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addressThere is no such thing as an opportune moment for a flat tire, only bad or worse times. It’s bad when you get a flat tire near your home and need to take the time to fill it up or fix it. It’s worse when it’s on the side of a busy highway. But the absolute worst time to get a flat is when you don’t have a temporary patch, your spare tire is also flat, and you’re nowhere near an air compressor.
Unpreparedness creates more headaches, wastes more time, and costs more money. One way to ensure you always have, at the minimum, a fully inflated spare tire is to keep a portable tire inflator in your car. You can use it to keep your tires at the designated optimum pressure at any time, and you’ll have a backup plan for your spare tire just in case.
These devices go by many different generalized names, including tire inflator, mini air compressor, and portable air compressor, which can be confusing when considering many people think of air compressors as the large tanks that sit in the corner of a garage. So is it really an air compressor if it doesn’t have a tank?
To clear up this confusion, the Guides & Gear team decided to “open up” a tire inflator and lay out all of its guts in an easy-to-understand explainer. Let’s begin.
Tire inflators are not the same as simple air pumps; they’re actually miniature air compressors. To better understand how they work, we’ve broken down the main components that make up these devices and explained how they work together to put air into your tires.
The most common types of portable tire inflators will plug straight into a wall, plug into the 12V cigarette lighter in your car, or use battery power. Each has its own pros and cons, but the type that plugs into the 12V port is the most universal for drivers.
The switch, whether in the form of a dial, slider, toggle, trigger, or a button, completes the device’s power circuit and turns the device on by engaging the motor. Essentially, the switch is how you turn the device on and off.
The internal electric motor is the tire inflator’s powerhouse. The motor’s output shaft is primarily connected to gears that transfer the energy to the piston. In some cases, however, the output shaft is also connected to a fan that spins while the motor is running to cool down the device.
In most tire inflators you’ll have two gears, one attached to the motor and one attached to the piston. When the motor moves, it turns its gear, which is inset with the piston’s gear. So, when the motor moves, the gears make the piston move. In some cases, there might also be a third gear to turn a fan.
It’s not exactly the same, but your gas-powered vehicle does share a component type with a tire inflator: a piston. Although the motor drives the mechanism, the piston and the cylinder in which it is housed is where the action happens.
As the gears turn, the piston is pulled down to bring air into the cylinder through an intake, then pushed up. When the piston goes up, the air is compressed and pushed through the tube that connects to the tire. The piston steadily repeats this cycle to continue compressing and pumping air into the tire.
Most tire inflators will be air-cooled by a small fan built into the device. The placement of the fan will vary, but it is likely next to or near the motor where a majority of the heat is created.
The piston wouldn’t be able to complete its purpose without valves working in tandem. The valve types, whether ball, flap, or other, will vary, but they all serve the same purpose: to get air into the cylinder when needed and prevent air from coming in when not needed.
Your tire inflator might also use a pressure sensor. This can be used for reading the pressure to display it on a digital gauge, and/or they might be used to control a valve for automatic closing.
The connector, or the tubing at the end of the tire inflator, is what pairs the inflator to the tire, ball, or whatever else needs inflating. It is typically made of rubber and is sometimes covered in a fabric wrap. Many new models offer a variety of tips that pair with the connector to allow for a variety of uses.
In short, you flip a switch, the motor turns on and drives a piston, which pressurizes and pumps air into your tire through the connector.
Technically, yes, a portable 12V tire inflator is an air compressor. However, it doesn’t have a tank to store compressed air, nor does it have the ability to power pneumatic tools. Therefore, it’s often referred to as a tire inflator or simply an inflator because that is the only specific job it is intended for and capable of.
You’ve got questions, The Drive has answers!
A. The motors inside tire inflators can heat up pretty quickly, and if the cooling isn’t adequate, they can’t run for very long. Some of the most common run times you’ll see are only for about 5-10 minutes, but each inflator will be different. Check the owner’s manual/service manual for specifics on your machine.
A. There are always exceptions, but a vast majority will not. Most tire inflators you encounter, especially if it’s new, are oilless.
A. To use pneumatic tools, you need an air compressor that can consistently produce high amounts of pressure and steady air flow for extended periods of time. Small tire inflators cannot accomplish any of these things, so they cannot power pneumatic tools.
A. Different size air compressors are used for different tasks, so it depends on your goals, your budget, and the pneumatic tools you will be using. For more detailed information visit our guide, how garage air compressors work and what size you’ll need,
A. This will be different for every vehicle and tire, so you’ll need to consult the information posted on the inside of your driver’s door or your owner’s manual. The tire itself will often show maximum tire pressure, but that’s not the same as recommended tire pressure.
