After becoming a grandfather, I decided to create something special for my grandson. I wanted him to have toys that not only entertain but also stimulate his imagination and manual skills. That’s how my adventure with crafting wooden plywood toys began.
First Steps
Initially, my projects were very simple. I created a small drawer where a ball needed to be placed. Later, I made a carousel that could be spun, producing sounds as it turned. Both projects brought my grandson great joy, which motivated me to keep going.
The Tractor
As time went on, my grandson developed an interest in vehicles, especially tractors. While models for assembling are available in stores, their delicate construction makes them more suitable for display rather than play. I decided to create a model that would be resistant to falls and impacts.
I used a CNC milling machine of my own design to create my first tractor model. Figure 1 presents my first completed model.

Figure 1 – The first tractor model
Milling significantly simplified the preparation of the model, but a real breakthrough came when I acquired a laser cutter.
Using FreeCAD, I designed the tractor model, primarily using 6 mm thick plywood. Laser precision allowed me to create more complex and refined designs.
With FreeCAD, I could easily verify the accuracy of the design and adjust the dimensions. Once all elements were assembled, I could generate a list of required components and save them in DXF or SVG format, which are easily read by software controlling laser cutters.
Continuous Improvements
During the “use” of the toy, various flaws became apparent, especially in the attachment of elements. As a result, I rebuilt the tractor several times. In the final version, I began using not only glue but also mortise joints, which significantly improved durability and functionality. Figure 2 shows a version where I used special rings to connect the wheels to the axles and reinforced the fender, which was prone to breaking in earlier versions when dropped from a height. 😊 I replaced milled wheels with multiple laminated layers of 6 mm plywood.
The new version of the tractor is also wider than the prototype since Duplo figurines couldn’t fit in the seat before. Now they do. This principle is also applied to my other vehicle models.

Figure 2 – The latest version of the tractor with improved attachments
The Tractor Trailer
Encouraged by the success of the tractor, I continued developing new models. Each new toy was an opportunity to learn and improve my skills. Creating toys for my grandson not only brings me immense satisfaction but also allows me to spend time in a creative and passionate way.
Every tractor is meant to pull something. Naturally, my first thought was a trailer. Just like the tractor, the trailer evolved based on user feedback. It is worth mentioning that my friends’ children (the children of my children’s friends) also tested my models.

Figure 3 – The tractor trailer
The original trailer had a simple hitch (which was too thin) and rigid axles. The final version features a tilting platform, a reinforced and adjustable hitch, and a drop-down rear gate (Figure 3).
The lifting mechanism utilizes a gear and rack system. Due to space limitations, the gear is mounted on a pivoting bracket.

Figure 4 – The trailer attached to the tractor
The Fire Truck Ladder
Apart from tractors, my grandson also has a great passion for fire trucks. This led me to create a fire truck ladder model.
The ladder is two-segmented, extending via a gear and rack system.
The lifting mechanism also uses a gear and rack, with descent being locked by a ratchet mechanism.

Figure 5 – Fire truck ladder on a universal chassis
The ladder can rotate around its axis, with an appropriate angle locked by a ratchet and spring-loaded tensioner. Behind the cab, I placed a reel for the fire hose.
At this stage, I decided that the ladder’s chassis should be universal, allowing different structures to be mounted on it.
I also designed front wheels to be steerable and planned for the possibility of adding an electric drive in the future. This resulted in the creation of a modular chassis with a Bluetooth BLE-controlled drive system.
The Vehicle Chassis
The vehicle chassis is designed to accommodate various body types, just like real cars.
The truck cab is tiltable, and where the engine cover would typically be, I placed a storage lock for the battery.
The design allows for a non-motorized version, with the option to add a drive system later when the child is older. Figure 6 presents parts of the universal chassis. This is one of the early prototype versions.

Figure 6 – Vehicle chassis with a mounted battery module and drive module
Power is supplied by a 3.7V 18650 battery, which can be charged either inside or outside the chassis through a built-in power module.
The power module provides 5V for the ESP32 microcontroller and 12V for the drive motors.
The ESP32 microcontroller is also used in the joystick. Communication is handled via BLE (Bluetooth Low Energy), ensuring low power consumption.
The chassis is powered by a 48:1 geared motor, while the front wheels are steered using an SG-90 servo motor.
A short video of chassis testing is available here.
The joystick (Figure 8) is built on a custom PCB, milled using a 3D CNC router. It includes a direction stick and four function buttons that can be programmed for lights, a horn, etc.
A video of the PCB milling process can be viewed here.
It’s worth mentioning that my friend Mateusz, who wrote the first BLE control code, coined the name ZET-TOY, which has since been adopted.
Since BLE control is often used in universal mobile apps, my toys also support this feature. However, I’m not sure if a phone in a toddler’s hands is a good idea. 😅

Figure 7 – Chassis components

Figure 8 – Joystick with visible PCB
Crane
After my experience with the fire truck ladder, building a crane (Figure 9) was a natural continuation.
The crane has a two-stage extendable arm controlled by a rack-and-pinion mechanism, a telescopic boom with a gear system, and a cabin with sliding doors. The rotation of the entire crane is managed by a ratchet mechanism with a spring-tensioned locking shaft.
The cable runs through a block supporting the hook, is guided through rails on the arm, and is wound onto a drum using a crank.

