Baby Carrying System for Disabled Mother

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Baby Carrying System for Disabled Mother

Designers: Idris Lawal, David Sewell, Asaf Stein
Client Coordinator: Michael Papp, Alabama Department of Rehabilitation Services

 

A child carrying system was built to assist a client with paraplegia and confined to a manual wheelchair, in transporting her toddler during daily activities.  The product had to safely support and restrain the toddler who, at the time was 12 months old, weighed 22.5 lb, and was 30.25 inches tall.  Also, the device had to be versatile enough to allow for his growth over the next two years.  The carrying system could not impede the mobility of the wheelchair; it could not bind or hit the sides of the wheel chair when performing turns or backing up.  The product was to be lightweight (<25 lb), and sufficiently collapsible in order to fit into the client’s vehicle (width of standard door = 32 in).  Once unfolded, the product was to be self-standing.  While seated in her chair, the client should be able to easily attach and detach the device to and from her wheelchair. The product had to withstand the stresses resulting from both the torque created from turning the wheelchair, traveling over uneven terrain, as well as the weight of the frame and child combined.  ASTM standards for strollers stipulate child restraints as well as folding and latching mechanisms that involve a two step process.  The stroller should support a static load of 100 lbs. in the center of the seat. The design team was allotted a total budget of $1,500 and a time of 15 weeks in which to complete the device.

TECHNICAL DESCRIPTION

 

The final design consisted of the main stroller frame (Maclaren Stroller, which met all design specifications and came with desired accessories, such as a rain cover) and rear swivel wheels (Sportaid Wheelchair & Stuff), which were purchased from commercial vendors.  A ball and socket “trailer hitch” included a 1 7/8 in. diameter stainless steel ball and allowed for ample rotation about three axes.  A one-half inch cylinder was bored out of the trailer ball to reduce weight.  The receiving socket was attached at the stroller’s front, and the hitch attached to the rear of the wheelchair via existing open ended tube receptacles. Aluminum tubing was chosen for the connector components because it is lightweight and strong.  Polyurethane swivel wheels were chosen for good traction and optimal wear properties.

The resulting device adhered to the safety standards put forth by the ASTM in regard to strollers and carriages. Bending, bearing and shear stress calculations were performed and the design was predicted to withstand the stresses resulting from turning the wheelchair, travel over uneven terrain, as well as the weight of the frame and child combined.  All results fell well below the ultimate and fatigue strengths of aluminum.  The completed project (Figure 4) was delivered to the client within the specified time frame.  The total weight of the product was 21 lbs and the total cost was $1260.

24 - baby carrying system