IN DEFENSE OF COMMON SENSE
By Hetty Gray
# 194
August 14, 2014
“New Housing Crisis Looms”
Every vocation has its own lingo — those words that resonate with those of a similar occupation that might fall on deaf ears of those unfamiliar with the particular line of work. Machines have parts. Parts have names, and a serious lack of parts can spell disaster for a company, an army, or a nation.
Karim Nice explains my part of choice today by posing a question that many of you may have asked in the past. “Have you ever wondered how things like inline skate wheels and electric motors spin so smoothly and quietly?”
The answer can be found in a neat little machine called a bearing. The bearing makes many of the machines we use every day possible. Without bearings, we would be constantly replacing parts that wore out from friction. Don’t despair, folks. There is a method to my madness.
First of all, courtesy of science.com/how stuff works, take a look at the types of bearings and their uses.
Cutaway view of a ball bearing
Photo courtesy The Timken Company
There are many types of bearings, each used for different purposes. These include ball bearings, roller bearings, ball thrust bearings, roller thrust bearings, and tapered roller thrust bearings.
Ball Bearings
Ball bearings, as shown below, are probably the most common type of bearing. They are found in everything from inline skates to hard drives. These bearings can handle both radial and thrusts loads, and are usually found in applications where the load is relatively small.
In a ball bearing, the load is transmitted from the outer race to the ball, and from the ball to the inner race. Since the ball is a sphere, it only contacts the inner and outer race at a very small point, which helps it spin very smoothly. But it also means that there is not very much contact area holding that load, so if the bearing is overloaded, the balls can deform or squish, ruining the bearing.
Roller Bearings
Roller bearings like the one illustrated below are used in applications like conveyer belt rollers, where they must hold heavy radial loads. In these bearings, the roller is a cylinder, so the contact between the inner and outer race is not a point but a line. This spreads the load out over a larger area, allowing the bearing to handle much greater loads than a ball bearing. However, this type of bearing is not designed to handle much thrust loading.
A variation of this type of bearing, called a needle bearing, uses cylinders with a very small diameter. This allows the bearing to fit into tight places.
Cutaway view of a roller bearing
Photo courtesy The Timken Company
Ball Thrust Bearing
Ball thrust bearings like the one shown below are mostly used for low-speed applications and cannot handle much radial load. Barstools and Lazy Susan turntables use this type of bearing.
Ball thrust bearing
Photo courtesy The Timken Company
Roller Thrust Bearing
Roller thrust bearings like the one illustrated below can support large thrust loads. They are often found in gear sets like car transmissions between gears, and between the housing and the rotating shafts. The helical gears used in most transmissions have angled teeth — this causes a thrust load that must be supported by a bearing.
Roller thrust bearing
Photo courtesy The Timken Company
Tapered Roller Bearings
Tapered roller bearings can support large radial and large thrust loads.
Tapered roller bearings are used in car hubs, where they are usually mounted in pairs facing opposite directions so that they can handle thrust in both directions.
A list of machines that require bearings would be far too extensive for any column such as this. The crux of the matter is that there is a real cost to losing that once-proud and sought-after label: “Made in America.”
My husband is a farmer and he can fix just about anything. In addition, he is an avid snowmobiler and he spends a portion of the summer tweaking his “sleds” and readying them for the upcoming winter season. Recently, he noticed that bearings in one of his sleds were pretty worn. That surprised him, given the age of the sled. Generally, he expected the bearings that were made in the USA to last for a certain range in terms of miles. The Timken name is well known and equated with quality.
Shopping for the new snowmobile bearings should have been easy, and it was. However, results were surprising. You see, while the bearing did have the familiar, trusted Timken name, another credit was etched into the bearing. You got it: Made in China. Store after store, the answer was the same. My husband could not find bearings made here.
So, where are we now? Nearly every machine has a housing and relies on bearings within that housing. How smart is it to be in a position where our bearings are made overseas? Oh, undoubtedly, there will be those who claim that Americans supervise the production. Well, if that is right, then why is the quality so much lower than in the past? Retailers and jobbers tell us that the quality has dropped precipitously and that the bearings imported today are not equal to those made here.
I said over ten years ago in one of my first columns that I feared America was feeding the tiger that would devour her. My opinion hasn’t changed. Isn’t it about time we brought at least a good percentage of the bearing production back home? Where will we be if the Chinese government stops shipping bearings? How long would it take us to begin to manufacture them again? How long would machines sit idle with no “guts” to run them? Machine housings need bearings.
Are we ready for this new housing crisis? I wonder if most of us even realize it exists. You had better think about this one. It could spell disaster for what is left of the mechanized portion of our economy.