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I am working on a piece of art that has parts that rotate slowly, at about 1RPM, thanks to a couple of bearings. There is a possibility that it might be installed beside a beach for about a week. The problem is that sand and bearings do not play together well.

Or do they? Is there a bearing type that can resist the ingress of sand, or failing that, a reasonably reliable and durable way of preventing sand entering?

Yes, I am considering covering it with boots, but this question is part of research to see if there is an alternative.

Steve
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6 Answers6

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A bearing with contact seals is reasonably robust against airborne dust. It is a rubber seal that contacts both the inner and outer ring, leaving no gap. Such bearings do not rotate as readily as unsealed bearings and non-contact seal bearings. This type of seal is identified by suffix -2RS in the bearing code.

Some bearings with contact seals additionally have IP69 rating. Most commonly these are sold as food safe bearings, because they have to stand to power washer cleaning in food production facilities. They are significantly more expensive than normal 2RS bearings.

jpa
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Since it's low speed you could just use bushings. Unlike ball bearings with open cavities inside for sand to get into, there shouldn't be any real open spaces for large grains of sand to get into if you have tight clearances

DKNguyen
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With high enough mechanical advantage (presumably you're gearing wind power or a large motor down heavily to make 1RPM), it's unlikely the bearings would fail you within a week even if scraping away totally packed with sand.

Just plan to inspect and replace any that are clearly having a bad time after their journey.

If you want to avoid replacement, follow @jpa's advice, though IP69 is probably overkill and you can save cost with a lower rating.

If you want the bearings to last tens of thousands of hours, you may want a lubrication system and scheduled inspections, though this would be spectacular overkill for your project
For completeness, Timken has some good reading
https://www.timken.com/resources/5892-bearing-damage-analysis-with-lubrication-reference-guide/

Another potential danger for your installation is the local salt water spray at metal interfaces; the dissimilar metals and brine can form a weak battery, greatly accelerating corrosion
https://en.wikipedia.org/wiki/Galvanic_corrosion

ti7
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Protect all the bearings.

Boots as used on cv joints will protect bearings.

But there are boots designed to mount on various surfaces.

Bearings that are not protected will suffer an increased rate of wear, as any wind will bring fine particles which act as a grinding material.

Solar Mike
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Bearings are cheap and consumable.

Simply fit new bearings after the installation leaves the beach and it will be as good as new.

Otherwise -2RS sealed bearings should be fine for months in a sandy environment. 1 RPM is not enough to create any measurable heat so these are low speed bearings, and probably low-load too given its a removeable art installation.

Another option is to add an additional cup/cover over the bearing, if the art allows this. Even gluing a piece of plastic over might be sufficient to minimise sand ingress.

I would not cover the outside of the bearing in excess grease - that will hold any sand in the area.

Criggie
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Bering's by name bear all of the friction at a point of two or more surfaces grinding together. They will all wear out. Your use case is "by a beach for a few days". Just suck it up and save ur money. They will work just fine. The art piece is not meant to last if it has moving parts.

Christopher Cameron
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