Well Windlass

Our second project was to build a small version of a well windlass.  There were many requirements:

• The design has to span 12 cm, the width of the "well".
• Limited to 500cm^2 Delrin sheet, 50cm Delrin rod, and 120 cm string.
• The windlass must lift a 1L bottle 10 cm above the table without buckling, breaking, wobbling, or shaking.
• One hand may be used to do the winding, and the crank or other mechanism must be positioned so it is not over the well.

1. Design Process
2. Engineering Analysis
3. SolidWorks and Construction
4. Final Product Testing
5. Accounting of Materials
6. Reflection

Design Process

My partner, Magdalena, and I began by sketching lots of ideas for windlasses. Our ideas included sides shaped like X's, triangles, rectangles, and more.  We brainstormed about ways to support the sides, ways to hold the rod, ways of attaching pieces together, and ideas for the crank.  

We eventually narrowed it down to a combination of rectangular sides shaped into a triangle, similar to the drawing at the very top of the image to the left.

Maggie and I decided on an overall triangular design because we thought it would stronger than a rectangular shape.  The design we chose combined multiple ideas.  The basic structure had two flat sides, two supports, the rod, and the crank.

The side pieces were rectangles that would lay together to form a triangle with notches to connect them at the top.  There would be two slots on each side piece for the supports to fit into. There was also one hole in the center of each for the rod. 

We had to figure out how tall the structure needed to be to span the 12 cm and also bring the bottle 10 cm above the table. We went through some math calculations, as you can see in the scribbles on our sketches 
(geometry was a long time ago). We approximated about 15 cm for the height of the triangle because we needed the rod to be at about 12 cm to 13 cm height to ensure the bottle would reach 10 cm.

We originally approximated the triangle as a 45-45-90 triangle, so if the height was 15 cm, the side would be approximately 21 cm.  (Later when we cut the design out of foam, we concluded that the triangle would be more little more upright.  The approximate angle measurements are in our detailed sketches in the next section).

One of our original sketches above had the supports above the rod because we didn't want the supports to get in the way of the bottle as came up.  We later switched the supports and the rod, like the picture to the left, so that the rod was higher, but we made sure the supports were far enough apart to allow the bottle to fit between.

Engineering Analysis

We chose this design for many reasons.  The rod is at the top of the triangular design, so there is only a small part of the rod that supporting the force of the string pulling the bottle up.  The sides support the rod so it won't bend as the strings puts force on it (if the rod was lower, it would bend more and wouldn't be as strong because the sides are further out). We also thought the triangular shape would be more stable than most of our other ideas. 

The horizontal support bars hold the two sides together, so that they won't collapse.  The supports are put through tight slots on the sides, and then fitted on the outside with very tight rectangular bushings to ensure they will stay.  We originally thought about making a notch and heat staking the end of the support, but eventually decided on rectangular bushings instead.  This way the windlass could be disassembled if we needed to change a dimension or rebuild it.

After sketching everything out, we created a foam mockup of our windlass. Even with just foam, it was fairly stable.  We didn't cut bushings out of foam because they are so small, and instead just built them in SolidWorks.After seeing the foam mockup, we made a few small dimension changes.  We increased the length of the sides from 21 cm to 22 cm and we shifted the rod up about 1 cm more.  These dimensions changes are reflected in the sketches above, and are the dimensions we used for the SolidWorks design. 

SolidWorks and Construction

After we constructed our foam mockup, we started on creating SolidWorks parts and drawings.  Before creating the large final pieces, we made test pieces to test parts of our structures without wasting Delrin.

Test Pieces:

Notches:  We made small pieces to test that the notches at the top would be a tight fit.  We made the widths of the tabs equal the first time, but this was too loose.  We changed the dimensions so that the tabs were wider, and the part the tab goes into was smaller.  This created too tight of a fit, even with some filing down, so we made a third test piece to find a fit between the two.


Slots:

We needed the supports to have a tight fit with the sides because they needed to hold the sides together and prevent them from collapsing.  We made a small piece with different size slots.  When we to print, however, we decided to use 1/8" Delrin when we had based measurements off of 3/16" Delrin.  This mattered because the width of the Delrin was the width of the slots.  We made a second test piece with corrected measurements.  We made a short version of the support piece, so we could test its fit with the slots.


