RE: [PSUBS-MAILIST] Manipulator actuation / design

[Phil Nuytten <pnuytten@compuserve.com>]

Hullo, Joe:
        Just back in  town, so. . . manipulator arm jettison design(s): On
hydraulic/pneumatic/water hydraulic actuated arms, first determine number
of functions - 6 function is usual (1. shoulder yaw/ rotate, 2.shoulder
extend 3.elbow extend, 4. upper wrist extend, 5. wrist rotate, 6.jaw open &
close.) 7 and 8 function are not unusual - about the least you can do any
effective work with is 3 (shoulder extend, elbow extend, jaw open& close. 
When you know how many functions, then you know how many hydraulic lines
you will require from the pump and back to the reservoir. Then determine
where you want the arm to break (jettison) . Wrist is easiest, but affords
least protection. Entire arm is best but requires most elaborate and
largest jettison section . 
        Most of you will be familiar with hydraulic or pneumatic QD's
(quick-disconnects). When a female sleeve is pulled back and tension is
placed on the line or the opposed parts, the QD separates - even under full
pressure or zero pressure. So . . . saw your arm off at some point where
you want it to disconnect - weld or bolt a plate to each cut end of ,say,
the 'bicep" section (midway between the elbow and the shoulder. Make the
plates (round or square) bigger than the arm diameter - so that you have
about an inch and a half flange all around the arm 'end'. If you put holes
in the  flange portion of the plates, you could bolt the arm back together.
But, instead, drill and tap (thread) the plates with as many holes as you
have hydraulic lines downstream of the plates/flanges. On one side of the
plate flange, screw in pipe- to- hydraulic line (female nut) nipples -
these will join to your hydraulic hoses. On the other side of the same
plate, install the same number of, say, female QD sleeves to pipe thread
fittings. Do the same with the other flange, but on the side facing the
sleeve fittings, thread in the male snout/nozzle of the QD. Then make up a
3rd plate that is the same diameter as your threaded plates (if your arm is
three inches in diameter, for example - you would have a 7 inch ID by 3
inch OD plate. Drill out and make this plate so that is attached to the
female sleeves of the QD. (Buy QD's that have a narrower 'waist' in the
middle of the sleeve for this purpose) Put a short hydraulic cylinder
between the threaded sleeve plate and the sleeve actuation plate. run a
hydraulic line to this cylinder and run the other end to a
manually-operated hydraulic hand pump (wobble pump)  in side the sub cabin.
If the arm gets stuck, open the bulkhead valve on your hydraulic
through-hull and pump the arm off. 
        Sounds a bit complicated, but there's nothing to it. 
If you use a valveless water-hydraulic suck/blow manipulator actuation
system, the manip detent is even easier. But . . .time for bed - more
later.
Phil   



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