Welcome to the June 8, 2011 edition of Drew’s Views. This is our first Video Blog. We look forward to showing you how air bearings work, and the value of the radial air bearings; the second houses three radial air bearings. The first block, with the four air bearings, is going to have a higher load capacity; but the second block, employing three radial air bearings, is a more kinematic mounting arrangement.
I show how the shaft is floating freely on these concave radial air bearings, providing smooth, non-contact linear and rotary motion, simultaneously.
Not surprisingly, after we spin this shaft up to a very fast rotational speed, if we were to turn the air pressure off suddenly, the shaft would come to a screeching halt. And it does. Quite literally.
Normally, you wouldn’t want to do this with an air bearing assembly, but with our air bearings it’s fine. Just turn the air pressure on again, and you’re back in business.
The reason that there is a ‘screech’ when you shut the air off is because the air bearings are already preloaded. There is less than ‘zero’ clearance between shaft and bearing. In fact, the structure is already a little bit ‘deformed.’
When we turn the air pressure on, these porous media air bearings are strong enough to bend the structure even more, making themselves some clearance.
So there you have it. The air bearings are stiffer than the structure. This is so because they are loaded in a column stiffness, but the structure is loaded in a bending stiffness.
That’s how an air film can actually have a higher stiffness than an aluminum or even a steel housing, and that’s why an air bearing is very seldom the weak link in any structural loop.