Fall 2015

The Bone Crusher

Final ReportJack Kim, Raga Komandur, Roberto O’dogherty, Hayden Plemmons, Mitchell Sella, Jacob Sigmund, Benjamin Theobald, Hannah Winegarden, Ethan Young

Executive Summary.....................................................................................................................................2

Introduction.................................................................................................................................................3

Background..............................................................................................................................................3

Specifications.......................................................................................................................................3

Bones...................................................................................................................................................4

Actual Machine....................................................................................................................................4

Brainstorming..............................................................................................................................................5

Alpha Design............................................................................................................................................5

Beta Design..............................................................................................................................................6

Bone Testing................................................................................................................................................7

Procedure for Bone Testing.....................................................................................................................7

Results.....................................................................................................................................................8

Falling Weight Calculations......................................................................................................................9

Clamp Testing........................................................................................................................................10

Design Revision..........................................................................................................................................11

Gamma Design......................................................................................................................................11

Decision Making........................................................................................................................................12

Decision Matrix......................................................................................................................................13

Fabrication.................................................................................................................................................13

Machine Testing....................................................................................................................................16

Budget.......................................................................................................................................................17

Lesson Plan................................................................................................................................................19

Computer Science..................................................................................................................................19

The Equation......................................................................................................................................20

Pre and Post Test...................................................................................................................................20

Conclusion.................................................................................................................................................22

Appendices................................................................................................................................................23

Bone Break Procedure...........................................................................................................................23

Customer Manufacturing Process.........................................................................................................24

Bibliography...............................................................................................................................................26

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Executive SummaryOur project creates a lesson for high school students that would incorporate a machine

that breaks chicken bones in several desired ways, allowing for students to understand how certain breaks occur. This machine is low-cost, efficient, safe, and simple to use because it is going to high school students. In order to create this machine, several designs are integrated into one “Gamma Design”. After proceeding with brainstorming and testing, we came to the realization that performing all of the desired breaks would be unrealistic considering our time constraints and resources, so we altered our design to maximize our performable bone breaks. Our final product incorporates two machines; one a winch based design that performs rotational breaks and the other (T-Screw) which includes a threaded metal rod that is screwed down onto the bone creating contact breaks. Our machines were approximately $100.00 to fabricate, resulting in around $50.00 remaining in the budget. A lesson plan incorporating a lesson on bone structure, computer science, and some physics was created to stimulate the minds of the high school students utilizing the machines that were produced. Hopefully resulting in the increase of students interested toward Biomedical Engineering and Computer Science. The final machine is able to consistently recreate three breaks: the fissure and greenstick done by the T-Screw, and spiral break done by the Winch Design.

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IntroductionOur project was given to us by The STEM Academy with the intention of promoting an

interest in STEM education (Science, Technology, Engineering and Mathematics) in high school students. They have asked us to create a lesson that incorporates AP Computer Science and is focused around the use of a chicken bone breaking machine which can replicate different fractures.

Background The STEM Academy is a national non-profit

organization that aims to improve STEM literacy among students nationwide. They are dedicated to certify instructors through national STEM instructor standards and STEM school accreditation practices. They attempt to improve “under-represented minority and low-income student growth, close achievement gaps, decrease dropout rates, increase high school graduation rates, improve teacher and principal effectiveness.”1 The STEM Academy organization creates routes to industry and post-secondary advancement for students. 2, 3(image)

SpecificationsThe lesson plan must fit into the AP computer science curriculum and it must incorporate

the hands-on implementation of the chicken bone breaking machine by the students. Also, and perhaps most importantly, it must generate an interest in the biomedical engineering area.

The chicken bone breaking apparatus must replicate fractures efficiently, consistently, and safely; however, it must also be simplistic enough so that any person can learn how to use it relatively quickly. Also the device must be low-cost (under $150), and built from parts which can be bought at Home Depot so that parts may be replaced.

1 “About”. The Stem Academy2 Ibid3 “STEM Academy”. Peen State, New Kensington.

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BonesFor this project we will focus on eight different types of bone breaks; transverse, oblique,

spiral, comminuted, impacted, fissure, and greenstick.

(Figure 1.1)4 Types of bone breaks that could potentially be recreated by our machine

All eight types of breaks can occur under more than one situation, but they are still very distinguishable from each other. Transverse breaks are fractures that cut across the bone unlike oblique breaks, which go diagonally across the bone. Spiral breaks occur when the sides of the bones are twisted, resulting in a fracture along the diaphysis that spirals around the bone. A comminuted fracture occurs when the bone is broken into more than two pieces. An impacted break occurs when the bone is pushed into itself. Fissures are cracks in the bone resulting from stress. Finally, the greenstick break occurs when the bone does not break all the way through. 5

Actual MachineIt is important to note that devices like the one we’re tasked on building already exist. One of these machines is the "MTS Insight" (Model 5kN), this device is used primarily for static testing on a wide array of materials, including metals, composites, adhesives, and more. Although this machine isn't used mainly for biomedical purposes, it can be utilized to test the strength of bones and the amount of force needed to snap these bones in accordance to the different kinds of breaks. The machine employs two "claw" clamps that attach to the ends of the material and subsequently apply stress, in the form of twisting, pulling, laterally moving, etc., until the point of breaking. Despite the usefulness of these machines, they are very costly and therefore out of reach of a standard high school classroom. This cost is what fosters a need for us to design a new "classroom friendly"

device.

