Air over hydraulic brakes

[harry kew]

On the air over hydraulic  brakes there are the two master cylinders
Is one for the rear brakes and one for the front brakes?
The lines up into the frame and are hard to follow
Just trying to find out how the system works
Thank for any help

1999 Patriot 40"

[Joel Weiss]

I'm sure that Dave Atherton can give a much better explanation, but it's my understanding is that the brake system works pretty much like a standard "split system" that you would find in most automobiles.  The "air" provides boost the same way vacuum provides it with a gas engine.  There's one master cylinder and the system isn't split "front and back" but essentially along a diagonal.  If you have a problem with your car's brakes you don't have "front/back" failure.

[Gerald Farris]

Joel,
You are correct about the hydraulic braking system with the exception of how the two compartment master cylinder is divided. It is split with one section supplying the front brakes and the other section supplying the rear brakes. This design is meant to prevent total loss of braking only if you develop a hydraulic leak. A diagonal design that would leave you with braking on one front and one rear wheel only would cause a severe pull in the steering upon application. Diagonal braking is used in stability control systems that are computer operated to regain directional control, and never manually operated.

Gerald   

[Joel Weiss]

Gerald:

With all due respect, diagonally split braking systems are not limited to vehicles with modern anti-skid systems.  With the advent of split systems several decades ago. both front/back and diagonal splits have been used.  Thanks for pointing out that my PT has a front/back split but I wanted to note that I've owned many vehicles with diagonally split systems.  Here's an article about split braking systems: http://www.mechanicalengineeringblog.com/5379-hydraulic-brake-system-of-an-automobile-construction-and-working-of-hydraulic-braking-system-components-of-an-oil-brake-system/

Joel

[Dave Atherton]

Gentleman, as first post pointed out there are ( 2 ) air brake chambers connected into ( 2 )
master cylinders. The air system is for brake actuator for the master cylinders. Going down
To foot brake and brake valve actuator. This is where you will split the system at the brake
Valve actuator port openings Which will make up duel circuit. Applying pressure on foot brake
a two part plunger within the brake valve moves, closing the valve's exhaust and opening
passage withithe valve that allows the air pressure to be delivered to the rear and front brake
systems. When driver removes all force from brake valve the internal return springs move back
to original position. Duel brake valves in most cases floor mounted, but indifferent cases can
be bulkhead mounted. This is also know split system is 60 % rear and 40 % front brakes
when applying brakes. Dave Atherton Retired Cat Mechanic