[PSUBS-MAILIST] Pneumatic Rotary Actuators

[Sean T. Stevenson]

I have built manipulators in the past using a small hydraulic motor to
rotate the inner half of a hydraulic slip ring, (outer half, motor and
arm structure all attached) with manipulator jaws attached that were
actuated hydraulically through the slip ring.  Not sure why you're
against hydraulics, but there's no reason you couldn't do the same thing
with an electric stepper motor and pneumatic actuation.

Sean


On 2014-04-05 13:39, Alan James wrote:
> Thanks Jim K & T,
> thats got me re-thinking things. I might be better to rotate via an
> electric
> motor inside the hull & hold with pneumatics outside. I've got an idea
> those
> rotary actuators are expensive.
> Alan 
>
> ------------------------------------------------------------------------
> *From:* "JimToddPsub at aol.com" <JimToddPsub at aol.com>
> *To:* personal_submersibles at psubs.org
> *Sent:* Sunday, April 6, 2014 2:43 AM
> *Subject:* Re: [PSUBS-MAILIST] Pneumatic Rotary Actuators
>
> Hi Alan,
> Could you use a sealed-unit worm gear operated by a small electric
> motor?  That would hold at 180 degrees or any other position you desire.
> Jim
>  
> In a message dated 4/5/2014 8:13:43 A.M. Central Daylight Time,
> kocpnt at tds.net writes:
>
>     Hi Alan,
>
>     If you use a thru hull, a linear actuator working at 12, 24 or 36
>     volts works well as well as giving more positive locations than
>     air. They are simple and robust however slower than an air cylinder.
>
>     You can find some examples at www.surpluscenter.com
>     <http://www.surpluscenter.com/>
>
>     Best Regards,
>
>
>     Jim K
>
>
>     On Fri, Apr 4, 2014 at 5:10 PM, hank pronk
>     <hanker_20032000 at yahoo.ca <mailto:hanker_20032000 at yahoo.ca>> wrote:
>
>         Alan,
>         you can rotate 180 degrees with a single air cylinder and a
>         watts link.
>         No need for an actuator
>         Hank
>         On Friday, April 4, 2014 4:04:18 PM, Alan James
>         <alanlindsayjames at yahoo.com
>         <mailto:alanlindsayjames at yahoo.com>> wrote:
>         Hi, 
>         I'm wondering if anyone has had any experience with either
>         pneumatic
>         rack & pinion actuators, or rotary vane actuators, operating
>         underwater.
>         I need to rotate something through 180 degrees & have it held
>         with a bit
>         of clamping pressure at one end of the motion.
>         One concern is seawater getting in to the gearing of those
>         items, & there reliability. 
>         Another option, could be a normal pneumatic cylinder with an
>         external
>         rack & pinion added. Am trying not to have to go to hydraulics.
>         Alan
>

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