A GUIDE TO THE BASIC REQUIREMENTS WHEN PURCHASING A CRANE
TRUCK MOUNTED CRANES
The cranes we are discussing are generally known as hydraulic truck loaders and are usually fitted onto trucks or semi-trailers and consist of: a base, mast, boom, secondary boom, extension(s) outriggers and hydraulic cylinders
Most makes of cranes are similar in size and shape however, much like trucks there are fundamental differences for diverse applications, general purpose, bricks, scrap, timber, construction, rigging etc
Most makes of cranes are similar in size and shape however, much like trucks there are fundamental differences for diverse applications, general purpose, bricks, scrap, timber, construction, rigging etc.
To verify the size crane you need we have to establish the ton meter. The size (lift capacity) of a crane is known as ton meter, this is determined by what it can theoretically lift at one meter.
Now cranes cannot lift a weight at one meter (Too close to the vehicle) however this is the internationally accepted standard of measure.
Let’s say a crane is able to lift 2 tons at 6 meters then theoretically it can lift twelve tons at one meter (2 x 6 = 12) it is then a 12 ton meter crane.
It is very important to determine the reach required and the weight that will be lifted at that reach. (See lift and reach)
Most cranes come standard with a one extension horizontal reach of between 5 & 6 meters. If a longer reach is required more extensions are added. Bear In mind the further a crane extends the less it will lift.
Vertical reach. If required. A crane’s reach is determined horizontally, to determine the approximate vertical reach (+- 75 deg straight up) simply add three meters to the horizontal reach. This is the height from the ground to the top of the chassis, (+- one meter) the height from the base of the crane to the top of the mast (+- 2 meters) plus whatever the horizontal reach of the crane.
e.g. 1 meter (Ground to chassis) + 2 meters (Height of mast) + 6 meters (Horizontal reach) = 9 meters vertical.
There are many different applications but let’s concentrate on the most popular.
This is important. Is it to be used for general purpose, or for a specific function such as bricks, timber, rubble, scrap, etc.
Standard hook applications have a hook on the end, and used for general purposes, typically operated by standing next to the vehicle.
Grab Applications are fitted with a grab in place of a hook and used to lift bricks, timber, scrap, rubble etc., the operator normally sits on top of the mast. (Known as top seat control)
CRANES FOR BRICKS REQUIRE:
Brick grab (to clamp the brick stack) Rotator (Fits between the end of the crane and the grab and controls the grabs rotation) Top seat (The operator sits on top of the crane) Grab lines (hydraulic hoses that operate the rotator and brick grab)
Timber Grab (To clamp timber poles) Rotator, Top seat, Grab Lines.
RUBBLE OR SAND APPLICATIONS:
Clam shell bucket, (To lift sand or rubble) Rotator, (Top seat optional) Grab Lines.
Scrap grab, (For lifting scrap metal) Top Seat, Grab Lines.
To operate a crane needs a PTO (Power Take Off) pump and sub frame.
A PTO is a mini gearbox that fits onto the vehicles transmission and drives the pump. The PTO can be supplied by either the vehicle dealer or crane supplier.
A pump fits onto the PTO and forces hydraulic oil through the crane which allows the various parts to Operate.
A Sub frame is a steel structure on which the crane rests, it runs on top of the chassis, to strengthen it and prevent cracking.
Note: Clarify who will fit the PTO and build the sub frame. Usually the vehicle dealer supplies the PTO and the body builder the sub frame.
Generally there are three options with different costs: Cab mounts (Right behind the cab) Rear mounts (At the rear of the chassis) and Trailer mounts (Usually in the middle of the trailer)
As regards the space required for mounting a crane, the rule of thumb is to allow a gap of approximately one meter. Obviously this will increase with larger cranes.
How to establish the size crane you need for a particular application.
It is very important to determine the reach required and the weight that will be lifted at that reach.
Ask this question. What is the average weight being lifted and at what distance.
The formula is weight x distance = Ton meter.
If you are lifting three tons at five meters simply multiply 3 tons x 5 meters = 15 ton meter crane
If three tons is to be lifted at eight meters then 3 tons x 8 meters = 24 ton meter crane with an extra extension (Remember standard reach is +- 6 meters)
If you want to lift next to the vehicle then work on two and a half to three meters which is commonly regarded as being next to the vehicle
In the case of grab applications include the weight of the grab and rotator plus the weight of the load (See applications)
eg. A load of bricks weighing 1800kg needs to be lifted @ six meters.
So, 1800kg (Weight) + 230kg (Grab) + 25kg (Rotator) = 2075kg x 6 meters = 12.330 ton meter.
The nearest crane to that will be a 13 – 14 ton meter (It is always better to over spec than under).
WE WILL BE ASKING
What vehicle will it be mounted on?
What is the application? (Standard hook or grab?)
What is the average weight being lifted?
What is the average distance needed?
What is the minimum and maximum reach required?
Where will it be mounted? (Behind cab, rear or trailer)
Who will supply the PTO? Who will supply the sub frame?
Remember: The weight of a crane reduces payload.
The size of the crane should complement the size of the vehicle. A heavy crane on a light vehicle will reduce payload, cause instability, extra wear on tyres, springs and chassis. A lighter crane on a heavier vehicle is acceptable.
For technical advice, pricing, vehicle load charts, etc. please contact directly. It will be a pleasure to assist you.
Disclaimer: The above technical information is approximate, there are many variations and applications, this is only a guide intended to provide information on the basic requirements when purchasing a crane.
The Crane Clinic Team