Easily the most difficult step so far of my PacificMeister inspired build has been the drive shaft. Like some others, I have found cutting threads and a hole for the prop pin impossible in these 8mm chrome plated high carbon steel shafts from Amazon. So I ordered one of these 8mm stainless steel shoulder screws which was easy to drill and already had threads. However, its actual diameter is 7.82mm (the carbon steel shafts are 7.96) so the fit into the spec’d blue connector is not as tight and introduces a slightly greater wobble issue. [Update 10/17/18 - For now I’m going with the aforementioned shoulder screw and blue connector]
After reading scores of posts I see that many are struggling with the same gearbox-shaft-to-prop-shaft connection. It’s failure – both the blue one above and several other types tried by forum members – has been blamed for many seal leaks (from the wobble), slipping shafts (from the connector grub screws not holding) and even at least one lost prop and shaft (from the whole shebang disconnecting).
So what have I learned? No surprise to see many smart people here coming up with many creative solutions. My plan is to find some shaft stock that is: A) Exactly 8mm in diameter (±.05mm) and B) Of slightly softer metal making it easier to thread, cut and drill than the original shafts. I have also ordered a couple of different couplers to try. Finally I may trot that original shaft off to a machine shop and let them have a go at machining it.
When the coupler fails it’s a lot of heartache to cut the pod open and fix it. I’m hoping to skip that step!
P.S. - The ultimate solution would be a Neugart PLE40 gearbox with a longer shaft negating the need for the coupler and shaft extension. I just wrote them about this (details HERE).