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Hi Alan. Ya, that's interesting from a "home made" view.
Using regular "all thread rod" and nuts creates friction and wear. The
"ball screw" actuators have little balls that mesh with the grooves so friction
is minimal. Even the "acme screw" type actuators have a different thread design
profile. The thread profile is square so a little lube reduces friction and
the force available is greater.
I'm using " Firgelli Automations" actuators because the outside casing is
easily adapted to adding rubber bellows. The dive plane actuators have a
6" stroke and are rated at 40 pounds push/pull with 100 pounds holding force.
They were $129 each.
The rudder actuator is rated at 200 pounds push/pull but with a 4" stroke.
Generally the slower the stroke the more force available. With the high strength
and short stroke of the rudder actuator the speed ( inches per second ) is good
for my application. Firgelli makes another model like the sleek bodied ones
I'm using for dive planes with a slower stroke and a 150 pound force. I have one
of those at 12" stroke to move my sliding ballast weight inside the sub so no
additional sealing will be required.
There are many brands of actuators out there and some are sealed to IP 68
but even at that they need to be sealed even more for submerged service. The
Minnkota and Lenco both are sealed to IP67 rating, meaning shallow submergence.
They run $260 each.
Making your own is a good exercise but with the low cost and
availability of easy direct bolt-on replacements, Your time has to be
considered in the mix.
Frank D.
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