Progress Documentation

The final design, differs slightly from the previous design iteration in that after conducting extensive finite element analysis via SolidWorks, a fourth member was added to the front assembly to reduce the maximum stress acting on the trike. Much of the geometry from the previous design are implemented barring a slightly different rear assembly arrangement, added seat supports, and a slight caster angle added to the front assembly. The rear assembly has been simplified by adding soft bends to the titanium fork that holds the rear wheel. Additional supports connecting the pilot seat to the center boom were added for increased stability. A caster angle of ~15º was added to the front head tubes for increased steering maneuverability. 

This was the "final design", pending verification of structural integrity from SolidWorks. It features a carbon fiber main axle with titanium front and back ends. The body, remaining low at about 18" (~46 cm) from the ground, will decrease the center of gravity of the riders and the tilting of the frame; while the carbon fiber axle will better support torsional loads and the titanium will ensure toughness. This design has also achieved significant weight and length decrease, measuring to 204.56 cm hub to hub and 10.18 kg without any attachments, exceeding the desires of Team Chase. The team also took the comfort of Lance as a priority when designing the shape and positioning of the seats and boom. Taking this consideration is actually what led to such a great decrease in the length. In the second iteration, the seats and boom were adjustable to allow for positioning of the riders, especially Lance, who needs the assistance of a least two other people to get into his seat. However, through further investigation, it was revealed that once his position is found, adjustments are no longer made. In designing a test rig to find Lance's optimal positioning, the team was able to remove this level of modularity to create a more static design tailored to Lance. The seat frames will attach to the trike frame by being epoxied to the carbon and welded to the titanium, and will reduce vibration felt by the riders with a mesh seat. The push bar, in the past only located in the back, now has arms that swivel into place on Lance's boom, to shift the forces from the push to center of the frame.

Due to failure occurring at the front boom with the aluminum trike iteration, a gusset was added to transfer the stress away from this problematic area. The geometry of the 2 carbon tube design stayed consistent. But because the team was able to shorten the length of the trike significantly, a single carbon tube could be constructed and implemented in the current design.

A 2 carbon base tube was selected as a restriction of the custom carbon tube length construction. The relative geometry of the all titanium trike was implemented but the team decided to move away from an all titanium frame due to heat deformation and a larger margin for error when welding.

One of the first design choices made was to use titanium for the frame for its toughness and light weight. The first trike iteration achieved toughness with steel but was very heavy. The second iteration achieved light weight but its toughness was compromised since annealed aluminum loses its structural integrity.