Axle Bearings and Seals in Saltwater

Pressurizing the axle may be the answer to keep the seals intact but it should be less than 12 PSI depending on the condition of the seals.

Keep condensation out of the axle by pressurizing with dry air (dessicant or full-fledged freon drier). Condensation occurs when moisture laden warm air is cooled below it's dew point which is based on barometric pressure.

The problem would be more with keeping barnacles and other small crustaceans from getting too close to the rubber seals when they attach to the metal of the shaft. Then when it turns, they scrape away the seal a little at a time.

You may want to alter the axle shaft seal and double up (they're cheap). Add one with a full metal face one the outside.

Hope this helps a little...

You have mentioned, "These will operate under up to 10ft of saltwater turning cement filled tires. I have concerns about sealing the axle housings at the wheel hubs and pinion shaft."

Is this shaft need to make continues rotation or only a portion of a rotation (turning or tilting cement filled tires)?

Can a simple sketch possible?

Use marine cutless bearings. They are bronze and rubber and are lubed by the water. You can pick up old prop shafts from yatch repair yard. They will likely have many different diameters and as long as 19 foot. These shafts are 316 stainless and always sent to scrap and chances are they will give you the old shafts of your choice. You can also pick up old shaft from prop shops for a price. Using cutless bearings, you will only need to build the mount for the bearing. You can find and buy them from any marine supply.

Will these be turning fast? many miles? I assume not, but need to ask. The axles you talk of would be major over kill for drive line, and just about right for load capacity. But that over kill might just come in handy. Is this for commercial use, or just for you?

This sounds completely hack, but drain the oil out and clean those axles, and just let them fill up with water. Keep the barnacles out of the gears and bearings so they just us water as lube & coolant. Again, I assume this is a very slow moving platform that will probably never go more than a couple hundred feet at a time. Might want to watch out for freezing if you're in a northern port, the salt water might prevent that though. I'm from mid west, and this time of year has me thinking of everything that will break when it freezes.

Might want to attach a couple zink or maganise blocks to the parts as sacrificial anodes to slow destructive corrosion of important parts.

Hope that helps more than it hurts.

Marine cutlass bearnings are designed to function with a "stuffing box" gland packing/ wet seal AND a drive (Prop) shaft flanged to a marine reduction gear box.

The load factor is designed for propulsion, not shear weight/power transmission which may be the originators intent.

Perhaps two cutlass bearings may be mounted together to achieve the load needed for the application. More detailed information is needed.

MM

You fail to mention the load or speed of the shafts or how long they will be required to turn. I have had extreme success with Igus brand plastic bearings as well as uhmw bearings that I have made myself. If the shaft speed is low and the bearing shaft is not loaded too extremely, the water acts as a lubrication. I have an application that uses a o.375 in. shaft and turns 90 degrees in 0.25 sec. that was made from a piece of white uhmw by drilling a hole in the material and inserting the shaft. The load is about 25 pounds and it has worked for over 9 years now. About 2 years ago I took it apart to check for wear and could not find any evidence of wear on the shaft or the bearing. I have successfully replaced several stainless pillow block bearings with UHMW bearings with no failures or danger of contamination from lubricants. I am the engineer for a bottled water company so this is a real plus as well. I have also used the IGUS product line and had very good luck. I think that if you do that you will not need any lube and no danger of leaking into the water. This all depends upon shaft speed and loading however, but I think that it would be worth considering.

Rich Hurd

with a Hundested variable pitch propeller, for polution reasons they use a water soluble grease, should be available either on line or through a ships chandler specialising in larger boats (not really a West marine product).

if you were to fully fill your diff and wheel bearings with this type of grease and add grease points around the axle and grease regularly till grease is starting to come past your seals you should be ok.

I'm assuming you are fashioning a type of travel lift, if so I'm also assuming it is a low speed aplication, therefore being low speed there will be very little heat build up in your bearings and gearing, so the chance of water being forced past your seals as the unit suddenly cools in the water should be nill.

also if you talk to your local bearing supplier he will probably be able to sell you a very cheap industrial greasing canister, it works very similarily to a bearing buddy but you are able to mount it anywhere with a long hose to where-ever required. some modern trucks even have them running to the center of there axle hubs with the grease cartridge mounted on the chassis.

Hope this helps

Thanks Rob and all who replied. I appologize for the delay in responding as I was away. Assumtions of use were correct. Intermittent low speed <12mph heavy load use over distances of under 1000 yards at a time. Based on your suggestions I will fasion a secondary outer stainless seal to keep barnacles away from the inner soft seal. Then fill the entire diff with water soluble grease. Great idea Rob.

Try contacting John Crane - Marine Seal Division in Morton Grove IL or Flowserve (seal Division in kalamazoo MI).