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Re: [PSUBS-MAILIST] question about general design?
----- Original Message -----
From: "Carsten Standfuß" <MerlinSub@t-online.de>
To: <personal_submersibles@psubs.org>
Sent: Friday, August 10, 2001 8:53 AM
Subject: Re: [PSUBS-MAILIST] question about general design?
>
>
> Captain Nemo schrieb:
> >
> > ----- Original Message -----
> > From: "Carsten Standfuß" <MerlinSub@t-online.de>
> > To: <personal_submersibles@psubs.org>
> > Sent: Friday, August 10, 2001 7:34 AM
> > Subject: Re: [PSUBS-MAILIST] question about general design?
> >
> > > "Expensive subs not automaticly good"
> > >
> > > Carsten
> >
> > "Inexpensive subs not automatically bad"
>
> "Fast and quick build sub not automatically fast but maybe quick
> diver.."
Ha! Alright!
And in case my statement above seems to contradict my earlier one: it's a
play on the difference between "cheap" and "inexpensive". There's a
difference between the two. One is a factor of quality, the other of cost.
>
> another one :
>
> "If a submarine works great - in general it looks also good."
Well.....yeah. I mean, beauty is in the eye of the beholder, isn't it?
I've seen some subs that looked like a plumber's nightmare, but they worked
really well. Now, somebody might think that kind of sub is ugly; but to me,
it's beautiful. There's a beauty in functionality. So yeah, I agree.
> "If a submarine looks great its not automatically works good."
Hey! You're not making fun of my NAUTILUS, are you!? ;-) I'll have you
know that (except for the minimal freeboard which was imposed by visual
design restrictions) that sub works really well (for a radical homebuilt
garage sub).
> The Alvin expirence : "Shut the hatch before you dive.."
The NAUTILUS 5th proving test experience, 1991: make sure the hatch is
properly sealed before you dive. Been there, done that. Got wet, too!
>
> The - Hamster - ball - bottom - sub - real - moment - of - inertia :
I can't believe you really took the time to do this. Taking a break from
welding on the X-1? ;-)
>
> here Crash Stop way : (be carefull - this is not real maths - is just a
> estimate - quick and dirty calculation - ..)
>
> Diameter : estimate 2 meter (6,55 feet)
In a previous post, I ran the numbers for a six-footer.
>
> Volume : 3,1415/6 x D x D x D or 0,5235 x D³
> : here 4,1887 m³
That's an interesting formula. Over here we use 4/3 PI x R3: When I figure
it out for a six footer using a hand calculator, it comes to almost 113
cubic feet. But I've also got a computer program that I just feed the
numbers into and it spits the answer out, and that says it's a little over
113 cubic feet volume for a six foot sphere. (I figured one a bit smaller
than you did.)
>
> Mass : in seawater with a mass of 1,025 x 4,1887 = 4,293 metric t
> equal to 4,293/1,016 = 4,22 ts at zero bouancy.
> equal to 42930 Newton
In my estimation of the Hamster Ball project, I computed the weight of a
6-foot sphere (smaller than yours) of 1/2 inch mild steel at well over 2000
pounds (the exact numbers are in the post, but I'm not going back to check
it now.) The displacement was well over 7000 pounds. I've got a calculator
program that would churn that out in Newtons, but I took one look at it and
stopped right there. That's one damn big ball, and it was obvious there
wasn't anybody from this planet that was gonna be rolling it around on the
bottom of the ocean with their feet! ;-)
OK, let me check the rest of this out. (I can't believe you did this!)
;-)
>
> Estimate speed : 1 km/h (3280 feet/hour)
> equal to 1000 m/h or 16,7 m/min
> or 0,277 m/sec (0,9 feet/sec)
OK. A velocity of almost one foot per second. Under most normal
circumstances, that would sound easy. But now we're talking about treddling
a four ton hamster ball over rocks, coral heads, sunken
ships.....hmmmmm......
>
> Power : 42930 N x 0,277 m/sec = 11892 Watt or - 12 KW -
> stored power in the mass moment of inertia.
......12 kilowatts of inertial power at a velocity of 1 kilometer per
hour.....
>
> Power of two person going a step of 1 feet by 1 feet
> estimate with :
......two people walking the hamster ball........
>
> Weight 2 x 75 kg = 150 kg or 1500 Newton
.....OK, two 165 pound people are worth about 1500 Newton total.....
>
> 1500 Newton x 0,3 m = 450 Watt or 0,45 Kw.
.....that much weight at the specified velocity gives us a stored inertial
power of less than one kilowatt.....
>
> Now I make a milkcan calculation :-)
.....Milch can calculation? Vas ist das? OK, I'm going to interpret that
as a "ballpark guesstimation".....
>
> 12 kw / 0,45 Kw = 26,7 steps stopway
.....the ratio of stored inertial power in a velocity of 0.9 fps, to the
power generated by our two "walkers"....
>
> Distance full stop = 26,7 x 0,3 m = 8 meters or 26 feet.
> Good look - nice experience - especially if the seabottom
> is not flat..
...Well, yeah, but in your equation you've already got the thing rolling!
Even so, I think 26 feet is still a generous estimate of how far they'll go.
We haven't considered form drag, friction between the ball and the seabottom
(and we both know it's not going to be flat), adverse hydrodynamic flow
(currents), silt, sand, or a big clam shell stuck underneath! Take those
factors into consideration; start from zero velocity, and this ball aint
rolling nowhere, brother! ;-)
>
> I have seen a wooden heavy plywood water surface wheel
> during a waterbike regatta race between the
> european naval/shipbuilding-students.
I can visualize it....
>
> Two person run this monster - more or less impossible to change
> the direction -
I can imagine. It must be heavy as hell...especially when it gets wet and
soaks up water....
you have to stop the thing before you can change
> the direction
And I'll bet that's not easy...
if not and you turn you body direction just a little
> the stored power of the inertia came from the side of you body -
> - and the wheel move quickly all the times from a
> Hamster ball to a washing machines.
And you're doing cartwheels seeing fish, sky, fish, sky, fish, sky....
>
> Even at start or stop manovers.
> Both person goes all the time "arm in arm" to make excat the same
> steps - during the first run they don't do this
> - if one runs - the other went over board or fall down..
Yup! Like one guy trying to stand on a floating log while the other is
spinning it with his feet!
>
> We took the about 0,4 t wheel later onshore - turn at 90 degree to
> the ground and use it as beer bar..
Ha! Now THAT makes sense!
> This wheel was a great fun for - the visitors.
> see you - Carsten
Yup! Been fun. Right now I'm going to go calculate how many gallons of
beer will fit inside a 6-foot steel hamster ball.... ;-)
Pat