A. First, if you are unaware, PSI stands for pounds per square inch and it’s a measurement of air pressure. When your inflator is plugged into your tire, it will register a PSI on the built-in gauge, if your device has one. But, those readings will be off while the tire is in the process of inflation. So, make sure you take your measurements while the inflator is turned off.
Now that we’ve explained what a tire inflator does and how it works, we’d like to show you what the parts all look like. In the video below, the presenter takes apart a cordless Ryobi unit that has had some issues.
We’re here to be expert guides in everything How-To related. Use us, compliment us, yell at us. Comment below and let’s talk! You can also shout at us on Twitter or Instagram, or reach us all here:
Millions of people use air compressors every day, but if one was in front of you, could you explain how it works?
You've probably seen where and how they're used over the years, but knowing the mechanics behind how the parts work together is more applicable than you might think.
Already know the basics? Read our Ultimate Air Compressor Guide to learn which type of air compressor is perfect for your application. This article is for the gearheads, the techies, and the innately curious.
Shop Portable Air CompressorsEarly humans might not have understood anatomy or physics, but they understood the potential of using forced air compressed by their lungs. By blowing on their fires, our ancestors were able to grow the flames into larger, more powerful sources of heat and energy.
Thousands of years later, the societies of the Iron and Bronze Ages had evolved to create useful tools that could be implemented on a larger scale. Metalworkers in China's Han dynasty used hand and foot-powered bellows to stoke the flames in their forges as early as the Third Century BC.
It wasn't until thousands of years had passed that an engineer named John Smeaton devised a way to compress even greater volumes of air in . His invention employed a water wheel to power a moving cylinder-a piston-that compressed air in a large chamber.
Smeaton's design led to further innovations, such as John Wilkinson's development of a machine with an efficient rotating cylinder in and George Medhurst's invention of a motorized air compressor in .
Since the days of wheels, belts, and metalwork, the most significant innovations in air compressors have taken place in the last 50 years. Today, the market continues to evolve to keep up with ever-increasing industrial demands.
The concept of compressed air is simple: when atmospheric air is stored under pressure, it creates potential energy that can be held inside a tank until it's needed. Just like a balloon being released, when the pressurized air is released, the potential energy is converted into usable kinetic (motion) energy.
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By harnessing that transfer of energy through pneumatic (air) tools, we are able to work on tasks that were before impossible.
The core of how air compressors work is boiled down to two methods of air displacement.
In order to compress air, the internal components of a compressor must move or change position to mechanically force the air through the chamber where it is compressed and stored until use.
Positive Displacement is the method that most compressors use. Air is pulled into a
chamber that opens and closes, where the internal parts reduce the volume of the chamber and compress the air. Once the cycle is complete, the air is pushed through the chamber and into a storage tank where it waits to be used.
Piston, rotary-screw, and scroll-type air compressors all use positive displacement to compress and store air.
Dynamic (nonpositive) Displacement uses rotating blades on an impeller to pull air into the chamber, where the energy from the motion of the blades builds air pressure. Often used with turbocompressors, this method of air compression produces huge volumes of compressed air quickly, and this technology is commonly found in cars that use turbochargers.
Air compressors that utilize this method of displacement are often reserved for commercial/industrial applications when large volume flow rates and constant pressure are needed.
Compressor drives are most commonly direct-drive or belt-driven systems. In a belt-driven system, as the motor turns, the belt turns with it, thus activating the pump in the system. This is the more economical option and is widely used across all compressor types because the belts can be adjusted to change with air demands.
In a direct-drive system, the motor attaches directly to the crankshaft of the compressor, allowing for smaller designs and fewer maintenance requirements. Although not much adjustment can be made to these drive systems, they are more efficient because less power is lost in the transfer of power to the crankshaft.
Another benefit of direct drive is the ability to provide compressed air without needing to fill a storage tank first, like using a DC compressor for off-roading.
Depending on the type of air compressor, basic air compression requires an electric-powered motor, a pump with an internal mechanism to compress the air, an inlet/outlet valve to draw in and release air, and-in most cases-an air storage tank.
Air is drawn into the compressor where the internal components reduce the volume of the air by creating a vacuum, which drives the pressure of the air up as it is pushed into a holding tank. Once the maximum pressure is reached inside the tank, the duty cycle is complete, and the compressor shuts off until the pressure falls below a set threshold. Positive displacement air compressors do this in different ways: by using pistons, screws, and scrolls.
