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Personal Load Carrying Equipment Conceptual Design Report

I. Overview: Our team was tasked with developing the conceptual design for the “Personal

Load Carrying Equipment Design Brief”. In this introduction, we will present our assessment and our reframing of the brief. We will then present three conceptual designs to the problem and provide our rationale for selecting the preferred conceptual design for the detailed design. II. Assessment of Brief

The brief addresses a valid concern; however, we do notice several key deficiencies throughout. A. Definition of Personal Efficiency

The brief does not give a clear definition of personal efficiency, without which the goal is likely to become ambiguous. We explicitly define personal efficiency as follows: “personal” as “[…] intended for use by one person”1 and “efficiency” as “accomplishment […] of a job with a minimum expenditure of time and effort”2. Therefore, a load-carrying equipment that enhances personal efficiency will reduce the time and effort, or to be consistent with the phrase used in the brief, “the convenience” of transporting a load for one person. B. Definition of Ergonomics The requested equipment is closely related to the idea of ergonomics; thus, we deem that a definition of ergonomics, missing from the brief, should also be present in this document. In general, ergonomics is concerned with “the understanding of the

1 Dictionary.com (2012) 2 Dictionary.com (2012)

interactions among humans and other elements of a system”3. Since the focus of this report lies only in physical devices, ergonomics refers to only physical ergonomics, or “human anatomical […] characteristics as they relate to physical activity” 4. C. Problem Definition

The brief focuses on the issue of load-carrying equipment for university students, who belong to a population neither too general nor too specific as to prevent divergent solutions. The brief gives a thorough account of the needs for personal efficiency consistent with the definition above. However, the brief makes claims in defining the problem without evidence to support it. Therefore, we decide to assess the claims made in the problem definition using research methods:

1. The brief claims that existing equipment for university students, mostly

backpacks, do not allow the user’s body to work efficiently. Backpacks use power generated from shoulders to carry the load, yet “the safest and most comfortable placement of loads is on the pelvic area (the lower back and hips). This area of our bodies has evolved to carry the weight of the upper body” and “due to the structure of the pelvic area, the weight of any load is distributed comfortably and safely through the hips and into the legs and feet”5. In addition, traditional backpacks are inefficient because the user has to lean forward to balance the load in the back while “a load carrying system which keeps [the user] upright will reduce energy consumption” 6 . Relevant improvement can be achieved by the reference design (Figure 1). The claim from the brief is valid as supported by the above statements from research.

3 IEA Ergonomics Human Centered Design (2010) 4 IEA Ergonomics Human Centered Design (2010) 5 North Peace Team (2012) 6 Aarnpacks (2012)

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Figure 1: FlowMo Bodypacks, example of a load carrying device where

the center of gravity of the body is vertically in line with the center of gravity of the load so that the person can remain upright 7

2. The brief claims that existing equipment for university students does not allow

the user to manage and retrieve items efficiently. Backpacks most commonly have one main large compartment (Figure 2)8 and as a result, the user must put items in the same section of the equipment. The claim from the brief is valid as supported by the lack of management capabilities of the backpack.

Figure 2: Picture of a traditional backpack, it consists of one large compartment and a smaller section in the front. 9

7 Aarnpacks (2012) 8 Wayfair (2012) 9 Wayfair (2012)

3. The brief claims that existing equipment for university students cannot keep its

content stable under shaky conditions. Traditional backpacks “must undergo the same vertical displacement as the hip, which moves up and down 5 to 7 centimeters during walking. As a result, the peak forces exerted on the body by the load can be twice as high when walking, and three times as high when running”10. The claim from the brief is valid as supported by the magnitude of the displacement and the forces exerted on the body.

D. Stakeholders

The brief did not explicitly state the stakeholders for the requested design. The main stakeholder can be inferred to be the users – university students – as the equipment will be specifically designed for this population. Other stakeholders include the rest of the general population that interacts with the load-carrying equipment (the design can still be used for people other than university students), manufacturers, competitors (example: backpack companies), schools and the environment (example: environmental organizations, as the environment has no voice). E. Objectives

The objectives of the brief are refined with metrics and grouped into three key objectives as follows: 1. The personal load carrying equipment uses the body efficiently to carry the load.

This is the main objective and is prioritized as this is the main problem of the backpack (shoulder loading).

