by:
Eric Spitz, Jordan Sadowsky, and John Schoenleber Duke University, Department of Bioengineering

Gardening enables millions of Americans to partake in a therapeutic physical activity that encourages relaxation, increases self-esteem, and allows for a sense of accomplishment. Unfortunately, users of wheelchairs typically have difficulty in performing a number of gardening tasks, and instead rely on the help of others for certain chores.

The solution to this problem? The Lawn Care Assisting Device.

A side view of the Lawn Care Assisting Device attached to a wheelchair

The Lawn Care Assisting Device (LCAD) is a specialized device that helps to make gardening more enjoyable and productive for individuals that use wheelchairs. It was designed in accordance with a senior capstone biomedical engineering design course, Devices for Persons with Disabilities, at Duke University's Pratt School of Engineering (see http:// courses.pratt.duke.edu/bme260 for more information and past projects). Dr. Larry Bohs, Assistant Research Professor of Biomedical Engineering, teaches the course each fall.

Sponsored by a grant from the National Science Foundation, six groups of three senior undergraduates each choose projects based on problems presented by people in the community. Each group designs and constructs a device - that is not commercially available - to fit a particular need presented by the chosen client. Another device this past semester included a bath chair for a boy with thrombocytopenia-absent radius (TAR) syndrome, a rare disorder characterized by a low blood platelet count and the absence of the radius bone in the forearm. Other projects from the fall of 2006 included an automatic rocking chair for children with disabilities, a wheelchair ramp assist device, a vibrating music-playing chair, and a wheelchair that can skate on ice.

The LCAD enables our client to transport yard waste (e.g. leaves), a water pail, and gardening tools around her yard while in her wheelchair. Furthermore, leaves can be raked directly into the main chamber and dumped out into a large pile. The device is composed primarily of Lexan®, a highly-durable polycarbonate thermoplastic often described as 'bulletproof.' A circular sander was used to smooth all sharp corners and gives the device a scratch-resistant, foggy look. Throughout the development of the device, several important objectives such as overall safety, device strength, wheelchair maneuverability, durability, and tool accessibility were taken into account.

The design process of the LCAD centered on four-steps: an initial idea to solve the client's needs, a spatial prototype, a functional prototype, and a final product. Taking the needs and specifications of our client into consideration, the preliminary design comprised a rigid frame attached to large wheels, a primary chamber designed to hold yard waste, and an elevated shelf to hold tools and water. Our client's wheelchair features two safety wheels that are easily removable and were thus seen as appropriate locations to attach the device. Moreover, the primary chamber was designed to contour the wheelchair. That is, once the wheels were cleared, the chamber widened to the width of the chair in order to maximize storage space in the main chamber. The initial plan also featured a rear flap that could be opened to rake yard waste into or out of the chamber. The final component was an elevated shelf - strong enough to hold all small tools and water - designed to be within reach of our client while seated in her wheelchair.

We then met with our client to take measurements of the rear of the wheelchair to determine the maximum size of the cart. From these, a spatial prototype was constructed out of tempered hardboard to test for size. Pieces were attached together using wooden blocks, screws, and nails as stability and aesthetics were not a serious concern. Caster wheels were bolted to the bottom of the cart and the shelf was made removable by resting it on blocks. A front attachment of scrap wood and PVC was created to slide into the safety wheel cylinders. This prototype was then tested in order to verify size and mobility.

After noting necessary changes during the testing of the spatial prototype, a functional prototype was constructed. Changes to the prototype included shortening the front part of the main chamber by four inches, lowering the shelf by one inch, creating a hinged flap on the back, and redesigning the attachment mechanism to fit and lock with the chair. The rear flap was hinged, and when closed, connected to an upper crossbar by Velcro®. A refined attachment mechanism consisted of two tubes that provided support in the vertical and horizontal direction, and a hinged hook provided support in the pull direction. The attachment mechanism was designed specifically for our client's wheelchair, and therefore would need to be adjusted to accommodate other wheelchair models. The testing of the functional prototype proved to be a resounding success, allowing us to begin the final stage of the project.

In constructing the final product, we sought to meet the functional specifications of durability and strength by replacing all wooden panels with Lexan® polycarbonate. The primary chamber was built with 0.375' Lexan® walls and a 0.22' polycarbonate base that was attached using stainless steel screws threaded into the Lexan®. Caster wheels were bolted onto the bottom of the cart, and the shelf (made from 0.375' Lexan®) was designed to rest on Lexan® blocks.

The front attachment mechanism comprised Lexan® blocks and aluminum rods, while the rear flap (a 0.093' sheet of Lexan®) was attached by a piano hinge. A lawnmower pull cord raised the flap, and magnets, inlayed into the crossbar, connected with metallic sheets inlayed into the flap to secure the flap. Ergonomic handles were added to the shelf and the inside of the front panel to facilitate lifting. Attachment hooks for the shelf were added to the side of the cart for use when the shelf is removed; drainage holes were added in the front of the bottom panel; and a circular sander was used to smooth all corners and give the Lexan® a scratch-resistant, foggy look.

An overhead view of the LCAD with the shelf stored on the right

After testing the final device with our client, the product appears to meet all objectives and exceeds our client's expectations. Gardening with fewer challenges, our client can easily carry a water pail, reach behind her chair to grab the pail, and then water her plants - all while sitting in her chair. Likewise, our client has no trouble lowering the flap and raking leaves directly into the main chamber.

In addition, she is able to raise the flap and dump yard waste into a large pile. The shelf is easily removable and the storage on the side of the cart is convenient. In regards to our client's tools, all of them fit either in the main chamber or on the shelf. The weight of the LCAD, a concern throughout the development, does not hamper her mobility even when carrying a full water pail, as she still can ascend the steepest incline in her garden. 'This cart has made it so much easier for me to garden,' our client explained. 'I really appreciate it. It is great!'

The LCAD assists with raking and transporting leaves with its rear flap

The major advantages of the LCAD over commercially available devices stem from its specialization of use. These advantages include its simple removability, minimal obtrusiveness, long-lasting durability, sufficient storage space, suitable strength, and additional features to aid in important gardening tasks (e.g. flap assists in raking, shelf increases the accessibility of hand tools and water pail). In the end, the LCAD has met all of our objectives and enables our client to actively and independently perform gardening tasks that she previously could not do.

Of course, those without an LCAD can still participate in gardening. The only necessary requirements are motivation to enhance one's garden and a bit of work. Although some individuals may require help for particular tasks, with the proper tools and a creative mindset, everybody can partake in the invigorating and stress-reducing physical activity of gardening.