TM 5-3815-221-14&P
extend, thus giving the impression that the backstop
CAUTION
clearance has been increased. If the operator should
Use care when swinging the
then raise the boom still further, in line with the apparent
revolving
frame
without
boom
increased backstop clearance, releasing the load will
attached. It will tend to be
allow the stretched boom hoist lines to contract. This
unbalanced toward the counterweight
contraction will force. se the boom against the backstops
end.
and major damage can result.
2. Swing the revolving frame and carefully move crawler
To install the hoe backstop assembly, proceed as follows
unit up to cribbed up gantry so that bore in gantry foot
(see Figure 3):
lugs line up with foot pin holes in auxiliary gantry.
1. Lay the backstop assembly on the auxiliary gantry.
3.
Attach auxiliary gantry to revolving frame with
Secure to the auxiliary gantry with the pipe spacers, cap-
pins and washers (2 on each side revolving frame bore).
screws, lockwashers and nuts.
4.
Secure pins with rod ends, capscrews and
2. Lift the machine end of the backstop assembly into
position against the machine. Install the backstops with
NOTE
base pin and secure with cotter pins.
Final gantry positioning is done when
3. Reeve the boom hoist cable. See REEVING later.
the backhoe boom is installed. Take
4. Raise the gantry to allow installation of the backhoe
up slack with the boom hoist drum to
boom.
support the auxiliary gantry in the
VERTICAL position.
BACKHOE BOOM
WARNING
To install the backhoe boom, proceed as follows:
Never allow a loaded boom to
1. Support the base of the backhoe boom assembly on
compress the backstop springs. If
cribbing. Use cribbing high enough to bring the boom
this minimum clearance is not
foot pin holes into position with the boom foot lugs on the
maintained, tension within the boom
revolving frame.
hoist lines may collapse the gantry
2. Carefully move the crawler up to the cribbed up boom
over the backstops.
so the bores in the boom foot lugs on the revolving frame
are aligned with the boom foot holes.
HOE BACKSTOP
3. Attach the backhoe boom to the revolving frame with
Backstops are used as a safety and warning device.
the boom foot pins and cotter pins. Use washer between
They are not intended to stop the boom during operation.
boom foot and revolving frame lugs.
The primary purpose of the backstops is to give the
operator a means of judging when to stop raising the
boom.
One point should be kept in mind by the operator when
using the backstops. If a load is picked up at a time when
the backstops are nearly bottomed, the weight of the
load will stretch the boom hoist cables, causing the
backstops to
Figure 3. Back Stop (2100N520)
3
