how do airbrakes work?

Answer 1

Air brakes are positive pressurized systems that are used in place of hydraulic fluids due to heat. When you compress fluids or air heat is created. Hydraulic fluids would boil and become ineffective if used to stop an 80,000 lb rig from 70 MPH multiple times. Imagine sitting in front of one a traffic light of w/o brakes as the approach you from the rear. Bad news: cars and trucks don't mix well. Air works well and sis safer to use. In winter months air systems may be treated with alcohol based products to disapate water that would freeze the air systems and related components rendering them useless.

Dual brake chambers used on modern trucks and trailers with air brake systems have coiled springs that in absence of air pressure to overcome the tension will lock and set the brakes. Air pressure over comes the spring pressure to release for driving. Air pressure is also used to apply for normal braking, hence the dual chambers for the dual operation. I have replaced the rubber "pancakes" numerous times when they burst or leak.

Older units from the early 1970's and back used a single chamber that when the air leaked off there were no brakes on trailers or the brakes would not release until the lost pressure was replaced. The system is made up of a compressor that can be belt or direct driven on the power unit, a hand operated brake valve in case the foot operated brake valve fails, reservoir tanks to hold air pressure in reserve for normal operation, a governor to regulate the pressure to between 60 and 120 lbs of operating pressure, various vales to allow proper operation and distribution of the air to the brakes and other systems. A variety of plastic, rubber and coppper lines are used to supply air to the various components and assemblies that they operate.

Other air operated equipment on trucks includes pasenger side windows, windshield wipers, 5th wheel locks and sliders, suspensions and cab suspensions, vac pumps.

Answer 2

Larger vehicles with air brakes have a small air compressor, driven by a fan belt, that fills surge tanks with compressed air... usually about 120psi. The systems on trucks are Negative systems meaning that it takes usually a minimum of 60psi to release the brakes so that it can move. If for some reason you have a lose of air, the brakes will set.

Anyway, the brake pedal rests on a valve so that when you apply pressure to the pedal, the valve opens and allows air to travel from the surge tanks to the braking system.

The trailers use the surge tank as it's air supply when attached to a rig. Same negative system. The trailer has 2 air hoses run to it... The red hose is the supply that releases the breaks from negative and it is also used to fill the air bags on those trailers equipped with air ride. The blue hose is the service line which actuates the brakes when you apply pressure to the brake pedal.

All that hissing and stuff you hear can be any of the following: 1) The surge tanks have reached their set, high pressure, limit and the pressure switch to the compressor disengages releasing any extra air in the system. 2) The driver is setting the parking brake to the trailer or the tractor. The constant pressure used to keep the brake shoes off the drums during driving is vented out of the system so that the brakes will engage for parking. 3) The driver is releasing air from his rig's air bags to lower his chasis so that the hitch plate will fit under the tongue of the trailer he is picking.

Overall, airbrakes are very reliable and easy systems to work with. They are, in most cases, safer than hydraulic systems due to their negative set up. They are cheaper to repair and require very little maintenance.

Answer 3

Simply put the same way normal brakes do, except for the fact that it uses pressurized air instead of brake fluid.

These systems (used to be) Positive, or Negative systems (it has been a LONG time since i messed with big trucks to say if they still use both.

Positive systems require air pressure to apply the brakes, Negative systems require no air pressure for the brakes (IE: a Vacuum).
Negative were supposed to be safer in that IF there was some problem that removed air pressure the brakes would engage.

The link below will help some.

Answer 4

air brakes work by realesing air pressure fro the brake actuator. so in the event of a loss of pressure the brakes apply to stop the truck and or trailer. trains run on the same principle. its a system that has a compressor and valves mounted throughout the system

Answer 5

Air pressure, not hydraulic pressure.