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Water tight shaft connection, WTC - How to do?

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Postby Robse » Thu Mar 20, 2003 6:46 am

Hi, fellow subbers.

I'm building a wet hull sub, and need the propeller shaft to enter the WTC without water comming in as well. The propeller shaft is 3/16" i dia.
I have an idea that I need a piece of pipe 2 -> 3" long, app. 0.3" (5/16"?) in dia., and then fill it with grease, and run my propeller axis through it. This should block out the water..... or does it?
How is this done the best way, when building your own WTC's?

(I'll copy the idea for the rudder rods as well.)
Yours Sincerely, Robert Holsting, Denmark
1/81 SSBN Ohio Class scratch builder, more at www.robse.dk

"Never be afraid to try something new; remember that it was amateurs who build Noah's Ark, and professionals who build the Titanic"
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Postby subdude » Thu Mar 20, 2003 9:03 am

Robert,
Do NOT use a stuffing box as you have described. On a surface ship that will work fine, as pressure is equal on both ends of the shaft. In a submarine, when you submerge, the external pressure builds. This will push all the grease through your stuffing box and into your hull, resulting in a large leak (and a big mess, if you get the boat back before it goes down for good).
:(

Use shaft seals for the rotating prop shaft at least, and either shaft seals or a bellows type arrangement for pushrods. Seals can be made from o-rings, or specific seals designed for the purpose can be bought from vendors.

Hope this helps!

Jim
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Postby 84-1046442519 » Thu Mar 20, 2003 9:50 am

G'day Rob
I used 3/16th lip seals for my type VII. I too made my own WTC and you can see photos of the shaft seals on my web site. Just click on the world symbol on this post and it will take you there. There is also a cad drawing of the design to go with the photo's. When you are in the site, go to the gallery and click on making of the boat.Hope this helps. Just send me an e mail if I can help any more.
Keith
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Postby Robse » Thu Mar 20, 2003 12:01 pm

Thanks, both!

Good thing I asked, otherwise I HAD gone forward with the
grease-box. I think I'll look towards seals, AND bellows just to play it safe.

Keith: Wow!! Nice sub! I'm impressed. :-)
Yours Sincerely, Robert Holsting, Denmark
1/81 SSBN Ohio Class scratch builder, more at www.robse.dk

"Never be afraid to try something new; remember that it was amateurs who build Noah's Ark, and professionals who build the Titanic"
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Postby 76-1048675655 » Wed Apr 02, 2003 5:59 am

Very cute sub, Keith!

Robse, this is how I solved the shaft problem on my LA-class (1:96 scale, wet-hull):

The engine is simply flooded. It's a 7.2v Speed 480 Race from Graupner currently in direct drive with a 6V pwer supply.

After hours of running submerged it still shows no sign of wear. However, I wouldn't use it in anything but fresh and reasonably clean water. These engines are cheap, so I don't really care, but I still dry the propulsion with a hair-dryer at the end of the day.

My servo rods are 'S'-shaped, they don't slide in and out of the WTC, instead they rotate in a silicone tube which acts as a seal. This silicone tube is of the kind used to feed model aircraft combustion engines.

Mail me for more info, drawings or picts.


Laurent
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Postby TMSmalley » Wed Apr 02, 2003 10:49 am

SUBTECH SEALS
Jim alluded to seals available from vendors ~ Many of us on this side of the pond buy prop shaft stuffing boxes and pushrod shaft seals from Skip at SubTech (he ships overseas as well.) That is, unless you are using a piston or compressor boat that build up a lot of pressure inside the WTC. They are not appropriate for that sort of application since the "V" seals he uses like the pressure on the outside of the WTC to keep out the H20. They also allow for more friction-free rotation of the shaft than a lot of "O" ring seals I've seen.

Might as well spend your sub-time crafting stuff you can't readily buy for a few bucks. One could also argue that risking the loss of an expensive model due to the failure of a homebrew shaft seal is probably a false economy. Then again, if you like to experiment with different kinds of systems and have the proper skills and equipment, have at it! That's what this oddball hobby is all about - having fun!

