Well Windlass: The Puzzle of Retrieving Water

The Puzzle of the Well Windlass...

For those who do not know, a well windlass is a mechanism used to crank a bucket out of a well instead of pulling the rope up manually. This makes it easier for the operator to retrieve more water with less effort.

Image from http://upload.wikimedia.org/wikipedia/commons/1/1e/Ramelli_windlass_well.jpg

For this project, my partner Christina and I were challenged to construct our own well windlass while simultaneously applying our new knowledge of fastening and attaching as well as our previous experience with cantilevers and beams. The deflection equation,

(F(L^3))/(3EI)

Where F = the applied force, L = the length of the lever, E = Young's Modulus (or the ratio of stress to strain aka stiffness) and I = the moment of inertia (the lever's stiffness of its cross sectional area). In addition, we were given specifications that we had to work within in order for our windlass to be considered successful:

1.) We only had 500^2 cm of Delrin, 50cm of Delrin rod and 120 cm of string to use
2.) Our windlass had to span a gap of 12 cm and be able to lift the top 10cm of the bottle above the gap
3.) The windlass had to support the load of a 1 liter bottle of water without wobbling or breaking
4.) The crank to wind up the string could not be over the gap

Needless to say, this was a bit more of a challenge than the bottle opener...


We started by brainstorming. The Delrin rod was too flimsy to support the water bottle on its own, so we decided to support the entire windlass with two large bases connected at intervals by cut pieces of rod. The shorter the rod was, the less it bent. This was due to the lever arm length affecting the applied torque. Once we shortened the arm, we lessened the torque and made the rod more effective.

Not the sturdiest of rods...

We wanted something that would utilize the strength of the Delrin sheets...

 But that would also carry the string away from the gap, like a crank and pulley system...

 Additionally, it had to account for all the forces applied to it, such as gravity, tension, and friction. It had to have wide 'feet' to keep it well balanced...

Finally, the pulleys and crank had to be easy to use and apply, and since we could only cut out pieces, the pulleys had to consist of one small circle between two large ones.

This design would utilize the strengths of both the rod and the 3/16 in Delrin: the Delrin would act as a support while the rods transferred the string away from over the gap to the crank. The pulleys would help take some of the force from the bottle off the crank and make it easier to turn. Additionally, they would also be able to spin freely if the friction between the them and the string proved too great once the bottle was lifted.

Without extra support, the two connected bases would have been unstable and probably fallen over if the right force was applied in the wrong way. We designed two identical feet and fit them to the bottom of the bases on either side of the gap. We used press fits for their simplicity and so that we could disassemble the product if we needed to once more parts were cut and ready to be connected.

After our brainstorming session, we made a foam demo of our model...

Once we were happy with our design, we began to build the various pieces into Solidworks. Whereas the bottle opener only required on part file, the windlass was made of several different pieces, and required multiple.  It was tricky keeping our files organized, both on the desktop and within the group Dropbox file. We eventually resorted to naming our files by our first names to help differentiate them.

The stabilizing foot

The loose and tight bushing

The pulley pieces

The base 

Partway through designing the various pieces, we realized that the Delrin rod would never work as a sufficient crank and spindle for the rope. The rod was circular, with no distinguishing features that could give the rope the friction it would need to wind around it.

Well, THAT'S not going to hold it...

We had to pause and redesign a crank and spindle that would work for us, using Delrin sheet.

The second crank iteration

Eventually, we came up with the idea to use Delrin in place of the third pulley. The Delrin would be rectangular in shape with two smaller rectangles erupting from its ends. A hole through its center would allow the rope to be fastened tightly to it, and therefore provide the force needed to keep it in place. The  small extremities would be filed down to fit into circular holes. This would also make it easier for them to spin. Finally, using a press fit, the handle would be attached. We measured to make sure it would not be so long that it would touch the ground on each turn.

Besides the crank and handle, several other pieces underwent mild modifications in Solidworks (see above pictures). The bases went from a multi-part design, to two single arches with an area for the crank. This edit saved material and helped make the windlass more sturdy. The arch design strengthened the bridge over the gap, ensuring that the water bottle would not break it once the crank began to lift the bottle.

