13.4 Implementation

Fabrication and Assembly

3D Printed Links

All links were 3D printed with 17 mm holes to press fit the 606 2RS ball bearings. The link dimensions were derived from our kinematic analysis and are listed below:

• a = 114.0 mm

• (triangular link combination — a link as base and l link as height)

• b = 124.5 mm

• c = 117.9 mm

• d = 120.3 mm

• e = 167.4 mm

• f = 118.2 mm

• g = 110.1 mm

• h = 197.1 mm

• i = 147.0 mm

• j = 150.0 mm

• k = 185.7 mm

• l = 23.4 mm

• m = 45.0 mm (crank)

3D Printed Gears

We also 3D printed two gears with a 2:1 gear ratio. Each gear included a bore hole for the 6 mm stainless steel rod. The combined gear radius matched link m (45 mm), which serves as the crank. The 2:1 ratio allowed the DC motor to provide sufficient torque while maintaining an appropriate walking speed.

Assembly

Each joint was assembled using a 40 mm × 6 mm stainless steel rod/shaft passed through the 17 mm bearing seats in the links. Two 606 2RS ball bearings were press fit into each link joint (24 bearings total across 9 joints) to ensure smooth, low friction rotation. The entire linkage mechanism was mounted onto wood scraps that served as the rigid frame/chassis. This frame was then secured to a small skateboard, which acted as the base platform and provided wheels for forward locomotion. Nails and screws were used to fasten the wooden frame and motor mount.

Bill of Materials

The following table lists all the parts used in our implementation:

We also 3D printed gears that were had a hole for the gear and a hole for one of the rods. The gear ratio was 2:1 with combined gear radius of link m(45 mm) which is the crank.

Then we

Electronics and Circuitry

The electrical system centered on a single 12V DC motor that drives the walking mechanism through the 3D printed gear train. The motor was mounted to the wooden frame and coupled to the crank gear via a stainless steel shaft.

our electronics were pretty simple, as stated before the motor was attached to the board and then we had an 8 double A battery pack attached to the board.

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Fabrication and Assembly

3D Printed Links

All links were designed in CAD and 3D printed using PLA filament. Each link was printed with 17 mm holes at the joint locations to press fit the 606 2RS ball bearings. The link dimensions were determined from our kinematic analysis and are listed in the Bill of Materials above. Link a served as the frame/ground link, while link m (45 mm) functioned as the crank, driven by the gear system. One link assembly used a triangular configuration, combining a standard link as the base with link l as the height.

3D Printed Gears

Two gears were 3D printed with a 2:1 gear ratio. The combined gear radius matched the crank length (link m = 45 mm). Each gear was printed with a center hole sized to fit snugly onto the stainless steel rods. The larger gear was fixed to the crank shaft, and the smaller gear was coupled to the DC motor output shaft. This 2:1 reduction gave us increased torque at the crank, which was necessary to drive the full weight of the linkage and skateboard platform.

Assembly Process

1. Bearings into links — Two 606 2RS ball bearings were press fit into each 17 mm hole on every link (24 bearings total across the mechanism).

2. Rods through joints — 40 mm × 6 mm stainless steel rods were inserted through the bearings at each of the 9 joints, allowing smooth rotation.

3. Frame mounting — The fixed frame link (link a) was mounted to a wooden base using screws and wood scraps. The wood base provided a rigid structure to hold the mechanism upright.

4. Motor and gear attachment — The 12V DC motor was mounted to the wooden frame. The small driving gear was attached to the motor shaft, meshing with the larger driven gear on the crank rod.

5. Skateboard platform — The entire wooden frame and linkage assembly was secured onto a small skateboard using nails and screws, allowing the mechanism to translate forward as the legs walked.

Electronics and Circuitry

The electrical system for this project was kept simple to match the scope of the mechanism. A 12V DC motor served as the sole actuator, providing rotational input to the crank through the gear train. The motor was powered by a 12V DC power supply. Wiring ran from the power source directly to the motor terminals, with the polarity determining the direction of walking (forward or reverse). No additional motor driver or microcontroller was required, as the mechanism only needed continuous rotation at a constant speed.

Software Development

This project did not require any software or microcontroller programming. The walking motion was achieved purely through the mechanical linkage geometry — once the DC motor was powered on, continuous rotation of the crank produced the desired walking gait through the kinematic chain. All trajectory and motion behavior was embedded in the physical link dimensions and joint configuration determined during the kinematic analysis phase.

Physical mount

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Initially, we designed a 3D printed stand for the AC motor to be attached to and mounted onto the skateboard.

However, due to motor malfunctions at the very end of the project, we were forced to scrap this design entirely. Because we had to switch from the AC motor to a DC motor with different dimensions, we needed a mounting solution that could be built quickly. We ended up going with wooden boards, as wood was the most readily available building material at that point.

We used three boards, each serving a specific purpose:

• Vertical Support Board: This board kept the entire linkage mechanism upright and was adjusted so that the legs would barely make enough contact with the ground to push the skateboard forward. Getting this height right was critical; too high and the legs would not touch the ground, too low and they would dig in and stall the mechanism.

• Base/Adjustment Board : This board was laid flat to increase the mounting surface area on the skateboard. The extra surface area allowed us to adjust the position of where the leg mechanism was placed, letting us fine tune the contact angle and alignment with the ground.

• Counterweight Board: The third board extended to the opposite side and acted as a counterweight to balance the mechanism. We attached the battery pack to this board, which served a dual purpose: it provided the necessary counterweight to keep the skateboard from tipping over, and it kept the power source securely mounted. This is another reason we went with wooden boards they gave us a convenient surface to strap down the battery pack.

All of these boards were attached to the skateboard and to each other using wood nails and wood screws. As stated before, due to the lack of time we had to scramble to get our materials, which is why our final product might look rough around the edges. However, the wooden mount ended up being surprisingly functional it was quick to build, easy to adjust, and rigid enough to hold the mechanism in place while the legs drove the skateboard forward.