02.2 - Design Process

Physical Prototype 

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Figure 1. Four iterations of the prototype design

The scope of this prototype was to achieve our desired motion for one paddle when powered by a hand crank. What remains is to be done for the final design are: 

1. Build multiple copies of this mechanism, so that we can have multiple paddles 

2. Build the gear trains to power the mechanisms 

3. Build the boat body 

4. Constrain the paddle angle 

5. Build the interface between gear trains and motors. 

6. Configure Arduino wiring 

7. Write Arduino code 

Iteration Documentation 

• Version 1: Familiarizing ourselves with the motion 

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Figure 1. CAD Model for the initial four bar mechanism

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Figure 2. Physical model for the initial four bar mechanism

The goal of this simple design was to familiarize ourselves with a 4-bar mechanism and see if it seemed like this would be an ideal approach for our design. 

• Version 2: Component refinement 

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Figure 3. Physical model for the second version four bar mechanism

This design was more involved and had the goal of being as close as possible to the design/dimensions of what we were going to work with on our final design. The path had not been finalized yet, and this still did not have a way to connect to a paddle. However, this version gave us more experience with designing what our parts were probably going to look like, and prepared us for when we started including the non-planar components. 

• Version 3: First Assembly Attempt 

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Video 2. Physical Demonstration for the first assembly attempt of four bar mechanism

This design was our first attempt attempt at making the mechanism look like our final design. It included a base, and all the non-planer elements. We learned a lot more about how the path of the paddle behaved relative to the slider crank motion and additionally learned where we could miniaturize/adjust so that the design would fit better on a boat of the size we’re dealing with. 

• Version 4: Our Current Design 

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Video 3. Trajectory of joints shown in MotionGen Animation

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Video 4. CAD Model for the current design of four bar mechanism

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Video 5. Physical demonstration for the current design version of four bar mechanism

This design is largely the same as the third version. The changes made are to miniaturize the overall assembly and provide a better path by adjusting our mechanism link shape. This design provides a much flatter path in the underwater portion of the stroke, as well as providing more verticality when moving the paddle out of the water and back to the start position. 

Draft Bill of Materials