Eagle Claw Product Reassessment

Ossur Prosthetics

From: Peter K. Rubin (Senior Mechanical Engineer)
To: Dave Coe (Product Manager)
Subject: Reassessment of Eagle Claw Rock Climbing Device

Foreword

     During the past two years, based on design models created by our engineering team, Ossur Inc. has manufactured and sold the Eagle Claw, a prosthetic rock-climbing leg for above-knee amputees (see Appendix A). Eagle Claws are now used by amputee rock climbers throughout the world who had difficulty climbing with their standard prostheses, which are often heavy, bulky, and poorly shaped for rock climbing. Ossur’s task-specific replacement prosthetic leg is comprised of a rigid, lightweight aluminum pylon connected to an aluminum foot with rubber gripping surfaces oriented to optimize the user’s ability to grip rock ledges. Using the design and manufacturing plan we developed, Ossur has produced 10,000 Eagle Claw devices.

     Since its release to market six months ago, the Eagle Claw has proven to be a huge success. Soon after the Eagle Claw was released, a second run of 5,000 Eagle Claws was manufactured to meet consumer demand. We have received countless e-mails from satisfied customers who enjoy rock climbing much more now that they have the proper equipment.

     In the past month, sales have begun to plateau. The first-generation Eagle Claw seems to be nearing the end of its initial life cycle. At your request, our team has evaluated the Eagle Claw to determine whether the product line has the potential for expansion or whether it should be abandoned. After thorough review, we have identified several innovations for refining the functionality and manufacturing methods of the current Eagle Claw. We have also developed a series of ideas for designing prostheses for non-traditional forms of climbing, such as bouldering, indoor climbing, and ice climbing, which are not supported by the current Eagle Claw device. This memo outlines our suggestions for modifying the Eagle Claw’s current design to create second-generation rock climbing devices that will undoubtedly surpass the original in functionality and profitability. We request additional funding to research and develop prototype models for these second-generation Eagle Claws.

Summary

     Our evaluation of the strengths and shortcomings of the current Eagle Claw device incorporates information obtained from many sources. We observed and interviewed Eagle Claw users, spoke with their prosthetists, consulted several engineers, in-house product testers, and workers involved in the manufacturing process, and obtained valuable information from Ossur’s marketing, sales, and warranty repair departments.

     Customers were generally pleased with the aesthetics and functionality of the Eagle Claw. Nonetheless, we identified potential for improvement in each of the Eagle Claw’s three main regions. First, the rubber toe tips could be attached more securely. Second, the foot claw could be made stronger and could be manufactured more cheaply if a different material and manufacturing process were used. Finally, the length of the leg could be made adjustable, which would make the product easier to fit and would expand the potential market to include growing children and teens.

     In addition to evaluating potential design improvements to the standard model, our team performed preliminary research on designing a series of three specialty Eagle Claw devices that could be the basis for expanding the Eagle Claw line. A bouldering prosthetic would be very short and light and have a large, padded, rubber surface to grip surfaces with few holds. An indoor prosthetic would likely be full length and use a single rounded toe to grip protruding artificial holds. An ice-climbing prosthetic would have razor-sharp metal spikes to dig into hard, steep frozen walls of ice. If Ossur develops these additional specialty climbing devices, the Eagle Claw product line will appeal to a greater portion of the amputee rock climbing community. These products will attract both new customers and previous customers eager to supplement their first-generation Eagle Claws.

Improvements on the Standard Eagle Claw

Introduction:
     The following sections describe the three most pressing shortcomings of the current Eagle Claw, which were mentioned above. For each, we explain the problem and discuss the research performed to understand the problem. We then discuss possible solutions to the problem and elaborate on our recommended solution.

Rubber Pad Modifications:
     Most customer complaints pertain to the rubber pads, which are currently attached with epoxy to the three toes and heel of the Eagle Claw (see Appendix B). To maintain the chisel shape of the toes, thinner rubber is used on the Eagle Claw than is used on the soles of standard rock climbing shoes (3mm rather than 5mm). Therefore, the rubber wears down quickly. The Ossur warranty repair department confirms that 80% of the returned Eagle Claws were sent back because of peeling or worn-down pads.

     Ideally, the rubber tips could be replaced by the user after extended use. Replacement is currently difficult, though, because we do not sell replacement rubber and because epoxy is messy and difficult to apply correctly. The rubber strips are currently attached carefully by hand by factory workers, which contributes substantially to the manufacturing labor cost. A differently-designed rubber tip could be made quickly by machine and would be easily replaceable by the user.

