View Full Version : Bearings for underwater duty?

06-02-2008, 12:15 AM
ok related to my other post, what bearing tech is out there for use in submergence in harsh environments? think sea water + sediment and a fair speed upto 2000 rpm approximatly.

I know a fair amount about bearings but never had to choose for underwater duty.

Forrest Addy
06-02-2008, 01:41 AM
A traditional bearing for saltwater are segmented rubber on metal shafting.

If the water is silty pressurized water can be fed to the center of the bearing to maintain a continuous purge. I've seen an oyster dredge set up this way. They ran cooling water from the S/Wpump through a strainer then to the strut bearing. Aint rocket science but there's a lot of maintenence cleaning strainers etc.

Here's a start.


or in England"


06-02-2008, 01:49 AM
I do a fair amount of this on Under water vehicles.
How deep are you going?
Pressure is the main design controller.

there are various dynamic seals that have a respectable life span at the RPM you describe.

Surface finish of the shaft is the first consideration, next is how steady the bearings are, third is how protected from the sediment are the bearings?

All of these can be optimized to make a system that will work in the most adverse environments.


farleymarinesystems@ olypen.com send me an e-Mail

06-02-2008, 02:11 AM
There are two materials that could work for you. Lignum Vitae and Rock Maple. Rolls Royce used lignum vitae for crankshaft bearings in their first engines and makes a very good foot bearing for vertical shafts under water. Rock maple can be run at higher speeds. I don't know if it can stand up to 2000 rpm but check the site in the title. Hope this helps, Peter

06-02-2008, 08:09 AM
A traditional bearing for saltwater are segmented rubber on metal shafting.

Here's a start.......

Thankyou Forrest, i had forgotten complelty about cutlass bearings which considering i see alot of them is kinda embarrasing to admit heh:o I worked on a setup similar to how you describe a few weeks back i guess it just slipped my mind, wouldnt be a big deal to rig a small pump to give a constant purge.

Paul, the prototype will see testing upto 100 foot so not a massive amount of pressure there. Need to get a few more thoughts lined up and then ill shoot you an email thanks

06-02-2008, 08:58 AM
Have a look at:-


There are competing products, of course.


06-02-2008, 12:43 PM
Interesting challenge Simon.

As you probably know, most bearing balls and races are made with 52100 (Chromoly) Steel, which rusts.
Sounds like you'd need to use stainless and/or ceramic bearings.

Assuming you can find a bearing seal that holds up under 3 atmospheres (100 feet), you can probably get by with chromoly balls, but the races need to be stainless or ceramic. $$$

06-02-2008, 04:21 PM
it would have to be ceramic, tho i still have the slight issue of silt, the project is becomming slightly less of a side project as theres been some local issue on it that and im working on submarine parts too (its safer not to ask, its for a friend :D )

had a sample from vesconite a few months back and a load of info about thier stuff seems pretty impressive and i was thinking of running a line of bushings and bearings for marine use for my customers, didnt think of trying it for this project.