(Figure 2.1)6 MTS Insight - Model 5kN

4 “Busy Bones”. ASU school of life Sciences.5 Ibid6 “Mechanical Testing”. BME Shared Lab Resources.

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Brainstorming Our team began by brainstorming individually, and then collaborated in small groups to

reach a consensus on two achievable designs. Lastly, our group came together to decide on two collective designs in which one would be chosen as our alpha (first choice) design and the other as the beta (second choice) design. This process was critical for the success of our device.

Alpha Design

Figure (3.1) Frontal view of our primary design

(Figure 3.2) Rear view of our primary design

Our alpha design was mainly focused on the use of a motor, while also incorporating falling weight. This design was thought to be able to perform the transverse, spiral, comminuted, impacted fissure, and greenstick breaks. As shown in figure 3.1, the bone would be placed between two clamps (labeled E) inside the box frame. The box frame would be crafted out of plywood on all sides but the front, which would be made out of a sheet of Plexiglas, to protect from potential flying particles of bones. The Plexiglas component would be removable to be able to place the bones in the device.

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To achieve the spiral and impacted breaks, a motor (shown in figure 3.2 labeled G) would spin a wheel which would move a belt (labeled F) connected to gears inside the side boxes (labeled C), which would then mechanically spin the clamp (labeled E) causing one head of the bone to rotate and create a spiral break. The other clamp (labeled D) remains stationary because it is clamped down to a fixed end and prevented from spinning thanks to its cubic shape. To perform an impacted break, the belt would be placed on the opposite gear box (labeled C) which would mechanically make the clamp (labeled D) laterally travel causing an impacted break, while the other clamp (labeled E) remained stationary. To recreate the transverse break, stackable weights would be dropped from the top of a cylindrical tube (labeled A) on to the bone. To integrate the computer science aspect, two acceleration sensors would be installed (labeled B) just below the end of the falling weight tube to capture the acceleration of the weights, thus, allowing for the calculation of force by the students.

Beta Design

(Figure 4.1) Front View of Beta Design

Our “beta” design is a machine that utilized twin vices which held the bone in clamps (labeled A in figure 4.1). These vices would then lower the bone onto an interchangeable spike (labeled B) on the bottom of the machine. This spike, depending on the type used, would break the bone in a desired manner. The twin vices (labeled C) would be lowered down on threaded rods (labeled D) by a hand crank. This machine would reign king in the consistency category, although it would be limited by the number of resulting breaks that the machine could accomplish on the bone and could require too much power from the user.

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Bone TestingThe primary set of data that we needed to acquire during testing was the force needed to

consistently break a chicken bone in half, which we expected to be a relatively small value due to the rather slim diaphysis of most chicken bones. To do this we hung weight (in the form of a bucket of water) from the diaphysis of the bone. Although we did not have any force or stress sensors to use on the chicken bones, if the mass needed to snap the bone can be calculated with the equation F=ma (newton’s second law) and the acceleration in this case would be that of gravity, 9.81ms-1.

Procedure for Bone TestingSupplies Needed: 25 mL Graduated Cylinder, 250 mL beaker, a scale (accurate to the second decimal place at least), paper towel, sink, string, bucket with handle, post it notes, two tables that are movable, duct tape, alcohol wipes, and a digital caliper.

1) The bag of chicken bones was opened and some of the bones were laid in a dry, warm area for 24 hours prior to testing in order for the bones to be adequately dried. Each bone was labeled by placing post it notes with the bones’ numbers on it underneath the bone.

2) The following day 6 of the bones were placed on a piece of paper towel and we measured the width of each end and the middle, measured the height of the middle and sides, and the length of the long way of the bone. The heights were measured using the end of the caliper with the little nub on it.

3) We filled a 25 mL graduated cylinder to the 20 mL mark with water from the sink and dropped each bone in individually. We recorded the resulting mL after the bone was dropped into the graduated cylinder.

4) The scale was cleaned with an alcohol wipe, and then each bone was individually placed on to the scale. The mass was recorded to the second decimal place. The weight of the string and the bucket were recorded. Next we set aside the bones numbered 4, 5, and 6 to dry and be measured the following day.

5) We took the bones over to two moveable tables and moved the two tables about an inch apart (enough so that when the bone is placed between them with just the heads at the end will still be on the table). Then we taped the heads of each bone to the table using duct tape, then draped the string over the center of the bone. The ends of the string were then tied to the top of the handle of the bucket.

