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Re: [PSUBS-MAILIST] Precision prop shaft

I don't know how yours is mounted, but the simplest way is to build a can which would contain the bearings, seals and shaft--the unit should have an equatorial flange welded around its middle (more or less) which would contain an O-ring seal and bolt pattern to mate with a matching flange in the hull. The nice thing about this is that you can pull the seal unit as a package, refurbish it as required, paint the mating surfaces on the sub (if they aren't SS) remount same and stick the prop on. The inboard end would have a flexible spider coupling to mate to the back of your reduction gear or motor if direct drive. That helps a bunch with alignment issues, as the flex in the coupling, though minor, will allow for some slight misalignment without vibration, etc.

Perry setups like this ran up to 15 hp with big reduction gears, turning a 1 1/4" prop shaft at appx. 275 to 325 rpm maximum. The 10 horse units for the PC-12 class turned narrow bladed 36 X 36 props that weight 160 pounds!!! You can believe they were robust bearings, to say the least. The penalty here is weight. I think the all the pieces (mounts, motor, reduction gear, seal, prop, prop ring, struts and rudder probably weighed six or seven hundred pounds. Of course, that's a reasonable percentage for an 8 ton submersible, and boy, what a kick in the tail!!!

Vance


-----Original Message-----
From: Smyth, Alec <Alec.Smyth@compuware.com>
To: personal_submersibles@psubs.org
Sent: Sun, 31 May 2009 7:40 pm
Subject: RE: [PSUBS-MAILIST] Precision prop shaft

Dang Vance, with I'd pinged you about that beforehand. I did in fact tap the shaft tunnel for a small pressure monitoring line just as you suggest, but hadn't put in an inboard seal for the simple reason I knew it couldn't run dry, yet didn't have the elementary idea of filling the whole thing with oil!  The inboard bearing seat is machined close enough that there should still be a pressure change to detect, but it would be much better to have this oil-filled arrangement you describe. I'll take a look at it and see if I can come up with a way to add that inboard seal, it should be feasible and I like the idea.
 
thanks,
 
Alec


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From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of vbra676539@aol.com
Sent: Sunday, May 31, 2009 06:36
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Precision prop shaft

One more thing. The void space between seals will need to be oil filled so that the inner seal has something to run in. If that one leaks, you'll know it pretty quick.
Vance


-----Original Message-----
From: vbra676539@aol.com
To: personal_submersibles@psubs.org
Sent: Sun, 31 May 2009 6:25 am
Subject: Re: [PSUBS-MAILIST] Precision prop shaft

What about doing the right thing up front and installing two seals in line with support bearings in the housing? Then this entire thread goes away. Install a fitting between the seals and run a small pressure gauge on a 1/8" hard tube to wherever you want it. If the outer seal fails you'll see the flooding internally. Then you don't have the issue of dinging a prop and knocking your shaft minutely out of line which would jam the works. I've put about a zillion hours on a shaft seal package like that and never had the first moment's trouble.
Vance


-----Original Message-----
From: James Frankland <james@guernseysubmarine.com>
To: personal_submersibles@psubs.org
Sent: Tue, 26 May 2009 6:48 am
Subject: RE: [PSUBS-MAILIST] Precision prop shaft

Hey all.

i thought of an idea for sealing a leaking through hull.

What about machining a very fine taper onto the outside of the shaft.  Then 
threading the inside of the shaft after it exits the through hull and fitting a 
wing nut and spacer?  Then if the seals leak, you could screw down the wing nut 
which would pull the taper into the gap and jam it shut?

What do you think?  Would pressure push the taper in anyway under normal 
conditions?   im thinking of doing this for the drop lead controlls, variable 
controll and rudder.  

Regards
James

----- Original Message -----
From: Smyth, Alec [mailto:Alec.Smyth@compuware.com]
To: personal_submersibles@psubs.org
Sent: Mon, 25 May 2009 21:30:02 -0400
Subject: RE: [PSUBS-MAILIST] Precision prop shaft

There shouldn't be friction, the shaft rotates freely. I do however plan to 
leave it out in the sun on the driveway when we get some good hot days, just in 
case hot temperatures are an issue. Though in the water that would be rather 
unlikely.

________________________________

From: owner-personal_submersibles@psubs.org on behalf of Jon Wallace
Sent: Mon 5/25/2009 8:42 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Precision prop shaft




Nice job Alec.  One question I have given the close tolerances.  I
wonder if friction caused by rotation of the shaft will cause expansion
of the shaft such that it binds or locks up.  Any thoughts on this?

Jon




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