The upper set of new engine mounts are now complete. This log documents both the design and the process of building the new mounts.
The new hardware is considerably different from the previous design. The prior mounts were originally a 6" piece of angle iron bolted to the slotted angle frame and had a slot cut out for the shaft. The shaft was held captive between two shaft collars that also served to transfer the thrust between the shaft and the shaft mounts. One of the previous shaft mounts can be seen below, just above the closest rotor.
The mounts for the Mk. II vehicle had to go from the shaft and mount to the three aluminum tubes that comprise the rotor arms. This required a custom part that could be bolted to the tubes and also act directly as the shaft mount, instead of using multiple shaft collars. The design process started by making a CAD object using Cubify Design.
After that, the next step was making some prototypes out of wood on the CNC router.
These were also used in the Jig to align the tubes for the rotor arms.
Next, it was time to make the actual hardware. The parts were machined out of 6061-T6 bar stock. The parts were cut on the CNC router. A CNC mill would be better suited than the CNC router, but I don't have one. That being the case, it took a couple tests to find the right settings on the CNC router. The first test run had some issues with galling. The galling causes the poor surface finish and the feathering on the edges.
The fix was simply to slow down the feed rates and lower the spindle speed. After that the roughing passes came out a lot cleaner.
Once the roughing pass was done, a waterline pass was made.
Next, a parallel pass was made in the Y-axis to clean up the upper surface.
The last pass was with a 3/4" diameter ball end to clean up the grooves.
With the machining on the CNC Router done, the next step was to drill and countersink the holes for the bolts to mount to the frame. The last step was to drill the holes for the mounting.
When everything is together the shafts will be mounted using half of a shaft collar.
With the parts complete, it was time to attach them to the upper frame.
The next part of the project is building the engine supports. To make sure everything is right before it's riveted all together, which means that the parts need to be scavenged from the first vehicle. More on that next time.