     We considered using a clamp rather than adhesive to hold the rubber strips to the surface of the foot. We concluded, however, that a more aesthetically-appealing but still economical option would be to use molded rubber instead of rubber strips to construct snap-on tips for the toes. Ideally, the rubber would be injection-molded around metal pins that would slide into the tip of the foot (see Appendix E). Further research will be necessary to determine whether it is feasible to manufacture these molded rubber parts.

Foot Modifications:
     The geometry of the first-generation Eagle Claw foot is successful, but a more streamlined manufacturing process could be used to create a similar foot. Currently, each foot is plasma-cut from plate aluminum and bent using a hydraulic press. Ribs are then TIG-welded onto the bottom of the foot. Hard anodizing is outsourced, and final assembly is completed in-house by hand.

     This manufacturing process could be simplified substantially if we changed the material of the foot from 5052 aluminum to 6061 aluminum. We originally selected 5052 plate aluminum because it is more ductile than 6061 aluminum. This made it possible to cold-bend ¼” plate aluminum to the correct shape without breaking or cracking. But the 5052 foot was not strong enough to provide sufficient safety, so it was necessary to TIG-weld structural ribs to the bottom of the foot. This process is expensive and created a bottleneck in the assembly line, since only one foot could be manipulated using the computer-controlled TIG welding machine at any time.

     For the second-generation Eagle Claw, the ribs and TIG welding could be eliminated if we used 6061 aluminum that had been annealed before it entered the assembly line. Annealing is a process that drastically softens certain metals that are held at a specific temperature for many hours, by rearranging their molecular structure. For 6061, annealing is performed at 775°F for two to three hours, followed by controlled cooling at 50°F per hour down to 500°F. Annealed 6061 aluminum would enter the assembly line and could be easily cut and bent. Before the foot was sent to be hard anodized, it would be heat treated. Heat treating restores the annealed material to its full strength and hardness (T6). One method of heat treating, solution heat treating, is performed by soaking the metal in a chemical bath, heating it thoroughly to 990°F, and quenching it in a water bath. Once heat treating was complete, the foot would be approximately 25% stronger than a foot of the same shape made from 5052 plate. This extra strength would allow the new foot to meet the same strength requirements as the old foot without adding structural ribs.

     Adopting this process would greatly increase the manufacturing efficiency of the second-generation Eagle Claw. Unlike the expensive and time-consuming step of TIG-welding ribs, annealing and heat treating are inexpensive processes. In addition, 1/4” 6061 plate is cheaper and more readily available than 5052 plate. Also, stress would be reduced on the bending press and tooling, since the metal to be bent is much easier to manipulate. Finally, eliminating the ribs would save material and make the second-generation Eagle Claw even lighter than the first.

Leg Modifications:
      The leg of the current Eagle Claw is simply a hollow aluminum pylon, which is shortened by the user’s prosthetist to match the length of the user’s other leg. This leg design is easy for us to manufacture, but it may not be the ideal solution. It clearly is not ideal for the user’s prosthetist, who must measure the size of the pylon for each user and machine the pylon to the correct length. While custom-fitting may be worthwhile for permanent prosthetics, it is perhaps too time-consuming for a temporary, task-specific prosthetic, and the added expense of custom-fitting might discourage purchase of our product. This conclusion was confirmed by all 12 of the prosthetists whom we interviewed. An obvious solution is to make the leg length adjustable.

      We propose to implement an adjustable leg by replacing the single aluminum pylon with two concentric tubes. The smaller inner tube will slide smoothly inside the larger outer tube. The two tubes can be freely adjusted and then locked into place using a hand-tightening clamp. The clamp could be similar to the clamps used on many modern bicycles to lock the height of the adjustable seats (see Appendix C).
More customers will buy an Eagle Claw with an adjustable leg, which will be easier to set up and use. While all prosthetic products must be purchased through a licensed prosthetist, a visit to the prosthetist will no longer be required to start climbing. In addition, parents of children and teenagers will be more likely to purchase the adjustable product, knowing that the leg can be easily extended as the children grow. In contrast, users of the current Eagle Claw must purchase and calibrate new pylons whenever they grow. Another benefit is that adjustable-length legs will allow us to manufacture and sell specialized Eagle Claw devices that function as “stubbies” – prostheses that are shortened to give the user increased leverage and control of the appendage. Stubby prostheses are used commonly by bilateral above-knee amputees, but could also be applied innovatively to sports prostheses. Stubbies are generally impractical for unilateral above-knee amputees because it is impossible to walk with a stubby. This would be a problem for rock climbers heading to and from the rock, who must navigate loose rocks, dirt, and hills between climbs. But an adjustable leg would solve this problem, as it would allow the user rapidly to extend the leg for walking and retract it for climbing.

