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Doug,
You
might want to think about using an aluminum scuba tank for your housing ,
as of Jan 1 they are not allowing the older aluminum alloy tanks to be
refilled, I know because my old Alum tank just became obsolete, it's sitting
here next to my lathe waiting to become something else. Maybe I'll
build and ROV !
Brian
----- Original Message -----
Sent: Wednesday, October 25, 2006
20:01
Subject: Re: [PSUBS-MAILIST] External vs
Internal Stiffners
Thanks for the input Ian. This hull is for an ROV
and only 6 to 10 in ID and I'd start with an extruded aluminum pipe
section most likely. It seems like it would have to be somewhat weaker
of a design. The solid weld will not help with
any out-of-roundness problems and would subject the stiffner to failure
due to stress cracks and weld failure.
By the way, my hat is off to the folks that put together the spread
sheet. I'll have some questions about it when I figure out what to ask.
:) --Doug J
In a message dated 10/25/2006 6:08:37 PM Central Daylight Time,
irox@ix.netcom.com writes:
It's been a while since I've done any pressure hull calculations,
but as far as
the math goes, there shouldn't be any difference between
internal and external
stiffeners.
From a construction point of
view external stiffeners will be a lot harder. The
weld has to be
load bearing (for internal stiffeners, the welds just need to keep
the
stiffeners in place). Also, external stiffeners will not help push the
cylinder
"into round" (since they will all come slightly out of round),
so any out of roundness
will have to be "fixed" before attaching the
stiffeners. The only benifits you get
are a slight more internal
space, and plenty of points to mount external equipment.
Using
internal stiffeners appear to be much more simpler, construction
wise.
Ian.
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