6) Two tests were then conducted: (1 Liter of water = 1000 grams)(Use three bones for each test)

a) The string remained on the bone the entire time, and water was slowly poured into the bucket (using a 250 mL beaker). Once the bone has observable bend

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we switched to the 25 mL graduated cylinder and added water until the bones broke in half.

b) The bucket was filled with a predetermined amount of water and the string was held exactly ten centimeters above the bone. The bucket was then allowed to fall. The amount of weight needed to break the bone was determined. (We kept in mind that the more tests done, the weaker the bone got. time.)

Results

Bone Number

Mass (g)

H2O (mL) Displaced

Density (g/mL)

Length (mm) (Head-Toe)

Width (mm) (Head 1)

Width (mm) (Head 2)

Dry 1 2.13 2.50 0.85 68.58 12.77 7.20

Dry 2 2.11 1.60 1.32 63.78 7.09 13.25

Dry 3 2.00 2.60 0.77 66.32 9.22 7.15

Averages 2.08 2.23 0.98 66.23 9.69 9.20

Wet 1 3.32 2.40 1.38 68.01 12.44 11.46

Wet 2 4.56 3.60 1.27 75.44 11.23 7.76

Wet 3 3.32 2.90 1.14 67.46 6.52 9.81

Averages 3.73 2.97 1.26 70.30 10.06 9.68

(Figure 5.1) Bone Measurements

Bone Number

Mass (g) String and

Bucket

Mass H2O to bend (g)

Mass H2O to snap (g)

Total Mass to Snap (g)

Table Void (mm)

Dry 1 1,600 5,000 16,750 18,350 32.11

Dry 2 1,600 4,000 17,750 19,350 31.83

Dry 3 1,600 4,000 20,000 21,600 31.87

Averages 1,600 4,333 18,167 19,767 31.94

Wet 1 1,600 4,000 4,000 5,600 31.42

Wet 2 1,600 N/A N/A 1,600 32.80

Wet 3 1,600 4,000 10,250 11,850 31.65

Averages 1,600 4,000 7,125 6,350 31.96

(Figure 5.2) Testing Data

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This data outlines the mass needed to snap a chicken bone. As shown in the data dry bone 3 required 21,600 grams of mass to snap, which equates to roughly 48 pounds hanging from the bone before it snapped. The amount of force needed to break bone 3 could also be calculated to be almost 212 Newtons of force. (Note: No relationship trend could be found between physical dimensions and force needed. Each bone is different because of variation in chickens providing specimens.)

Our test data was extremely discouraging because our initial design utilizing the torsional strength of an inexpensive motor was deemed implausible due to the amount of force required. The force required (212 Newtons), which is significantly larger than expected. Even for a strong motor would have trouble fracturing the bone, as breaking a bone requires more initial force and acceleration than the constant torque that a motor would provide. Our initial design also incorporated a falling weight component that would cause a transverse break on the bone by applying an immense force on impact to snap the bone in half. Using the data (from our toughest wet bone) collected during our bone testing, we were able to calculate the mass and heights associated with breaking a chicken bone (wet) consistently.

Falling Weight CalculationsHeight (m) Mass (lb) Mass (lb) Height (m)

0.1 261 2.50 10.50.2 130 5.00 5.220.3 87.1 10.0 2.610.4 65.3 20.0 1.310.5 52.3 35.0 0.750.6 43.5 45.0 0.580.7 37.3 50.0 0.520.8 32.7 60.0 0.440.9 29.0 70.0 0.371.0 26.1 100 0.26

(Figure 5.2) Falling Weight Calculations

These calculations show the amount of mass needed to break a bone when height is the independent variable (Left) and the height needed to break a bone when mass is the independent variable (Right). These calculations where done using the formula F=mgh (where “m” is mass “g” is gravitational acceleration and “h” is height) where the force was the one needed to break wet bone 2 (116.2485 N). 

If we consider 20 pounds to be a reasonable amount of weight for an individual to lift to the top of the machine, then the tube would need to be more than one meter in height to achieve

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the necessary force upon impact. This is not a reasonable height or weight for our device; thus, our design needed to be completely changed. Although our testing data was extremely helpful in determining an effective design, the downward force data wouldn’t help us determine the amount of force needed for the torsional break.

Clamp TestingPerhaps one of the most important components of our device is the way we choose to

hold the bone to the mechanism, as regardless of the effectiveness of the rest of the machine, if the “bone holder” fails to grip the bone, the device would be rendered useless. We decided that we should test using clamps to hold the bone, as well as screwing the bone in place. The issue with clamping the bone is the fact that the heads of the bone, (which is the most rational place to clamp the bone) are relatively soft and have been shown to break under the amount of clamping force needed to get a torsional break in the bone. Consequently, we used a pliers, screws, and a vice to test where to hold the bone to get an optimal break.

(Figure 5.3) Testing Clamps

One half of the bone was placed in the vice and the other half was turned manually with the use of pliers (shown in the Left of figure 5.3). The bone broke between the spot clamped by pliers and place clamped by vice (right). The head of the bone is shown to be cut up when the screws unsuccessfully spun the bone. (left)

During this test it was deemed implausible to use screws to drill in and hold the bone in place because the head was too soft and the shaft was too hard to drill into. Tests where we clamped the head of the bone obtained the spiral fracture where the head and diaphysis come together, making the fracture oddly shaped. The pliers, on the other hand, were able to hold the bone well while twisting. However, the most important conclusion obtained from this testing was we should clamp the bone in the diaphysis as this results in only the diaphysis of the bone getting the spiral fracture.

