BENDIX BW1660 User Manual download pdf

SD-03-1061A

Bendix

R-8P

™

Pressure Equalizing Pilot Relay Valve

DELIVERY

PORTS

SUPPLY PORT

SPRING

FIGURE 1 - CUTAWAY AND EXTERNAL VIEW

VENT

PISTON

BODY

SERVICE

(CONTROL)

PORT

EXHAUST

INLET/EXHAUST

VALVE ASSEMBLY

DESCRIPTION

The R-8P

™

pressure equalizing pilot relay valve is a device

designed to reinforce the control signal on long wheel base

towing trailers and converter dollies.

Unlike a standard relay valve which typically has a 4 p.s.i.

crack pressure and similar differential between control and

delivery, the R-8P

™

valve has a 0 p.s.i. differential.

On the converter dolly and long wheel base towing trailers,

the R-8P

™

valve reinforces the service brake application

signal without the differential found in standard relay valves.

The 0 p.s.i. differential of the R-8P

™

valve assures that all

trailer and dolly brakes will receive the same strength control

signal even during light brake applications.

By providing a balanced pressure signal to all trailer and

dolly brakes, the R-8P

™

valve helps achieve overall vehicle

brake balance and stability. The R-8P

™

valve also helps

improve brake lining wear balance on combination vehicles

by causing even the most distant brake to contribute its

share of braking effort.

OPERATION

APPLICATIONS (FIG. 2)

When a service brake application is made, air delivered from

the brake valve enters the service port of the R-8P

™

valve.

As air pressure fills the space above the piston, it begins to

force the piston down. Because of the spring force above

the piston, the piston exhaust seat is already in contact

with the inlet/exhaust valve, sealing off the exhaust. As the

piston begins to move downward it forces the inlet/exhaust

valve off the inlet seat, allowing air from the reservoir to be

delivered out the delivery ports of the R-8P

™

valve in direct

proportion to the pressure received at the service port.

Any differential between service and delivery pressure caused

by friction or resistance to the movement of the piston

(commonly called crack pressure and normally in the range

of 2 to 4 p.s.i.) is eliminated due to passage of air through

the orifice in the piston.

COVER

SUPPLY PORT

DELIVERY PORT

PISTON

ORIFICE

1 2 3 4

Summary of Contents

Page 1 - SD-03-1061A

1®SD-03-1061ABendix® R-8P™ Pressure Equalizing Pilot Relay ValveDELIVERYPORTSSUPPLY PORTSPRINGFIGURE 1 - CUTAWAY AND EXTERNAL VIEWVENTPISTONBODYSERVIC

Page 2 - PREVENTIVE MAINTENANCE

2FIGURE 2 - OPERATIONAL VIEW OF APPLICATIONFIGURE 3 - OPERATIONAL VIEW OF BALANCED POSITIONBALANCE (FIG. 3)The air pressure being delivered by the ope

Page 3 - PERSONAL INJURY OR DEATH:

3FIGURE 5 - SCHEMATIC OF TYPICAL DOLLY SYSTEMCONTROL FROMTOWING TRAILERSUPPLY FROMTOWINGTRAILERS = SUPPLYSUPPLY TOSECOND TRAILERRE-6™ RELAYEMERGENCYVA

Page 4 - INSTALLATION