synthetic bearings

The modern rail industry sometimes uses high-density polyethylene [HDPE] as a slide material at slide chairs/baseplates, where the switch rails at a junction slide from side to side. They need little-to-no grease to operate properly.

Polytetrafluoroethylene [PTFE] is another useful material. It has a low co-efficient of friction, and a high temperature withstand capability. It can be filled with glass beads to extend the upper temperature range, and is sometimes called "polyfill" when in use as the seats in valves that are used in connection with high temperature steam; the polyfill material extends the upper temperature limit.

All the above have excellent water rejection properties.

Look at Rulon it is teflon material which has been modified to be rigid. Has a low coefficient friction and is self lubricating.

There is all so hybrid ball bearings. Where the balls are if a cermet material. With the races of steel to thermoplastics.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V5B-47CH71N-5&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=829202370da791a0b600ccb0c321bcfe

Hi Willem46,

if trying to go to sliding bearings I would first try to minimise the shaft diameter by selecting a high strength stainless steel: ? 17-4-PH?

then as recommended by others look to the various Teflon + another material.

From these you need in addition to your list of requirements a high thermal conductivity.

The heat that is generated by the bearing acting with friction has to be dissipated else temperature will rise and load capacity will vanish.

So I think Teflon-Mica, Teflon-MoS2 and Teflon-Bronze will be good candidates.

(From the last two I have samples, If you want some, send your address.)

There is also a variety of Teflon used in machine-tool slide-ways that is said to be very good and there is a castable plastic that very likely incorporates Teflon and Ceramics.

(I have the manufacturer somewhere, to be searched if needed.)

Greetings from the equally cold and rainy Germany.

RHABE

You could contact john.p.baker@skf.com

He's been in the bearing industry for over 30 years and will be able to direct you to any one of SKF's engineers.

Rulon has already been suggested and is a good candidate. In addition, I would consider a Dupont product called Vespel, and if you prefer a natural product, try Lignum Vitae. I suggest you not use Teflon because of its cold flow characteristics.

One problem you will have with plastic bearing materials will be cold flow, all of them do it to some degree. And the PV ratings of them all will be much lower than a sintered and oil impregnated bronze bearing would be. some of the better load bearing ones will be PEEK, PEK, or PPS. All three have very low water absorption/swelling. Rulon is in the PPS family if memory serves. You can increase the load bearing by additions of carbon or glass fiber. 40% glass fiber fill goes a long way to increase bearing capacity and reduce cold flow.

Willem, I'm a victim of my own prejudices, when I saw the words "maritime winch" in my mind's eye I envisioned a giant mooring winch for shipboard use or something of that sort. I was not thinking racing yacht sail line winches. You'll NEVER be able to get the efficiency of a roller element bearing out of a plain bearing. Plain bearings are good for high loads and slow speeds, at the cost of higher friction. Might I suggest angular contact ceramic ball bearings instead of roller bearings? You'll get corrosion resistance, low friction, and higher speeds without stick-slip.

Dear Rorschach, Sorry for the late reply but I was in the Provence mountains in France and my company was on holiday. Loads on sailboatwinches can be extremely high, we tested a 8,6 Kg. aluminium winch up to a load of 5600 Kg. without any damage to the synthetic bearings or gears. So the load per Kg. of weight is rather high. I will use a few ceramic bearings inside the gearing system but for the main bearing which takes the load from the drum I need I.D's of 180mm up to may be 500mm! I couldn't find any large diameter ceramic bearings on the Internet. I did use smaller stainless steel ball bearings in the past but none of them are seawater resistant. That is the background of trying to find a suitable synthetic bearing material. I have room enough to use a large size bearing in order to reduce the load per sq. cm. but it may never have the efficiency of a ball or rollerbearing. I also will CNC machine some larger diameter roller bearings with PEEK rollers to test.

I will inform you aboat the future bearing system as soon as I made up my mind.

Kind regards and thank you for you assistance. Willem

You might check with Kaydon, they make some large diameter thin section roller and ball bearings, many of which are used offshore.

You are making me jealous you do know that right? =D

Back to the salt mines for me...

perhaps this can help:

http://www.kaydonbearings.com/catalogs/catalog300.pdf#page=119

Hi Willem 46,

there is no chance with plastic rollers in highly loaded bearings!

If you need the low friction of roller bearings then very tough rings are necessary (above 1000N/mm² yield strength).

If you wish to try sliding bearings then contact area has to be much bigger than the very small contact area in a roller bearing - according to the ratio of strengths.

If you want to get ultimate performance you should add spiral-groove structures that drag seawater into the bearing surfaces and minimise friction. (Airbearing example below).

Muijderman, Bootsma and Reinhoudt did the pioneering work with Philips in the 1960ies.

RHABE