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RE: [PSUBS-MAILIST] Trim Tank Idea
Thanks again Carsten,
It looks as though it is not really a practical option, even as a variable
ballast or trim tank. Thank you for taking the time to run through the
calculations. By the way I visited the site you highlighted, the models look
very good indeed.
Harry
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Carsten
Standfuß
Sent: Wednesday, August 15, 2001 9:26 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Trim Tank Idea
Harry Spillett schrieb:
>
> Thanks for your reply Carsten,
> Was your description based on using a piston tank at a MBT or a trim tank?
In this example as MBT - but you are right - maybe easier to use as
small regulator- or trim tank only.
> I had anticipated many of your concerns, however I has hoping that for a
small
> one person 1 atm sub it would be a possibility to have conventional MBT's
> and use these tanks as the VBT and fore and aft trim tanks. hopefully
> because of the small size of the sub the trim requirements would be less.
>
> Also if I were to ensure that one side of the piston contained a
> compressible air pocket could this not help to counteract the diving
> pressure on the other side of the seal? By building this side of the
> cylinder to differing volumes you could predict what pressure will be
> generated as the piston compresses it.
Indicates that the cylinder must be longer than the shaft - and the
drive
must be inside.
>
> I look forward to your comments, I thought I was on to something there!
> Just goes to show the value of the group where we can get a new
perspective
> on our pencil sketches.
Piston tank as Regulator and Trim Tank - second example calculation:
Example Boat : Sgt.Peppers
Pressure hull length : 2000 mm, 2 m or 6,6 feet.
maximun length of the cylinder : 1/2 pressure hull length, rest for the
shaft.
Numbers of cylinders : two, one with the water part forward and the
shaft aft, the other in opposide direction, both close together on
the bottom inside the pressure hull.
Maximum outside diameter of the cylinders for space reasons :
100 mm or 3,94 inch.
Cylinder material : optical acrylic because of his mirror inside surface
and easy to control. Thickness about 10 mm should resistant the dive
pressure
easy. A security hand vale for saftey reason should be fitted on the
both entrance pipes.
Useful inside diameter : 100 - 2 x 10 mm = 80 mm or 3,149 inch.
Volume of one cylinder estimate calculate with 5 Liters.
Two cylinders have a volume of 10 Liters.
Trim the boat: one person move 10 cm for or aft.
65 kg x 2 x 0,1 m = 13 kgm moment.
Trim the boat with the cylinders
5 kg moves 1,0 m = 5 kgm moment.
No very useful as trim tanks but can work.
Displacement of the sub 570 Liter,
Cylinder regulator contains 10 Liters or 1,75 Percent of the
displacement.
In general the regulator should have at least estimate 3 %
Conclusion : not very usefull in Sgt Peppers - not the space in this sub
for
bigger cylinders.
For the guys which don't know what we are talking about, look at :
http://home.t-online.de/home/cord_schroeder/Bilder1.html
the pictures number 7, 17 and 18 shows the pistton tank unit.
regards Carsten
> Harry