Update! 3D printed mock up and design finalisation
Hey guys I ‘ve spent the last couple of weeks taking everyone’s feedback on board as best I could, and I have made tweaks to the design. I’ve also been 3D printing all the parts and physically testing the assembly, I’m glad I did! Because I identified some issues that would have gone unnoticed in CAD. What did people do before 3D printers, testing designs must have been a real pain!
Some of the most notable changes to the design are:
Increased the thickness of the motor mount plate. I designed the gear drive to be a thin as possible without sacrificing the gear width, however what I didn’t consider is that the motor shaft would be too short (22mm), resulting in you not only having to cut the shaft down to size but also the keyway. In this design revision the motor shaft is 26mm long and the pinon gear utilises the full length of keyway making it stronger and removing the need to cut down the keyway as well as the motor shaft. This does have an advantage, as the drive should be stiffer now and resolves a concern @ShutterShock had:
I’ve also come up with a new wheel mounting method, I didn’t like the way that the extended bolts just slotted into the gear drive hub mount before, and @sleepless has his concerns as well:
This new method uses custom round nuts as a replacement for the for the wheel hub hex nuts, and then the round nuts slot into the hub mount of the gear drive and everything is retained with the truck axil nut. I think this is a more elegant method and there shouldn’t be issues with the bolts wearing through the hub mount like with the previous design iteration.
@jack.luis I have come up with a method using thrust bearings in that would make it impossible for the pinion gear to come loose from the motor shaft due to helical gear axial force; his method would also negate the use of Loctite retaining compound. However, it adds too much cost to drive and thus not really affordable for most eskate builders, so I might develop this idea separately as pro version of the drive.
I made other minor changes such as making the motor mount gasket wider, adjusting tolerances etc… but I won’t bore everyone with the details.
The 3D printed mock works quite well, ABS is pretty strong, but I will wait until the I have the first metal functional protype before properly testing the drives. I did have some issues cutting the neoprene rubber gaskets using my girlfriend’s Cricut Maker, it’s basically too stretchy for the drag knife to cut through it effectively. I’m going to try laser cutting the gaskets or having some die cuts made, this is pretty much the only manufacturing detail left unsolved now.
The next step is to fully lock down the design, get the first protype manufactured and test it to see how it performs on a mountain board.