CORRECTLY SPECIFYING A CRANE: The three most
important factors that need to be known:
1. How much weight will be lifted?
2. How far out from the center of rotation is the load?
3. How often will the lift be made?
MAXIMUM CAPACITY: Advertised maximum capacity is a statement of the maximum winch
capacity of the crane. Liftmoore does not recommend purchasing a crane for use
at its maximum lifting weight. A cranes capacity at a particular load radius is
determined by its Moment Rating. Understanding this is essential to getting the
crane you need.
MOMENT RATING: Moment Rating is a mathematical equation
determined by the WEIGHT times the LOAD RADIUS.
LOAD RADIUS: This is a measurement from the center of the crane’s rotation
axis to the center of the load in a horizontal plane.
WEIGHT: The amount of weight to be lifted includes all rigging used,
including the travel block, any chains or slings, and the hook.
Cranes with a max lift
capacity of 10,000 Lbs with a 72,000 Ft-Lb. Moment Rating.
72,000 Ft.-Lbs. divided
by 10,000 Lbs. equals 7.2 Ft. This is the maximum load radius with this load.
For a 12 Ft. radius the
maximum load is: 72,000 divided by 12 equal 6,000 Lbs. Note the rapid decline
in capacity as the radius increases.
At a 20 Ft. radius the
capacity is only 3,600 Lbs.
Always consider the size
of the object and that the crane is mounted on a truck. The distance to the
edge of the truck must be included in the load radius.
CONTINUOUS ROTATION: Many crane manufacturers claim to have
continuous rotation, however, the rotation may be limited at 375 or 400 Degrees
at which point the rotation will stop and must be reversed. This limitation
must be considered when positioning the truck to perform the work at hand.
UNLIMITED ROTATION: Liftmoore cranes typically have unlimited
rotation. There is either an electric or electric and hydraulic swivel that
allows this important feature. As a result there is no limitation by a
mechanical or electrical stop on the crane’s rotation.
DUTY CYCLE: Hydraulic crane duty cycles can be nearly
continuous depending upon reservoir size and hoist operating temperature.
Electric crane duty cycles should be limited to 10 to 15% when heavy loads are
being lifted. Auxiliary batteries are required by these cranes.
BATTERIES: All 12V DC powered cranes will benefit by
having a battery as large as possible located near the crane. Motor and
Solenoid life will be extended if an additional battery is mounted near the
crane. The two batteries under the hood of a Diesel engine truck are NOT
adequate to power an electric crane. The DC voltage line loss increases
dramatically as the length of wire is increased and the voltage at the crane
can only be maintained with an additional battery near the crane.
POWER DISCONNECT: Turning off power to the crane will increase the
life of its electrical components. Electrolysis causes corrosion which will
reduce component life and may cause intermittent electrical problems. All
Liftmoore cranes are supplied with a master disconnect switch or a mecon quick
disconnect for disconnecting the crane from its electrical power source.