CONSTRUCTION
The idea was to make the design economically reasonable as possible. There were a lot of ways to promote this; one was to self-manufacture as many components as possible. It was more cost efficient by purchasing the acrylic sheet and bending it around a jig, instead of purchasing the manufactured piece. Having to buy a component that was either casted or machined made the project excessively expensive and pointless. Every component of the pneumatic leg extension was manufactured or modified; all components except the lockable gas springs and the rollers. The remaining components were manufactured or modified here at Central Washington’s work shop. The following list demonstrates each component and the work behind it.
0. Skeleton: This jig is not a part of the pneumatic leg extension, but it was constructed to help form the frames and the elevator units. This tool was built from 2 metal base plates that were around 3/16 in thick. The metal plates had the frames’ semi-circle shape. Seven rods that were 1 in. in diameter were welded onto the base plates with a potential height of 30 in. The height of the jig needed to be larger than the frame height, in order to get better results. A 1/8 gauge sheet metal was then bent around the 1 in. rods, taking the semi-circle shape. The sheet metal was tack welded with the MIG welder. The dimensions of the jig were based off of the frame itself. In other words, the jig’s outer radius took the inner radius of the frame because the acrylic sheet was bent over the jig. After the frames were shaped, the jig was dismantled and re-modified to the elevator units’ dimensions. The shape was intentionally different and definitely smaller than the first-made jig. The modified (smaller) jig was scaled down to form the elevator units.
1. Frame LL & RL: These frames were initially sheets of acrylic that were table-sawed down to dimension. The frames were longer than any oven dimensions around campus, so a second alternative was sought. A drape molder was used to preheat the acrylic. The acrylic needed to be heated up to 380 degrees Fahrenheit before it started to deform. Once, the acrylic started to deform, it was pulled out of the machine and was molded around the jig and clamped in place with boards supporting the sides for it to bend more consistently. Once the acrylic cooled down a little, the formed-frame was removed from the jig and the sides were opened, again by using boards (for consistency) to avoid inward-warping.
The vertical mill was used to mill a 0.358 in. slot on the outer side of the frame. Once, the slot was created, three ½ in. bearing grooves were milled on the inside of the frame (the opposite wall where the slot was milled). The horizontal mill was used to create the ½ in. bearing grooves. The grooves were ¼ in. deep; they were deep enough to prevent any bearing shifting.
2. Elevator unit LL & RL: The elevator units were formed by the scaled-down jig and heated by the construction management oven. The same molding process that was used to mold the frames was followed for the elevator units. Once the elevator units were formed, they were used to trace an acrylic base, which was glued (acrylic glue).
3. Lockable gas springs: This component was purchased from online from an office chair-parts distributer. This component is basically the cylinder piece of an office chair. No modifications were made to these components.
4. Support Plate LL & RL: This component was made of a 3/8 in. x 2 ½ in. x 3 in. aluminum plate. The component was milled to dimension. Two holes were drilled and tapped on one end face. The holes were tapped for two 10-24 in. x 1 in. aluminum machine screws, which assembled the support plates to the elevator units. The support plates were later spray painted red to hide the raw aluminum color.
5. Collet: This component was an aluminum pipe, which was mig-welded to the support plate and epoxy glued to the cylinder. A boring tool was used to tight-fit the collet to the cylinder (ID machined). The collet was spray painted red to hide the raw aluminum color.
6. Rubber padding: General Purpose Rubber (GPR) was cut to dimension and epoxy glued to the base of the frame. The frame was used to trace the GPR shape desired. Oil was placed on a cutting knife to smoothen the cut and reduce the required force when cutting the GPR.
7. Roller (bearing balls): The carbon steel bearing balls were purchased from an online website. No modifications were made to this component.
8. Secure Strap: The polypropylene and plastic latch materials were purchased in ACE hardware store because of the low cost. A needle and stitching string was used to stitch both pieces together to form a secure strap.
9. Cylinder base padding: This component was constructed by using the extra GPR, which was used to make the rubber padding of the device. The cylinder was used to trace the GPR shape desired and a door knob cutting tool was used to cut the extrusion for the cylinder to rest in. The GPR is 0.5 in. thick so, a 0.25 in extrusion was machined. A cutting knife was used to cut the OD of the GPR. After all of the cuts were made, epoxy glue was used to assemble the base padding to the bottom of both cylinders.
10. L-Brackets: 1/8 gauge aluminum sheet was used to manufacture the L-brackets. There were 8 strips cut to 1 ½ in. x 4 in. and were bent 90 degree to form the L-shape. A hole was drilled on each end to hold in place 10-24 x ½ in. aluminum machine screws. The L-brackets were painted black to hide the raw aluminum color.
11: L-safe lock: The L-safe lock was purchased as an L-beam. The aluminum component was cut to length, using the vertical band saw. A ½ in slot was milled to reduce excessive weight. The slot was made on the side that was screwed onto the frame to reduce probable deformation will the device is operated. Two holes were made to assemble this component to the frame. The holes were large enough to tight fit an 8-23 x 3/8 in. aluminum post screw. A red spray coating was sprayed on the L-safe lock to neglect the raw aluminum color.
12. Screws: Aluminum screws were purchase at the local ranch & home hardware store. There were 16, 10-24 x ½ in. aluminum machine screws purchased to assemble the L-bracket to the elevator unit and hold it in place. There were 4, 10-24 x 1 in. aluminum machine screws purchase to assemble the support plate to the elevator unit. All screws were sanded down to flesh with the elevator unit and the support plate.
13. Post screws: There were 4, 8-32 x 3/8 in. aluminum post screws purchased and used to assemble the secure strap to the elevator unit wall. No modifications were made.
14. Spray paint: Black and red spray paint was used to spray paint the support plates, L-blocks, and L-safe locks. These spray cans were found lying around the house garage.
15. Epoxy glue: This product was purchased at the ranch & home hardware store. This item was used to assemble the bottom acrylic base to the elevator unit walls and the collet to the cylinder. The epoxy was also used to glue the GPR to the cylinders and the frames. There were no modifications to this product.