We have finished our validation. We measured the dimensions of the prototype, and it was 5.2 ft^3 which meets our desired goal of having a device of no more than 8 ft^3. It fits easily into the trunk of a sedan, as seen in Figure 1. The prototype is 43.5-lb., heavier than we would like but still less than the NIOSH recommendation of 51-lb. for single person lifting. The team also tested the device’s lifting capacity/range with two different loads: 55-lb. and 100-lb. The deflection of a roller arm and the tilt of the upper/loading arm were measured for each load, which is depicted in Figure 2. The data is presented in Figure 3.
Load | Roller Arm Distance to Ground* | Tilt Angle | Concern of Failure? |
0 lb. | 8.88 in. | 4⁰ | No |
55 lb. (Wheel) | 7.88 in. | 10⁰ | No |
100 lb. (Wheel & 45 lb. of Weight Plates) | 7.5 in. | 20⁰ | Yes |
Figure 3: Deflection & Tilt Angle Data
The deflection and tilt angle data show the prototype was reaching its breaking point with a 100-lb. load. It had difficulties lifting the 100-lb. load, and the upper arm had a significant tilt when it reached its maximum possible lifting range. For the 55-lb. load, the prototype experienced no difficulties lifting and holding it at full extension. This data reflects that the prototype cannot "safely" lift 100-lb wheels.
Another validation experiment we conducted was the measuring of strain at one of the scissor jack arms (Gage 1) and at a support bracket (Gage 2). Their locations are specified in Figure 4, and the data is recorded in Figure 5. The scissor jack was at full extension, and the load was gradually increased. Both strain gauges returned approximately to their original readings after loading and unloading. These results might indicate these areas only experienced elastic deformation. The support bracket experienced more strain, evident by the max micro-strain of 1013 for Gage 2 compared to the max micro-strain of 375 for Gage 1.
The prototype was partially successful because we didn’t meet every specification, but it has basic functionality. The team believed the prototype performance showed that it was more of a proof of concept. It can lift and rotate a wheel while being relatively compressible. We intended to be able to lift a 100 lb. wheel 12 inches off the ground with ease, but we only achieved 7.88 inches off the ground with extreme difficulties. If we pursue this project further, many refinements would need to be made. The prototype’s weight relative to its lifting capacity (with ease) makes it impractical. To be a more attractive product to consumers, it should weigh less and compress to a smaller size while being more rigid while lifting 100 lb. wheels.
We have finished all the validation experiments we deemed necessary and feasible to measure the prototype’s performance. Based on the results we have collected and feedback from validation, we will try to install a rope or Velcro strap to make a wheel more stable when rolling the prototype around. We will also try to develop a further method to reduce the tilt and strain on the support brackets.
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