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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.
"Idealism increases in direct proportion to one's distance from the problem."
~ John Galsworthy
Cheers
Szybowski
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