ENGS 21 Summer 2022

Introduction to Engineering

Topic:  Safety

Final Report

Group Number: 2

Group Name: Trap Bar Buddy

Group Members:

Natalie Grover

Hannah Sheehy

Selena Han

Jihwan Choi

Federico Goudie

TA:

Judy Guo

1. Executive Summary

The use of free weights – or weightlifting – is a popular means of exercising in the United States. In 2021, there were approximately 52.64 million users of free weights aged six years and above, making up roughly 17% of the population of the US. While these weightlifters incorporate various exercises into their routine, there are three main powerlifting-focused exercises: the bench press, squats, and deadlifts. Of these exercises, deadlifts are recognized to be particularly beneficial as they strengthen the entire body; apart from engaging the lower body, deadlifts engage both the upper and lower back as they work to support the weightlifter’s torso as they pull the weight from the floor. 

Despite its benefits, deadlifting risks straining one’s back muscles. Due to the difficulty of this helpful yet strenuous exercise, many weightlifters with back pain, injuries, or other weaknesses have turned to trap bar deadlifts, a safer alternative to the conventional barbell deadlift. Trap bars were introduced in the early 2010s but have since skyrocketed in popularity over the last decade. We conservatively estimate that there are roughly 7.2 million users of the trap bar in the age group of 13-25 year olds given that there are 8.5 million student-athletes in both the high school and collegiate levels. Unlike conventional barbell deadlifts, trap bar deadlifts allow the weight to be closer to the weightlifter’s center of gravity, significantly reducing the risk of lower back injuries. Nonetheless, even with these safer alternatives, there is still a risk of unnecessary back strain, injury, or reinjury while loading and unloading the trap bar as the associated movement forces the weightlifter’s back to withstand force at an awkward angle. One interviewee on the Dartmouth Women’s Rugby team recounted a time when her entire lower back spasmed while adding an additional 45-pound weight plate onto an already loaded trap bar, forcing her to stop mid-workout; while she could deadlift the 135-pound trap bar with ease, it was the act of loading the weights that set her back.

To address this issue, our team has designed a trap bar jack, which can help lift the bar off the ground while the weightlifter loads and unloads weight plates. Since the progress report, we have incorporated feedback from the initial prototype to create two more iterations of our product. As further explained below, our final prototype (Figure IV) firstly was built using steel as it is the most cost-effective material with economies of scale accounted for. Secondly, we changed the loose strap to a sturdier handle that fits snugly with the model. This handle was designed to be longer so that the user has to bend less to remove the device from the bar. Lastly, we redesigned the back of the prototype so that it was more ergonomic to step on and also blasted and powder coated the final prototype  in black for a more aesthetic look. 

From user testing and post-test interviews, we were satisfied to see that we addressed many of the feedback related to ease of use, aesthetics, and efficacy we were hoping to eliminate since our initial prototype. For future designs, we plan to incorporate rubber padding underneath our product to decrease the loud sounds users complained about during final testing and mitigate the possibility of damaging the gym floor.

Moving forward, we created a business plan with financial projections over the next three years. Under the assumption that we take out a $205,457 loan at 10% interest rate compounded annually, we deduced that our business will break even in September of the first year. The loan amount was calculated by finding the capital required to fund the first half of the first year of our business and averaging that out on a monthly basis. It was also assumed that our product will be priced at $50 – an amount that was determined through user feedback as well as market research. For future steps, we plan to get our design patented through the help of Dartmouth’s Technology Transfer Office, and we are currently in the process of getting our invention disclosure form approved. 

2. Problem Statement 

Gym-goers using trap bars to conduct their deadlift workouts alone run the risk of straining their back while putting on weight plates. 

3. Potential User/Purchaser 

The primary users of this product will be weightlifters who frequently lift alone and incorporate trap bar deadlifts into their workouts. The potential stakeholders or purchasers of the product will be commercial gyms, athletic teams, and individual weightlifters. For the scope of our project, we conducted user testing on 12 student-athletes at Floren Varsity Gym and weightlifters at Alumni Gym. We also made sure to gain feedback from those who had the chance to test out our initial wooden prototype. 