Before we sent our files to the laser cutter, we practiced making our own bushings and press fits to ensure that our pieces would fit together perfectly. Otherwise, we might have ended up wasting a lot of material.

Our final design began to fall into place. Our bushing and press fit measurements were spot on, thanks to the margin of error information we learned during our fastening and attaching session (see fastening and attaching post). We knew that any piece that needed to fit tightly would have to either have a .5 mm added/subtracted from it in order to actually fit snuggly.

It was time to start cutting.

The initial cut went very well, but we ended up having to re-cut several bushings and parts to the handle for size reasons. The handle's notches did not reach far enough to create successful press fits and several of the tight bushings ended up being more loose than expected and did not keep the pulleys pressed tight enough.

Otherwise, we were very frugal with our material and wasted very little.

Once all the pieces were cut, we began to assemble our 2D parts into a 3D windlass. All the press fits and bushing worked perfectly.

Using only 5 inch of the provided Delrin rod, we assembled our two pulleys, attached the string, placed it over the gap....and did our official (and probably only, given how little time we had left) test run.

Our presentation run (not the test run, but they are essentially the same)

We were pretty satisfied with our results...

The windlass worked better than expected. The pulleys kept the string aligned with the crank. The crank was easy to turn and never let the rope slip. The base remained mostly stationary and easily lifted and supported the weight of the bottle thanks to the double overhanging beam design, along with the arched sharp, which maximized its strength against the bottle by minimizing the affects of the two beam's moment of inertia. We could not control lever length, as the beams had to be a minimum of 12cm to span the gap, but we could control how well supported the two beams were, and made sure they would be strong enough to complete their task. All in all, we were two very happy engineers.

Side view with bottle

Looking through it

Long shot

Crank handle

Crank handle and spindle

Feet and base

Top view of pulleys

As a final edit, we connect the handle and the piece that attached it to the spindle with a heat stake, to ensure no amount of force could cause it to fall off mid-crank. Aside from this connection, the entire windlass can be disassembled into a neat, easy to transport pile.

In total, we used 12.7 cm of rod and 273.12 cm^2 of sheet.....well under our limit for the Delin. 

We had to use all of the 120cm of provided string, though, as the distance from the crank over the pulleys and down to the bottle lid barely left enough string to attach it securely. There was no way to adjust for this, so we used all of it. Because we kept our shapes basic, calculating the total Delrin used was simple. We used basic geometry equation, like the areas of a circle triangle. Our specific calculations and estimations can be seen below.

Geometry calculations

Geometry calculations, again

Even though our product worked extremely well, if we had enough time, there are still a few edits we would like to make. While we cranked the base moved slightly due to the force acting on the handle. If we could re cut the two base walls, we would add hooks to go over the lip of the gap on either side to make the windlass more stable and secure. Additionally, we would also make the spindle more like the pulleys, with a small gap in between two large buffers, so that the sting could not slip off it and become lodged between the spindle and the wall. This made the crank slightly harder to operate. As an extra edit, we could probably honeycomb our two bases, and thus use even less of the material we were given, but we did not want to compromise the strength of the bases, since they were supporting the brunt of the applied forces.

The demo and final product

I guess I won't have to lift my textbooks from my bag to my desk anymore.....assuming a one liter bottle weighs about the same as a Physics book.

The Puzzle of the Bottle Opener (2 of 2)

Albert Einstein once said,

"Insanity: doing the same thing over and over again and expecting different results."*

With that in mind, since Sam and my first two designs didn't work, there was no point in simply editing iteration two 'slightly'. We sat down and did a massive redesign and this time we included the aesthetic aspects from the very beginning.

We started by asking what would make our bottle opener exceptionally intuitive and decided to make the design fit the purpose. Our third iteration would visually portray what it would do.

We wanted our final design to actually look like a bottle with the lid popping off.

Over the course of the rest of the week, Sam and I took careful measurements to insure that our bottle opener would work properly. We made the two prongs approximately 1.3 cm apart in length and .9 cm apart in height, so they would not get in the way of each other and would be able to comfortably fit over the lid. We kept the handle a solid six inches long so as to give our product the maximum torque possible. In addition, we made the lower prong much thicker and designed the point upwards to ensure it would not continuously break off. All the physics fro our previous designs was still applicable, but this time we wanted a cantilever with better grip.