Bushings:
We wanted these rectangular bushings to be as tight as possible.  The first test bushings were too loose.  We think it was because it was they were too thin on the outside,  so the material was bending as we put it around the support.  The second test, the bushings made a very tight fit with the support bars.

Holes/Circles:
We wanted the hole for the crank to be tight so the crank and rod would move together, not separately. We found that our test piece holes were not tight enough, so decided to just change this on our final piece (we made it slightly more small, so we could just sand it if needed).   
Also, the sides needed a loose hole for the rod to rotate in.  Maggie had a great idea to make it an ellipse instead of a circle. This way the rod wouldn't slide or move from side to side at the windlass was cranked, but the rod would be able to lie at an angle because the ellipse is tall in the vertical position.  We made a quick test piece to make sure it would fit right.  


After our dimensions were decided from testing parts, we sketched our final parts in SolidWorks.  We made drawings from the parts to print on the laser cutter.

We thought we were done when we printed our final pieces, but we had a few problems.  On CorelDraw, we couldn't make the ovals on the side piece hairline width, and when we hand-drew the oval in CorelDraw (and made it hairline) and ran it again, the Delrin had shifted or warped and made the holes in a slightly different place.  We had to reprint the sides a second time, and this time were very careful about placement.  Also, we had a lot of trouble heat staking the rod and the crank, and when we turned the crank it kept breaking off the rod.  We printed it a second time with a much smaller hole to try and fix this problem.

Final Product and Testing

Finally, we finished our well windlass!  We had time to test it once before the demo and it worked.  The class demonstrated our windlasses on Friday.  Ours worked and was able to lift the bottle 10 cm above the table without too much trouble and with only one hand doing the cranking.  Using one hand on the crank was doable, but a bit difficult.  Our structure was very strong though, and showed no signs of strain or breaking.  

It was also great to see the rest of the class's amazing designs!  It was a big step up from all of our one piece bottle openers.  As we watched the other demos, I took mental notes of certain design elements that were interesting, that worked well, and some that everyone struggled with.  Many designs had a spool for the string to wrap around when winding, larger than a single rod, making it faster to bring the bottle up the well, which I thought was a great design element.  Also, it was interesting to see some of the arched or rounded designs, which were aesthetically pleasing, and to see those that enclosed or supported the rod completely with Delrin parts so it wouldn't bend.  Some projects had multiple rods for their axle that were connected to the crank, and this not only made their axle strong, but also helped the crank move with the axle and not slip.  One thing that most designs struggled with was the crank.  Many were difficult, as with ours, to crank with one hand.  There are definitely improvement opportunities for the cranks.

Accounting of materials

Our limit for materials was 500 cm^2 of Delrin and 50 cm Delrin rod

Sides:        22 cm  x  9 cm = 198 cm^2 (x2) = 396.0 cm^2
Supports:   20 cm  x  1 cm =  20 cm^2 (x2) =   40.0 cm^2
Crank:       pi(2)^2 cm + (4x2) cm               =   20.6 cm^2
Bushings:   9.15 x 15.8 = 144.6 mm^2 (x4)  =    5.8 cm^2

Total:  463 cm^2 Delrin, 25 cm Delrin rod

Reflection

Overall, I'm proud of our design for working and meeting all of the requirements.  Our design was simple, and we were able to incorporate different ways of attaching Delrin together.  We also learned how to use many new power tools in the Engineering Lab and improved our skills with SolidWorks parts, assemblies, and drawings.

Some improvements I could think of for our design would be for the design to be a little more appealing and use less material.  For example, we could probably create the triangle shape without using so much material for the sides. Our overall design could be scaled down about ten percent because we had plenty of wiggle room in the 12 cm width as well as the 10 cm bottle height requirement.  Also, our crank and axle can definitely be improved to make it easier to rotate with one hand, maybe creating a longer handle or a different design.  Creating a spool for the string to wrap around would also be a good idea because we had trouble with the string wrapping all around the rod and not being able to turn it any more because the string hit the sides.

Also, Maggie and I worked really well together and communicated well.  We both made great design contributions to our windlass and we were able to combine and improve each others ideas.  (Fun fact: we figured out we took PHYS 107 together last semester, but we didn't really know each other at the time!)

We're now starting a new project, with a new partner (I enjoy changing partners and getting to know everyone in the class through projects).  Kasirha and I are working together for the next project, building a Lego racer.  When we started on Friday, we got super excited about gears and Legos and are eager to work on building our car!