Ball Races and 'Brinelling' (whatever that is).

I wonder if the huge bearings on wind turbines suffer from this when the blades are stationary on calm days. There must be a huge static load under those conditions.

Doug

Hopper is almost correct !

There is true brinelling (TB) and false brinelling (FB), quite different things.

True brinelling (TB) is caused by the application of heavy loads when the bearing is stationary or virtually stationary. Clive's Saab wheel bearing is an example of this. In other equipment TB very rarely happens unless something has gone badly wrong.

Every other case mentioned is either FB or a more generalised fretting damage. FB is just a special case of fretting damage where the damage is restricted to ball contact points as a result of very small movements that displace the lube film. These contact points then wear due to the lack of lube and cause the formation of hard ferric oxide which accelerates the wear process. The pits can become highly polished. Visually they resemble the marks from a brinell test. But whereas a brinell test makes indents that are plastically formed, 'false brinell' marks are basically abrasive wear pits.

TB and FB both affect bearings in three ways. They put perturbations in the generally uniform friction torque, create noise and vibration if you run at high speed, and potentially reduce the fatigue life of the bearing. For clockmakers the first is the general concern. In electric motors, fans etc, its the second. One rarely gets to the third in industrial equipment because the noise will upset people first and the bearings will be replaced.

As mentioned, FB is caused by local lube film breakdown. This happens with greased bearings and it takes usually tens of thousands of small angular oscillations, such as one would get in a pendulum suspension or pallet arbor. One can combat this to some extent by stuffing lots of grease into the bearing such that the local grease displacement around the rolling elements can't happen. But if it's a clock, this excess of grease drastically increases the friction - which is the very reason for using a rolling bearing in the first place. Oil is very effective at stopping FB but you need seals to keep it in and they add friction torque too.

Gerry

Doug, there are huge loads on turbine bearings but they also have large bearings to carry these loads. So there is no TB (true brinelling) generally. But FB (false brinelling) can be an issue if they remain static for months and months and its cause by the continual flexure in the structure. That said, friction increases and noise are not problems so the damage is generally just accepted as an ageing characteristic, generally.

Gerry

Many years ago, I was told - and shown - that the generators in the nuclear power station where I was working on the construction side were constantly rotated at a few RPM by electric motors when not in use. Now it all makes sense

Rob

When US automakers first started shipping cars and pick ups by rail, often stacked near vertical, wheel bearings suffered premature failure due to brinelling. because of the Static Load + Vabration during transit.

Loading in the normal horizontal mode (load spread over four rather than two wheels ) and improved suspension of the wagons (freight cars ) improved the situation.

Howard

The parking of bells in the mouth down position is (I understand) also intended to foil the deliberate efforts of small boys, and the careless misunderstandings of others, as the ropes just hang there and anyone wandering by could just pull, causing a lot of clanging and consternation - especially if a service was going on.

Cheers, Tim

Here we go again. Yet another fantasy problem for our wind turbine haters.

The cause is known. Engineers are not stupid once they are aware a problem they take remedial action. Wind turbines are designed to last twenty five years without swapping bearings at regular service intervals. They are likely not stationary - there is probably some tiny electric drive barring the rotor gently, while the turbine is out of service.

Here we go again. Yet another fantasy problem for our wind turbine haters to latch onto.

The cause is known. Engineers are not stupid once they are aware a problem they take remedial action. Wind turbines are designed to last twenty five years without swapping bearings at regular service intervals. They are likely not stationary - there is probably some tiny electric drive barring the rotor gently, while the turbine is out of service.  Or a high pressure oil pump working away steadily to ensure the bearings are sufficiently lubricated to avoid metal to metal contact.

Edited By not done it yet on 08/03/2021 19:51:23

You’re correct, the normal ‘parking’ position is mouth down BUT....

in order to actually ring them, beforehand they are ‘rung up’ through half a rev and ‘parked’ mouth upright. From that point on, during the actual ringing they are swung through 360 degrees in one direction, then 360 degrees in the other. This can carry on continuously for anything from a few minutes on a practice night to over 4 hours for a full peal on heavy bells.

This animation shows the action...

https://washingtonringingsociety.org/galleries/animations

Lets not forget the idea of leaving a large weight resting against a 50x50 stick of ash. Or the even smaller peg screwed to the bottom of that stick if you're afflicted with Hastings stays.

Ringing them down is the simple, common sense(that dreadful phrase again) way of preventing problems.

.

Or maybe they are very big, and almost incredibly well made: **LINK**

https://youtu.be/qvZZq7WmVoo

... a few glimpses of Timken's manufacturing ^^^

MichaelG.

Those would probably have had white metal bearings if they are like the usual thermal power station generators. Barring gear motors usually keep the whole shebang slowly turning over to stop the steam turbine rotor shaft from sagging if its left in one position. 80 tons or more of large diameter wheels of blades all sat on a relatively small diameter shaft. Once they cool down to ambient temp they can be left stationary if necessary, as they often are for maintenance etc.

Interesting. Thanks for posting the link.

$20,000 bearings six-foot in diameter. Three weeks to heat treat (reduced now to one day) etc. There's a bit more to it than your average car wheel bearings!

I hadnt realised those gennies were so big when you see them up close. Different view from when you drive past them in the distance. Would be a nice job putting them up.

Ah, now you mention it, I think they did mention shafts bending.

Rob

Edited By Douglas Johnston on 10/03/2021 11:34:31

Yes I think they are rather beautiful to watch slowly turning away too. Then again, I always regarded thermal power station cooling towers to be works of art too.

Hard drive bearings,disc spindle and actuator arm, in my day spindle bearing ball races had more than standard clearance and had preload via a spring,the lubricant and the quantity was to a special spec as a min 5 yr life was specified,I would not bother to re use these bearings in another application. I have seen severe brinelling on motor cycle head races particularly on competition bikes, I had a new Greeves trials bike back in 1961,which one of the first bikes to have timpken taper roller, after a couple of years use I removed the forks to check the bearing condition and lubrication as there was no greasing nipple,the bearing outer race surface had bright spaces,separated by black line of corrosion as the steering lock limits the travel of the rollers,very slight wear could be detected on the bright areas,in those days Timkens were expensive,so the old bearing continued in use and still being an apprentice with limited funds,replacement of chains and wheel bearings was deemed more important,after the overhaul when riding the bike on the road there was a very slight shimmy felt through the handlebars. Back then a lot of trials competitors rode their bike in competions at the weekend and it used it for road use during the week, summer holidays would be spent giving the bike an annual overhaul,,One thing I read about recently was that some road racers still prefer the cycle cup and ball bearing assembly compared to taper bearings as they reckon the bikes steer better.

Could be less friction perhaps. Point contact rather than line. Longevity would be the roller's main advantage so not an issue in racing where regular replacement could be done.