Once we were happy with our design, we built it in Solidworks using the initial base from our previous models.

After we inserted extruded bosses into the existing cuts, we made new cuts and incisions to our model until we had a design that was to our liking.








We added design elements that made our product visually appealing, including cuts to look like the flutes on a bottle neck, an angled cap cut-out and the Coca-Cola logo (which had to be traced into the design by hand). We made sure that the decorative cuts, such as the bottle flutes, logo and cap, were placed so that they would not interfere with the overall integrity of the piece.

Once we had our design fir to cut, we made our third iteration. The initial cut did not go well, as the Coca-Cola logo proved to hard for the laser to cut without melting the surrounding plastic in the process. As a result, we were forced to engrave the logo instead. The second time went extremely well, and although we actually got a model slightly scaled down from our digital design (this must have happened somewhere between the computer and laser cutter) overall, we were very happy with the results.

Now that we had the final product in our hands, all that was left to do was to test it...

It worked perfectly!

The two prongs grip the lower lip and top of the cap extremely well, with a lot less sliding than the first two models. This is probably because the curved design of the handle allows for a better grip and the palm and fingers can naturally find comfortable places on it. Additionally, the flutes through the handle help increase the friction between the hand and bottle opener. Though it took several tries, we eventually made a design that covered all the aspects we needed it to cover. 

Except for a few minor details, Sam and I were very happy with our results. The bottle opener looked nice, was easy to use and performed its task without fail time and time again. If we had more time, we probably would have altered the logo's scale to see if the laser could actually cut it out properly, but Sam found a creative way to make it stand out using a red expo marker...

She colored over the logo with the marker and then wiped it away. Any dye that bled into the engraving stayed behind. Beyond this, the only other thing I would like to have changed was the scaling problem. We had encountered size problems before with our first iteration, and because the final product is a little smaller than than what we specified, the problem must have occurred in Solidworks. However, since we'll both get more practice with Solidworks as the semester continues, I'm sure we'll be able to fix this and prevent it from happening in future projects. 

For the moment though, I never knew how much better soda could taste when the bottle is opened with your own handmade bottle opener. Cheers!

*http://www.brainyquote.com/quotes/quotes/a/alberteins133991.html

The Puzzle of Fastening and Attaching

Today in class, my fellow engineers and I explored the attaching options that would be available to us when we began to make out well windlasses. These options included using a heat stake, piano wire and notches made with a laser cutter. As a bonus, we also learned about bushings, and the impact small variances in size can have on out prototypes.

Heat Stake

Heat Stake

The heat stake is a machine used to melt the ends of small bits of plastic into 'bulbs' to permanently attach items together.  It requires that the plastic have a small hole pre-cut into it, and that the inserted piece's prong be longer than the depth of the hole, so it can create an effective bulb. Once the prong it threaded through the hole and the two pieces are carefully secured on the base (usually using a second piece of plastic with a hole in it to stabilize them), the heat stake can be gently lowered onto the prong. At 400 degrees Fahrenheit, the heat stake melts the plastic into a condensed half-sphere, which is wider than the opening of the hole cut in the plastic. 

Bulbs created by heat stake

Once excess plastic begins to leak around the edges, pressurized air is blasted at the tip and the

heat stake is turned off. After fifty seconds of cooling, the newly joined piece is finished. 

The heat stake is very effective at joining pieces together with minimum effort from the user. The two pieces do not have to fit perfectly and can have some wiggle room between them (unlike with a press fit, but that comes later). The heat press, when applied correctly, can solve any looseness between the two individual pieces. In any situation where water or excess moisture might be in contact with a product, this method of joining pieces might be particularly effective, as the low-friction Delrin won't slip (it might with a press fit) and won't rust or become water damaged (as the piano wire might). Things built for the outdoors in temperate and tropical regions are an example of such products. However, it does have some drawbacks. Unless the user breaks the bulb off the tip, there is no way to separate the pieces. 

Therefore, if someone wanted to make any minor adjustments to a piece after testing it, they would either have to find a way to break off the bulb or make two new pieces and use the heat stake again.

