This week we made our preliminary designs for Jake’s wheelchair compartment. As you can see in the screenshots below, we went with a compartment with 4 separate slots that are each wide enough for a card to fit in at a 45 degree angle. We chose this design for two main reasons. First, it is crucial that we created a model that Jake would be able to use given his limited movement and dexterity. Knowing how much mobility Jake has, we knew we had to design a compartment where Jake could “slide” cards in and out of with his hand, instead of grabbing or picking up cards with his fingers. This is why we created 4 separate slots, each to house one card (or a money clip), that are wide enough so that a card will lay at a 45 degree angle in the slot. This allows more surface area of the card accessible to Jake so that he can more easily slide the card out of the slot. Second, the curved entrance not only allows for more room for Jake’s hand in the slot, but it also creates a nice ramp for the card to slide down onto Jake’s leg from the compartment. Jake is able to pick up the card with his fingers once a card is on his leg, so we designed the lid so that it acts as a ramp for the card to slide down right onto his leg. The lid will also keep the cards and cash safe and secure in the compartment.
We also added a fixture on the top of the compartment that will fit in the T-slot on the underside of Jake’s armrest so that the compartment can be easily taken off of the wheelchair. The dimensions for the T-slot were based off of measurements that Jake’s father took and sent to the group.
When designing the model, there were a few measurements that we had to make in order to know how to dimension the compartment. We knew we wanted the card to lay at 45 degrees, so we first found the height of a credit card (2.125 in). Then we performed simple trig to determine how wide to make the slot so that the card did in fact lay at 45 degrees. Based off of these calculations, the slot width was set to 1.5 inches for each slot. In terms of depth, we found that a card is 3.37 inches long, so we made the depth 3.5 inches to accommodate the length of the card in the slot. As mentioned before, T-slot dimensions were based off of measurements provided to us, and we verified that the entire compartment would fit under Jake’s armrest without causing him any issues.
As seen in the picture on the left below, we decided to implement a ridge on the front of the lid so that Jake can open the compartment. Originally, we were going to add a loop on the front of the lid that Jake could put a finger through and pull down. After talking with Jake about this idea, we decided that the curved ridge would be much easier for him to open as he can place the back of hand against the lid so that it lies in the ridge and he can pull down. In terms of the hinge, we decided to go with a standard hinge that will use a pin to keep the lid and compartment together. Since we are using FDM to print our first prototype, we have not designed the pin for this assembly in CAD yet. We plan on printing the final assembly using powder bed fusion so that the entire assembly can be printed together as one piece. While we considered integrating a pre-made metal hinge/pin into our design, we ultimately decided it would be easier to print the entirely assembly as one and have a working part out of the printer. Adhesion to the plastic was the main concern that deterred us from installing a metal hinge to connect the lid and compartment.
Finally, it should be noted that this model was designed using SolidWorks. While there are numerous modeling softwares available to use, our group felt most comfortable using SolidWorks since the majority of us have experience with it.