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Design RevisionFrom our test results it was deemed necessary for us to go back to the drawing table and

create a design that would be successful under the new force requirements determined for breaking the bone. Although we needed a brand new, innovative design that did not mean that we had to throw out the successful components of our previous designs. This new design, which was to be a collection of new and old ideas, is our final design, the “Gamma Design”.

Gamma DesignAlthough we initially created two designs where one would eventually be fabricated, we

decided that our initial designs may have been irrational in multiple ways judging by the results of our testing. This conclusion led us to combine the best part of our designs into one final design that our group would end up fabricating. This design combined the hand power of the vice design with the downward force of the falling weight design. Our “Gamma” design was split into two mechanisms so that it could perform different types of breaks. One is a crank powered mechanism that achieves a spiral break. The other is a T-Screw design that would achieve a greenstick and a fissure break.

(Figure 6.1) The T-Screw design: (front view)

The T-Screw portion of our “final” design adopted a threaded rod with a handle at the top that would be spun down onto the top of the bone to achieve several breaks in the diaphysis of the bone by applying force from the top. The bone would be held in place by clamps on either side holding the head of the bone, which would result in a 3-point bending system allowing for the accurate relationship of displacement and force to be calculated. This relationship would be

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utilized in the computer science component of the project (Refer to Computer Science Section). In addition, in order for the machine to be able to withstand the upward force from the T-Screw, this mechanism would be housed in a sturdy metal box.

(Figure 6.2) The Winch Design: (Figure 6.3) The Winch Design

(Side View) (Gears Enlarged)

The winch portion of our final design was mainly thought up for the purpose of producing a spiral break, a break resulting from torsion on one side of the bone while the other side remains stationary. This mechanism wielded a long lever that would allow any person, regardless of physical prowess, to be able to consistently break any size chicken bone. To do this the lever would be connected to a gear box, which would employ gear ratios and a ratchet. Lastly, the machine would hold the bone with two clamps and one clamp would be attached to a metal plate in order for the clamp to remain stagnant while the other would be connected to the gearbox (on the opposite side of the lever) and free to move in a circle to achieve the spiral break.

Decision MakingOnce finished with brainstorming, we were left with three designs to decide from that

would adequately achieve our project of breaking the bone. Our indecision with which design to proceed with prevented us from moving forward fabrication. Since we needed the most logical way to decide on our final design, we used a design matrix the rank the three designs.

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Decision MatrixFactors T-Screw/Winch Double Vice Falling Weight-Motor

Cost (4) 20 (5) 16 (4) 8 (2)Longevity (3) 12 (4) 15 (5) 6 (2)Consistency (5) 15 (3) 25 (5) 25 (5)Safety (4) 20 (5) 12 (3) 12 (3)Replaceable Parts (3) 12 (4) 12 (4) 6 (2)Minimal Size (2) 10 (5) 6 (3) 2 (1)Portability (1) 4 (4) 3 (3) 2 (2)Appearance (1) 4 (4) 4 (4) 4 (4)Ease of Use (4) 16 (4) 12 (3) 8 (2)Number of Breaks (5) 15 (3) 15 (3) 15 (3)Totals 128 120 88(Figure 7.1) Decision Matrix for Machine (Number in parenthesize underneath design name is unweighted score given to each machine, the weight is indicated in parenthesize next to each

factor)

The designs that we were deciding between were the T-Screw/Winch, Double Vice, and Falling Weight-Motor designs (Alpha, Beta, and Gamma designs respectively). The factors that were taken into account were based on specifications instructed to us by the client, such as safety, cost, and consistency. The designs would be graded in each factor on a scale from 1 to 5, value which would then be multiplied by the weight of the factor (which is determined by the importance of this factor). The higher the assigned value means it is a better option.

We labeled the number of breaks and the consistency of the machine as the most critical factors to the success of a design, this is shown as the factors are “(5)” for each. The number of breaks is a crucial component because in the specifications the client required that multiple types of breaks were possible in order to teach students about the greatest number of breaks as possible. Consistency was also highlighted as important because our machine needs to be able to produce the same results every time regardless of the variation in bones, which is a limitation of the T-Screw/Winch design specifically.

After debating each factor as a team and giving them all a rank depending on the effectiveness in the specific design, we calculated the sums of the weighted scores to find out which design received the highest ranking. These results show that the T-Screw/Winch (Gamma) design is the most practical in our opinion, so we began fabricating this design.

FabricationAfter determining the design we would use, we had to choose the materials needed to

complete the fabrication of our design. The T-Screw design would take a lot of force pushing back on the structure causing inflection in the housing material (due to the inherent nature of the

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design), so we decided to fabricate the housing out of steel plates. We also had to decide between using a fine threaded rod or a coarse threaded rod, which was decided to use a fine threaded rod to allow for more accurate calculations for the equation portion of our lesson plan (see equation section).