Piano Wire

Piano wire requires a bit more work than the heat stake, but it is easier to disassemble if needed. Piano wire is what it sounds like: thick, metal wire.

Piano Wire

Drill Press

Using a drill press, the user first bores a small hole in the desired piece of plastic The drill press is designed with an adjustable set of grabbers to accommodate any drill bit. Because of its versatility, the user can make the hole either a tight or loose fit for their wire. A large hole would make it easy for the wire to slide around in and let the plastic slide with it. This called a hinge. If the hole is snug for the wire, then it is considered pinned in place and cannot move. This kind of attachment could be very useful for materials that need strong hinges. In fact, this method is already used in products like door hinges, as the strong attachment can both swing freely and support the weight of the door.I imagine for our purposes that if a product required a movable joint that could stand up to large forces and constant motion, the piano wire attachment would be a perfect candidate.

Although both pinning and hinges are effective ways of connecting pieces (especially ones that need to be able to move easily), it does have its drawbacks. If the cut wire is not perfectly straight, pushing it through the drilled hole can be extremely difficult and can make the joint cockeyed or even unusable. Additionally, the user has to be careful that the drill bit they are using is the desired thickness (especially if they are looking for the wire to fit snugly). Without careful measurement beforehand, the user could accidentally make all their holes too large and render their pieces unusable. Double checking with a digital caliper is very important with this piece of machinery.

Notches and Press Fits

The third option for attaching pieces of Delrin together is by using notches and press fits. Using the laser printer and careful measurements, the user can cut out individual pieces designed to fit snugly together without any extra help. 

Separate pieces

Connected pieces

A press fit is when the two pieces fit together and (through pressure created by the geometry of the two pieces) remain stuck, like a peg in a hole. They can only be removed when a sufficient amount of force is applied correctly. Usually, this requires pliers, as Delrin has a very low coefficient of friction.

Despite the threat of the pieces coming loose, this method is very effective for a user with limited supplies. The pieces, when cut right, hold together quite well. For an engineer building a three dimensional object without excessive material or access to heat or wire, this method is perfect. Rural villages and other such machinery-lacking places would probably utilize this kind of attachment often. For our purposes, any connections that may or may not be permanent and don't have to stand up to excessive force, this kind of attachment would work very well.

However, one of the major difficulties in using this kind of attachment method is the small margin of error. The difference between a tight fitting and a loose fitting notch was very small. A tight notch was about .124in in width (.315cm) and the loose notch was .131in in width (.333cm), leaving only a .006in  (.015cm)  margin between them. As a result, this method requires extremely accurate measurements to be effective. 

Bushings

Bushings are small, circular cylinders with holes through their centers used to either hold objects in place on a rod, keep them spaced evenly or prevent them from falling off.  For our purposes, when can

Bushings

either have the bushing fit our rods loosely or snugly. Both loose and tight fitting bushings are important. Loose bushings will allow easier movement for other pieces flush against them. They will be able to move freely and have less of a frictional impact. Tight bushings can hold objects firmly in place, even in specific places, on the rod and prevent them from coming loose or falling off. They do not require any other aid in staying put. These would be very useful for keeping tires in place, aligning gears correctly and keeping various pieces spread out on an axle or rod.

However, the bushings suffer from the same drawback as the notch method: the margin of error between a loose and tight bushing is extremely low. A tight bushing measured .252in in diameter (.640cm) while a loose bushing was .261in (.662cm). An error of more than .09in could result in a series of bushings that can't hold objects in place.  

The Laser Cutter

The final thing we reviewed was the discrepancy between the measurements in the computers and the measurements on the laser cutter. The laser itself has a width, which can cause the length of various cuts to be slightly off. In Solidworks, my partner and I had measured our bottle opener to be exactly 4cm across. When we cut it out of 1/8' Delrin, though, it was only 3.9cm in width. With the 3/16' Delrin, it was only 3.95cm. It is possible that for the thinner Delrin the laser melts a little more away more quickly than the thicker Delrin. These differences did not affect the functionality of our bottle opener's handle, but they could have a very big impact when cutting out notches and bushings. Particularly with the thinner Delrin. For example, the difference between a tight and loose notch was .015cm. In this case the discrepancy caused by the laser cutter would render any tight notches unusable as their diameters would be too small. Additionally, loose notches would be too tight.


