Can anyone explain the difference between Vacuum operated brakes and Air 
Am i right in thinking with Vacuum if there is a failure the brakes are off via Air were air loss would result on the brakes been applied?
My head hurts?
Bones:
Can anyone explain the difference between Vacuum operated brakes and AirAm i right in thinking with Vacuum if there is a failure the brakes are off via Air were air loss would result on the brakes been applied?
My head hurts?
I thought vacuum brakes were just air over hydraulic by another name. sort of servo assisted fluid pushing pistons.
Wikipedia here I come 
Pressurised brakes are far better than vacuum brakes because you can only bring down air pressure by around 10 psi whereas you can build air pressure to any amount. Pressurised brakes also can be made “fail-safe”.
Vacuum braking was used in early vehicles, particularly railway trains but it became “old technology” a hundred years ago.
Here we go.
A vacuum servo is a component used on motor vehicles in their braking system, to provide assistance to the driver by increasing the braking effort.
It is used on virtually all vehicles which use hydraulic brakes for their primary braking circuit. Vacuum servos are not used on vehicles which use cables, rods (or other mechanical linkages), or pressurised air systems for their primary brake circuits.
It uses a stored vacuum to multiply braking force applied by the driver to the brake pedal, before applying the transferred force to the brake master cylinder.
The vacuum is generated in two distinct methods, dependent on the type of internal combustion engine, or other motive force (as in electric vehicles). In petrol engines, the manifold vacuum is utilised, whereas in diesel engines, a separate vacuum pump is used. The vacuum is transferred to the servo along semi-rigid plastic lines, and is stored in the servo by using a non-return valve.
Cheers,
thats got me on the right track.
There’s no comparison it’s like comparing apples with oranges and bananas.A vaccum servo just used manifold deppression to pull a bellows against the piston in a hydraulic master cylinder on light cars.Air over hydraulic systems use air pressure to push the piston forwards with more force than the vaccum servo can.Air brakes use much larger capacity/area diaphrams in their actuators than any hydraulic piston can provide in a hydraulic system and provide more force to the brakes and they incorporate spring actuation as well for fail safe.
A servo works on the vacuum principle but this is not the same as vacuum brakes. If I have understood the OPs question properly.
Harry Monk:
A servo works on the vacuum principle but this is not the same as vacuum brakes. If I have understood the OPs question properly.
In that case it would just be vacuum operation of the brake actuators pulling the diaphrams instead of air pressure pushing them and a vacuum pump being used instead of an air compressor? but there probably is’nt any way that the vaccum system could be made to provide as much force at the brakes as the air pressure system can which is probably why air brakes won out?.Suppose the simplest way they should be described is vacuum over hydraulic for the vacuum servo system.Air over hydraulic is as described.Air brakes and vacuum brakes are just as they are described but they are all as different as apples,oranges,and bananas?.
don’t discount 10psi either, of vacuum or air pressure, it is certainly enough to implode or explode a road tanker and blow your face off.
Wheel Nut:
don’t discount 10psi either, of vacuum or air pressure, it is certainly enough to implode or explode a road tanker and blow your face off.
Not if it was loaded with liquid oxygen and it ran into another one loaded with liquid hydrogen.Did you see the way that Saturn 5 went up into orbit in 1969.
Carryfast:
Wheel Nut:
don’t discount 10psi either, of vacuum or air pressure, it is certainly enough to implode or explode a road tanker and blow your face off.Not if it was loaded with liquid oxygen and it ran into another one loaded with liquid hydrogen.Did you see the way that Saturn 5 went up into orbit in 1969.
Forget Saturn 5 
That is what a vacuum does 
Wheel Nut:
Carryfast:
Wheel Nut:
don’t discount 10psi either, of vacuum or air pressure, it is certainly enough to implode or explode a road tanker and blow your face off.Not if it was loaded with liquid oxygen and it ran into another one loaded with liquid hydrogen.Did you see the way that Saturn 5 went up into orbit in 1969.
Forget Saturn 5
http://www.youtube.com/watch?v=0lkFnSDsqHU
http://www.youtube.com/watch?v=yGYo7wG1x5A
That is what a vacuum does
No vacuum ■■■■■.That’s just 14 psi atmospheric pressure difference on that tanker because someone forgot to vent it to air before tipping it??.That Saturn 5 did’nt stop until it reached the moon and that was only because that’s as far as the guvnor told them to take it before coming back.There’d be a great photo of a simultaneous caravan implosion and explosion after it had an argument with a 24 Tonne cement mixer on the caravanners should be shot topic if only I could get photobucket to upload the thing I’ve e mailed it to Rikki but no sign of it yet.