With the rotational break design, we had to produce an immense amount of torque by just using human hand power, which has to be applicable for students with varying degrees of strength. We decided to use a boat winch because it is robust and is able to apply the mechanical advantage and leverage that we would need to break the bone by using ratcheted gears. We also chose to use a clamp to hold the fixed side of the bone and a drill chuck to hold the rotational side of the bone, the drill chuck adds more points of contact to prevent the friction from destroying the head of the bone that is being clamped. Both clamp designs allowed the bone to be held with evenly distributed pressure, so it will not only stay in place, but it will also not break at the brittle ends.

During the fabrication process the team came up with new ideas to improve the designs. For the T-Screw design a metal plate was added at the bottom of the threaded rod to act as guide so the rod would not slip off the bone. Another addition is that the bone is being held in place by two metal concaved plaques so the device can adjust to fit different types of bones. These are set in place by screws which extend from side to side on the device. For the Winch design, a screw was added to hold a slab of wood over the base. This screw functions so that the clamp and the drill chuck can be modified by loosening the screw.

(Figure 8.1) The fabricated T-Screw design

Once we received our supplies from Home Depot, we were able to start manufacturing. We began fabricating the winch design by creating a plywood template for the box. We then cross-cut flat bar steel stock into four sections for the four sides of the box, which were then placed in the mold, tapped, and welded on both the outside and inside edges. The box was

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grinded and filed to produce a consistent, smooth finish. A hole was then drilled and tapped to the same thread pitch as the rod, and another piece of bar stock, which would be used to guide the metal rod, was cut and rounded to fit inside the box frame. This guide rod was riveted to a cut plate of aluminum that was shaped to keep the guide from moving around. A hole (that would allow the rod to go through smoothly without friction) was drilled into the center of the guide and the rod was then secured through the guide with two jam nuts and a metallic tip, whose end was shaved to reduce rolling-off on the bone. Then, the rod was secured to a handle, which had to be fitted with a correctly threaded nut and pinned with a nail. Two more pieces of bar stock were cut, and a V was filed into each. Two holes were drilled in each piece, and these holes were matched to both sides of the box where more holes were drilled. Two rods were inserted into these holes and secured with lock washers and nuts on the outside, and the V-shaped bar stock pieces were secured on these rods. The bone is designed to rest on these rods at the bottom of the box.

(Figure 8.2) The Fabricated Winch Design

The spiral break design was based around a winch, so fabrication started with the disassembly of the main bolt connecting the large gear to the winch base. A longer bolt with different threading replaced the original bolt. A hole was drilled through the main ratchet wheel and bolt, and an R-pin was inserted to keep the bolt in place. A drill chuck with the same threading was placed on the bolt, as well as a nut to jam the chuck in order to keep it from rotating off of the bolt. A piece of oak was cut for the base of the design. The corners were cut and edges were routed for aesthetic value and cleanliness. A dado was then cut along the board. This fit the rabbet joint cut on a slimmer board which would house the movable clamp end. A hole was drilled through both boards, where a bolt was inserted to hold the clamp. A jam nut was then placed on the bold to keep the clamp in place.

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Machine Testing

(Figure 9.1) (Figure 9.2)

Testing the T-Screw Design Testing of the T-Screw Design

(The Greenstick Break) (The Fissure Break)

Testing the machine after the manufacturing is complete is an important aspect of the project so we know how the machine will work once given to the customer. The machine was tested with the same chicken bones that will be used in the classroom. Testing was first done on the T-screw design and it gave positive results, however not those that were expected. Due to the acceleration rate at which the point of pressure is lowered the device game us a greenstick break rather than the expected transverse break; however; the bones broke with ease, right where the machine was designed to break them.

Other unexpected bone breaks were found possible with this design while the testing was underway. While testing the team discovered that by placing a small metal gear underneath the bone the comminuted break would occur. And based on these testing results, the machine can achieve a comminuted and a greenstick break; therefore, these are the breaks that will be used for the computer science component (refer to computer science section).

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(Figure 9.3) Testing of the Winch Design

Next the rotational break design was tested and some problems were found. First, the drill chuck works great as a clamp, but the other stationary clamp is not as effective. The bone will spin in its grasp, so we do not get a clean spiral break. Second, the clamps have to be tightened so much that they sometimes crush the end of the bone. Finally, when both clamps work correctly, the bone often breaks near where the clamps are attached, not cleanly in the middle of the bone.

BudgetOur budget of $150.00 was a limiting factor when it came to designing our final machine,

although the majority of the parts we needed were relatively cheap and affordable. Our group was given access to a space that had spare parts lying around that we were allowed to use, which we ended up utilizing for a few parts on our machine for the sake of affordability and convenience. We were required to order all of our parts from Home Depot, which wasn’t the case when we used the lone parts that we had found in the store room, in order for relative ease in fixing any malfunctions in the machine; however, we were able to find the equivalent part at Home Depot that we had found in the store room in our lab.