Today's lesson showed just how vital it is in engineering to measure twice and cut only once.

The Puzzle of the Bottle Opener (1 of 2)

The first project my partner, Sam, and I tackled in this course was the bottle opener.  We went through several iterations to our design, focusing mostly on how the product would 'grip' the bottle. We wanted to make sure there would be minimal slipping (and thus, minimal injuries) when using our product.

Our initial designs varied from a version of pliers (top image, subject 5) and levers (top image, subject 3; bottom image, subjects 11 and 12) to a simple circle with a slit through its center (top image, subject 2).

However, after reviewing the physics of cantilevers and torque, we had a basic idea of what we wanted out final product to look like. Our chosen design oriented the the bottle opener as a lever with the fulcrum located where it would be in contact with the bottle. Additionally, we made the handle as long as possible to achieve an easy grip as well as provide a mechanical advantage with torque.

Since torque is the cross product of force and distance, a longer handle would make the bottle opener easier to use, a feature that would not have been available with the circle and slit design, which would have kept the handle closer to the fulcrum point.

Additionally, our chosen design allowed us to utilize the thickest version of the Delrin available, making our handle thick and steady (a feature that may not have been available on some of the other designs). This also helped with the deflection of the material. Since deflection is equal to:

(F(L^3)) / (3EI)

Where F = the applied force, L = the length of the lever, E = Young's Modulus (or the ration of stress/strain, or stiffness) and I = the moment of inertia (or the lever's stiffness of it's cross sectional area). Though we had no way of controlling Young's Modulus because we only had one type of material to use, we could alter the length and stiffness (by selecting what thickness to use) in order to get the most out of the applied force.




Thus, the thick material and the design of the handle helped minimize the deflection and make the handle strong and stable. Our design united all the qualities we wanted in our final product, including sturdy handle, a solid place to grip the bottle cap and maximum torque so the user could apply less force to open their bottle. We made the neck 2' wide. The maximum length was 6'. 










Once we were happy with the dimensions, material and initial outline, we made a mock-up out of foam to visualize the final product.

                                                   

After we had our demo, we built our model into SolidWorks.

In Solidworks, we made a part file and used basic shapes, like circles and lines, to construct our model. Once the sketch was finished, we rendered a 3D model in the program and tweaked it wherever we thought was necessary, such as filleting the pointed tips so they would not wear down as easily.

Once this was completed, we printed out model and.....

It was not quite as large as we expected it to be (the first cut is on the bottom of the above image). After  a few careful measurements, we discovered that the printer had interpreted our model as half its original size.

After a few adjustments, we managed to print a correct scale piece. However, the initial test of our product did not go well. The lower tip of the pointed portion continuously broke off with each attempt and was quickly worn down to an unusable stump. We noted the problems and edited our design.

Our second iteration bore striking similarities to our first model, however it had several major differences. 

1.) The lower point was curved upwards to make it as thick as possible in the hopes this would keep it from breaking. 

2.) The upper prong was filleted and tapered in a thick curve to give it more contact on the lid and distribute the force more evenly. The first iteration made 'deep' indents in the cap.

3.) We added a half- circle to the bulb for easy storage and carrying (it originally was intended to be a second bottle opening option on our model, but was scraped when we decided to use the thickest type of Delrin)

The initial test of our second iteration revealed that the two prongs (which we had made parallel in respect to their tips) were unable to fit under the cap and onto of the cap respectively because they each prevented the other from reaching its destination. In short, they were not aligned properly. After several minutes of intense filing, we managed to remove enough of the upper prong to allow the hooked prong to fit under the cap. It took three tries, but the second model managed to remove the bottle cap. No pieces broke off this time.

Although our second model did achieve its purpose, it has problems that need to be resolved before it can be considered a finished product. The alignment problem between the upper and lower prongs nearly rendered the second model unusable. 

My partner and I plan to edit out Solidworks design to eliminate this issue, as well as add details and embellishments to make the product more eye-catching and aesthetically appealing.