Project Garage Part V: Air Compressors

Many times I've struggled with stubborn bolts, cursing car manufacturers wth a number of expletives in languages I didn't know I could speak. Stripped, rusted, or fused, these bolts can make any breaker bar retire early and hit happy hour. Unfortunately if I ever wanted to mod any of my cars, my only other option was blowing off some steam… well, hot air really. My air compressor is not only convenient, but necessary.

Compressors come in many shapes and sizes. Most of the larger compressors can run longer, more efficiently, and have tanks to store the compressed air for maximum use. Compact air compressors don't usually have storage tanks and must run continuously to provide an adequate air supply. They are good for small jobs, anything from refilling tires to blowing up inflatable dolls, right Kojima? 😉

Ingersoll Rand air compressor
This is like the grand daddy of air compressors.  It's a two stage, two cylinder splash lubricated belt-driven (dirty talk, I know!) air compressor with 14 horsepower and pushes 25cfm at 175psi (seriously!).  You'll have to cough up a few g's to own this baby.

Air compressors convert electric energy into kinetic energy. Some use rotating impellers to generate air pressure. Most use a reciprocating piston to increase air pressure by reducing the size of the space where the air is contained. A conventional piston compressor uses a crankshaft driven by an electric motor or gas engine as well as a connecting rod, piston, cylinder and valve head. The valve head contains the inlet and discharge valves. Air enters the inlet valve and fills the space above the piston. When the piston moves up, it compresses the air, which exits through the discharge valve into the tank or an air hose. 

Single Stage versus Two Stage
A single stage compressor has one piston that compresses and transports air to the tank. It can be a single or multi cylinder compressor. Single stage compressors are usually good for air pressures up to 150 psi. Two stage compressors are usually used for continuous or heavy duty use or if maximum ratings above 150 psi are necessary. One piston compresses the air and delivers it past a check valve where it is cooled. A second piston compresses the air even further and delivers it into the storage tank.
 
Oiled or Oil Free
If you can't remember the last time you checked the oil in your car, you should stick to an oil-free compressor. They have permanently lubricated bearings and don't require oil changes but are usually noisier, direct drive, and designed for home and not commercial use. Oil lubricated compressors have automotive pistons and rings with dippers on the bottom of the connecting rod which splash oil around to lubricate the bearings and cylinder walls. Just like any engine, keeping the oil at its proper level is required to ensure a long lifespan. Oil and filters should be changed every 500 hours of use and the compressors should be used on level surfaces to guarantee the motor stays lubricated.
 
Direct drive versus Belt drive
Direct drive compressors are connected directly to the motor shaft and turn at the same speed as the motor. Some have been designed to rotate up to twice the speed of the motor though they usually are louder. Belt drive compressors are quieter and better for continuous or high use. They last about 3-4 times longer than direct drive compressors but the belts need adjustments and may need to be replaced.

 

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