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Re: [PSUBS-MAILIST] thru hull fittings
I just posted a drawing (or at least i hope i did) to Moki files of a thru
hull fitting. It is just an idea for solving 2 problems: weakening the shaft
and machining an O-ring grove in the fitting. Maybe it is a solution.
Have a look at:
http://www.prismnet.com/~moki/subfiles.html
Greatings,
Thijs Struijs
The Netherlands
----- Original Message -----
From: "Brian Cox" <ojaibees@ojai.net>
To: <personal_submersibles@psubs.org>
Sent: Sunday, February 29, 2004 7:54 PM
Subject: Re: [PSUBS-MAILIST] thru hull fittings
> Ok , so if I'm understanding this now the issue here is the strength of
the shaft. If that is the only issue I would have to say that it would not
make any difference whether the o ring is on the shaft or the inside the
fitting. Since it would be much easier to machine a O ring grove in the
shaft and also easier to inspect for burrs and put chamfer on the edges of
the grove I submit that putting the O rings on the shaft would be more
advantages. If you have to turn that 1/2" shaft hard enough so that it
would sheer off then there is some other problem. Am I missing something?
>
> Brian
> ----- Original Message -----
> From: "Dan H." <jmachine@adelphia.net>
> To: <personal_submersibles@psubs.org>
> Sent: Sunday, February 29, 2004 10:08 AM
> Subject: Re: [PSUBS-MAILIST] thru hull fittings
>
>
> > Brian,
> > No, no Not at all.
> >
> > Either O-rings on the shaft, or O-rings in the housing will work. As
far as
> > leaking, it's the shaft to housing clearance and the proper groove depth
> > that matter. And yes, hydraulic applications do sometimes use O-rings
in a
> > shaft but not as a rule. If the shaft is the critical component, the
O-ring
> > grooves are in the housing. Grooves in a shaft weaken it.
> >
> > Maybe I didn't explain myself well before. What I meant by my earlier
> > posting was, if you groove the shaft, the groove diameter, minis a
little
> > factored in for the stress risers created by the groove, becomes the
working
> > diameter of the shaft. The weakest point! A groove does create stress
> > riser. If you break a shaft with grooves in it, it will always fail in
one
> > corner of a groove. A properly designed O-ring groove has small radii
in
> > it's corners, but still it's a week spot. If you take the same shaft
size,
> > but put the O-ring in the housing, you can design around the full shaft
> > diameter.
> >
> > I tried to keep my shaft diameters from getting larger then needed
because,
> > as a shaft get larger it takes more force to turn when your deep. At 400
> > feet a one inch shaft has 160 pounds of force pushing in on it. That
> > creates friction that you have to overcome to turn it.
> >
> > Dan H.
> > ----- Original Message -----
> > From: "Brian Cox" <ojaibees@ojai.net>
> > To: <personal_submersibles@psubs.org>
> > Sent: Sunday, February 29, 2004 12:14 PM
> > Subject: Re: [PSUBS-MAILIST] thru hull fittings
> >
> >
> > > Hi Dan,
> > > I knew that would draw a response ! I really don't
> > follow the reasoning on this. I simply do not understand what you are
> > saying. Don't most hydraulics have the O rings on the the shaft and
with
> > those we're talking 3000 psi. If I had the O rings on the shaft are you
> > saying that I would not be able to turn the shaft? And the O ring would
> > leak because there is more stress on the corners of the O ring grooves?
I
> > don't get it ! Sorry to be so difficult and annoying !
> > >
> > > Brian
> > > ----- Original Message -----
> > > From: "Dan H." <jmachine@adelphia.net>
> > > To: <personal_submersibles@psubs.org>
> > > Sent: Sunday, February 29, 2004 5:19 AM
> > > Subject: Re: [PSUBS-MAILIST] thru hull fittings
> > >
> > >
> > > > 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
> > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > >
> > > >
> > > >
> > >
> > >
> >
> >
> >
>
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