Figure 9 – Crane model on a universal chassis.
Excavator
After the fire truck ladder and the crane, the next toy I designed was an excavator.
Designing the control mechanism took me several days. The challenge was to create a mechanism that would allow a child to operate the excavator arm with one hand while simultaneously controlling the bucket to scoop sand or other materials. Normally, real excavators use multiple levers, and each segment is operated by hydraulic cylinders. Since making wooden cylinders is quite complicated, I opted for a gear-based control system.
By carefully selecting the gear ratio and adjusting the arm lengths, I ensured that the excavator could be controlled with just one hand. A knob on the right side of the toy’s rear arm allows simultaneous movement of the front arm and the bucket with a single rotation. The knob also serves as a lever for raising the rear arm. A short video can be found here.
Another challenge with the excavator was the tracks. Real excavator tracks consist of metal segments connected by pins. I built my model’s tracks similarly. The 26 segments are made of three layers of 6 mm plywood. For the pins, I used 3 mm diameter wooden skewers. The outer segments are glued to the pins, while the middle segments remain loose, connecting the outer segments. A special tensioner with an M5 screw guided through a threaded hole is used to tighten the tracks. The tracks have small ridges that allow them to grip rough surfaces (e.g., carpet) and move effectively.
Due to the number of components, assembling a single track takes almost an hour, but I think it’s worth it.

Figure 10 – Excavator with a mechanism allowing one-handed control and moving tracks.
The track itself is shown in Figure 11. This was the first version, which was later replaced with a design that includes end stops to prevent the tracks from slipping off the drive wheels.

Figure 11 – One of the first versions of the excavator track.
Dump Truck
Once I had built the excavator, I needed a way to transport what it dug up (at home, we use chickpeas and a large 50×50 cm tray for play).
The dump truck needed to be able to unload its cargo. However, there was a challenge with the tilting mechanism. As I mentioned earlier, all vehicle bodies share a common chassis, and in this chassis, the space beneath the body is occupied by the drive system. I had to design the lifting arms so that they bypassed the drive and fit into the limited space in front of the wheels.
I used the same principle as in the tractor trailer, but this time, I positioned the mechanism on the sides. Using two synchronized gears made assembly a bit more complex, as both lifting arms had to be installed simultaneously (Figure 12).

Figure 12 – Dump truck with a visible gear-driven lifting mechanism.
The dump truck, of course, has a tilting tailgate for easy unloading.
Concrete mixer truck
The most challenging project so far has been the concrete mixer truck. First, its drum is essentially a series of cylindrical segments. Second, inside the drum, there is an auger that mixes the cement during transport and allows it to be emptied by reversing its direction. Third, the drum is powered by a bevel gear system. Given that my laser cutter only cuts at right angles, this was a tricky problem to solve.
Before designing the model, I thoroughly studied the construction of real cement mixers. I also had a conversation with a mixer truck driver who allowed me to take detailed photos of all the mechanisms and the interior.

Figure 13 – Concrete mixer truck.
Regarding the auger inside the drum, the solution was to use thinner 2 mm plywood. Initially, I planned to score the plywood to make it bendable (a common technique in 3D wooden models). However, after testing and dividing the entire spiral into four separate sections, I found that short segments could be stretched without breaking the plywood. In Figure 15, you can see the drum with the rear section of the auger installed.
The model includes all the necessary functional parts. The rear of the mixer features a ladder with an operator’s platform, a chute for loading “cement,” and a rotating discharge chute for unloading the mix (Figure 14).
The component sizes are large enough to use chickpeas or another safe material for play.

Figure 14 – Rear section of the concrete mixer truck.

Figure 15 – concrete mixer drum with visible auger inside.
For the cylindrical shape, I replaced it with a 24-sided polygon, assembled with precisely cut panels. This approach requires a lot of patience and careful sanding after gluing.
The bevel gear mechanism was another major challenge. Bevel gears typically have helical teeth, and their design reduces noise and increases contact surface. However, wooden toy gears only need straight teeth, so the main issue was how to cut a gear with teeth at a 90-degree angle.
In professional laser engraving and cutting, cylindrical objects are handled using specialized rotary attachments with three-jaw chucks. However, the required wheel dimensions would have necessitated not only purchasing such a system but also modifying my entire laser cutting setup. Since my laser machine is enclosed in a tent, with an overhead camera for precise image alignment, raising the platform by 20 cm was impractical. (Eventually, I did modify the setup, but much later.)
The solution I used involved cutting individual teeth separately and inserting them into a ring with corresponding slots. Although the teeth are not helical, the clearance from laser cutting, combined with the use of 6 mm and 3 mm plywood layers, allows the drum to rotate smoothly (Figure 16).

Figure 16 – Gear mechanism for rotating the cement mixer drum.
Summary
These are my current models. If I develop new ones (I’m working on a garbage truck and forklift), I will describe them here.
On the following pages, I provide materials to facilitate assembling my designed models. I also include links to my YouTube channel, where I post instructional assembly videos—don’t expect flashy effects or TikTok-style content, but you can always speed up the playback. 😊
Toy assembly kits are available in my Allegro store. You can also order them directly by emailing me at zbigniew.wlodarczyk@zetsystem.com.pl.
I’m happy to answer questions and assist with assembly. If anyone is interested, you’re welcome to visit my workshop in Poznań. I’d be glad to help if you’re planning to design your own toys. I can share how I do it using FreeCAD. Feel free to reach out.
I wish you enjoyable time crafting and playing with children.
Best regards,
Grandpa Zbyszek