Monday, March 5, 2012

Plain Ball Bearing

If you ask me Bearings are the most worderful inventions in the Mechanical heirarchy. But going deeper in the topic of bearing in a single post  will make will just make you mad. So I planned to learn one by one. 
    First of all what is the basic definition of Bearing, It is a assembly which allows restricted relative motion between the parts especially for shafts and axles. A Ball bearing uses Balls to allow the above said constrained motion. These bearing are used if one wants one axial to rotate about its axis and other should be stationary but both should have a contact.

How it works?
   Bearing has a simple mechanism so anyone who thinks can understand. So, its not a big deal. I thought of showing a pic which I found in Wiki so that understanding gets easier.

     The Axle which is going to be rotated is fixed in contact with the inner race. And the Axle which is going to be stationary is fixed in contact with the outer race. Thus when one rotates the other will remain stationary.

How it is made?
   Bearings are made of steel because it is the most elastic metal and comparatively harder one. The most important part in a bearing is Balls. The machinery cuts small steel with and then slowly it is shaped into a exact sphere. It should withstand so much of heat so it is heated in a furnace for some time to make it heat resistant.

What are the types of Ball Bearing?

  1. Angular contact
  2. Axial
  3. Deep-groove

Which Lubricant to use?
    The choice of lubricant is based on the application of the ball bearing. If it is going to bear huge load one lubricant is used, if speed is primary one lubricant is used like that it goes on. Applications that require extremely low torque or narrow range of torque variation are 
suited to use oil as a lubricant.  Depending on the application, it is possible that an oil 
lubricant may not meet a specific requirement.  Grease is an oil to which a thickener has 
been added.

Oil : Oil is the basic lubricant for ball bearings.
Grease : Grease is an oil to which a thickener has been added to prevent oil migration from the lubrication site.
Petroleum Mineral Lubricants : Petroleum lubricants have excellent load carrying abilities and are naturally good against corrosion, but are useable only at moderate temperature ranges.
Super-Refined Petroleum Lubricants : While these lubricants are usable at higher temperatures than petroleum oils (-65 º to  350 ºF), they still exhibit the same excellent load carrying capacity

Does direction of load matters?
   Of course, it matters a lot. There are two types of loads that may act on a bearing. 
Axial Load and Radial Load.
Axial Load : This load will be in line with the axle. For this kind of loads usually Thrust bearings are used. Again they are of two types. A self-aligning roller thrust bearing and A thrust ball bearing
Radial Load : The load acts perpendicalar to the axle. Most of the bearing are made for this kind of loads.

How long a bearing can live?
    Ball Bearings life span is inversely proportional to speed. If the load is doubled, the bearing may lose about 1/8 of the bearings life span.So speed gives a major problem in manufacturing companies. 90% of the bearings are worn out due to the dirt the enter between the balls. Most of the Bearing are made for inner rotation. But some of the applications need outer rotation. Bearing that are of these kind will have a life reduced by approximately 20%

Which is World's Smallest Ball bearing?

Bearing size compared to a Mechanical PencilBearing on a Rice Grain 

How small is small? With an outside diameter of 1.50mm, inside diameter of 0.50mm, width of 0.65mm, and capable of high speed rotation of more than 5,000 rpm, this new ultra small ball bearing is definitely tiny.
Manufactured in stainless steel, the new ultra small ball bearings have the same high precision, durability and rigidity structure as all the other miniature ball bearings that Minebea manufactures. The width of 0.65mm can be slimmed down to 0.4mm for low speed. This ultra small ball bearing contains 6 balls with a diameter of 0.25mm.

Which is World's Largest Ball bearing?
     The largest ball bearings in the world are in the San Francisco Bay area of the USA, within the Benicia-Martinez Bridge, three parallel spans that carry 100,000 vehicles a day across Carquinez Strait west of Suisun Bay. As part of California Interstate Highway 680, these bridges link the town of Benicia at the northern end to the town of Martinez at the southern end. This segmented concrete structure was originally built in 1962 as a replacement for the car ferry services across the strait; the newest span was constructed alongside the original by the T. Y. Lin International construction firm, and was opened to the public on August 25, 2007.

1 comment:

  1. That would be really nice if you list more of all the kinds of bearings you have there.

    hydrodynamic bearings