Tandem Brake Valve With Treadle Pedal; Description; Maintenance - Manitowoc Grove RT880E Service And Maintenance Manual

RT880E SERVICE MANUAL
TANDEM BRAKE VALVE WITH TREADLE
PEDAL

Description

The tandem brake valve with treadle pedal is located on the
floor of the cab. The tandem brake valve provides split
system braking for the primary (front) brakes and the
secondary (rear) brakes.
The valve is a closed center spool design which modulates
the output pressure [1500 psi ±75 (10,342 kPa ±517)] to the
brake actuators. The valve is mechanically actuated by a
treadle pedal (see Figure 2-28). The direct acting spool
provides a pedal feel which accurately represents the brake
pressure, similar to automotive style pedal feedback as the
brake pedal pressure increases, the pedal effort increases
proportionally. As the pedal is initially actuated, the tank ports
are closed off from the brake ports. With further application of
the pedal, the pressure ports are opened to the brake ports
until the pedal actuation force and the hydraulic pressure
force are balanced.
Also when the pedal is actuated, the integral proximity switch
is engaged to provide an electrical signal for brake lights.
When the pedal is released, the valve and the pedal return to
the non-applied position.
3
Valve Hydraulic Schematic
Item

Description

1 Port B1
2 Port B2
3 Pressure Port P1
4 Tank
5 Pressure Port P2
Grove
1 2
Published 11-10-2014, Control # 524-00
The tandem brake valve consists of a tandem valve body, a
closed center spool, a treadle pedal, an integral proximity
switch and a mechanical spring assembly to limit the output
pressure to the brake actuators to 1500 psi ±75 (10,342 kPa
±517).

Maintenance

Removal
1. Tag and disconnect the electrical connector to the valve.
2. Tag and disconnect the hydraulic hoses from the valve.
Cap or plug the lines and ports.
3. Remove the nuts and bolts securing the valve to the cab
Floor. Remove the valve.
Installation
1. Secure the valve to the cab floor with the nuts and bolts.
2. Connect the hydraulic hoses to the ports on the valve as
tagged during removal.
3. Connect the electrical connector to the valve as tagged
during removal.
4. Start the engine and check valve and hoses for leaks.
Make repairs as needed.
4
5
5
3
HYDRAULIC SYSTEM
4
2
7716-03
1
FIGURE 2-28
2-53
2