Re: [PSUBS-MAILIST] Sub with arm

["Marsee Skidmore" <heyred@email.msn.com>]

Stan,

If I'm understanding your manipulator description correctly, you'll be
working against outside pressure. At 45 feet, that's around 20 psi pushing
against each of your cylinders. A one inch diameter cylinder (for example)
has an area of .8 in^2, so 20 x .8 = 16 lbs. Not impossible, but you may get
more of a workout than you planned. Somebody already suggested using smaller
diameter cylinders inside to obtain a mechanical advantage, and that may do
the trick.

What's the vacuum supposed to do?

Joe
----- Original Message -----
From: Stan Muller <smuller@iland.net>
To: <personal_submersibles@psubs.org>
Sent: Friday, May 11, 2001 10:31 PM
Subject: Re: [PSUBS-MAILIST] Sub with arm


> Hi Dan H.
>    I had thought about the need for a stable platform from which to work
> with the arm. This is the reason my arm will be mounted on the side of
> the sub, below the conning tower. Set up this way, the mass of the hull
> and tower will help prevent the boat from moving when a force is applied
> to the arm. Initially I had thought to put it on the bow, but was
> concerned about the torque applied to the arm moving the boat.
>    > but than I have done some back yard,
> > picnic table, fish pond engineering myself a few times.
>    One thing I have found to be common among the backyard shade tree
> engineering types, Is they, as a group, tend to over engineer, usually
> ending up with a 300 % or better fudge factor. As the case in point, my
> hull; The tanks are 1/8th inch aluminum, I don't know what they were
> built for, but they have the manufacture ID tags on them showing that
> they were pressure tested to 175 lb per sq. in. over which I will lay a
> minimum of 1/2 inch of epoxyed fiberglass, (woven), and laid on the bias
> of each preceding layer. Since the deepest dive we can make in our local
> lake is 45 feet, and our operating depth will be no more than twenty
> feet, my buddy and partner in crime, made the suggestion that we use my
> two cylinder vacuum pump to draw a vacuum inside the hull of twenty to
> twenty five inches while the sub is down there. I am sure this is
> overkill, but that is what makes empirical engineering such fun. ;-)
> Just think of the bang and the fish kill if it implodes. ;-)
>
> Hi Phil,
>    Your arm, is just what I am trying to accomplish. My reason for going
> the hydraulic route instead of the air was to have more control than the
> on / off of an air set up. I will, however, incorporate the  weight
> reduction holes in mine, just so it will look cool.
> > The air manip worked well, could easily attach a lift line to an
outboard,
> > collect specimens into a screen tray, retrieve small object s directly,
> > etc.
>    This is exactly what I plan on doing with mine, plus some sampling
> functions. Did you use the same "hand" for all your applications? I
> found it easier to have a "change hands" ability for different jobs
> rather than try to design one to do it all.
>
> Thank you, one and all, for your assistance, Stan, the shade tree
> mechanic that has survived, 'cause he's chicken!