Hydraulic Controls

TM 5-5420-279-23

shoot bolts. An A-Frame folding cylinder is attached to the lower A-Frame transverse beam and

to each outer A-Frame leg.

Extension of the cylinders rotates the outer A-Frame legs from their stowed position about

their upper and lower hinge points. When fully deployed, counterbalance valves hold the A-Frame

folding cylinders in this position until the outer A-Frame legs are pinned securely in position.

To allow the launching vehicle to be leveled laterally on the bridge build site a hydraulic

cylinder is incorporated within the outer A-Frame leg. The cylinder is attached to the outer leg and

to an inner sliding stabilizer leg. Once both stabilizer cylinders have been extended and the

ground bearing pads are in contact with the ground, only the stabilizer on the low side of the

vehicle needs to be further extended to level the vehicle. A level is incorporated on the lower A-

Frame transverse beam to indicate when the vehicle is level. Once level counterbalance valves

hold the stabilizer cylinders in their respective positions until the stabilizer legs are pinned

securely in position.

An A-Frame raise hydraulic cylinder is attached to the upper sliding section of each outer

leg and supports and moves the upper A-Frame transverse beam for bridging module

deployment. Counterbalance valves hold the raise cylinders in the raised position until the upper

A-Frame transverse beam is pinned securely in position.

Two articulating cylinders are connected to the launch beam drive pivot pin and the

articulating cylinder cross member. They are used to articulate the launch beam to accommodate

varying bank heights and to lower the far bank support to the ground once the launch beam is

fully deployed. To allow bridge build to continue the articulating cylinders have to be detached

from the cross member and raised. To facilitate stowing of the articulating cylinders a stowing

cylinder is used. When retracted they rotate the articulating cylinders clear of the bridge surface

during building.

1-10-13 Hydraulic Controls

The hydraulic operation of the A-Frame is controlled from two locations on the vehicle. The

A-Frame fold and rotate functions are operated from the interface cabinet located above the tool

chest on the side of the launching vehicle. The A-Frame fold pushbutton is pressed first and its

associated light will indicate when the operation is complete. The A-Frame rotate function is

operated in a similar manner but can not be commenced until the A-Frame fold sequence is

complete. Limit switches are incorporated into the circuit to guard against incorrect sequencing of

operations.

The A-Frame stabilizer legs are operated by two manual levers mounted on the rear face

of the lower A-Frame transverse beam. The levers have a spring loaded central `off' position and

must be manually held against the spring in the appropriate direction for the required function to

operate.

Once the launcher has been deployed, hydraulic control is carried out via the launch chest

pack. Should electrical failure occur all cylinders and motors can be operated manually.

The A-Frame raise/lower control is an electro-proportional valve mounted on the stabilizer

leg and weighs 44 lb. (20 kg). It is a two-`slice' valve similar to the above and can be operated

1-11