Manual Wheel-Chair Design - Essay Example

Manual wheel-chair design Manual wheel-chair design Introduction Over the years, wheel chairs were produced based on standard designs with limited variation options. The manual wheel chairs were primarily the standard, hemi and reclining models. In case of a need for adaptations, such had only to be done to respective clients. However, the world has largely changed and today, wheelchair manufacturers offer a wider variety of wheelchairs. Nonetheless, the basic models are still vast and serve clients with less-specific needs despite the emergence of many varied models. Most modern models have however been benchmarked using the basic models with only a few modifications to serve the needs of the divergent market (DiGiovine, 2010). Variations cover aspects such as sizing, accessibility, shapes and materials used, among others. Wheel chair design concepts should take into consideration multiple areas including: Source of power which may include arms, feet, motors, attendant, or any other appropriate source. Chair frame orientation whether upright, reclining, or tilted Seat frame movement whether tilted, reclined, elevated, stand, or power legs Materials and overall design whether standard, heavy-duty, light-weight, or ultra-light. Construction of the chair frame whether foldable or rigid These are the basic consideration in design of wheel-chairs although more considerations can be made for the case of the sophisticated models. This paper considers the ergonomic and economic considerations associated with design of a manual wheel-chair. To achieve this, a current design is considered, its disadvantages highlighted and accessibility issues the people with disabilities face, highlighted, and on this basis, improvements will be suggested. Additionally, the risks associated with wheel-chairs are discussed. Disadvantages of the current design Below is CAD drawing of the existing manual design’s image. A number of disadvantages are identified in the current design. Firstly, is not that the leg rest included in the current design is fixed and hence the users can only rest their legs at the fixed position. This can be extremely tiring and boring. Conventionally, humans prefer flexibility of motion or rather, ability to change their leg positions more freely. Secondly, the seat itself is not quite confortable and forces a specific seat position. The seat is made of canvas and so is the back rest. Sadly, canvasses are not known to be all that comfortable. Additionally, lots of metal are used in construction of the design and hence this is likely to marginally increase its costs. Such high costs prevent people from buying the wheel chair. Additionally, the design has no provisions for temporary storage of items by the users. It is also important to note that that the current design is not adjustable and hence limits mobility and comfort (Cooper, 2008). Conventionally, adjustability is important given that it allows wheelchair to be set-up for optimal propulsion efficiency, and hence lowers the risk of injury. Frames may be folding or rigid. Rigid frames tend to perform better when maneuvering. Folding frames are often easier to transport, although many rigid chairs can get to a very small size by removing the wheels and folding down the backrest. Based on the identified disadvantages, the paper proposes a number of modifications to make it better. Proposed modifications Three modifications are proposed to the current design Modification 1: add a cabin below the seat for temporary storage The cabin will allow the wheel chairs users to temporary store items such as files which may come in handy from time to time. They can also bring them along when they move and hence not need to go back to a table to get them each time they need to use them. Modification 2: create modifications to allow for rotary motion of the foot pads as well as ability to raise them up and down. The flexible foot rests/pads will allow different foot rest positions. It is made in such that it can rotate 180 degrees and can move up and downwards. Modification 3: replace the metallic wheel spikes with thin less costlier and easy to replace wires. Using block metals instead of wire spikes increases the overall cost of wheelchair tires and hence the cost of the wheel-chair. Replacing this wire spikes, similar to those used in conventional bikes can marginally lower the overall costs of the wheel-chair. Suggested improved design Risks associated with use of manual wheel chairs Pushing, maneuvering and handling of clients in manual wheelchairs are largely associated with musculoskeletal injuries. Multiple researchers have reported increased risk for staff when pushing bariatric wheelchairs as a result of increased size and weight of not just the wheel chair but the users as well (Fitzgerald, 2001). Some of the potential risks associated with wheel chairs include; Exertion of high forces to push and pull combined weight of wheelchair and client Sustained forces Awkward, unsafe postures including over-reaching, bending and twisting while using the wheel-chair Awkward postures when maneuvering large pieces of equipment Faulty equipment such as, flat tires and failed brakes Physically injury risks when moving on steep, uneven, slippery floor surfaces as well as ramps Physical injuries when navigating obstacles in the pathway and insufficient space for client and staff Manual handling problems due to lack of adequate training in risk management and safe handling techniques/principles The final proposed design is a folding cross-brace frame style measuring 18x18 in terms of seat depth and seat width. The leg rest angle is set at 60 degrees. Further, there are 15 degrees of back-rest angle adjustment from vertical position. The seat dump allows for adjustment from horizontal to 7 degrees below horizontal through change of axle position. The rear axle has 8 probable positions which range from 3.75 inches front to back and 1.5 inches upwards and downwards. The caster angle is adjustable 10 degrees from vertical position in order to keep caster stem in a direction perpendicular to ground. The footrests can be moved to 3 positions with a range of 3 inches. The materials manufacturing processes to be used in the wheel-chair’s designed include; bent welded mild-steel tubing and 2mm thick flat stock, aluminum sand castings, hand cycle bearings, rubber casters as well as bushings, turned-brass bushings, non-structural plastic and stamped sheet of metal (International Standards Organization, 2004). Also used are pneumatic tires, rubber-bushings at caster and axle attachment locations and seat cushions are proposed to increase shock absorption. The proposed new frame is to be made of 1020 steel alloy tubing, bent using a hand tubing bender and then, brazed together. References Cooper, R.A. (2008). Wheelchairs: A Guide to Selection and Configuration. Demos Medical Publishers, New York, NY DiGiovine, M. M. (2010). User Assessment of Manual Wheelchair Ride Comfort and Ergonomics, Archives of Physical Medicine and Rehabilitation, 81, (4), pp. 490-494 Fitzgerald, S. G. (2001). Comparison of Fatigue Life for Three types of Manual Wheelchairs, Archives of Physical Medicine and Rehabilitation, 82 (10), pp. 1484-1488 International Standards Organization (2004). Committee draft ISO/CD 7176-8(E) Wheelchairs- Part 8: requirements and test methods for static, impact, and fatigue strength. Technical Committee 173, Sub-Committee 1, N 200, Zurich, Switzerland Read More