2. The personal load carrying equipment contains space which can be organized (books, lunch bags, electronic equipment). This is the secondary objective as space management is more prioritized than stability due to its impact on personal efficiency – it influences both time and effort of retrieving and adding items to the equipment.

10 Physics.org (2012)

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3. The personal load carrying equipment can keep the inside content stable during fast movement (includes portability on a bicycle and the transit, considering that some university students are commuters). This is the tertiary objective, and focuses on the target population for the designs (university students).

F. Metrics for Each Objective 1. Weight of the load not carried by the shoulders (for example: on the pelvis or on

the ground), measurable by total weight of the equipment minus the weight on shoulders using a pressure sensor

2. Number of sections and amount of time it takes to access the easiest accessible section, measurable by a timer, including the time that it takes to open and close a section

3. Displacement of the equipment from the body (both horizontal and vertical) compared to the position of the equipment from the body at rest, measurable by a motion analysis system (PONTOS) 11

G. Constraints The constraints in the brief were overall reasonable; however, the values in the constraints were not justified with evidence. The constraints in the brief were reframed with new values and justified: 1. The maximum carrying weight must be no less than 15kg which is reasonable as

“An individual in good health should be able to carry 20% of their body weight”12 which is around 18kg for a 90kg person.

2. The maximum carrying volume is pushed back to 20L. This is because 30L is determined to be too large and is unjustified. This is based on the space under the lecture seats, (not including leg space) which were around 30cmx30cmx30cm (27L). The volume required for the equipment would not be able to fit under the lecture chairs considering that the backpack is designed for a

11 Trilion (2012) 12 ProliteGear (2012)

university student. The maximum carrying volume must be no less than 20L taking into consideration the volume under the lecture seats.

3. The self-weight is pushed back to 3kg. A self-weight of 1kg is determined to be overly restrictive on the conceptual design and is unjustified. This is because a traditional backpack weighs around 3.1kg13 and a ultra-light backpack (reference design) weighs around 0.9kg and “are typically made out of a lighter weight fabric that may not be as strong as the material used in a pack weighing over 7 pounds [3.1kg]”.14

4. The attachment volume of 5% of the carrying volume is determined to be reasonable considering the aesthetics of the load-carrying device.

5. The portability of the equipment for running and biking is mentioned and found to be reasonable activities for a university student. The equipment must also be portable on a public transit.

6. The number of sections both internal and external to the equipment is pushed back to be 5. This is because 10 adjustable sections is found to be too great a number and may actually reduce personal efficiency due to the time of searching through the different sections. The use of the word “adjustable” also implies a solution, as a space can be manageable without being adjustable. One constraint that was not considered by the brief was the safety of the

equipment. Therefore we have imposed an additional constraint to the conceptual design in that the conceptual design must attempt to reduce the risk of severe hazards occurring. H. Criteria The criteria of the brief included that were measurable are reasonable; however, three of the criteria included cannot be measured. These criteria are refined to be more specific and to include a numerical way to determine the success of the design:

13 ProliteGear (2012) 14 ProliteGear (2012)

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1. The self-weight to self-volume ratio of the equipment, which means the equipment should have lower density materials so the load not concentrated on one area of the body (lower is better)

2. The self-weight to carrying-weight ratio of the equipment (lower is better) 3. Water permeability: the volume of water that the equipment gains during a 30

minute shower under a non-pressure dropper rain simulator15 (lower is better) 4. Durability: the amount of time that the equipment can withstand on the shock

tester with shock levels that mimics the shock during walking without visible damage16 (higher is better)

5. Cost: the estimated material and labor cost of the equipment (lower the better)

However, we feel that these criteria are not sufficient to evaluate the success of the personal load carrying equipment, as they are not related to metrics from the objective. Therefore, we have added 4 new criteria so that the success of the equipment is relative to how well the equipment meets the objectives in addition to the criteria from the brief: 1. The percentage of the total load distributed away from the shoulders of the user

(higher is better) 2. The total time required for users to add and remove an item from five sections

that take the least time to reach (lower is better) 3. The speed of movement of the user while running until the displacement of the

equipment from the body is greater than 5cm17 compared to the position of the equipment on the body at rest (higher is better)

4. The total amount of time to make the equipment ready for usage on (1) public transits, (2) a bicycle and (3) for walking with the starting condition of the equipment in its most compact form (lower is better) The priority of each criterion relative to each other will be further defined in the rationale.