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(Figure 10.1) Budget Pie Chart

The cost of fabricating the machine remained substantially under budget, an astounding $47.65 under the delegated amount of money. The disparity in the money used and the amount given was then viewed by our team as a cushion in case something on our machine did not function properly and we would need the extra money to compensate for the error in our design (thankfully this did not occur).

Part (Home Depot #) Cost Part Cost

Jacobs 26BA-1/2 Professional Duty Keyed Drill Chuck (#205565150) $39.97

Everbilt 1/4 in. x 36 in. Zinc-Plated Fine Threaded Rod (Internet #204604741) $2.27

TowSmart Zinc-Plated Trailer Winch

(Menards SKU #2618751) $18.99 1 in. x 1-1/4 in. Beam Clamp (#237037) $2.25

2 in. x 10 in. x 8 ft. #2 and Better Premium Douglass Fir Board (#915564) $7.98

1/4 in.-28 tpi Zinc-Plated Hex Nut (10-Piece) (#308737) $1.18

Crown Bolt 1-1/2 in. x 48 in. Plain Steel Flat Bar with 1/4 in. Thick (#368148) $11.63

Everbilt 3/8 in. Zinc-Plated Steel Flat Washer (8-Pack) (637009) $0.98

Everbilt 1/4 in.-28 Thread Pitch Chrome Cap Nut (3-Piece/Pack) (Internet

$3.21 Everbilt 3/8 in.-16 tpi Coarse Zinc-Plated Steel Jam Nut (6-Pack) (#315084)

$0.98

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#204604730)

Everbilt 3/8 in.-16 tpi Coarse Zinc-Plated Steel Tee Nut (2 per Pack) (#185422) $0.98

Crown Bolt 1/2 in.-13 x 6 in. Zinc-Plated Grade 8 Hex Bolt (#581211)

$2.28

Everbilt 3/8 in.-16 tpi x 4-1/2 in. Zinc-Plated Coarse Thread Carriage Bolt (#473481) $0.82

2 in. x 4 in. x 96 in. Premium Kiln-Dried Whitewood Shed (#161640) $2.18

Everbilt 1/2 in. x 13 in. Zinc-Plated Grade 8 Hex Nut (#600131) $0.52

Budget $150.00

Total $96.22 Remaining $53.78

(Figure 10.2) A chart with names and prices of materials from Home Depot used in Fabrication

Lesson PlanThe lesson plan is designed so that any teacher can look at it and be able to explain the lab to his/her students and get similar results. It is formatted so that the teacher is given additional information and can answer potential questions proposed by students. It walks through everything from set-up to the lesson itself and the final evaluation.

There is a pre-test and a post-test and they are identical. The purpose of this is to compare the knowledge before the lesson and after to see the improvement students make. Students are tested on their knowledge of the types of bone breaks, bone composition, and their understanding of force (the equation to calculate the amount of force exerted on the bone by our device is given in the computer science activity, but an overall understanding of force is essential to understanding bone breakage.)

Computer Science

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Our initial idea for the computer science lesson was to use the programming language C, which is compatible with the Arduino R3 board (which was recommended for us to use) however, after a design change that eliminated motors from our design, the Arduino R3 board was not beneficial to use for the computer programming component. With our design change, we decided to approach the computer science section in a simpler way that would complement the lesson plan. We decided to teach students the basic components of using the computer programming language “C++”.

This lesson would consist of a pre lab worksheet that gave a skeleton of a code that allows you to input values in the equation relating force and displacement of the bones (refer to Equation section) to find the amount of force the students applied to break the bone. The more complicated portion of the computer programming will be provided and students will fill blank spots on the worksheet that are more simple inputs. After completing the worksheet, they can type their program into website (cpp.sh). This program will read the code and allow then to run it and use it. The program works by the site asking the user, the student, a question about the value of an input, and the student is then able to respond by typing in the independent value. This value is then stored in the program and the student is asked for the rest of the inputs for the equation. Once all inputs are entered, the program will display the number of rotations of the pin required to break the bone that the student is testing. Allowing the students to see the skeleton of the code for this equation will show them the basics needed to use computer science and the “C++” computer language.

The Equation

F=n 48 EIsL3

The equation demonstrates the relationship between the number of rotations (threads) performed in the t-shaped threaded rod and the force (in Newtons) applied to the bone. In the equation "n" is the number of complete rotations performed on the T-shaped threaded rod, "L" is the length of the bone from head to head measured in millimeters, "E" is the bones elasticity modulus (a number that is experimentally determined based on the stress and strain on the bone) measured in Nmm-2, "s" dictates the relationship between the displacement of the center point of the bone and rotations (threads) measured in mmt-1 (where "t" is threads), and "I" is the second order moment of inertia (the moment of inertia for a static object) measured in mm4.

