Manufacturing & testing
Tooling: An aluminum billet was bought from Winona Boiler, a company in Winona. The billet was cut to appropriate dimensions on a band saw before being squared and faced on a CNC machine. Next, the mold was milled in a Hurco VM-1 CNC machine. The mold was designed by the Mount'N Lion team in SolidWorks and then converted to a MasterCAM file by an outside source. Once the file was received the two halves were machined according to plan. A picture of the finalized mold can be seen above.
Manufacturing:A 4-Harness Satin Carbon Epoxy Prepreg was cut according to a template then laid into two halves of an aluminum mold. Each half contained 10 plies. Then a vacuum bagging arrangement was placed on the interior cavity of the mold. The mold halves were then closed and screwed together. Once this was complete a vacuum bag was placed around the mold sealing the cavity bag to the exterior bag to ensure cavity compaction. The part was then cured in an autoclave for 2 hours at 350 degrees C and 40 psi. Finally, the part was demolded, cut to final dimensions, holes were drilled and hardware was attached.
All tests were performed with custom fixtures.
The mount was tested in tension to simulate hauling a load. The failure occured as a shearing failure from the bolt hole to the end of the part. This failure along with the other premature failures the part saw are being addressed with an aluminum insert which should provide the support required to inhibit shear failure in this manner.
The mount was tested in compression to simulate a deceleration or stopping with a load on your trailer.
The compression failed in the same place and manner as the tension failure with a shearing from the bolt hole to the end of the part. The aluminum insert will address this.
A flex test was conducted to simulate the load on the mount itself, or how the mount would react when encountering a rough ride.
The Flex failure was caused due to stress concentrations by the sharp end of the receiver. Later tests will be conducted with a fixture that has had the steel edge softened with a file so as to avoid stress concentrations leading to failure in this manner.
Finally Transverse Flex was performed to simulate turning with a loaded trailer. Transverse Flex was performed and the part met the requirement outlined by the VESC.