As discussed in previous reports, back injuries have led many weightlifters to switch from using conventional barbells to trap bars as it allows the weights to be closer to the weightlifter’s center of gravity. Since 2010, trap bars have been rapidly growing in popularity, becoming more common in weight rooms across the country. We conservatively estimate that there are roughly 7.2 million users of the trap bar in the age group of 13-25 year olds given that there are 8.5 million student-athletes in both the high school and collegiate level. This number was deduced using a penetration rate of 85%, which was determined with the input of Dartmouth College’s strength & conditioning coach who claimed that the “majority of athletes utilize trap bar deadlifts into their workouts.” This specific group of weightlifters are the ones that we aim to target with our product.

In particular, weightlifters without a lifting partner are at a higher risk of straining their lower back as they are forced to simultaneously lift the trap bar and slide the weight plates onto the bar without the help of another person. As such, a trap bar jack that could lift trap bars off the ground without adding stress on the lower back on would be marketable to not only weightlifters who utilize trap bars to avoid spinal injuries but also weightlifters and athletic teams that incorporate trap bar deadlifts for injury-prevention purposes. 

4. State of the Art Limitations 

Existing mechanisms that focus on improving an athlete’s ability to set up a free weight exercise center around the conventional barbell, so there are limited innovations for trap bar loading and none that have been patented. There are primarily two types of inventions/patents that aim to reduce back strain caused by loading the trap bar. The first is a complete redesign of the exercise that aims to get the same muscular results without using the trap bar. The second is a redesign of the trap bar itself, which is usually a standing version of the current trap bar; free-weight apparatus companies Eliko and Kabuki are primary sellers of these new trap bars. These two options either change the fundamental exercise or require purchasing whole different equipment that can cost anywhere between $300 to $600. There also are barbell “jacks” that aim to make loading of a barbell easier, but these inventions cannot be utilized with a trap bar. In sum, the state-of-the-art research indicates that if consumers are willing to purchase a new trap bar, there is likely an appealing market for a simpler, more cost-effective mechanism to reduce the risk of unloading/loading weights onto trap bars. 

Apart from official patents, further research was conducted to look into “hacks” weightlifters use to load weights. We found that a trick used by athletes is to have one person prop the trap bar into a standing position while the other loads the bar. The clear limitation of this is that it requires two people to execute. Moreover, we came across a “DIY trap bar jack” on YouTube that used similar mechanisms as the barbell jack. This method is further analyzed in the experimentation section of the report (Figure 13). 

5. Key Specifications 

As we performed user testing, ease of use was an essential specification for feedback, as we wanted our prototype to give users a pain-free method to quickly load/unload plates. To measure this, we collected user feedback using a 1-10 scale on measures of intuitiveness and ease of use. With efficacy being another important specification, we aimed for the solution to also have high efficacy, reducing back pain while also providing no safety hazards to users. To test this, we used a torque equation, a friction force equation, and gathered user feedback.  We additionally maintained our sub-twenty-pound weight specification, a key specification in narrowing down to a one-sided jack solution. We also kept our weight-bearing strength specification of 405 lbs.

The remaining specifications have stayed consistent in description and quantifications with the version in our progress report, including durability, adoptability, feasibility, safety, cost, and aesthetics:

Table I: Key Specifications

6. Rationale for Selected Alternative 

Our alternative matrix (Table II) remains the same as the one from the progress report, especially considering the outstanding performance of our arm jack prototype.

We re-examined our material matrix (Table III) after talking with the review board as we discovered that steel was much cheaper than we originally expected. When buying in bulk, there is a high discount rate on tons of steel, so we could financially capitalize on economies of scale. Moreover, after observing that the plywood prototype was chipped slightly after one round of user testing, we decided to pivot to the ⅛ steel for our final product. We also added a new “recyclability” specification to our material matrix for environmental considerations. Specifically, we researched the recyclability of plywood and ⅛’’ steel since they were our top contenders in our matrix. Both are recyclable; however, plywoods can only be recycled when they are untreated, unpainted, and unstained. Steel, on the other hand, is 100 percent recyclable, so recycling would not decrease its quality, making it especially sustainable. 

7. Experimentation & Benchmark Testing 

In deciding benchmark testing, we looked at the various mechanisms trap bar users utilized to load the bar. The overwhelming majority of those we talked to did not use any mechanism to reduce back strain but cited back strain or discomfort when setting up the trap bar exercise. As mentioned in the state of the art analysis, we came across a DIY trap bar jack that essentially created a standing trap bar. We decided to prototype this invention with foam core but quickly realized that it was not intuitive to use (Figure 1). It also required using a pin, and the width of the jack had to be custom to the trap bar it was intended to be used on. Alternatively, when lifting in groups, athletes lever the trap bar into a standing position, but this method requires at least two people. While these alternative methods exist, they are not widely adopted by gym goers. As a result, we conducted our ease-of-use benchmark testing against not having a mechanism at all.

