A mechanism will be built for a child who struggles with strength and mobility to provide an easier alternative for getting in and out of a swimming pool. This mechanism will carry both the child and her medical devices.
This project will create a device that will allow a child who struggles using a traditional pool ladder/staircase to get in and out of an above-ground pool with ease. The device will also account for her medical equipment such as her ventilator. Though the child is capable of walking, she still struggles with using the ladder to get in and out of the pool. This device will circumvent the ladder and lift her to a waiting area in the pool and back out of the pool.
There are currently a few assistive devices that help with pool entry. Most are a version of two different methods. One is the use of parallel arms attached to a seat with safety belts. The other is a hoist with a seat that swings from the top of it. Not many options were found for above ground pools without a deck/patio and the options listed above do not account for transporting additional medical devices.
8 Leg Pulley
This concept has 8 legs and a very complicated and lengthy pulley system. Each side lifts up simultaneously and is powered by a winch or motor.
6 Leg Pulley
This concept has 6 legs and a pulley system. Each side can be lifted by a winch or motor.
This has a scissor lift on the outside of the pool to bring the child from the pool to the ground or up to the pool. The other side has an adjustable bench that multiple kids can sit on. The lift can be actuated by either a piston or with an ACME threaded rod with a carriage.
Our selected design is not one of our concepts. We decided to work together with group 1a to split up the workload and design.
We took aspects of our concepts and group 1a’s concepts to create a final selected design. This deck-lift combo makes it overall simpler and cheaper to manufacture while still including all design specifications
After further consideration with Dr. Canfield, we came to the conclusion that we would need to omit the lift portion of the deck. The lift could be a future addition to the deck for another DOM project in Dr. Canfield’s class. The following engineering analyses feature the lift which could not be manufactured this semester.
This design features a quarter-deck built from wood with a low slope staircase of only four inches per step. For access into the pool, there is an automated lift powered by a winch or motor with a pulley system. Our group focused on the lift. The platform slides up and down rails with trolleys.
For this analysis, a 500 lb load was put onto the crossbar of the main structure with the end plates fixed. This is to simulate the load from the pulley that will go over this bar. The 500 lb load was chosen as that should be more than the child and a parent sitting on the system. The image shows the maximum displacement of the structure which is just under 1/2 a mm. The stress also isn’t a concern as the minimum factor of safety of the design is 6.5. This analysis shows the structure itself is good, so long as the part of the deck it is connected to is as well.
This analysis allows us to determine how much force our winch/motor needs to be able to pull. We assumed an extreme load of 500 lbs. Our Solidworks model gave a weight of 18.66 lbs. This means the winch/motor needs to be able to pull at least 518.66 lbs. Realistically, the load will be much less than 500 lbs, so our winch/motor pick should have plenty of power to move the platform.
An analysis was performed on the lifting platform to determine the reaction force needed by the trollies to preform safely. Two 250-lbf point loads were position at the end of the platform while the locations of the trollies were fixed and evaluated for reaction forces. Each trolley has a working load of 600-lbf, so the analysis was used to find the height of the platform assembly so that the support bars can allow for less than 600-lbf reactions at each trolley. It was found that 12 inches was sufficient.
The first step was to dig post holes and bury the 4×4 posts with concrete. We let that sit and harden over a few days. Next, we returned to the site to frame the deck and make sure everything was squared and leveled. We then set all of the joists to screw the floorboards into. Next, the floorboards were attached and trimmed to match the curvature of the pool. Finally, the handrails were stood up and the gate was added at the top of the stairs.
To ensure safe use on the deck, use the handrails when ascending or declining the stairs or standing near the edges. Always keep the gate closed when people are using the deck to avoid injury from the stairs. The deck should periodically be checked for weather damage. The top surface of the deck may get hot after being exposed to the sun for long periods of time during the summer.