Piston-type air compressors operate similarly to the combustion engine in your car. When the crankshaft's rod raises the piston inside the cylinder, it forces air into the compression chamber. This decreases the air volume (thus increasing air pressure) as the crankshaft drives the piston closed and pushes the compressed air into a storage tank. Then, the piston opens again to draw more air in.
Piston compressors can achieve a full compression cycle (stroke) in 1 or 2 stages:
Piston compressors are notorious for being louder because the internal components rub together and create friction. However, advancing technology is improving the way they operate by introducing dual and multi-piston, single-stage models that use up to 4 pistons inside the pump.
By using multiple pistons, the work of a single piston can be divided up, extending the life of the unit and achieving a supremely quiet air compressor.
View: Best Quiet CompressorsInstead of using a piston, rotary screw compressors squeeze air between two helically-opposed screws that don't touch, reducing noise and maintenance.
These compressors were created for heavy-duty applications that require high power during extended periods and are ideal for maximum air intake and production.
Rotary screw compressors are oil-sealed and have fewer moving parts, so they operate more quietly and require less maintenance because of the design.
Shop Rotary Screw CompressorsThe third type of positive displacement compressor, scroll compressors, are known for their highly efficient, oil-free, and quiet operation. Similar to rotary compressors, the scroll design uses two interwoven metal pieces that work together but don't touch to create a vacuum.
Two spiral-shaped circular pieces rotate around one another to compress incoming air. One scroll is fixed in place and doesn't move, and the other fits inside the stationary scroll and moves in a tight circular motion without rotating.
Just like your car uses oil, air compressors need lubrication to continue running smoothly over time.
Lubricated air compressors use oil to reduce wear and friction on their moving parts. In the case of piston compressors, the oil is applied to the system in one of two ways:
Non-lubricated compressors are also referred to as oil-less or oil-free because their parts are coated in special chemicals or materials like Teflon to reduce friction instead of conventional oil. The solution here is permanently-lubricated components. The drawback of non-lubricated compressors is that they heat up faster, and aren't the best option for heavy-work environments.
Most oil-less air compressors are used in industries where clean air is required for manufacturing, such as in the food, beverage, and electronics industries. For example, scroll compressors are used in the dental industry because of their continuous clean and quiet operation.
Oil vs Oil-Free CompressorsWhen it comes to sizing an air compressor for airflow and air volume, there are two criteria professionals use to determine if an air compressor can properly handle an application and determine the kinds of tools that will be compatible with your air compressor.
1. Pressure is the amount of force applied to the surface of a given area. For compressed air and gases, this force is measured in pounds-force per square inch, or PSI. The higher the PSI rating, the greater the amount of force applied to the air within a compressor.
2. Airflow volume is a measure of the rate at which air can move into a compression cylinder and the machine can compress it. For air compressors, the volume of air is measured in
cubic feet per minute, or CFM. The higher the CFM value, the greater the volume of air a compressor can generate.
An easy way to understand how pressure and volume work together is to think of a garden hose. By putting your thumb over part of the hose opening, the same amount of water is forced through a smaller space, thus increasing pressure at a constant flow. By increasing the amount of water coming through the hose, more work can be done faster.
Air compressor technology used to be expensive to produce and used a lot of energy to power, making it only affordable for the commercial industry. Even today, commercial air compressors still use significant energy.
As a general rule, you can expect to spend about $500 per horsepower (HP), per year using an industrial air compressor in continuous use. For example, a 10 HP compressor will generally equal $5,000 in operations costs per year.
In efforts to bring down costs and increase efficiency, new technologies are being introduced each year that innovate the possibilities and capability of compressed air. Engineers are finding ways to make compressors more powerful and energy-efficient, such as through variable speed drives (VSD) that allow the compressor to change motor speeds and voltage as air demands change, saving energy and money.
Even newer is the variable frequency drive (VFD) technology that takes this concept a step further. This technology allows the compressor to control the motor speed and torque by alternating from A/C to D/C power and controlling the input frequency and voltage, meaning the most efficient power usage available on the market.
Other innovations, including changes to the rotor speeds of rotary screw compressors, the use of water as a lubricant in place of oil, and the incorporation of remote monitoring systems all promise to deliver even greater improvements to efficiency in the near future.
The short of it is: air compressors aren't going to disappear, but instead continue to allow millions of people to get more work done faster and more effectively.
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