Brent, Pretty cool idea. Not sure that I would use PVC though after having to work with it daily. It becomes embrittled real quick with exposure to UV sun light. I would not use it in any application that is tied to hull penetrations. Besides cannot find it referenced in ABS/PVHO for any applications like yours. Remove the PVC from being a week link on the hull penetration and you should be good to go. R/Jay Resepectfully, Jay K. Jeffries Andros Is., Bahamas Save the whales, collect the whole set. From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent Hartwig Subdudes, I've been working out ideas for the rotating thruster thru hulls I need for KL-250, and wanted to use the FPR flexible shaft that can come with the Minn Kota thrusters. I've been told those shafts are killer strong, so I also considered using Sch 80 PVC piping with the proper compression threads added to make the shaft easier to brake off in a collision. The tube would be filled with potting epoxy which would add to it's strength, but the epoxy would brake if need be. I've added a machined cut in the FRP shaft next to the SS rotating rod that goes into the hull, as the weak point in the assembly. I have 3.25" holes in my hull after removing the existing thruster thru hulls, and wanted a larger SS welded in thru hull there any way. So I like using the larger thru hull. I might support it on the inside with gussets as Emile worked up. But I might not need to since I have a pretty good weak point designed in, and I have a pretty substantial thruster guard with all the tubing that makes up the inflatable ama decks and what not. There are two Delrin bearing and centering parts and rotary O-rings thru out. The gasket under the outer Delrin part is Sikeflex, so that will keep that part from leaking a rotating there. The double holding screw arrangement inside the housing is to hold the flexible shaft and thruster in place to the larger SS rod that rotates with all of that from inside control handle. I've not finished up all the bits inside, like the retaining collar and secondary electrical wiring seal. There is a Sikaflex plug caulked into the end of the threaded end of the flexible shaft to allow for the potting resin to be added later inside. Much like what Greg was talking about doing with the thicker 3M epoxy. There are two thick SS rings that are machined to a tight fit and then TIG welded on the the SS rotating shaft, then final machined, to keep the assembly from extruding thru to the inside, and to make it cheaper to make the part. One could of course make it from one solid piece of SS if they needed the shavings for pot scrubbing at Disney world. Ya I know it has more then three parts to it. But I needed lathe machining practice any way. I'm almost finished with a second much simpler and smaller assembly that will allow the thruster to brake completely away, with disconnecting wire connections inside the flexible shaft. But it lacks some features I like in the above embodiment. I might whined up blended the two designs together. Will have to see what issues you guys see first, then put it all together again.
~ John Galsworthy Cheers Szybowski |