Our group was tasked with designing and installing a swing set which will renew a playground for further use and fun.
A local development center wants a playset with swings that would allow the children to have fun outdoors. The playset will need to be able to be big enough for kids who are of adult size and weight. For the playset, we want to design it to have two swings and and a saucer connected to it, while also incorporating a water feature that was mentioned as being something that the kids would enjoy. The playground will be completely cleaned of debris and organized to improve the quality of the area.
Needs:
When discussing different types of playsets, we decided a simple, two swing, frame would be the most reliable and cost effective solution. The material of choice for the project is metal and was determined the best size for the frame of the set would be at minimum 2 inch, 40 schedule carbon steel piping. A bracket needs to be made to connect the legs and span of the swing set. These materials should be easily sourced and easy to work with. We found that these materials would be adequate for a playset. When considering the water feature, we found that a simple pipe with holes drilled in it would provide a sort of sprinkler / water curtain that the kids can swing through. This can be hooked up by a simple hose attachment.
This playset was based off of a traditional style set, more specifically a prefab set meant for smaller children. Since the center wants the set to be accessible to larger kids, the design would be scaled up into adult size. Originally the center wanted to see if a slide was possible, but the was eventually optioned out.
This design features arch supports, along with a singular vertical support bar between the two swings for extra bracing. This plan gives extra support if needed and would allow expansions of the number of seats.
For this design concept, the swing set has the arched support structure with two swings. This design has the support posts partially buried with a cross bar that will sit on the ground to prevent further sinking. This design implements a water spray bar above that the kids can enjoy in the summer, since the children’s love for water play was brought up. The spray bar can be a simple PVC pipe with small holes drilled into it and will be easily attachable to a standard hose running from the available water spigot.
The team decided to go with design three, as it features the best qualities of the ideas we had while making a rough design.
While the initial design showed a slide and platform being used, this was dropped for a possible future group.
SWINGSET: The swing set will be made from 2 3/8 inch schedule 40 galvanized steel. The top span features a 8ft span while the legs will be at a 65 degree angle to the ground. These will be attached to the brackets with 1/2 inch bolts. The leg length is roughly 9.36 ft long, pending the depth of the hole dug for the legs to go in. The height of the swing will be 9 ft.
BRACKET: A bracket will be constructed out of 2.875 inch outer diameter, 2.49 inch inner diameter galvanized steel. The bracket will have a 45 degree angled mount for the bar spanning across the swing set. The mount will accommodate the angle of the legs to be 65 degrees from the ground. Holes will be drilled and 5/16 through all bolts will be used to secure the brackets to the swing set legs and span. This will be welded together and powder coated
WATER FEATURE: A water feature will be added to the top of the swing set to act as a curtain of water while swinging.
An analysis of the 8ft, 2 ⅜ steel pipe was done to determine the deflection of the swing as well as a safety factor. Using concepts from Mechanics of Materials, the deflection was found. To find this, the Moment of Inertia, then sections modules and cross sectionals were calculated. The vertical reactions were found based off of the force of a 250lb person seated on both swing seats. The stresses were combined to find the shear stress. The combined stress was 9,492 psi, and when compared to the max vertical psi load, the safety factor was 3.79, more than adequate for a swing set. The deflection equation was found to be and the final amount of deflection was 0.00375 inches which is near non factor. This analysis was redone to a 12ft span, giving similar satisfactory results for the larger span.
For this analysis, the model with the twelve foot span was analyzed using the expected forces on the swing set. This gave the expected results that showed the design would hold up to the expected forces.
The ramp was analyzed under a distributed load of 400lbs over 5 feet to simulate the potential of two 200 pound people standing on a small section of the ramp for a confident overestimate of reasonable loading. The deflection was approximately 5mm which is quite reasonable and should remain solid considering the wood should be somewhat elastic. Ultimately this analysis was dropped as the ramp was pushed out for another group to possibly do in a future semester.
For the swing set, a bracket was made from 1/4 inch steel plating measuring 7.5 inches x 4.5 inches. The 2.875 inch wide tubing was cut at 45 degrees and 22.5 degrees for each respective tube. Once these cuts were made, hole were drilled 2 inches apart through all of the tube before being welded together. Each bracket was tacked together, then welded all the way around forming a very strong bond. For the bracket powder coating was used, and the legs and span were painted on site. The legs were cut at 10.5 ft long, giving us 1.5 ft to concrete and bury in the ground. The span was cut to 12 ft. Once on site, four holes were dug 12-18 inches deep, and concrete was dry poured around the legs. All of the hole were drilled out and the bolts were inserted. The swings were finally mounted and tested. For the water feature a 10ft pvc pipe was cut in half, end caps where glued onto each end, and holes where drilled at equal distances apart. Holes for the water to flow out of were drilled and the hose pipe was attached to the swing set. Foam padding was added to the outside of the legs for extra safety.
The swings were tested by swinging on the swings themself. Initially our plan was to bury it deep into the ground and use off the shelf anchors, but after letting the set sit for a moment, we decided to add a concrete footing to the swing. The swing set itself flexes a good bit as expected to dissipate the load of the swinging children. For the water feature, it was initially installed with too much downward angle, then adjusted to the best operating angle. The swing set was stress tested with the three heaviest people of our group all swinging as hard as we could. There we no issues and the deflection was as expected for a metal swing set.
For this swing set, the instruction are similar to every other swing set. While swinging, do not walk in front of the swings. Jumping from the swing set is not allowed as this can cause injury to someone while swinging. Side to side swinging can cause injury due to collisions users. Do not climb or jump from the swing.
Overall, this project was a great learning experience in for an intro to an engineering project. This gives a taste of what our jobs will be like once graduated. There where struggles such as sourcing the metal for the legs and the span. Changing design elements like the actual material of the legs and bracket angle set us back, but we were able to make changes and move onto a the next steps. On site there were a couple of issues such as a drill bit being broken several times and changing the plan of burying the legs with more concrete. This part of the project demanding as installing the legs and digging the holes where very time consuming and hard work. However, the project being completed was very rewarding. The teamwork with a group over a whole semester was great and proved to our group what we were capable of. Thank you to Jeff Randolph for shop help and David Trotter for transportation.
