Very low friction rotary shaft seals or systems

[bobp]

I am an artist wishing to improve the weatherproof rotary shaft seals on outdoor kinetic scuplture.

I need to seal 3/8" and 1/2" stainless steel precision ground shaft exposed to the elements in any climate and at any angle. e.g. -40F to 140F, 0 psi, rainproof.

The lip seals I have tested have a high coefficient of friction for my needs since they are designed for pressure.

Any very low friction rotary shaft system will be considered, loads are from 1 to 30lbs currently.

Any suggestions for a simple, scalable solution, or resources for further information would be greatly appreciated.

 

[Egress]

Dear Bobp

Here are some quick sugestions, which may be useful if
your designing from scratch, less so if your retro fitting.

1) Use a stainless steel deep groove ball bearings with 2Z
bearing shields. These are noncontact sheilds wich keep the lubricating grease captured and dirt out. The very small clearance will also tend to resist the ingress of water through capiliary action. They are usualy prepacked with grease, however you should be able to specify one with a suitable temperature range. I have used such bearings on
rollers of cooling tanks for the extrusion of plastic profiles where verry low rolling resistance in a wet environment is required.

2) Same as above but use units with low friction contact seals. If the friction is still too great try running in the bearing before use ( ie for 100hrs, this is a guess).

The advantage of using a sealed bearing is that tolerancing
and alignment issues are taken care of, wrt the seal so you
will know what the worst case level of friction is.

You will have to machine up bearing housings to end up with
an aesthetic solution. If there are shaft alignment issues
(which is most likely) try using the self aligning ball type
although I havent ever used these with a Z shield.

Given that it is an art piece you may be able to overcome
alignment issues by allowing the bearing support structure
to flex enough to over come variations (I assume
shaft speed is verry low).

The bearings mentioned are all generic types, so speak to a rep from you local bearing supplier.

Good Luck

 

[adche]

Hello Bobp,
I agree with Egress on the sealed greased brgs, but If I may add and indeed if it does not impinge on the artistic aspect of your sculpture!!! to add a shield (Chinese hat sort of thing) fixed to the shaft i.e., to enjoy the spin, and which you would extend downwards as far as you desire ( I am assuming the water is rain and hence falling from above!). The extension would be to guard from sideward ingress e.g.: dust wind..etc.

Of course I also assume that the rotation is within the artistic realm as opposed to technology cutting edge, otherwise you need to think about balancing!

Enjoy the show
Why don't you send us a picture of the thing!

 

[dougholmes]

For the lowest friction, it might be a good idea to look at labyrinth seals.

A carbon filled molybdenum disulfide filled nylon bearing could handle the load and would not be bothered by rain. This kind of bearing would not need much in the way of seals, perhaps just a dust cover. For what you have described it might be easiest to get a block of moly filled nylon, mount it on your sculpture and drill a hole for the shaft.