15 FAO Natural Resources Management and Environment Department (2012) 16 L.A.B. Equipment, Inc. (2010) 17 Physics.org (2012)

III. Conceptual Designs In this section, three conceptual designs to the problem will be presented. A. Conceptual Design A: Padded Belts and shelf

This conceptual design concentrates on the aspect of even distribution of weight and shelf section to increase the user’s personal efficiency. The design will be a set of accessories for standard backpacks, containing two padded belts and a shelf section.

Primarily, the belts will be attached to the shoulder strips as removable features. One of the belts is designed to be attached around the waist of the user, and its thickness will be 1 cm so that more weight could be distributed on the waist, which is a more efficient body part than shoulder; the other will be around the user’s belly. Both belts will be adjustable in order to enable the user to wear them wherever they fit the user’s body, and they will be attached to the shoulder strips by clips on each end. The belts will help distribute the weight of the backpack and split the pressure on shoulders to waist and hip in order to prevent pains on shoulders with too much pressure. The belts will also function when the user is biking or running. They keep the backpack closer to the user’s body compared to a standard backpack so that the backpack will not sway horizontally as much, reducing damage to the content inside after a series of movements. The following is an image that demonstrates how the belts appear.

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Figure 3. CFP-90 military issue field pack.18

Secondly, the shelf section in the accessories set could increase personal efficiency by allowing the user to manage the inside space of the backpack wisely and for various purposes. The shelf consists of four rigid dividers sectioning the space in a standard backpack into five parts in which regular shaped items such as binders, lunchboxes and water bottles can fit. The shelf section is designed to be placed into the main compartment of a standard backpack. It will keep items from centering at the bottom of the backpack and causing damage to the body and allow the user to manage items in the bag more efficiently by enabling the user to take things in and out without messing things in other sections. With the padded belts and a shelf system, the backpack would be safe enough for a university student as the weight is redistributed and the chance for the weight to cause body injury is reduced. One risk could be the possibility of the belt breaking, releasing sudden extra pressure on shoulders and causing potential harm to body. A sketch of the shelf system with dividers is shown in Figure 4.

Figure 4: Shelf system and padded Belts Sketch

18 Loadup(2012)

Ø Summary of the Padded Belt Design: 1. Redistribution of load:

The belt redistributes load from the shoulders of the user to the pelvis. The center of gravity of the load is moved closer to the center of gravity of the body as the belt holds the backpack closer to the user.

2. Space and content management: The shelves divide the main compartment of the backpack into different components as to allow for organization.

3. Stability and Portability: The belt holds the backpack closer to the body of the user.

B. Conceptual Design B: Vest Backpack Ø Strap Design:

Backpack traps should be loaded on deltoid rather than on the shoulder because more muscle is concentrated around the deltoid19. Thus, to evenly distribute the load, the top portion of the attachment trap near the shoulder blade will be extended so part of the load will be distributed onto the deltoid.

Ø Reference Design of the Front Section:

The front attachment of the bag to the body will resemble a vest, in order for some load to be distributed on the front. This is because it would be ideal for maintaining balance if the load were distributed on both front and back20. Those vests can help to place some load on the front for balance without impede walking and sight. An example is one of the reference designs in Figure 5:

The problem with this reference design is that first, it is too hot to put on for

the summer, second, the shoulder strap is too narrow and does not extend to the deltoid and third, this does not meet the constraint of having the attachment volume 5% of the original volume. 19 Hobottraveller (2008) 20 Hotbottraveller (2008)

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Figure 521: Reference Design of a Vest Backpack Ø Development from Reference Design of the Front Section:

Thus, this design will be based of the reference design with the following three key modifications, which will be illustrated in Figure 6.

Firstly, the bags in the front will be detachable in order for the vest can be worn during all seasons. The bags in the front are attached to the vest through hook and loop closure and can be taken off in the summer. This allows air to flow in and out quicker for cooling affect. Even when the bags are taken off, there are still straps left in the front to help distributing some weight in the front. Note that the bags in the front do not count as part of the attachment volume.

Secondly, for the closure of the vest, hook and loop closure will be used instead of zippers used by the reference design, in order to avoid the problem of getting zippers stuck when zipping up clothes.