8. Analysis

As shown in the diagram below, there are two primary ways that the weightlifters load and unload the weight plates on and off the trap bar. The first method involves simultaneously lifting up the trap bar while sliding the weight plates onto the bar. The second method involves sliding the weight plates across the floor without lifting the trap bar – overcoming the friction between the weight plates and the gym floor. Our final prototype eliminates these uncomfortable movements by elevating the trap bar enough for the weightlifter to slide the weights onto the bar without back strain. 

Regarding the first method, we utilized the torque equation to determine how much less torque is required from the lower back to perform the action of loading and unloading weights. Shown below is a screenshot of a user loading weights, the corresponding free body diagram, and the calculations of the torque eliminated:

To find the torque, we needed the following parameters: r, F_t, and θ. r was calculated by averaging the length between the shoulder and hip bone of 5 users. F_t was calculated by measuring the weight of 45lb weight plates on one side of the trap bar for three different scenarios: 1 plate, 2 plates, and 3 plates added onto the bar. Finally, the θ was calculated by measuring the angle between the three corresponding points in the above diagram. From these calculations, we were able to deduce that our final prototype eliminated 153.262Nm, 260.814Nm, and 368.367Nm of torque from the lower back when one, two, and three weight plates were loaded respectively. 

Regarding the second method, we utilized the friction force equation to calculate the force of friction that was eliminated from the use of our prototype. The corresponding free body diagram and calculations are shown below:

To calculate the friction force eliminated, we needed the mass of the plate as well as the coefficient of static friction between the weight plate and the floor. Fn was calculated by finding the Fg of one 45lb weight plate. The friction coefficient (0.6) was determined by researching the coefficient of static friction between rubber and concrete under the assumption that rubber plates would be used on a concrete gym floor. From these calculations, we were able to deduce that our final prototype eliminated 117.72N of force. 

9. Initial Prototypes

After completing our initial alternatives matrix, our team built a scaled-down trap bar out of chopsticks and foam core and completed a total of six rough prototypes out of a range of materials. We built small-scale prototypes of the lever jack and hydraulic pump jack out of chopsticks and foamcore (Figure 1) and a full-scale benchmark foamcore prototype of the DIY trap bar Prototype (Figure 2). Due to material constraints, the prototype could not hold the weight of the trap bar but served as an important comparison to our designs.

We also built a small-scale prototype of the tilt cart, our original frontrunner design (Figure 3). Upon completion, we began to build a full-scale prototype of the tilt cart out of foam core but soon realized the design was quite large, unattractive, and would be quite heavy. Upon this realization, we referred back to our specifications and revised our alternative matrix to focus on a lighter-weight, more feasible option.

Our last foam prototype was a small-scale angle jack, with an 85° angle to lever the weight up using the inside handlebar (Figure 4). We decided to move forward to create a full-scale model out of steel tubing (Figure 5). As we welded the prototype with Hutch, we struggled to create an appropriate attachment for the jack and decide on an appropriate height to hold the plates up. At first, we used the jack near the weight plates but then experimented with lifting it from the inside of the hex-bar. We really liked this way of lifting the weight, especially in combination with the mechanism of stepping on the jack in order to lever the weight up as it could be performed intuitively. 

10. Prototype Progression 

Scrap Step-On Jack                 Angled (single) Arm Jack #1        Angled Arm Jack #2               Angled Arm Jack #3

Inspired by junk materials we found outside a fraternity, the Scrap Step-on-Jack (Figure I), was our first working prototype. The simple, angled design and lifting mechanism was the start of development for our final prototype. Specifically, once discovering the ease of lifting the bar using the inside grip bars, we continued to iterate using this mechanism. The angled metal piece, which looked almost like an arm curling the bar to lift it, also served as inspiration. This prototype, combined with our testing of the angle-jack prototype (Figure 5), led us to our most successful angled-arm prototype. 

                

Figure I: Scrap Step-On-Jack (rubber bands, wood, scrap metal)

Our next prototype, on which we performed seven initial user tests on, is the angled-arm prototype (Figure II). With a 2-inch solid steel-wheel serving as the main point of leverage, the design is simple: it attaches to the bar under the handle of the trap bar and rolls under to leverage the weight up (Figure 8). 

