Well Windlass

Here are all of our sketches that we made during the brainstorming process. We decided to go with the cubic structure because we thought it would be sturdiest. 

Here is our first physical mock-up. After building this and trying to wind the string around the pencil, we decided that the rod and holder needed some more work. We decided to put the rod through holes in the taller sides of the top of the cube in order to make sure we met the requirement that 10 cm of the water bottle be above the table. Putting the rod through holes instead of just setting it on curves in the frame would also ensure that it would not come out of the structure when we were cranking it.  We also decided that since torque = radius * force, we could increase the torque of the rod and pull the water bottle up faster by increasing the radius around which the string rotates. We decided we would make some kind of a spool to slide onto the middle of the rod in order to accomplish this. 

Here's a SolidWorks drawing of the base of our windlass. One thing we had to account for when designing our parts in SolidWorks was how different the dimensions of pegs and slots would be after the laser cut them out. We therefore designed the slots to be 0.2 mm smaller than we wanted to ensure we would have a tight fit. We also printed small testers for our pegs and slots to check the fit before printing the whole part. 

Here is the first iteration of our base. We soon realized after printing this that, since we had changed the side through which the rod would go, we needed to rotate the slots in our base. Otherwise, we would have to put the short side of the rectangle (11 cm wide) over the 12 cm gap between the tables, and that wouldn't be very sturdy. 

Here is the first complete iteration of our well windlass. At first, it didn't work because the rod was rotating inside the handle and the spool and the spool (made of 6 pieces) was sliding apart and the string would get stuck between two pieces. We drilled two horizontal holes through the spool and added piano wire to hold all 6 pieces together, and then we drilled a vertical hole through one spool and the rod and inserted piano wire to ensure that the spool and the rod would turn together. We also drilled a hole and added piano wire to the handle and the rod to cause the rod to turn when the handle was turned.  We bent all the ends of the wires sideways so that they wouldn't come out.

A close-up of our final design sitting over the "well." I worked pretty well, but the base moved quite a bit while we were lifting the water bottle. We decided to make a stabilizer to help with this. 

This is the part we made to stabilize the base. It went inside our windlass, between the tables, and clipped over the slides of the windlass. It provided a little stabilization, but was a little too loose to really help. With some more iterations, it would probably work really well. 

Here is our calculation of how much Delrin was used for a final product, approximately 490 squared centimeters. 

Engineering analysis: As mentioned above, the main physical consideration was how to increase the torque of the rod in order to lift the water bottle within the time limit. We accomplished this by increasing the radius of the rod where the string was by adding the spool. Another consideration that was problematic for some was the deflection of the rod. Since deflection is proportional to L^3, the length played a big roll in determining how much the rod would deflect. Our rod was pretty short, since it only had to be a little longer than the 12 cm gap, and therefore it did not deflect enough to cause problems for us. 

If given more time, we would work to make sure the stabilizer fit securely between the tables, and if we had a higher Delrin budget, we would add a second stabilizer. We also might work on making an equally sturdy design while decreasing the amount of Delrin used, perhaps by using a triangular design for the sides of the windlass instead of rectangles, like some of the other students did.