Truss Design
Problem Statement:
Our task was to design a truss based on tests and research that performs better than test trusses. It must be an efficient and quality product that is only made from balsa wood, glue, and paper. The paper gussets could not be larger than the test gussets. The truss had to fit in the apparatus (span > 6 ⅞ inches; height < 4 ⅝ inches) and use only 36 inches of balsa wood.
Test Truss:
Our test truss broke at 51 pounds at the angled member B. It probably broke in this spot because it was not joined completely symmetrically. The member also might have been weaker or had chink in the wood.
I expected the truss to break at the vertical member because it appeared to have the most weight on it. I now know that there was no possibility of vertical movement unless one of the angle members broke. The vertical member was supported by the two angled members leaning in on each other which made it impossible for it to break at the vertical member until one of the angled members broke.
Research Results:
After doing a bit of research it appeared that the strongest trusses were ones with some sort of zig zag pattern forming triangles throughout. I saw that many trusses also included a central vertical support which seemed to be a good idea. Stronger trusses also had more supports.
Our task was to design a truss based on tests and research that performs better than test trusses. It must be an efficient and quality product that is only made from balsa wood, glue, and paper. The paper gussets could not be larger than the test gussets. The truss had to fit in the apparatus (span > 6 ⅞ inches; height < 4 ⅝ inches) and use only 36 inches of balsa wood.
Test Truss:
Our test truss broke at 51 pounds at the angled member B. It probably broke in this spot because it was not joined completely symmetrically. The member also might have been weaker or had chink in the wood.
I expected the truss to break at the vertical member because it appeared to have the most weight on it. I now know that there was no possibility of vertical movement unless one of the angle members broke. The vertical member was supported by the two angled members leaning in on each other which made it impossible for it to break at the vertical member until one of the angled members broke.
Research Results:
After doing a bit of research it appeared that the strongest trusses were ones with some sort of zig zag pattern forming triangles throughout. I saw that many trusses also included a central vertical support which seemed to be a good idea. Stronger trusses also had more supports.
Design Idea:
My design idea was based on a mix of a few trusses and involved a central support with angled beams supporting it through the frame. I thought it would be a quality design because of elements from a few different common trusses. A total of 32.5 inches of balsa wood are used in my design and it is statically determinant because 2*10 = 17+3.
My design idea was based on a mix of a few trusses and involved a central support with angled beams supporting it through the frame. I thought it would be a quality design because of elements from a few different common trusses. A total of 32.5 inches of balsa wood are used in my design and it is statically determinant because 2*10 = 17+3.
Decision Matrix:
Michael’s design was based on the Double Howe Truss and was similar to it in that it had right triangles throughout. Michaels’s design differs however, in that the triangles are flipped the opposite direction (upside down). It is fairly complicated but looks like it would support itself well. It seemed like it would be too many supports to get exact in the given time limit.
Joanna’s truss was very simple and provided for an easy design. The truss was made with a central support and two supports holding the angled outside members. It did not have a lot of support but looked like it could hold a decent amount. It was definitely a viable option in the decision process.
Michael’s design was based on the Double Howe Truss and was similar to it in that it had right triangles throughout. Michaels’s design differs however, in that the triangles are flipped the opposite direction (upside down). It is fairly complicated but looks like it would support itself well. It seemed like it would be too many supports to get exact in the given time limit.
Joanna’s truss was very simple and provided for an easy design. The truss was made with a central support and two supports holding the angled outside members. It did not have a lot of support but looked like it could hold a decent amount. It was definitely a viable option in the decision process.
(Michael's Truss)
Our criteria were simplicity, static determinacy, strength, wood length, and feasibility. We chose these criteria because they show an all round view of what the truss is like. Joanna’s design ended up winning due to its superior simplicity.
My sketch of the final Design
Official Test:
When we put our truss in the SSA it broke at the bottom member after 23 pounds of force were applied. The bottom member broke exactly where it was held up in the SSA machine. Our truss weighed .15 ounces and supported 23 pounds so its efficiency was 245333.33%.
When we put our truss in the SSA it broke at the bottom member after 23 pounds of force were applied. The bottom member broke exactly where it was held up in the SSA machine. Our truss weighed .15 ounces and supported 23 pounds so its efficiency was 245333.33%.
MDsolids sketch of Joanna's truss
before and after with completed truss
Graph of forces applied
Teamwork:
Joanna: Joanna came up with our truss design and scanned our documents. She also helped build gussets and the truss. She helped our group succeed.
Michael: Michael was influential in building the truss and also helped the process. Michael was the only group member to have done the test truss and provided guidance to us.
Rory: I helped build the truss and present it. I knew how it should be built so I helped the other members build in a uniform manner.
Reflection:
1.
I think our truss failed where it did because it was not supported how we had planned. The SSA machine supports were too far toward the center of truss and resulted in all of the pressure being applied on top of a weaker beam. The member that broke was not the member with the most force but ended being in a different spot than we had expected so it broke.
2.
With our immediate design I would have added supports directly down from the angled members to the base to support the spot that broke. If I were to completely redesign it I would create a triangle with every support going from the top joint to someplace on the base the distribute the force
Joanna: Joanna came up with our truss design and scanned our documents. She also helped build gussets and the truss. She helped our group succeed.
Michael: Michael was influential in building the truss and also helped the process. Michael was the only group member to have done the test truss and provided guidance to us.
Rory: I helped build the truss and present it. I knew how it should be built so I helped the other members build in a uniform manner.
Reflection:
1.
I think our truss failed where it did because it was not supported how we had planned. The SSA machine supports were too far toward the center of truss and resulted in all of the pressure being applied on top of a weaker beam. The member that broke was not the member with the most force but ended being in a different spot than we had expected so it broke.
2.
With our immediate design I would have added supports directly down from the angled members to the base to support the spot that broke. If I were to completely redesign it I would create a triangle with every support going from the top joint to someplace on the base the distribute the force
example of new design