Due to the large number of variables, we decided to make a few of them constant in the formula, as students may not be able to measure these values, and a constant value would give a very close estimate. "E" the elasticity modulus will be 3200 Nmm-2. We obtained this value from

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an experimental procedure found online7. The value "I" is one that changes drastically from bone to bone, and this value is determined by the following equation:

I=π (ro

4−ri4)

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In this equation "ro" is the outer radius of the bone (diaphysis) and "ri" is the inner radius of the bone (Medullary Cavity). As previously mentioned this equation will give us the second order moment of inertia. The problem with these values (ro, ri) is that one needs a Vernier Caliper, and even with this tool it is difficult to get a good measurement. Therefore, we decided "I" should be a constant value obtained from the average of bones we measured ourselves, and this value is 59.6428mm4 for this lesson. With this in mind the only values students will need to calculate and therefore set as the independent variables in their codes are “n” and “L”.

Pre and Post TestA requirement for the lesson plan for our project was to include a pre-test and a post-test

designed to test the knowledge acquired throughout the lesson. Both tests are identical in order to see the student’s improvement from beginning to end, which is the main goal of this entire project. The tests mainly quiz the students on their knowledge of basic physics and intermediate bone knowledge, the latter being the topic that they will learn the most about throughout the duration of the lesson. Below is the list of questions that will be provided to the students before and after the lab (the underlined portion is the question and the bolded portion is the answer).

1. The computer programing website generates a code using A++ language. False

2. The number of rotations for the T-Screw Design is the same for each bone. False

3. Name the following types of Bone Breaks:

7 “Three Point Bending Chicken Bones”. Oocities.

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A) Normal B) Transverse C) Oblique D) Spiral E) Comminuted

F) Avulsion G) Impacted H) Fissure I) Greenstick

4. Name the Parts of the Bone:

Diaphysis: H

Bone Marrow: E

Epiphysis: G

Compact Bone: C

Periosteum: F

Spongy Bone: B

Cartilage: A

Medullary Cavity: D

ConclusionIn conclusion, the lesson plan that was created for “The STEM Academy” meets the

requirements and specifications given by the client, while even showing some previously unforeseen advantages. The project was deemed a resounding success in our opinions, even though not all of the breaks could be recreated with our designs. The bone breaking machine may not be able to reproduce every break that was desired, but the design incorporates ideas with ingenuity and simplicity that meet the specifications as fully as were possible under time and money constraints.

Both chicken bone breaking machines, the T-Screw design and Winch design, were able to consistently create the greenstick, fissure, and spiral fractures. In addition, both of the machines were able to compensate for different sized bones that may be used throughout the duration of the lesson. The machines mechanism is easy to understand and therefore one can learn how to use it by simply looking at a diagram showing the placement of the bone, which allows for ease of use in an environment where simplicity is essential in creating a stimulating and interesting environment. The machines do not require an extreme amount of force to operate, thus allowing almost any person to be able to use it regardless of their strength or limitations.

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Finally, there is a clear link between the computer science component of the lesson plan and the machine, which was outlined in the specifications of the project.

Students will be able to test their knowledge of coding while simultaneously being able to discover and explore interesting topics in biomedical engineering. The different types of fractures that they will be witnessing will not only keep the students captivated with their bone breaking prowess, but they will also be learning important aspects of bone structure, which can relate to medical and engineering careers. The lesson was adequately designed to tap into the abundant, innate curiosity found in high school students, and also their destructive tendencies (controlled on the bone, of course).

Future additions to the design, for example, may include replacing the stationary clamp on the winch design in order for the two clamps to be closer to the center of the bone, resulting in a clean spiral break. Lesson plan improvements could also be made by creating activities designed to challenge the students to the point of failure.

The Bone Crusher, overall, was a resounding success and is now an object of great pride in the eyes of our entire team. The durable, efficient design of our machine will hopefully break numerous bones in its life time. The lesson plan integrated the device into an engaging and informative lab, which will potentially spur immense interest in the medical field as well as aid in creating the next generation of biomedical engineers.

Appendices

Bone Break ProcedureNote: ALWAYS wear safety glasses when operating machinery. An instructor must supervise students conducting the procedure.

Winch Machine

Spiral Break

1. Pick a bone which has an end diameter that can fit inside the drill chuck.

2. Adjust the drill chuck to open until the bone can fit inside.

3. Tighten chuck around the bone. Tighten until the chuck has a firm grip on the bone, but not until the point where the bone breaks.

4. Loosen the bolt on the 2 in. x 4 in. slide only until the slide can be easily adjusted. Adjust the slide so the other bone end rests in the clamp. The setscrew should be lined up on the shaft of the bone before the large end, not directly on the end.

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5. Tighten the bolt loosened in Step 4.

6. Tighten the setscrew in the clamp to hold the bone in place.

7. Slowly crank the handle of the winch. Count the clicks it takes to break the bone so results of different bones can be compared.

Note: If the bone comes undone from the set-up, try tightening the chuck and/or the clamp setscrew more than the previous trial.

T-Screw Machine

Fissure Break

1. Measure the length of the bone in millimeters.

2. Place the quarter inch steel bar stock in-between the two v-blocks.

3. Place a nut on top of the surface of the quarter inch steel bar stock and directly below the screws point of contact.

4. Place bone so that the diaphysis is in-between the v-blocks, the epiphysis’ are outside the v-blocks, and the bone is resting on the nut.