We had incorporated the wheel design on the first iteration of our initial prototype (Figure 6) as the wheel allowed for a less-taxing method of moving up the weights. Due to it having only one arm, however, the initial design was unstable. Consequently, for the next iteration (Figure 7), we included two arms connected by 2 steel rods with large red wheels. Upon testing, the second iteration worked well. Nonetheless, the rolling of the jack underneath the bar was hindered by the size of the red wheels – they were almost an inch below the model. To fix this, we replaced the wheels with a solid aluminum rod which hits the ground just below the model (Figure II). This made getting the model underneath the trap bar easier, confirmed by “ease of use” ratings during user tests.

                Figure II: Angled-Arm Prototype 2 – Version 2 (scrap plywood, aluminum dowels)

One of our most important specifications to evaluate qualitatively and quantitatively during testing was ease of use. Thus, during the testing of our second prototype, each user responded to the prompt “is it intuitive and easy to load/unload weight plates comfortably?” with numbers 8 or higher on a scale of 1-10. 

Efficacy was another main specification as it is directly related to the extent to which our product relieves back strain and reduces injury risk. We underscored this specification by asking our testers “do you feel that this relieved back strain?” All users agreed, one commenting, “Definitely… I would use it again for back relief.”

For our next prototype, we decided to address users’ wishes for a wider foot platform to reduce risk of getting their foot stuck in the jack, a more secure handle for better leverage, and an aesthetic that fits the gym setting. We also wanted to incorporate the review board’s suggestions for hooked clamps to hold the bar. 

After brainstorming different ways to incorporate user feedback, we created our third wooden prototype (Figure 9) with hooked edges for increased bar security and a flatter platform – unlike the rounded platform from previous iterations (Figure II) – to increase foot stability. The double aluminum bars at the back also allowed users to place their entire foot on a larger platform, further increasing stability. This was confirmed by multiple user testers who had used the previous prototype. 

Figure III: Angled Arm Jack #3 (scrap plywood, aluminum dowels) and sketches

11. Our Prototype 

   Figure IV: Angled-Arm Final Prototype (steel, aluminum dowels)

Our final prototype, the Trap Bar Buddy (TBB), was the result of weeks of testing and redesign. Even though we had established the optimal shape/mechanism during the building phase of our initial prototypes, there were still a few aspects that we had to change. First, we plasma-cut the steel pieces to create the respective parts for the lever arm handle as well as step-on platform. Both of these additions to the design came from user feedback and brainstorming sessions as a team (Figure 9). We then welded these individual parts together to create our final product. We also added sandpaper on our step-on platform to ensure that the user had more grip while using the product – addressing an issue of foot security previously brought up in the user testing of our initial prototype. Additionally, we designed a fixed handle that fits snugly in the angled corner of the prototype, as opposed to a rope/strap that could easily get caught under the model. A notable feature of this new handle is that it is longer than the original strap. This allows for the user to bend over less to remove the device from the trap bar, ultimately reducing the torque required from their lower back. The design of the “hooks” was also altered because the previous design made it more difficult to slide the bar into position. Furthermore, a small rectangular piece of steel was welded to the bottom of the prototype and covered with gaffing tape to reduce the damage dealt onto the floor and increase friction between the prototype and the ground to reduce sliding. Finally, the steel parts were also bead blasted and powder coated, which contributed to the sleek, gym-like look of the final prototype (Figure 11). 

Upon user tests and interviews with twelve student-athletes and two strength coaches from Floren weight room, we found our final prototype was successful in covering the majority of our specifications. We measured ease of use, one of our most important specifications, by asking users to rate both the intuitiveness of our device and ease of use on a scale of 1-10. Users’ ratings for intuitiveness averaged a 7.8 and for ease of use, an 8.4. These ratings were confirmed through observation and video footage. 

Another key specification considered was efficacy – does the TBB actually decrease back strain? Nine test users reported unloading and loading the trap bar to be an uncomfortable/painful experience and half of the users reported ongoing back issues; 100% reported that the TBB relieved back strain. This was an important metric as it represents the intersection of our efficacy and strength specification; with the risk of back strain increasing as the trap bar is loaded to the maximum capacity of 405lbs, it was determined that back strain decreased accordingly as more weights were added onto the trap bar. 

