Propshaft seals and pressure ratings - Running models at depths > 5M

[crashtestmonkey]

This is my first post here and I hope someone can help me with some information.

For my first sub project, I want to build a vessel that can 'go deep' and relay video to the surface. My problem is finding propshaft seals that can withstand the pressure at those depths 'off the shelf' for shafts of around 5MM.

I contacted SubTech but the stuffing box they sell is only rated to about 12 feet or less than half the depth I want to dive to. Most other model sites do not have ratings for their seals to refer to.

Does anyone here know of a high pressure seal for small diameter shafts or have they ever made one? I have read up on just about every stuffing box type there is, mechanical seals, PSS seals and so forth and have a good idea of the principles involved but sadly do not have access to the workshop tools to manufacture turned components.

I would be very very grateful for any URL's for potential suppliers/designs/sites or advice from anyone who has already invented this type of wheel.

Thanks in advance.

[anonymous]

Simrit do a huge range

Simrit do a huge range of shaft seals.

They are mentioned in Norbert Bruggens book and I have used the 4mm seals successfully to 20 feet. Not particularly cheap, I'm afraid!

Search the threads on this board and have a look at the Simrit website for local stockists, technical info etc.

There will be other seal manufacturers but I only have experience of Simrit.

David

[crashtestmonkey]

Thanks David I will check

Thanks David I will check out the tech specs.

To make life more difficult for myself, I have considered eliminating a prop shaft altogether! I had an idea about a brushless motor arrangement with a solid state switched coil. In brief, the coils would be mounted inside a plastic sealed tube that extends from the hull. The magnets are mounted in a cylinder with propeller attached that slides over the coil tube. By switching the current through the coils, the sleeve would be forced to rotate, turning the propeller.... ta da! This way there is no hull breach with the propshaft therefore no need for seals. Like a PC CPU cooling fan but bigger!

I did think about water jet propulsion as well but thats another story!

Thanks again for the info

Ian

[captain nemo12]

Thanks David I will check

Thanks David I will check out the tech specs.

To make life more difficult for myself, I have considered eliminating a prop shaft altogether! I had an idea about a brushless motor arrangement with a solid state switched coil. In brief, the coils would be mounted inside a plastic sealed tube that extends from the hull. The magnets are mounted in a cylinder with propeller attached that slides over the coil tube. By switching the current through the coils, the sleeve would be forced to rotate, turning the propeller.... ta da! This way there is no hull breach with the propshaft therefore no need for seals. Like a PC CPU cooling fan but bigger!

I did think about water jet propulsion as well but thats another story!

Thanks again for the info

Ian

Why not simply use a magnetic coupling instead? That way, there is not contact between the propshaft and the motor inside the WTC. No need of puncturing the WTC wall.

[crashtestmonkey]

Thats the description I was

Thats the description I was looking for! Magnetic coupling!

Exactly what I meant but wasn't sure about WTC wall thickness and magnetic fields etc. etc. so the coil/magnet idea seemed a logical choice, more volts = stronger field kind of thing.

Has this been done before does anyone know? It could be a simple way to get below the 30M mark with a well made WTC.....

Thanks for the 'Eureka' moment!

Ian

[Guest]

Magnetic couplings



Edited By Sub culture

Magnetic couplings



Edited By Sub culture on 1153166428

[crashtestmonkey]

Just goes to show there

Just goes to show there aint much new around these days!

That is pretty much how I imagined the assembly to look funnily enough. For magnets I was looking at these e-magnetsuk.com. The magnets I was thinking of are the EP300's. I was thinking about something circular with a lip, like a jar lid, with a propshaft to resin pot 10 of the magnets (south pole outwards) into and the same on the inside of the WTC (north pole facing outwards) witha clamp for the motor spindle.

If I get round to knocking something up soon, I will post some pics!

Thanks for everyones help it is greatly appreciated!

[virg]

Hi,

The larger Niko submarines use

Hi,

The larger Niko submarines use magnetic coupling for everything. You might want to get your hands on one as there are a couple on E-bay now. It's really a pretty neat setup even if it is considered a "toy". Check it out.

Virgil