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Re: [PSUBS-MAILIST] thru hull fittings
Thijs,
Measuring an internal groove is difficult but it's not that difficult to
machine. I put internal grooves in all my thru hulls. Some were as small
.625 inch shaft diameter. I put one O-ring in each end of my thru hull for
a double seal. That's the way Kittredge has it on his K-250 and K-350
plans. All it take is a lathe and a tool ground to cut the internal groove
width you want.
Once you finish the bore to the finished diameter, put the internal grooving
tool in the lathe. Crank it into the bore to where you want the groove.
With the lathe turning, crank the compound out until it just touches the
wall of the internal bore. Now you know where the tool is. In my case, at
.625 diameter. Now, with the lathe still turning, crank the cross slide out
to the diameter of the root of the groove, and that's that.
There isn't any real need to measure the finish groove if you follow that
procedure. If your still not sure of yourself, make a test piece. Make it
the same way I described for the groove, only instead of putting the tool
way in the bore, cut your test as an internal shoulder where you can easily
measure the diameter you get. When you have what you want, go farther in
the bore and make your groove cranking in the same amount with the cross
slide as you did for your test.
The tolerance of the groove isn't as critical as the annular clearance,
between the shaft and thru hull. If your a few thousands either way, an
O-ring will still seal fine. The larger the O-rings cross section the more
forgiving the groove tolerance. A .139 cross section ring is a good size
to use. Not to big, and yet if your four thousands of an inch this way or
that, it will still work fine. The groove length is even less critical but
be sure you have room for the squeezed O-ring to push into. Follow the
chart for the dimensions.
Sorry, I see I got a bit wordy and I apologize. :-()
Dan H.
----- Original Message -----
From: "Thijs Struijs" <thijs-struijs@planet.nl>
To: <personal_submersibles@psubs.org>
Sent: Monday, March 01, 2004 4:15 PM
Subject: Re: [PSUBS-MAILIST] thru hull fittings
> Brian, Alec,John,
>
> I made the drawing. Machining an o-ring grove in the fitting seems rather
> difficult to me so i thought instead of making a grove in the shaft why
not
> do it this way. It's not according the books, but i can not imagine why it
> shouldn't work.
>
> John, i am also interrested in your ideas on machining internal groves.
>
> Greatings,
>
> Thijs Struijs
>
> ----- Original Message -----
> From: "Alec Smyth" <Asmyth@changepoint.com>
> To: <personal_submersibles@psubs.org>
> Sent: Monday, March 01, 2004 3:53 PM
> Subject: RE: [PSUBS-MAILIST] thru hull fittings
>
>
> > Yes, this is for the drop weight, but no, I didn't do what Thijs just
> > proposed. I'm afraid to say I just went with plain old grooves on the
> > shaft. The grooves will weaken it a bit, its true, but on the other hand
> > the shaft is pretty massive and is supported where the grooves are.
> >
> > Alec
> >
> > -----Original Message-----
> > From: Brian Cox [mailto:ojaibees@ojai.net]
> > Sent: Sunday, February 29, 2004 11:28 PM
> > To: personal_submersibles@psubs.org
> > Subject: Re: [PSUBS-MAILIST] thru hull fittings
> >
> > Thijs,
> > If I'm not mistaken I think that is what Alec has done.
> >
> > Brian
> >
> > ----- Original Message -----
> > From: "Thijs Struijs" <thijs-struijs@planet.nl>
> > To: <personal_submersibles@psubs.org>
> > Sent: Sunday, February 29, 2004 12:21 PM
> > Subject: 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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> > > waar op wordt gecontroleerd.
> > > >
> > >
> > >
> >
> > ================================================================
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