ENGR 111: Final Report (Archery Stand)
Chelsie Ahn, Micah Fong, Selina Huynh
Abstract
Harbor Camps is a nonprofit organization that provides facilities and activities for youth and families that may feel marginalized. This semester, our team worked to create an archery stand for children with and without disabilities to hold a bow and shoot an arrow by themselves. When we first met with our client, Madi, she mentioned that she usually stands to the side and holds the bows for her students. While helpful, this limits both Madi’s and the children’s freedom and flexibility when participating in this sport. To this end, using steel posts, a wooden dowel, and rope, our team designed a six-foot archery stand that is adaptable to children’s heights and the different types of bows they will be using.
Our Design and Methodologies
Design Specifications:
The Base
The posts we decided had to be metal because wood was just too flexible and would bend when under pressure. They are 6 feet tall to accommodate for the tallest height Madi imagined this would be needed for, around 5’5″. The height and width of the posts are 1.5 inches by 1.5 inches, which made it heavier and bigger than we originally wanted. McMaster did not sell all the compatiple parts we needed for a smaller post, so we had to go with 1.5 inches.
The wooden base is around 2 feet by 1 foot. It allows someone to stand on the build to give it more support. The posts are placed with 43 inches between them, making sure to accommodate a wheelchair user.
The Cord
The paracprd we used is 0.18 inches in diameter, strong enough to not break or stretch and thin enough to fit inside one of the holes in the posts. The cord has 2 caribiners, each one fit to hook onto a different type of bow, which was necessary because the bows have different centers of balance and not every bow could be hooked in the same way at the same point.
The shelves and bar
There is a wooden bar going across the middle to give the user something to pull against. The shelving system allows the user to place the bar at around every 2 inch interval. The shelves are only 2 feet tall, given the size constrictions and the Weissman Foundry laser cutter. The bar is 42.5 inches long, as the shelves take up a half inch of thickness away from the original 43 inches of distance.
Design instructions:
https://docs.google.com/document/d/134N70zATRTBk74HgoEkzIS6IjVYVGYuG7f857xtk3lA/edit?usp=sharing
Choosing a Design:
Initially, we went with the “suspension” concept because it was more adaptable and low cost than our other concept idea, which involved clamping the bow to some kind of arm. After creating and testing our scaled-down sketch model, it became clear the suspension idea alone would only be helpful to users who can pull the string of the arrow with one hand and hold the bow itself in another hand. We moved forward with a narrowed goal, and used Pugh charts to determine the mechanism we’d use to anchor the posts to the ground. Out of the six ideas we came up with, a simple platform connecting the two posts excelled in stability, manageable weight & volume, low cost material, ease in setup, and versatility. After trying wooden dowels, we upgraded to square metal posts and brackets on a wooden platform. Height adjustability was important to the client, but the adjusting mechanism had to be easy to reach. We used bolts at the bottom of one side of the left post to loop the suspension cord around, allowing the product to be used with the bow hanging at a variety of heights. This framework tested well for people who could hold the bow and pull the string, but the client requested a product that would support the bow entirely, allowing the user to pull the string with two hands. To accommodate this, we added a dowel that sits between the metal posts and allows the user to pull the string against it, without any hands on the bow. We tested several designs to support this center dowel, settling on a custom laser cut wooden shelf we installed on the inner edge of the posts.
Features
- Adjustable height
- Can use with any type of bow (recurve, compound, stick)
- Can use indoor or outdoors
- Can use without touching the grip, using 2 hands to pull the string
Instructions
- Step onto wooden platform, facing toward the target.
- Use the velcro on the carabiner to strap the bow to the cord and place the looped end of the cord around the appropriate screw at the bottom to adjust bow height.
- Insert the wooden dowel at the height of the middle of the bow on the shelves, ensuring it rests between the bow string and the inside edge of the bow.
- Fire away!
Final Prototype and Results
On the last day of classes, our team met with Madi at the KSC to reveal and demonstrate the workings of our final prototype. Madi seemed to like our model; she tried our archery stand using multiple bows and said she could imagine the kids at the camp using it. Moving forward, in order to further refine our model, we would need to lengthen the pole notches that hold the wooden dowel in place. This is an easy addition, as the only setback was the dimensions of the laser cutting machine in the WeLab.