Thirdly, an additional strap will be added a couple of inches beneath the armpit in order to act as a back straightener and help to improve the users’ postures.

21 Loop(2012)

Figure 6: Front View of the Vest Design

Ø Sections inside the backpack:

Ivar backpacks suggested to use diagonal shelves to maintain the shape of the backpack so that the weight load will not all go down and be concentrated on lower back and hip, as illustrated in Figure 722.

Figure 7: Shelf System of Ivar Backpacks

22 Ivar (2012)

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The problem with the shelves in this figure is that the diagonal shelves make the space inefficient for carrying large objects such as laptops and lunch bags. Also, the shelves made it inconvenient to retrieve items on the bottom shelf. However, diagonal shelves prevent all the weight from going down, and therefore they will be kept but with the following modifications.

Firstly, an extra vertical shelf will be added to provide spaces for large books and laptops. Secondly, zippers will be added to allow quicker access to the books on the bottom and an extra section will be added in the bottom to allow lunch bags to be placed. The bottom section is a lunch bag so retrieving lunch does not interfere with the process of receiving the books from the shelves. Thirdly, the shelves are foldable so that when they are not in use, they can yield more space for larger items.

The sections are shown in Figure 8:

Figure 8: Side view of the Vest Design

Ø Summary of the Vest Design: 1. Redistribution of load:

The vest redistributes load to be more concentrated on the deltoid. The vest moves the center of gravity of the load to coincide with the center of gravity

of the user due to both front and back loading, so that the user can remain upright while using the equipment.

2. Space and content management: The vest has multiple sections as represented in Figure 8.

3. Stability and Portability: The vest holds the loads closer to the user’s body due to the additional attachment areas on the body.

C. Conceptual Design C: Pulley

Another conceptual design which is a solution to the problem is a pulley. This consists of several plastic containers, which fulfills the requirement of having different compartments as stated in the objectives, and a collapsible metal frame with two swivel wheels at the front, as seen in Figure 10, and a frame and handle that can be compacted, as seen in Figure 1. The collapsible frame is designed to be even more compact than the frame shown in Figure 1 by utilizing frame components which can be inserted into each other (Figure 12). The reference design for an even more compact frame is from the collapsible handle of the telescopic umbrella (Figure 13). To allow the frame to be collapsible, the handle of the pulley is changed from the handle with double attachments in Figure 9 to the reference design for the handle on Figure 14. However, the design in Figure 14 does not have finger grooves and for a better grip, finger grooves are added to the design for this pulley (Figure 12).

Figure 9: Frame 23 Figure 10: Swivel Wheels 24

23 Ebay (2012) 24 Berry Land Campers. (2012)

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The metal frames and box should be less than 45cm in width25 so that it can be

easily carried through a lecture hall (take into account the height and length). The metal frame is collapsible so that it can be stored without taking up much space especially in a cramped dorm room. The plastic containers should opaque so as to provide privacy for the university students.

As all of the plastic containers of varying sizes are detachable, the university students can attach the number of containers as they see necessary depending on the amount of load which they plan to take that particular day.

Additionally, the containers can be bought separately so it gives flexibility to those students, who do not require so much space, would not have to unnecessarily buy all the plastic containers with the metal frame.

The containers would also have a hinged door which will allow students to access the contents as seen in Figure 11. The top lid of each box contains a ribbon as shown by the black ribbon in Figure 15 so that each box can stack on top of the other. The ribbon should fit tightly as to prevent the containers from falling off of the frame. The bottom box is secured with a spring mechanism (Figure 12).

Figure 11: Plastic Container with Hinged Lid 26

Furthermore, the swivel wheels will be able to move in any direction, which increases mobility and safety as the user would be able to alter their direction in relative cramped spaces (e.g. taking public transit) with relative ease.

The containers can be made with durable plastic which is water-proof and can be manufactured using injection molding.

25 Sauder Manufacture Co. (2012) 26 Welco (2012)

However, the pulley is not very aesthetically pleasing because it is mainly consists of rectangular containers which is not particularly visually appealing. The cart is also more difficult to use in severe winter conditions as due to the resistance of the wheels in the snow.

