Hi Alan.Good photos. The use of a bicycle innertube is a good idea as it
will expand and is easily replaced.
Might be a little thin though. The power steering boots I'm using are
pretty strong at about 3/16 inch thick.
I had originally planned on using a plastic tube bladder that
could collapse as the oil was drained away, like has been proposed for
the Minnkota motors for compensation but the actuators move more oil in/out
than the motors would, so I went with a larger bladder.
As for depth, well, it's true that the pressure is equalized. That's the
whole purpose of "oil compensation". But it just seems that a more "robust"
system like high pressure hydraulics would be more likely to withstand the
rigors of deep diving.
I really went with the electric actuator method because I liked the idea
of using electrical thru-hulls ( only takes one) over a supply/return
hydraulic system where two thru-hulls are needed. OK provided I can get it
sealed up.
That, and the fact that an electric pump and all the related plumbing and
pressurized oil reservoir of a HP hydraulic system makes the system more
complicated ( high maintenance) and expensive to build and
maintain/replace.
For "position sensing" I wonder if it's possible to add a magnet to the
stroke some where and then put a series of sealed magnetic switches next to it
to sense position. One problem I foresee would be the number of wires
needed to get the signal from several positions. The wires would be quite
small but a multi prong thru-hull can get pretty complicated.
Seems like it would be better to just shell out the money for the
MinnKota actuators and use the "off-the-shelf" rocker switch with the led
graph. The Lenco actuators can be had on Ebay and they too have an LED thing
to show position. Again, the wiring is a six wire cable making the thru-hull
more complicated.
I've been leaning toward adding another pair of windows to the sub on the
sides so the dive planes would be visible. My current window design needs some
additional work to reach my intended depth so when I fix that problem I will
be adding the other two windows also. Always better to have good visibility.
For now though, I'm still trying to get her ready for the July convention so
any big changes will have to wait for next year.
I made a quick sketch of the CV joint bladder. It fits in the little
space between the hull and ballast tank and if it works will be easily
maintained. Once all these components are fabricated I'll pressure test them
in a bench-top chamber to see what problems pop up.
Frank D.