The Children’s Stair Trainer
The Children’s Stair Trainer
Client: Marliese Delgado, UCP Hand in Hand
Marliese Delgado at Hand-In-Hand requested a piece of playground-like equipment that could be used to teach stair climbing to disabled children up to age five. The product would be placed in an indoor gym-like playroom, but would need to be portable and small for storage purposes. Other requirements included: 1) Product should have 2 sets of stairs, preferably one set that is less steep than standard and one set that is standard stair height, 2) Product would be freestanding in the center of the play area. Safety considerations were primarily for prevention of head or limbs being entrapped and to have no sharp edges on the product. The preferred storage area was approximately 5’ x 10’. The product needed a reward at the top of the stairs, which would be a slide that was safe for disabled children. The entire product must be light enough for two men to carry. CPSC guidelines: Stair railings must be approximately 22” – 26” in height. Handrails must be 0.95” – 1.55” in diameter. All open spaces, cracks, or crevices must be less than 3.5” or greater than 9”. The stairs were to be greater than 12” in width, depth must be greater than 7”, vertical rise must be less than 9”, with slope less than 35o with the horizontal. The slide must be less than a 30 o slope with the horizontal, the height-to-length ratio must be less than 0.577, and must have sides of at least 4” for safety. The exit platform must be at least 11”. e) The top platform must be greater than 22” square, and have guard rails greater than 29”.
In order to meet CPSC guidelines and customer requests a tripod assemblage was designed comprising of two sets of stairs and a slide separated 120o from each other and connected by a central base. A composite made out of high density polyurethane foam laminated with carbon fiber were selected. The PUR foam with 6K tow plain-woven carbon facesheet sandwich composites were produced using the hand lay-up method. A 4ft by 5 ft sheet of glass was used as the lay-up surface. The PUR foam was cut to the appropriate shapes (stairs, risers, side panels, and platform) using a band saw. For each piece of PUR foam, a piece of carbon fiber was cut that would wrap around the edges and come together on the other side. Corner pieces of carbon fiber were cut to cover exposed corners. The resin system used was F-82 resin and TP-41 hardener having a mixing ratio by weight of 5 to 1, respectively. Resin was mixed and the carbon fiber was wetted out using rubber squeegees. The fiber was then transferred to the lay-up surface. Microballon was mixed another batch of resin and was used to wet the surfaces of the PUR foam. Once wetted the PUR foam was placed on top of the wetted out fiber. The fiber was wrapped around the foam piece. A vacuum bag of appropriate size was used to cover the laid up sandwich composite, and was sealed to the glass sheet by the tacky tape. The part was then placed under vacuum for 24 hours. The part was removed from the lay up surface after 24 hours. The part was then grinded at the edges to remove any pooled resin. The glass surface was cleaned again and the processing continued until all pieces were completed. The pieces were fitted together and FM-73, an adhesive film, was used to bond the components together. Holes were drilled for placement of the hand railings and connection of the pieces. Bondo was used to fill in any gaps between the components. The exposed surfaces were sanded to obtain a smooth surface. Two layers of primer were used to coat the structures prior to painting. Several layers of paint were applied. The hand railing and the slide was then attached to the completed PUR foam/carbon fiber structure. Attachment of the safety nets to the railings completed construction. The completed project is shown in Figure 5, and cost $1,349.