Well Windlass

The Assignment:
For this next project my partner and I had to build a model of a well windlass that can span a well of 12 cm and lift the cap of a 1 liter bottle of water at least 10 cm from the top of the table. This must be done using a sheet of delrin with a total surface area of less than 500 cm^2 that is either 1/8 in or 3/16 inches thick.

Brainstorming:

Before putting pen to paper I thought about mechanisms that I see in my everyday life that function similarly to a windlass and what makes them effective. Since I swam in high school and worked as a lifeguard for two summers, the thing that stuck out in my mind was the mechanism that is attached to the end of a lane line that is capable of cranking the lane line until it is taught. As well as the giant spool that was used to take the lane lines out of the pool entirely. I also considered how the tuning pegs of a stringed instrument make the strings wind around the pegs until they too are taught and thus tuned properly. With those two designs in mind my partner and I set about generating designs. We decided that a wheel/spool in the center would be best. We added lateral pegs so that the user wouldn't have to crank so many times to get the bottle to rise by increasing the circumference that the wire must travel with one crank. We also decided that a triangular upright would be stronger than a square upright. We also added lateral supports to ensure that the structure could support the weight without wobbling or breaking.

Test Pieces:

 

To prevent unnecessary iterations, my partner and I created a test piece to check the fittings of all the bushings, pegs, notches and holes with varying dimensions. 

 

As you can see, even our test pieces required 2 iterations! The first time that we converted the file into the program used by the laser cutter it cut, but didn't cut deep enough into the delrin in order to cut all the way through the sheet of delrin. After our second cut we were able to figure out the appropriate measurements for both tight and loose bushings as well as the notches and pegs. From there we adjusted the measurements of our main pieces.

Assembly:

 

 

We took our paper design then drew it in solid works. From there we printed it out and assembled it. Our main attachment methods for this project were press fitting. Originally we thought that we would need to piano wire the lateral axis to the reel, but because our press fit was so tight, the piano wire proved to be unnecessary. A similar thing happened with the four rods which connect to the edges of the reel. Originally we thought that we would need to heat press them, but we found that our press fitting was tight enough that, that too was unnecessary.


Testing:
Once we tested this design we found that it was sturdy and was able to reel the bottle 10 cm above the table top, as was specified on the hand-out. We did find the adding the handle to the crank made the whole structure want to slide around on the table. Once we took that off it was better, but the windlass still slid on the table top since the table and the delrin are both slick surfaces. In order to address this issue we created prongs that extended from each leg and hugged the table (pictured below). This way the windlass wouldn't slide and have the danger of having one of the legs fall in the opening. This was a major improvement to our design and contributed greatly to its success on presentation day!

  

    

Accounting for Materials:

Windlass:

Piece	Quantity	Area of component (cm2)	Total Area (cm2)
Upright	2	115.74	231.48
Disk	2	35.94	71.88
Crank Handle	1	16.71	16.71
Lateral Supports	4	26.26	105.04
Bushings	5	0.71	3.55
Rod (support)	4	5.84	23.36
Rod (central)	1	26.16	26.16

Total Delrin used: 428.66 cm<sup>2
Total Delrin rod: 49.62 cm * we had 5cm of total extra length on the ends of the axle which we chose not to cut off.

Additional Pieces for Stability:</sup>

Piece	Quantity	Area of component (cm2)	Total Area (cm2)
Hook	4	22.92	91.68
H connectors	8	3.11	24.88

New Total of Delrin used: 545.22  cm²
*We chose to create the prong pieces rather than reprint the entire upright in order to save delrin, however if we had printed the 2nd iteration of our uprights to include that then we would have had a total delrin usage of 502.66  cm^{2, which only exceeds the limit by 2.66}  cm^2.


Engineering Analysis:
There was a lot of geometry related design elements which increased the success of our design. The triangular uprights were stronger than a square base design, but less strong than an arch would have been, We chose however to do a triangle because it saved delrin. Also, we realized early on that if the string were to wire around only the delrin rod, it would not be able to bear the weight and that it would take very long to wind up. Therefore we added a reel to the main turning axle which increased the amount of string taken up by a single rotation. This reflects the relationship between linear and angular velocity.

angural velocity = (linear velocity)/(r from the center)
so as the length of the radius increases so does the linear speed reflected by the increased take up in string.

Torque = Frsin(theta)
This equation is relevant to our crank because as the length of the crank increases, the less force is needed to exert the same torque on our axle in order to rotate it. This however must also be considered with the canteliver beam equation



As with the bottle opener, E (Young's Modulus) is constant since the material used was delrin. We also cannot control F since we cannot tell what force the user will put on the handle For the purposes of this analysis I will assume that a reasonable amount of force capable of a normal person is being applied to the bottle opener. That leaves only L and I for us to consider in our design. In the Equation, L is raised to the 3rd power, while I is in the denominator. This suggests that as the L (length) of a design with a given I increases, the deflection of the design increases exponentially. Also, this suggests that as the I of a design with a given L decreases the denominator gets smaller allowing the numerator to get much larger. Based on this mathematical reasoning a shorter length and larger I would give the lowest deflection. Which is what we want!

If this is applied to the central delrin rod axle though, we now can control the F since F = (mass of the bottle)(gravitation contstant or 9.8m/s/s)

Reflection: 
After watching the presentations of all the windlasses in our class, I was struck by how each one was so different that the others. It also stuck me that each design had elements that were ingenious, and other elements that could use further tweeking. This has made me realize that in the real world of design and engineering working in groups and reviewing each other's designs is extremely important. The other person might just have an idea that would make your design that much more effective and efficient.

I also learned the value of creating an efficient test piece which will prevent unnecessary iterations, By making sure that all the measurements would work, we were able to only do one iteration of our main design with only one added feature.