Well Windlass

The second project of the class was to create a well windlass that would span a 12 cm gap between two tables and be able to lift a filled 1 liter bottle 10 cm above the gap in less than 45 seconds, and if possible under 30 seconds. We were limited to using 50 cm of Delrin rod and 500 square cm of 3/16" Delrin sheets. My partner for this project was Nanaki.

example of a well windlass

We started brainstorming ideas of how we wanted our windlass to be. We knew we needed to make the round part of the windlass which the string would wound around, a crank to turn the round part, and a base to hold it. 

During brainstorming, I focused on how to make the string wound around more of the round part so that it could pull up the bottle faster. I thought that perhaps cutting the rod into four 10 cm rods and one 2.5 cm rod and 7.5 cm rod and then attaching the four rods onto two round pieces of delrin sheet would create a larger area for the string to wrap around instead of just having it wrap around one rod. The 2.5 cm rod would then be attached to one side of the round part and the 7.5 cm rod on the other side. The rods and sheets would be attached through the hole and peg mechanism where the rod would be the peg and the holes would be in the sheets. 

We then had to figure out what would hold the round part of the windlass. We decided to have two rectangular sheets standing on each side of the 12 cm gap with a slot on the top for the round part of the windlass to rest on. These rectangles would then be attached to a square sheet and then a thin rectangular part would stand on an angle to connect the square part laying down and the rectangular part standing up. We also decided to have a smaller rectangular part attach to the square part to kind of hug the table. We thought of attaching the base parts by heat staking them since we wanted our base to be pretty strong and not to pop off of holes.

We also thought of using gears in order to have the crank turn the round part faster. We saw a video on YouTube which made us think of building the round part as two tubes of different diameters so that the bigger tube rotates in one direction while the smaller one goes the opposite way. This would allow the bottle to be steadily pulled up. 

We made a cardboard prototype of our first idea and reserved our gears and alternating tubes ideas to be thought of more for the next day. 

We decided that it would very complicated to learn how to draw gears on SolidWorks and we could not figure out how to make the alternating tubes idea and so we just stuck with our first idea.. So we then calculated an approximate area of our windlass and it was well over 500 square cm and so we decided to decrease the area of our windlass by creating triangular cutouts on the base parts. 

As Amy went around seeing how our designs were coming along, she let us know that we would encounter the problem of the weight of the bottle pulling the two base parts inwards towards the gap and so we would need something to push back the base parts. So we then decided to add two beams that would span the gap and be attached to top portions of the two standing rectangular parts. Because the round part was much taller than the base, we needed to add 5 more cm to the top so that we could attach the beams and the round part could still turn.

We began creating our SolidWorks drawings and by the end of the day we had drawings of two of our base parts: the square lying down with holes and pegs, and the rectangular hugging the table with holes on one side. 

We then printed out practice holes and pegs to make sure that they would fit tight enough. We made the pegs 3/16" by 3/16" +0.3 mm since the sheet was 3/16" thick. We added the 0.3 mm to account for the laser cutter cutting more than what the drawing states. The holes were 3/16" by 3/16". Although we initially thought of heat staking the holes and pegs together, we found that our holes and pegs were a very good tight fit. The holes for the Delrin rod were best tightness at 6.25 mm. 

We printed one side of our base and we found that we cut out too much. The base seemed too thin and not stable enough to hold standing rectangle and the round part. 

We also wanted to change how we turned the round part. Initially we thought of turning it from the middle of the round part but it would be more effective to have the crank on one side of the circle so that per turn we did the round part would turn the same amount.

So we decided to rethink our design to incorporate a larger, stronger base that could possibly hold our new-ish round part. We came up with triangular bases with one side being an A that would have a hole near the top where one side of the round part would attach to and the other triangular base would be half a triangle with one side of the round part sitting on it. Another curved part would attach to the half triangle to hug the round part of the windlass and hopefully hold it enough. Two beams would go across and attach the two triangles and keep them from being pulled inward by the weight of the bottle. 

When we printed out our design though we found that the half triangle did not keep the round part steady at all as it turned. We thought of perhaps extended the half triangle so that it would hug half of the round part but we decided to print out another one of the A triangle to attach the round part both in the middle. By doing this though, we would be able to directly turn the round part like we planned. We solved this problem by attaching another round part on the outside of the triangle with a rod attached to it. We could then turn this wheel in order to turn the round part of the windlass. 

When we printed out the parts and put it all together, we found that the structure could hold the weight of the bottle but it was not able to turn and pull it up because the holes for the rods were not tight enough and so every time we tried to turn the wheel, only the rods would rotate around their holes and not rotate the whole round part. Other people were having this problem and they told me that I had to connect the rods to the circles using piano wire. A bushing would be attached to the circles perpendicularly using piano wire and then piano wire would be used again parallel to the circles and through the rod. This only had to be done to the side of the crank but it had to be done to the crank it self as well as the circle part it was attached to. But after all that work, we finally had a working windlass! The only thing we had left to change was to make a slightly larger rectangular base since our base was a bit small and if the windlass slid around, it would just fall into the gap.

Engineering Analysis:

We tried solving the problem of beam bending by having shorter rods to hold the water bottle and there were more of them a little bit spaced apart so the downward force of the bottle would not only be exerted on one rod at a time but two at a time. The structure was pretty sturdy due to the triangular standing parts being thicker and they were attached to larger rectangular bases. We tackled the time specification by first having a round part that would wind up more of the string per turn but also by making the crank easy to turn. Having a wheel like crank made it much easier to turn the whole round part which allowed us to bring up the bottle in less than 30 seconds. 

Reflection and the future:

It would have been really nice to figure out our first few designs would not be stable enough or would not work at all much earlier in the process. It's a lesson to us to next time try to create our drawings and prototypes much sooner so that we have more time to address their problems and create solutions. 

If we had a bit more time, I would love to add a part that hugs the table so that I would not need to hold down one side of the windlass as I turned it. I would also try to thin out the base in order to use less material. I would also like to try using the square/rectangular beams for the round part that the string would wind around. Another team did that and I thought it was amazing. It was such a great idea so I would really love to see how it would help my design. It would most likely remove my need to piano wire the circle parts and the rods together which would be really great since the piano wires kind of stick out a bit and could possibly be a hazard. 

Accounting:

Triangle Base Part (A): 102.31 sq cm each * 2 = 204.62 sq cm

Rectangular Base Part: 20.08 sq cm each * 2 = 140.16 sq cm

Circle Part/ Wheel: 45.67 sq cm each * 3 = 137.01 sq cm

Bushings: 2.84 sq cm each * 8 = 22.72 sq cm

TOTAL: 504.51 sq cm

All 50 cm of Delrin rod was used.

The four bushings in the round part are not really necessary so if we removed them, our area would instead be 493.15 sq cm. We added them to the structure at the very end to hopefully keep the string in the middle of the round part.