BENDIX TCH-003-002 User Manual

Technical Bulletin

Bulletin No.: PRO-03-02 Effective Date: 10/30/69 Cancels: N/A Page: 1 of 9

Subject: 1970 FORD “L SERIES” MODEL DUAL AIR BRAKE

SYSTEM

The purpose of this bulletin is to generally familiarize you with the dual air brake system
standard on all 1970 “L Series” Ford Trucks. Both four wheel and six wheel systems are
offered with either wedge or S Cam foundation brakes. We have attached lithos of these
systems (SA 8042-63 used for six wheel, SA 8042-64 for four wheel) for your reference.

These systems provide a modulated emergency application of the Spring Brake
Actuators and a full spring application for parking. In addition to normal service braking.

Three new Bendix Commercial Vehicle Systems LLC devices are used in these
systems:

1. E-7 Dual Brake Valve

2. R-7 Modulating Valve

3. VM-1 Control Valve Manifold

E-7 Dual Brake Valve

B-W Pc. No. 282410

Ford Part No. DOHA 2A 270-C

1. The E-7 Dual Brake Valve is a suspended pedal, firewall mounted, foot operated
dual brake valve with two separate supply and delivery circuits for service and
emergency braking. An air manifold is bolted to the back of the valve to
accommodate the piping. Sealing of the ports between the manifold and valve is
accomplished with the use of o-rings.

The E-7 Dual Brake Valve is similar in operation to that of the E-4 Dual Brake Valve
in that the primary portion of the valve is mechanically operated by the pedal, and the
secondary portion of the valve is pneumatically actuated by primary circuit delivered
air pressure acting on a relay piston.

If loss of primary air supply occurs, extended treadle travel and mechanical force will
actuate the secondary portion of the E-7 Dual Brake Valve. The primary circuit of the
brake valve is supplied by No. 1 Reservoir, and the secondary circuit is supplied by
No. 2 Reservoir.

R-7 Modulating Valve

B-W Pc. No. 283036

Ford Part No. DOHA 2B431-A

2. The R-7 Modulating Valve performs four functions:
A. Modulates spring brake actuator applications should a failure occur in the service

brake system. If a loss of air should occur in the primary delivery circuit of the
Dual Brake Valve, the R-7 Modulating Valve exhaust air from the spring hold-off
cavity of the spring brake actuator, resulting in an application on that axle which
is proportionate to the braking on the other axles. If a loss of air should occur in
the secondary delivery circuit of the Dual Brake Valve, rear axle braking is
assured because the primary circuit supplies rear axle service brakes; therefore,
the Spring Brake Actuators will not be actuated.

B. Provides for quick release of the spring hold-off cavity of the Spring Brake

Actuators, allowing a fast application of the Spring Brake Actuators.

C. Limits hold-off pressure to the Spring Brake Actuators. This hold-off pressure can

be adjusted by the adjusting screw on the Modulating Valve.

D. Prevents compounding of push rod forces when the Spring Brake Actuators are

in the applied position.