FIGURE 1 - ATR-2
™
ANTILOCK TRACTION RELAY VALVE
DESCRIPTION
The ATR-2
™
antilock traction relay valve is a specialized air
brake valve developed for use on Bendix antilock/traction
equipped tractors only.
It is essentially three separate valves working in combination
in a single housing. An R-14
™
style service relay valve is
the base valve and is fitted with a modified cover containing
a bobtail tractor brake proportioning valve (reference Bendix
Service Data Sheet SD-03-1067) and a traction control
solenoid. The ATR-2
™
valve contains both air and electric
components and provides both the service braking and
traction control (differential braking) functions. A Bendix
antilock traction controller can be mounted to the ATR-2
™
valve or a cover plate can be installed and the antilock
controller mounted elsewhere on the vehicle.
The ATR-2
™
valve replaces the standard relay valve used to
control the rear axle service brakes and performs the
standard relay function during tractor-trailer operation. During
tractor bobtail operation, the ATR-2
™
valve reduces brake
application pressure to the lighter rear axle(s) brakes to
improve vehicle controllability and minimize rear axle(s)
wheel skid before antilock is required. The ATR-2
™
valve
provides added vehicle braking control and reduces the
number of times antilock is actually needed.
Like the standard relay valve it replaces, the ATR-2
™
valve
and its attached antilock controller is normally mounted
near the service brakes it serves. A mounting bracket,
furnished with the valve, permits either frame or cross
member mounting. All air connections on the ATR-2
™
valve
are identified with cast, embossed letters for ease of
identification and installation. The letter identification and
air line connections are shown below for reference.
ATR-2
™
VALVE
AIR CONNECTION
EMBOSSED IDENT.
Supply (to reservoir)
SUP
Delivery (to brake chamber)
DEL
Service (to brake valve rear delivery)
SER
Control (to delivery of trailer supply valve)
CON
The ATR-2
™
valve is part of the R-12
™
family of relay valves
which includes the R-12
™
, R-14
™
, BP-R1
™
, AR-1
™
valves.
The internal components of the relay portion of all of these
valves are interchangeable with the R-12
™
valve and therefore
the same basic components are used to service all of them.
The ATR-2
™
valve is available with various crack pressures
to accommodate specific applications, however the standard
is 4 psi.
NOTE: AN OPTIONAL COVER PLATE IS INSTALLED OVER THE TOP WHEN THE
ATR-2
™
VALVE IS MOUNTED REMOTE FROM THE ANTILOCK TRACTION CONTROLLER
CONTROLLER OR COVER
PLATE MOUNTING HOLES:
SEE NOTE
MOUNTING
BRACKET
BODY
SUPPLY PORT
BOBTAIL
PROPORTIONING
VALVING
SERVICE PORT
CONTROL PORT
DELIVERY PORT (4)
2 PIN SOLENOID
CONNECTOR
SUPPLY
PORT
COVER
TRACTION CONTROL
SOLENOID
®
SD-13-4812
Bendix
®
ATR-2
™
AntiLock Traction Relay Valve