     An adjustable leg would slightly increase the weight, material consumption, and production costs of the Eagle Claw, since an extra pylon and a clamp must be either manufactured or outsourced. Some of this added cost would be absorbed by decreased shipping and storage costs, since the disassembled adjustable Eagle Claw would be approximately half the size of the standard Eagle Claw. Because the added cost of an adjustable leg is minimal and the benefits are many, it seems clear that the second-generation Eagle Claw should include this feature.

Specialty Eagle Claws

Introduction:
     The exceptional popularity of the original Eagle Claw demonstrates the high demand for prosthetic rock-climbing devices. However, we have not come close to saturating the prosthetic rock-climbing device market. Many amputee rock climbers are not yet being targeted by the Eagle Claw product line.
The Eagle Claw is optimized for traditional outdoor rock climbers. A second-generation Eagle Claw that includes the modifications described above would improve the experience of traditional rock climbers, but would not address the needs of climbers who participate in alternative forms of rock climbing, such as bouldering, indoor climbing, and ice climbing. The Eagle Claw’s curved, chisel-shaped, rubber-covered toes are optimized to grab small rock ledges, but they are not the best design to frictionally engage flat surfaces, dig into ice, or grip indoor climbing holds.

Bouldering:
     Bouldering is an increasingly popular form of non-traditional rock climbing in which climbers perform repeated short climbs on large boulders. Rather than using ropes and harnesses to protect them from falling, they place padded mats underneath as they climb. Because hand and foot holds are often sparse on boulders, climbers often “smear” their climbing shoes against the rock, providing frictional forces strong enough to support them as they move to more secure hand and foot holds.

     Because the techniques used for bouldering are different from the techniques used for traditional rock climbing, the Eagle Claw would need to be redesigned for this sport. The chisel-shaped toes of the Eagle Claw are excellent for gripping rock ledges and wedging into small crevices, but they are too rigid and have too little surface area to be effective for smearing. The ideal bouldering prosthesis would have a large, padded surface for smearing. The leg would be as short as possible to provide the user increased leverage, while allowing the user to support himself as close to his center of gravity as possible. It might be possible to attach the prosthesis directly to the user’s outer socket. In the simplest case, the prosthesis might consist of a lace-up padded sleeve covered with rock-climbing rubber that fits over the user’s outer socket (see Appendix F-left).

Indoor:
     Indoor rock climbing is also very popular, especially for beginners and for any climber who wants to stay in shape during the winter. Indoor climbing walls generally consist of plastic footholds mounted on flat wall panels.

     Because artificial holds are much more pronounced and more evenly spaced than natural rock holds, an ideal indoor foot would be slightly different from the standard Eagle Claw. The rubber tips on an indoor foot would not need to be as durable as the tips on an outdoor foot because they would not endure damage from weather and sharp rocks. The foot could consist of a single toe designed to wrap around exaggerated protruding foot holds. The leg of this indoor climbing device should be full-length, since indoor climbing holds are spaced evenly to make climbing easy for someone with two legs of average length. The Eagle Claw could be customized for indoor climbing by replacing only the foot of the outdoor claw, while keeping the same leg pylon. This would be more cost efficient for users and would attract the many users who enjoy indoor climbing (see Appendix F-right).

Ice climbing:
     Ice climbing is a less popular and more extreme form of “rock” climbing. Expert climbers scale ice formations and frozen waterfalls using highly specialized equipment designed to dig into rock-hard ice, such as ice axes, ice screws, and crampons. A specialized ice climbing Eagle Claw could be modeled after crampons – footgear featuring 10 or 12 razor-sharp points that allow the user to gain traction on steep icy slopes. Making a prosthetic device to achieve a similar purpose would be technologically feasible, although it is not clear that a sufficient market is available for such a product (see Appendix F-middle).

Conclusion

     After reassessing the Eagle Claw project, we recommend that Ossur continue the Eagle Claw product line with a second-generation standard prosthetic rock-climbing leg and additional specialized prostheses. We are confident that a set of second-generation Eagle Claws designed according to the criteria described above would have the potential to become one of Ossur’s defining product lines. We urge you to authorize additional funding to our team so that we may continue research and development of the second generation of Eagle Claw devices.