For the traditional pump or Propel gas boat, the SubTech seals and stuffingboxes are inexpensive and are just about foolproof. (Then again, as the old saw goes..."Nothing is foolproof in the hands of a sufficiently talented fool.") :D

SubTech site link
Tim Smalley
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Postby Robse » Wed Apr 02, 2003 1:48 pm

Hi again.

I've just bought the stuffing box from the UK'ish department of SubTech called Pandan Models, a 4" SBS-2.
I ordered it late friday afternoon, prepaid by VISA, and today (Wednesday) it arrived together with my ballastpump in a nice little package. Can it get faster / easier than that? Don't think so. :-)
The SBS is just a pipe with a rubber ring in it... lookes a little "simple", but I guess it works. I'm not diving deeper than 6-8" anyway, so I guess it can withstand the pressure, and the max. 5600 RPM on the prepeller shaft.

I like the idea with the "S" shaped rudder rods... I'm gonna go with that, sounds like a great idea.

Thanks, guys! :-)
Yours Sincerely, Robert Holsting, Denmark
1/81 SSBN Ohio Class scratch builder, more at www.robse.dk

"Never be afraid to try something new; remember that it was amateurs who build Noah's Ark, and professionals who build the Titanic"
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Postby robert lipsett » Thu Apr 03, 2003 7:51 pm

i have a question about the subtech seals. my sub has 2 dry compartments built into the sub. a 3/16 od brass tube is already epoxied into the hull. my shaft is 1/8 does sub tech have a seal that I can fit on this boat without ripping out the current brass tubing. and how would this work? the holes in the hull go right into the dry compartment (no wtc pipe arangement in boat)
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Postby Bob the Builder » Fri Apr 04, 2003 10:35 am

Best thing to do would be to contact da man himself. Skips a great guy and can probably talk you through anything that you need help on.

I run Subtech seals on my sub (although they haven't seen the water yet) and I'm very happy with them so far. The stuffing box is set up to accept 3/16" shafts.
"SBS - 2 Stuffing Box w/Seal: Combining a very high sealing ability with very low friction the SBS - 2 Stuffing Box with Seal provides a substantial waterproof seal without a heavy dose of messy grease. Low friction results in lighter load on the battery which gives more run time. For 3/16" dia. shaft. Available in any length from 2" to 12"."

You may want to talk to him about his SSS seal that he offers for the Albacore.
"SSS Seal: Designed for use in the USS Albacore kit, the SSS Seal can be used in any application where a 1/8" diameter shaft and a 1/4" diameter shaft housing are used."

I'm not familiar with it at all, but Skip can steer you straight.

Speaking of Skip... has anyone heard from him lately? I've tried e-mailing him a few times now with no response. That's not like him at all...
Bob Martin,
RCSub homepage: http://www.rc-sub.com
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Postby Seasub88 » Fri Apr 04, 2003 11:59 am

Bob the Builder wrote:Best thing to do would be to contact da man himself. Skips a great guy and can probably talk you through anything that you need help on.

I run Subtech seals on my sub (although they haven't seen the water yet) and I'm very happy with them so far. The stuffing box is set up to accept 3/16" shafts.
"SBS - 2 Stuffing Box w/Seal: Combining a very high sealing ability with very low friction the SBS - 2 Stuffing Box with Seal provides a substantial waterproof seal without a heavy dose of messy grease. Low friction results in lighter load on the battery which gives more run time. For 3/16" dia. shaft. Available in any length from 2" to 12"."

You may want to talk to him about his SSS seal that he offers for the Albacore.
"SSS Seal: Designed for use in the USS Albacore kit, the SSS Seal can be used in any application where a 1/8" diameter shaft and a 1/4" diameter shaft housing are used."

I'm not familiar with it at all, but Skip can steer you straight.

Speaking of Skip... has anyone heard from him lately? I've tried e-mailing him a few times now with no response. That's not like him at all...

I think that Skip said something about a symposium in
Toledo. :(
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Postby boatbuilder1 » Tue Apr 08, 2003 10:26 pm

:D
I have done the stuffing tube job but using prather cable grease and it never leaks at any depth it is very thick stuff is impervious to heat up tp 600 o and cold down to 30 below it need to be injected with a large serynge hobby type

but the best type of seal is skips bulkhead seal from subtech

imo :cool:
charlie



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its all relative
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