I've often wondered why they don't put air brakes on cars. They're obviously safe or they wouldn't have them on trucks, busses, etc. You could use the same compressor to power the brakes, steering, A/C, and other things too, I would imagine. Seems like it would make for a more efficient, lighter, cheaper solution than the current setups. Can anyone shed any light on this?
Air brakes on cars
- Thread starter Cogito
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It is because inappropriate, excessive use of the brakes in an airbrake system will deplete the air pressure reserve, causing the brakes to completely lock up (which is the safety feature incase the air pressure drops too low).
The sort of driver who hits their brake pedal every few seconds..and we've all been behind these drivers..would not be a good match with airbrakes.
The sort of driver who hits their brake pedal every few seconds..and we've all been behind these drivers..would not be a good match with airbrakes.
I bet vacuum booster systems are pretty cheap too.
Diesel engine= no vacuum, and size of the components becomes an issue when overall vehicle weight gets over ~ 10000 lbs.
Might be the new "rice" thing for hummers etc to make a "psst" air brake noise every time they stop. Sssshhhh...
Diesel engine= no vacuum, and size of the components becomes an issue when overall vehicle weight gets over ~ 10000 lbs.
Might be the new "rice" thing for hummers etc to make a "psst" air brake noise every time they stop. Sssshhhh...
I think one of the main reasons for air brakes on trucks is because they switch trailers often.
This way the trailer can get the same air pressure as the tractor instead of surge brakes or electric brakes.
This way the trailer can get the same air pressure as the tractor instead of surge brakes or electric brakes.
Cars normally don't have a trailer to power the brakes for as well. One of the main reasons for air as opposed to hydraulic brakes is the constant coupling/uncoupling of trailers-sometimes multiple trailers with converter gear in between. It can't be easily done with hydraulic systems.
Air brakes are a real pain-especially in the super sub-zero winter when the slightest moisture in the system freezes and the compressor can't charge the tanks.
By the time you tack on the compressor (which runs off the engine and robs horsepower), the air tanks (at least a couple for redundancy) it becomes a much more complicated, heavy system. Makes no sense to try to modify that for a car.
Air brakes are a real pain-especially in the super sub-zero winter when the slightest moisture in the system freezes and the compressor can't charge the tanks.
By the time you tack on the compressor (which runs off the engine and robs horsepower), the air tanks (at least a couple for redundancy) it becomes a much more complicated, heavy system. Makes no sense to try to modify that for a car.
That's the most significant reason. Air power is a terribly inefficient way to convert and transmit power.
Compare the size and weight of an air compressor plus air powered drill to an equivilant powered electric drill.
As to why you have air brakes on big trucks:
If you break/crack a hydraulic line on a brake system, you lose your brakes. If that happens on 30 tonnes of truck and trailer, well bad things can happen.
Now, if an air line breaks on a tractor/trailer, the brakes apply right away and stop the action until the problem is fixed.
Air brakes don't really have "feel" like hydraulic brakes do, it is more of an on-off affair. Add to that a requirement for a noisy air compressor, parasitic drag of that compressor, noise everytime you release the brakes and you get the idea. Car owners wouldn't appreciate that.
If you break/crack a hydraulic line on a brake system, you lose your brakes. If that happens on 30 tonnes of truck and trailer, well bad things can happen.
Now, if an air line breaks on a tractor/trailer, the brakes apply right away and stop the action until the problem is fixed.
Air brakes don't really have "feel" like hydraulic brakes do, it is more of an on-off affair. Add to that a requirement for a noisy air compressor, parasitic drag of that compressor, noise everytime you release the brakes and you get the idea. Car owners wouldn't appreciate that.
Some H1 Hummer drivers would because the noise would annoy other drivers.
If you have ever driven a big truck with air brakes, there is actually some delay from when you put on the brakes until they actually work. You get used to it but it is a definate delay compared to hydraulic. For cars, I'd lots rather have hydraulic.
Down here in south FL, it seems that every person with a Hummer H2, Dually or other large pickup truck has installed a train horn to scare the **** out of people and annoy everyone on the road.
Like punisher says, it is a back up system for trailers.
When the air is released from a compromised system, the brakes will lock up. This in theory will keep the trailer from wildly careening along.
We have no need for this complication in our street cars.
When the air is released from a compromised system, the brakes will lock up. This in theory will keep the trailer from wildly careening along.
We have no need for this complication in our street cars.
Cars are actually heading in another direction, electric. Electrically boosted steering is already on a lot of new cars and that eliminates a belt driven pump and hoses altogether. Electric brakes, which have been on small trailers for decades are now being used in a few very high-end cars, eliminating vaccuum systems. This also will allow diesel cars and light trucks to have power brakes without a vacuum pump. Electrically driven water pump is on new BMWs and A/C compressors are the next logical step.
The new Boeing 787 is using electric systems to replace air driven ones for efficiency.
The new Boeing 787 is using electric systems to replace air driven ones for efficiency.
IIRC Mercedes-Benz ditched their overly complex electric braking system, and have reverted to conventional brakes.
I'm not sure if anyone currently uses them, but I could be mistaken.
Though I do know that Siemens is still pursuing electric brakes, at least they are still working on them.
I'm not sure if anyone currently uses them, but I could be mistaken.
Though I do know that Siemens is still pursuing electric brakes, at least they are still working on them.
Exhaust brakes are nice for heavier vehicles, or any vehicle that travels on hills a lot. We go thru a lot of pads and rotors on the Taurus sedans, in part because the auto is worthless for engine braking. Even for a pickup a decent exhaust brake on a diesel will generate over 200 braking HP, and it will also help to keep the engine warmer during extended idling, like being stuck in taffic.
Of course, the hybrids are partly braked by regeneration in the electric motor, capturing some of the energy for reuse.
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