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# Simple Roller Bearing

## Simple Roller Bearing

(OP)
Dear All,

I am a civil engineer and I am facing a problem that I think is related to mechanical engineering.

I am trying to design a modular roller system that consists of stainless steel rollers connected to a shaft which is supported by a short cylinder with a slightly larger diameter. For illustration please refer to the figure below.

How can I calculate the friction coefficient and the required pulling force for this system?

Also, if I want to reduce the friction using bearing, is there a suitable bearing for underwater marine conditions?

Best regards.

### RE: Simple Roller Bearing

Underwater? I suggest a non-metallic or composite bearing. The manufacturers will list friction coefficients for their materials.

### RE: Simple Roller Bearing

(OP)
Yes, part of the structure will be underwater.

Any idea about the friction coefficient in case of not using bearings as shown in the above figure?

### RE: Simple Roller Bearing

SKF has some good stuff:

https://www.skf.com/us/products/rolling-bearings/p...

I'd think seal drag would be the most significant contributor. A ball bearing in salt water might require unusual seals. I'd be looking for supplier that has bearings that are designed for this as a first step.

### RE: Simple Roller Bearing

I'll posit that there aren't any good 'book' values for calculating the friction of rollers immersed in seawater. If that's actually how your design will function, you'll have to test or make conservative assumptions to get started.

If the bearings will have conventional lubricants (oil or grease) and seals, then I agree with BrianE22 that it's reasonable to assume the seals will be the bulk of the friction and the seal supplier should be able to offer estimated values.

David

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