5. Slowly rotate the handle until you reach the initial point of contact with the bone.

Greenstick Break

1. Measure the length of the bone in millimeters.

2. Place bone so that the diaphysis is in-between the v-blocks and the epiphysis’ are outside the v-blocks.

3. Slowly rotate the handle until you reach the initial point of contact with the bone and stop rotating the handle.

4. Rotate the handle by quarter turns until the greenstick break occurs and record the amount of turns you did.

Computer Science

1. Use the Basic Coding Worksheet to fill out the skeleton of the Computer Science Code.

2. Using an internet browser type into the url http://cpp.sh/.

3. Once at the site, type in your code from the skeleton worksheet.

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4. Run your code. If there are errors in your coding, then the program will not run. Check your code to make sure you typed it in correctly.

5. The program will ask you two questions:

1. "What was the length of the bone (millimeters)?"

2. "How many twists did it take to break the bone?"

3. Input your values and the program will calculate the approximate force used to create each break.

Customer Manufacturing Process

T-Screw Design

Pre-fabrication

1. The frame of the design will be cut off of 4x4 steel stock so there will be no welding necessary.

2. The frame will be prefabricated with all the holes drilled.

3. All bolts and parts will be shipped along with prefabricated frame.

Customer Assembly

1. Fit bolts through the two holes near the bottom of the frame on the sides.

2. Fit adjustable bone rests on bolts and screw on nuts to secure the bolts.

3. Thread the longest bolt through the top hole.

4. Insert the guide and fit onto the longest bolt.

5. Screw nuts and cap on the end of the longest beam to support the guide and give a good point to break the bone with.

6. Finally thread handle on the top of the bolt.

Winch Design

Pre-fabrication

1. The base of the design will be prefabricated out of a 2 in. x 8 in. hardwood board and a 2 in. x 4 in. hardwood board.

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2. They will have the holes pre drilled and have a dado cut so the 2x4 can slide back and forth on the base.

3. The 2x4 will also have a slot pre-cut to allow a bolt to slide back and forth, as well.

4. The bolts, nuts, clamp, drill chuck, winch, and R clip will all be shipped with the prefabricated boards to be assembled by the customer.

Customer assembly

1. Slide the 2x4 into the dado cut on the 2x8.

2. Fit bolt through the slot in the 2x4 and through the pre drilled hole in the bottom of the 2x8.

3. The I-beam clamp will be threaded on the rod which will be attached to the 2x4.

4. Take the larger winch gear bolt out of the winch and put in the longest ½ bolt.

5. Drill through both the ½ bolt and the winch axle.

6. Put R-clip through both holes to make the bolt spin simultaneously with the winch axle.

7. Put a jam nut onto the long bolt.

8. Thread the drill chuck onto the same bolt and tighten jam nut.

Bibliography1. MacMillan, Leigh. “VUMC study shifts thinking on how bone fractures heal”. Research

News at Vanderbilt. http://news.vanderbilt.edu/2015/08/how-bone-fractures-heal/ (12/6/2015)

2. Parker, Josh. “Normal Stress, Bending Stress & Shear Stress”. Strucalc. http://www.strucalc.com/engineering-resources/normal-stress-bending-stress-shear-stress/ (12/6/2015)

3. Poruthur, Jocelyn. Tannir, Justin. “Three Point Bending Chicken Bones”. Oocities. http://www.oocities.org/watrlilies/Professional/BEW6E7.pdf (12/6/2015)

4. Unknown Author. “About”. The Stem Academy. http://stem101.org/about.asp (12/6/2015)

5. Unknown Author. “Beam Bending Equations Calculator, Supported on Both ends Single Load at Center” Engineers EDGE. http://www.engineersedge.com/beam_bending/beam_bending2e.htm (12/6/2015)

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6. Unknown Author. “Busy Bones”. ASU school of life Sciences. https://askabiologist.asu.edu/how-bone-breaks (12/6/2015)

7. Unknown Author. “CPlusPlus”. http://www.cplusplus.com/ (12/6/2015)

8. Unknown Author. “Fractures Without Significant Trauma”. UW Medicine, Department of Radiology. http://www.rad.washington.edu/academics/academic-sections/msk/teaching-materials/online-musculoskeletal-radiology-book/fractures-without-significant-trauma (12/6/2015)

9. Unknown Author. “Mechanical properties of bone”. DoITPoMS. http://www.doitpoms.ac.uk/tlplib/bones/bone_mechanical.php (12/6/2015)

10. Unknown Author. “Mechanical Testing”. BME Shared Lab Resources. http://sharedlab.bme.wisc.edu/teaching/2005/ (12/6/2015)

11. Unknown Author. “STEM Academy”. Peen State, New Kensington. http://www.nk.psu.edu/CE/45439.htm (12/6/2015)

12. Unknown Author. “Structure and Composition of a Bone”. DoITPoMS. http://www.doitpoms.ac.uk/tlplib/bones/structure.php (12/6/2015)

13. Unknown Author. The STEM Academy. http://learn2.stem101.org/ (12/6/2015)

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