Mechanical engineering - bearings?

Question

I need to support a shaft that will be the axis of a centrifuge. The shaft will spin round at about 1000 rpm. It will be loaded axially by 1 ton, which will have to come through bearings. The centrifuge will be out of balance. The rotating out of balance load will be equivelent to a radial force of 5 tons. What type and size of bearing do I need?

Answer 1

Centrifuges, any centrifuge, has inherent risks, and improperly designed can be quite dangerous or even downright lethal. Assuming you have calculated your radial load correctly you're not quite in the "grenade" range yet, but you still best contain that thing in some kind of cannister. It's not possible to guess at your centripetal force without knowing the weight of your workpieces and the radius of your rotor, so no suggestions at containment can be made, but here's a suggestion on bearings for the drive end of your device based on the inadequate information you've given. Find one of those axles used to transport mobile homes, they're cheap and very common, and you'll have a bearing setup well in excess of the speed and load you're working with, both radially and axially. Cut the spindle from the axle tube, use the hub itself to mount to the frame of your machine, they're massive and pretty accurately made. Take your spindle to a machine shop and have your driveshaft (I suggest inch and a half cold rolled steel) centered and welded onto the back side of it leaving enough room for a taperlock pulley between your drum and the trailer hub for a drive belt. At 1000 rpm you can use any weight or grade of grease in the bearings, it's not a critical factor at that speed (up to about 4000). The whole ball of wax shouldn't cost you more than a couple hundred bucks and the safety factor (depending on the quality of the machine work) will be in the hundreds of percents. Here's another important consideration also, if your "out of balance" load is farther above your inner bearing than half the radius of your drum you had better put another bearing on the top of the thing, otherwise with a five ton centrifugal potential it will simply walk out the door or shake your building off it's foundation. Hope this is helpful.

Answer 2

Wow. You really haven't given enough information to make a bearing selection. First you'll have to size the shaft to take the massive bending load exerted on it and the attachment ot that shaft from the centrifuge basket. As a first look at bearing types though, I'd look at heavy tapered roller bearings because they both can withstand heavy loads and vibration better than ball bearings, but you need to look at individual bearing catalogs to determine exactly what bearing will do the job. The load capabilities vary quite a bit and you also need to establish what space parameters you are constricted by, so you'll know whether to get a thinner bearing set with greater numbers of smaller rollers or a thick bearing set with fewer numbers but larger rollers. Look online for 'bearings,roller' and see what vendors you come up with. their online bearing catalogs should lead you right to the bearing you need. By the way, your bearings may be the easy part of this design effort because depending on the rotational speed of this thing, external support is probably going to be your greatest challenge. Just think of a washing machine with a load out of balance and extrapolate to the five ton mark. You may have to consider support on both upper and lower ends of that shaft. Good luck.

Answer 3

Since you have an axial load in addition to the radial load I would suggest tapered roller bearings. The size bearing will depend on several factors, one being what B10 life you require. A bearing rep will be able to help you select the one that meets your needs as well as lubrication requirements and preload.

Answer 4

Mechanical Engineering technologies is the sphere or degree you learn in. A mechanical engineering technician is the interest you get when you graduate. surely they're the comparable, yet one is a learn and the different is a individual...