Re: [PSUBS-MAILIST] thru hull fittings

["Dan H." <jmachine@adelphia.net>]

Brian,
O-rings on the shaft create areas of higher stress in the corners of the
O-ring grooves.  Also your shaft diameter is the area that the sea is acting
on when calculating how much force is pushing inward on the shaft.  At depth
that force creates some resistance to turning.  But, for sheer, tension and
compression, your shaft diameter is only the root to the O-ring groove minus
a bit for the stress risers in the groove corners.

It's a bit more difficult putting the O-rings in the thru hull, but the
shaft in one size and most efficient.

Dan H.
----- Original Message -----
From: "Brian Cox" <ojaibees@ojai.net>
To: <personal_submersibles@psubs.org>
Sent: Saturday, February 28, 2004 6:54 PM
Subject: Re: [PSUBS-MAILIST] thru hull fittings


> Dan,  thanks for the insite,  I'll probably go bigger on the drop weight.
My "O" rings are going to be on the shaft.
>
> Brian
> ----- Original Message -----
> From: "Dan H." <jmachine@adelphia.net>
> To: <personal_submersibles@psubs.org>
> Sent: Saturday, February 28, 2004 5:50 AM
> Subject: Re: [PSUBS-MAILIST] thru hull fittings
>
>
> > Brian,
> >
> > You sound like your on the right track with your through hulls.  One
thing
> > to consider with your drop weight through hulls is, how your going to
attach
> > the handle inside the sub.  If your going to drill through the shaft you
may
> > want to consider a shaft larger then a half inch since it's holding the
drop
> > weight and will get yanked through the hull if it breaks or of the bolt
> > shears.  When making mine, I was visualizing the drop banging up and
down on
> > it's shaft while tailoring down the road.  Then I want to depend it to
hold
> > the weight when diving.
> >
> > I had a bit of trouble with the through hulls necking down in the weld
area
> > but cured the problem with a hand reamer after welding.  Use two
O-rings,
> > one near each end, for double protection and then you won't be welding
or
> > reaming where they will be.
> >
> > Dan H.
> >
> >
> > ----- Original Message -----
> > From: "Brian Cox" <ojaibees@ojai.net>
> > To: <personal_submersibles@psubs.org>
> > Sent: Saturday, February 28, 2004 1:00 AM
> > Subject: Re: [PSUBS-MAILIST] thru hull fittings
> >
> >
> > > Alec,   If I'm envisioning that piece correctly it started out as a
1.5"
> > dia shaft and a portion was machined down to 1" , then the part is
inserted
> > from the outside of the sub where the  lip keeps the part from blowing
into
> > the sub under pressure.  I probably don't have your dimensions quite
right
> > but I think I see the part.  Are the shaft and hole 1"  +/-  2
thousandths?
> > >
> > > Brian
> > > ----- Original Message -----
> > > From: "Alec Smyth" <Asmyth@changepoint.com>
> > > To: <personal_submersibles@psubs.org>
> > > Sent: Friday, February 27, 2004 4:28 PM
> > > Subject: RE: [PSUBS-MAILIST] thru hull fittings
> > >
> > >
> > > > Yes, there's a reason. Because the sub is hydrobatic, when the sub
is at
> > a 90 degree roll the drop weight will exert a bending moment. So I made
it
> > stubby. The maximum diameter is 1.5", and its set in an insert that is
3" in
> > diameter. The difference between the diameters of the shaft and the hole
is
> > only 2 thousandths of an inch, so that the O rings cannot extrude and so
the
> > insert will help the shaft resist the bending moment. And the reason I
said
> > "maximum diameter" is that there is a 1" section on the shaft too, to
> > prevent the ambient pressure from shooting it into the boat after
releasing
> > the drop weight, or when the sub is inverted.
> > > >
> > > > Sorry for writing a book on such a small topic...
> > > >
> > > > Alec
> > > >
> > > > -----Original Message-----
> > > > From: Brian Cox [mailto:ojaibees@ojai.net]
> > > > Sent: Fri 2/27/2004 5:40 PM
> > > > To: personal_submersibles@psubs.org
> > > > Cc:
> > > > Subject: Re: [PSUBS-MAILIST] thru hull fittings
> > > >
> > > >
> > > >
> > > > Thanks Alec,   I read a few posts back that your drop weight shaft
was
> > like 2" or something,  it seamed rather large was there some reason for
> > that?
> > > >
> > > > Brian
> > > > ----- Original Message -----
> > > > From: "Alec Smyth" <Asmyth@changepoint.com>
> > > > To: <personal_submersibles@psubs.org>
> > > > Sent: Friday, February 27, 2004 1:28 PM
> > > > Subject: RE: [PSUBS-MAILIST] thru hull fittings
> > > >
> > > >
> > > > > With a 1.25" insert, you have added much more reinforcement than
the
> > material you removed with a 0.5" shaft hole. If I remember right, the
rule
> > of thumb is that you should add twice as much as the hole removed. So it
> > should be sufficient.
> > > > >
> > > > > Alec
> > > > >
> > > > > -----Original Message-----
> > > > > From: Brian Cox [mailto:ojaibees@ojai.net]
> > > > > Sent: Fri 2/27/2004 3:51 PM
> > > > > To: Personal_Submersibles@psubs.org
> > > > > Cc:
> > > > > Subject: [PSUBS-MAILIST] thru hull fittings
> > > > >
> > > > >
> > > > > Hi All,    I am in the process of machining thru hull fittings
(316L
> > ss) that will have 1/2" shafts running through them to turn valves, turn
> > rudders, and other functions as well, drop weight, and possibly move
trim
> > ballast ;-)     .  The fittings that I am machining at the moment are 1
1/4"
> > od  with the 1/2" id ( for the shaft)  is that 1 1/4"  a big enough
chunk of
> > steel to be welded through 1/4" A516 70   or should that OD be larger
for
> > some reason?
> > > > >
> > > > > Thank You
> > > > >
> > > > > Brian Cox
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > >
> > >
> > >
> >
> >
> >
>