Well Windlass (Part 1 of 3)

For our second assignment, we were asked to design a well windlass that spans a gap of 12cm between two tables and has a crankshaft that can be used to lift a 1L bottle of soda 10 cm above the table. We were limited to using 500cm^2 of Delrin sheet and 50 cm of Delrin rod for our final model.

Brainstorming

Kirsten and I decided to work together for this assignment and came up with some ideas for our windless design. 

Our first idea was the trapezoidal windless, where we would have two trapezoids as support and the Delrin rod going through the middle. However, this idea did not seem structurally stable.

The second idea was the pyramid windless, where we would have triangles as the support and a short piece of Delrin rod running through the middle for the string to wrap around in. We thought using a shorter piece of Delrin rod will decrease the deflection. However, with a flimsy and thin Delrin rod, it would take a lot of effort to pull up the soda bottle with this model.

Our third idea was to make a wheel using the Delrin rod and have the string wrap around it. This would drastically decrease the amount of rotations the crankshaft would need to make in order to pull up the bottle. Since we are making the wheel with multiple Delrin rods, the force from the bottle (mg) would be distributed amongst the rods rather than having one Delrin rod bear all the force. Also, our roof-like triangular shape provided structural stability because it has less degrees of freedom than a trapezoid shape.


One problem we ran into with the wheel model is figuring out the best positioning of the wheel. If the wheel was on top of the roof, it would be awkward to turn the crankshaft because the person would have to reach up to the top of the roof. We then had an idea of attaching the wheel directly to the roof, but that also had some problems because it would be hard to have the wheel secured onto the roof while still being able to rotate it around the axis. 

Brainstorming

 

 Finally, we decided to have a support for the wheel that would be press-fitted onto the roof. This way, we could turn the wheel without having to worry about the wheel falling out.

Rough Sketch of the Model

 Based on our sketch, we wrote out some dimensions of the parts before making the foam core model.

Dimensions

Making a Foam Core Model

Foam Core Model

We made a simple foam core model using the rough sketch of the windlass. When we tested our foam core model, we realized that our roof was too narrow for the bottle to fit through the supports. In order to fix this problem, we decided to make the roof wider. To compensate for the materials used to make the roof wider, we also decided to decrease the diameter of the wheel by a centimeter and make the roof shorter.

(To Be Continued.......)