It’s still early days in terms of cat training on the treadmill, and they are learning at their own pace, often not quite as I envision, but the journey of designing and constructing it has been incredibly rewarding.
Why embark on building a cat treadmill myself? The simple answer is that existing solutions, both commercially produced and DIY designs, didn’t quite meet my criteria for various reasons, prompting a more personalized approach.
Design Journey: From Concept to Creation in Fusion 360
My starting point was extensive research into how others had tackled the challenge of building cat treadmills. I observed that many designs revolved around a central tube connected to bearings or similar configurations to what I envisioned. While acknowledging the success of center-mounted designs, I was concerned about potential cantilever issues and bending, steering me towards a different structural approach.
The entire design process unfolded within Fusion 360, a powerful 3D modeling software.
My core concept was to construct the treadmill using rails and interconnected planks. The initial hurdle was designing the rails themselves. I aimed for an I-beam shape, renowned for its exceptional stiffness-to-weight ratio. This design choice was crucial because, with one particularly active cat, minimizing the risk of the wheel toppling over was paramount. The I-beam structure allowed for the integration of small supporting side wheels, effectively preventing any possibility of the treadmill falling.
For the diameter, I settled on 120cm, a dimension that seemed appropriate based on commercially available models and suitable for comfortable cat movement. Furthermore, I prioritized a smooth, circular wheel motion over a polygonal one to minimize noise during operation, enhancing the user experience for both cats and humans.
I-Beam Rail Design and 3D Printing Considerations
The I-beam rail design was an iterative process. I started by creating a profile that I believed was sufficiently robust, imported it into a slicer software to estimate its weight, and then refined the dimensions based on these estimations. The goal was to achieve a balance between strength and material efficiency.
My intention was to print the rails on their side, oriented at a 135-degree angle. This orientation results in a manageable 45-degree overhang, easily printable on most 3D printers, followed by a 10mm bridge, also well within my printer’s capabilities. Looking back, I believe further optimization for weight reduction through more simulations could have been beneficial, although the current design proved functional.
Modular Rail System for Large-Scale Printing
Given that my 3D printer’s build plate (210x250mm) was too small to print a 120cm diameter ring in one piece, I opted to split the rails into segments for printing and then join them. M5 bolts and nuts were chosen as the joining mechanism for their ease of use and secure fastening.
Both ends of the rail segments were designed with interlocking features to ensure precise alignment and easy assembly. The printed parts indeed interlocked as intended, simplifying the construction process.
Wheel System: Ensuring Smooth and Stable Rotation
The wheel system was conceived to support the treadmill’s rotation from below with main wheels and prevent lateral movement or tipping with side wheels running along the I-beam rails.
Having a surplus of 608ZZ bearings readily available made them the natural choice for this project.
Assembly of the wheel system relies on M8x50 socket cap head screws, washers, and locknuts. Holes were intentionally designed undersized to be drilled out post-printing for enhanced precision. Elongated slots at the base of the assembly allow for frame mounting adjustments, accommodating potential inaccuracies during frame construction.
The most challenging aspect was determining the correct spacing for the side wheels. Initial measurements proved too tight. A slotted design for adjustability was considered but deemed cumbersome. Ultimately, precise measurement of a printed rail segment provided the accurate dimension for the final wheel spacing.
The wheels themselves were printed using a flexible filament branded as Noctuo grip soft, described as being similar in hardness to cooked spaghetti. The exact material composition remains unclear, but its flexible nature was ideal for providing grip and reducing noise.
Robust Steel Frame for Stability
Welding was chosen for frame construction for two primary reasons: personal enjoyment of welding and the inherent stability offered by a heavy steel base, which lowers the center of gravity. While a wooden frame could suffice, potentially weighted down with concrete slabs for added stability, steel offered a more robust and streamlined solution.
The final frame, although dimensionally consistent with the drawing, features slight design variations. Wheel assemblies are secured to the frame using M8 bolts and rivet nuts.
Track Construction: Plywood Planks for Feline Footing
The treadmill track is constructed from 30cm wide, 9mm thick plywood, cut at a 5-degree angle. A total of 36 pieces were required. The precise plank width and mounting hole placement were determined by the preceding design dimensions and finalized through measurement.
Plank mounting involved attaching one plank to a single rail segment and the subsequent plank spanning across two rails, aiming for increased stiffness. M5 countersink screws were used for a flush finish. Holes in the rails were designed undersized for tapping, totaling 144 holes. In retrospect, heat-set inserts might have been a more efficient and less error-prone alternative to tapping, as some tapped holes proved less secure.
Assembly Process: Bringing the Treadmill to Life
Assembly commenced with welding the frame (unfortunately, photo documentation is limited) and printing wheel assemblies and initial rail segments.
A test fit confirmed the design’s feasibility, prompting the continuation of parts printing. The project then experienced a multi-month pause. Resuming, I focused on plank fabrication. A custom sled with a 5-degree angle was constructed to ensure precise and repeatable plank cutting from 30x100cm plywood sheets.
After cutting the planks, holes were drilled and countersunk for flush screw mounting.
The planks were then coated with a matte floor lacquer for durability and a desirable finish.
With all components prepared, final assembly proceeded systematically from the base upwards.
The completed DIY cat treadmill:
“And what am I supposed to do with it, human?” – a common feline sentiment upon encountering new contraptions.
Future Enhancements
Several improvements are planned for the cat treadmill:
- Adding adjustable feet to level the frame on uneven surfaces, replacing makeshift cardboard shims.
- Constructing paneling for the frame to enhance safety and aesthetics.
- Incorporating a brake mechanism to prevent unsupervised use, especially important when it’s located on the balcony.
- Applying carpet to the track surface to provide better grip and prevent slipping for the cats.
Bill of Materials
- 36 rail segments (3D printed)
- 36 plywood planks
- Stainless steel fasteners:
- 144 M5x30 countersink screws
- 72 M5x45 socket cap head screws
- 72 M5 nuts
- 16 M8x30 socket cap head screws
- 16 M8x50 socket cap head screws
- M8 washers
- 24 608ZZ ball bearings
- PETG filament (for 3D printed parts)
- Flexible filament (for wheels)
3D Printing Settings
- Walls: 4 per part, 999 for wheels (solid fill)
- Layer height: 0.3mm (fast profile for Prusa MK3S)
- Infill: (Retrospectively) 2 walls, potentially 4 in high-stress areas, minimal infill for rails to reduce weight.
