Motor Bearings

Hello nirav soni

You have answered your own question.

At the DE = Driving end, there is normally some unbalanced load, or greater load on the bearing.

Many large electrical Motors 50kW and above, use the same bearing both ends, to simplify manufacture and parts stocking.

To save money, and if you make millions of motors the same size, it was worked out years ago, that the NDE = Non Drive End, did not require such a sized bearing as the motor DE.

Thus came the smaller bearing at the NDE system.

I don't like it, but we have to put up with it.

Kind Regards....

The DE end bearing observes the driving torque first. At the same time shares the coupling load. Hence the design needs to be robust than the NDE bearing.

i have got the answer

thank u vr much.

thanks a lot.

You're looking at horizontal shaft motors where the greatest load is on the DE. If you look at vertical shaft motors, like those used for RADAR or gun platforms, you'll see the opposite since the greatest load is on the NDE.

Thanks for additional info about vertical application.

Regardless of orientation, either vertical or horizontal, the drive end would still be the drive end so it would still carry bulk of the load.

I disagree. Think about turning a fairly small motor vertical and putting a 1000 pound, well-balanced load directly on top of the shaft. The NDE works better to carry that load. I agree that you could do it at the DE but I think it's easier at the NDE.

Well as per your example, you are probably correct. But i have yet to see a design (actual application) where "a fairly small motor vertical is fitted with a 1000 lb load".

If you're not in those fields, you likely would never see them. They're somewhat odd, like gun platforms, telescopes, radar units, and ...Here's the oddest looking one I could find a picture of that wasn't copyrighted. This is from Scott Wood's work for Johnson Space Center. The guy and the "chair" are sitting on what looks like maybe a 80 ft-lb torque motor. It's probably 15" diameter x 18" long. So, it's probably only about 500 lb, but you get the idea.

Yes. I got the idea. Thanks for the info.

My explanation would tend to be that motors are often utilised in driving belts, therefore the bearing has a side load as well, hence the need for the larger bearing.I think this is born out by looking at the bearings used in the older car dynamos, if I remember correctly, the non drive end had a plain bearing.

That's the coupling part with the load. It may be direct couple, By belt, through gear, Hydraulic coupling etc.

The Drive end (DE) is not always larger than the Opposite Drive end (ODE).

In the case of a horz with Split sleeve, they are the same size.

Refrain from NDE, that acronym is for Non Destructive Examination. You would do NDE on a bearing to check Babbitt material adhesion etc.

T Man,

That's a good suggestion (ODE); I never liked NDE but learned it from the old Westinghouse guys.

Double Yoi, Myron.

Motor rotor shaft supporting bearings being always dissimilar is not true. However, in majority of cases this is true.

Bearings are decided based on the duty and orientation of the motors. If you do a study on types of bearings you will realize that there are bearings for different kinds of loads. Such as, rotational, angular and thrust. Considering these as major classifications, there comes in other aspects later on, for example, the rpm, duty etc.

The motors you've seen till now are probably meant for similar applications and therefore you are forming an opinion that the end bearings are dissimilar. Look up a motor such as used in bench grinders and you will find that both the end bearings are same.

You have actually answered your own question only that it should have been 'type of LOAD on shaft rather than 'LOAD on shaft'.