The remaining specifications of weight, durability, strength, adoptability, cost, safety, and aesthetics were also met. In terms of weight, the final prototype came in at 10.2lbs, 9.8lbs below our max weight goal. Concerning aesthetics, users gave TBB an average score of 8.7 on a ten-point scale. Further, by using 10-gauge, ⅛” steel, we increased durability in comparison to plywood along with decreasing the cost of production. Our final weight and aesthetic score, increased adoptability of the TBB, becoming a device that can easily integrate into different gym settings (Table I). 

Aside from general specifications, we asked users the likelihood they would implement this into their lifting regime on a scale of ten, yielding an average score of 8.7. Regarding pricing, users said they would pay an average of $50 for the TBB. 

12. Business Plan  

After conducting user feedback interviews and market research, we priced TBB at $50/unit. We priced our product significantly below the jacks/redesigns of companies such as ‘Rouge’ and ‘Eliko’ – costing anywhere between $200 to $600 – as our product is comparable but does not have the name brand recognition. To find the predicted cost of goods sold, we broke down the components of our product and priced material accordingly. We then calculated the potential discount rate of bulk buying materials by consulting experienced experts as well as conducting research on websites from online retailers. The two pieces of capital equipment required were the plasma cutter and hypertherm table which we each assumed a 10 year life cycle and no salvage costs for. For predicting the number of units sold, we assumed that 500 units would be sold in the first month and then intuitively predicted a 12.5% month on month growth rate for the first year and subsequent 7.5% and 5% growth rate for Y2 and Y3, respectively. Our COGS/unit for 2023YE is $36.05 and our hypothetical selling price is $50. We predict needing a $205,457 loan, which is six months of revenue and we assume to pay a 10% interest rate compounded annually on this loan. Following these assumptions, the breakeven point should be around 2023Q3. 

As we have explained in the part about the material matrix, steel, the main component of our final prototype, is 100% recyclable and sustainable. Our second major material is aluminum, whose recycling rate exceeds 90% according to the Aluminum Association. Additionally, the energy required to produce recycled aluminum is only 5% of that required to produce new aluminum. The main manufacturing process is plasma cutting, which is safe and energy-efficient with few byproducts. Thus, our prototype is completely recyclable and environmentally friendly.

13. Conclusions and Recommendations 

As mentioned earlier, moving forward with future designs we would like to incorporate rubber padding underneath the TBB to decrease both the loud sound users complained about and the likelihood of damage to the gym floor. Further, through our project, one of our testing locations, Alumni Gym, bought new trap bars. Upon testing on these new trap bars, we found our grips were not big enough to hold the fatter handles. Additionally, while we did not design for barbells, as we tested we realized our device could aid in both the loading and unloading of trap bars and barbells In fact, the TBB was able to lift the entire barbell, despite not having big enough grips for the fatter gripped barbells (Figure 12). To increase compatibility, in future designs we would aim to create larger grips to include both barbells and fatter grip trap bars. We might also consider replacing the aluminum with steel as well to avoid corrosion.

Under the recommendation of Professor Baker, our team is currently in the process of acquiring a patent for our product. We have been in communication with Cheryl Junker as well as Dartmouth’s Technology Transfer Office to move forward with the patenting process. We have filed the Invention Disclosure Form and are waiting to hear back on further feedback from the TTO. We hope to possibly market our product across college level athletes across the nation, starting with Dartmouth then possibly expanding to Ivy League and other institutions part of the NCAA. 

Appendix 

  Table II: the Alternative Matrix

  Table III: the Material Matrix

Figure 1 (left): Lever jack and hydraulic pump small-scale model (foam core, chopsticks)

Figure 2 (right): Full-scale DIY trap bar Prototype (foam core)

Figure 3: tilt cart small-scale model (foam core, chopsticks as trap bar)

Figure 4: Small-scale angle jack (foam core, wooden dowel, chopsticks)

Figure 5: Welded angle jack prototype (aluminum tubes)

Figure 6: Angled (single) Arm Jack Prototype #1 (scrap wood)

                Figure 7: Angled-Arm Jack Prototype #2 – version 1 (scrap plywood, aluminum dowels, wheels)

Figure 8: Angled-Arm Prototype #2 CAD Model

Figure 9: Second round and final prototyping sketches 

Figure 10: Angled Arm Prototype #3

Figure 11: Angled Arm Prototype #4 CAD model

Figure 12: Angled Arm Prototype #4 Lifting Barbell

Figure 13: DIY jack and “hacks”

(https://www.youtube.com/watch?v=5usBJ78C5Zs&t=328s) 

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