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Figure 12: Visual sketches relating to the pulley

Figure 13: Telescopic umbrella frame as reference design for a collapsible frame27

Figure 14: EZ Pull Handles as reference design for the handle of the pulley28

27 Umbrellaman (2012) 28 Doug’s Wagon Walker (2012)

Figure 15: Stacking Totes, reference design for stackable boxes29

Ø Summary of the Pulley Design:

1. Redistribution of load The pulley moves the load off of the body of the user to be carried by the ground. 2. Space and content management The pulley contains attachable boxes which can be mounted onto the frame. 3. Stability and Portability The containers locks into place by the stacking ribbon and the bottom container is locked in by a spring mechanism. The frame can be compacted for portability.

IV. Design Rationale: Reason for Chosen Design The final design was selected based on a comprehensive analysis and assessment of the three candidate designs against the chosen criteria. A weighted table was used to help our decision as follows.

29 Amatech (2012)

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Criteria Weight Belt & Shelf Vest Pulley

Self weight vs. self volume 1 3.5 4 3

Self weight vs. carrying weight 5 3.5 2.5 2.5

Water permeability 1 3 2.5 5

Durability 4 3 3 4

Load Distribution 7 3.5 4 5

Organization of Sections 5 3.5 3.5 1

Stability of Equipment 4 3.5 4 1

Portability 1 5 5 2

Total 28 97 97.5 82.5 We chose a scale of 5 because only the conceptual designs are evaluated and

not the detailed design. Therefore, there would not be enough detail for each design to justify a gradient of 11. The chosen criteria are defined the same as the nine criteria we came out with in the earlier section. “Self weight vs. self volume” refers to having low-density materials to efficiently distribute the load. “Self weight vs. carrying weight” is self-explanatory. “Water permeability” refers to the volume of water that the equipment gains during a 30-minute shower under a non-pressure dropper rain simulator. “Durability” refers to how well the device can withstand in shaky condition. “Load Distribution” refers to how much the percentage of total load is redistributed away from shoulders. “Organization of Sections” is self-explanatory. “Stability” refers to how much displacement the device undergoes away from the body while the user is running or biking. “Portability” refers to the amount of time the device can be packed/unpacked for usage.

As for the weight of each entry, we decided on the numbers purely according to how closely they are related to the objectives. “Load Distribution” is of the uppermost priority, thus assigned a weight of 7. “Self Weight” and “Organization of Sections” are two of the major setbacks of the existing reference designs, thus assigned a weight of 5. “Durability” and “Stability” are two criteria we deem significant as to maintain the device in a sustainable condition compared to the remaining ones, thus given a weight of 4, and the rest given a weight of 1.

Based on a thorough assessment as shown above, we conclude that the final conceptual design chosen should be the vest. Although it exceeds the belt and shelf design by only a minimal “0.5”, it does a better job of distributing the load and is more stable. These two criteria are of the uppermost importance among the eight listed. Furthermore, although our assessment of the two designs on stability is almost identical, a vest is still more effective at keeping the backpack tight compared to only straps and belts attachment. Thinking of the two in general, we think that the vest is also more revolutionary in terms of its possibility of resembling any reference designs. In addition, the vest provides additional support to hold the user’s body in an upright position, a rather significant aspect that we did not include in the criteria listed, as it would be difficult to judge for the pullet system. As such, the most feasible solution to the load-carrying issue for improving personal efficiency is the vest design. V. References

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12. Ivar (2012). Ivarpacks. [Online]. Available: http://ivarpack.com/ 13. Loadup (2012). CFP90 Military Woodland Field Backpack and Patrol.

(Online). Available HTML: http://west.loadup.com/military/surplus/13179.html

14. Mountain Equip Co-op. MEC Campus Book Bag. (Online). Available JSP: http://www.mec.ca/AST/ShopMEC/GiftIdeas/ForMen/PRD~5026-296/mec-campus-book-bag.jsp

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20. Berry Land Campers. (2012). Skid & Swivel Wheels. [Online] Available HTML: http://www.berrylandcampers.com/rv-parts/new-used/Skid--Swivel-Wheels-p-1-c-438.html

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24. Doug’s Wagon Walker. (2012). The Ez Pull Handle. [Online] Available HTM: http://www.wagonwalker.com/ez_pull.htm

25. Amatech. (2012). Stacking Totes. [Online] Available HTML: http://www.amatechinc.com/products/boxes-totes/stacking-totes.html