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I want to build a small remote-controlled submarine, and have been thinking about how to handle the ballast tanks. The simplest option seems to be a piston shaft, which fundamentally needs some kind of (sealed) linear actuator with sufficient force to overcome water/air pressure at reasonable depths (say 0m to 50m).

The problem is I don't have an infinite supply of power available on-board and all the linear actuators I found use ludicrous amounts of it, such as over 1 amp at 12 volts... but I only need to move the piston every now and then, most of the time it just needs to sit wherever I tell it to and not move.

My question is, once a linear actuator has been "actuated" into place, can I de-power it and expect it to hold up to its maximum rated load? Does it depend on the design of the actuator? If not, what are some engineering approaches I can use to mechanically lock the piston into place until I need to unlock it, so that I can trade off precious electrical power for mechanical strength?

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  • $\begingroup$ I would take a look at the actuators (and the digital RF communications hardware) used in R/C airplanes, sailboats, etc. So far as I know all of them are "set and forget," i.e. they stay where positioned. $\endgroup$
    – Carl Witthoft
    Commented Jul 18, 2016 at 12:34

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Some linear actuators are self-locking — they can't be back-driven by force on the output connection. A leadscrew with a fine enough thread pitch is one example, and since you don't need a lot of speed for your application, wold probably be a good choice.

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