A guide to the basic requirements when purchasing a crane

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

STANDARD crane with one extension

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.

View Schematic of a crane

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.

CRANE WITH VERTICAL REACH

It is very important to determine the reach required and the weight that will be lifted at that reach.
(See lift and reach)

crane with extensions

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.

eg. 1 meter (Ground to chassis) + 2 meters (Height of mast) + 6 meters (Horizontal reach) = 9 meters vertical.

There are many different applications but lets 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.

brick grab

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 cranes:

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 cranes:

Scrap grab, (For lifting scrap metal) Top Seat, Grab Lines,

timber grab scrap grab brick grab clamshell grab rotator

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

cab mount rear mount trailer mount with top seat

Lift and Reach

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.

It’s this easy

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)

Brick grab +-230 kg
Timber grab +- 90 kg
Scrap grab +- 155kg
Clamshell +- 160kg.
Rotator +- 25kg

eg. A load of bricks weighing 1800kg needs to be lifted @ six meters.

So, 1800kg (Weight) + 230kg (Grab) + 25kg (Rotator) = 2075kg x 6 meters = 12330 ton meter.

The nearest crane to that will be a 13 – 14 ton meter (It is always better to over spec than under)

exceptions to the rule

Shipping containers, tanks, cable drums, transformers, machine tools etc.

crane with weight and reach

Shipping containers & tanks are relatively light but bulky so a larger crane is required to reach over them and extend further to prevent damage to the hydraulic cylinders.

Cable drums, transformers & machine tools are not only bulky but tend to be heavy so when calculating the size crane it is important to work on a minimum lifting distance of four meters from the side of the vehicle.

Note: For these types of applications it is always best to consult with the crane supplier.

Establish the following

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?

Bear in mind the following when costing

Cost of crane
Cost of pump
Cost of PTO
Cost of sub frame
Cost of mounting (Cab, rear or trailer)

With grab applications include these extra costs

Cost of grab,
Cost of rotator
Cost of top seat

Remember: The weight of a crane reduces payload.

The size of the crane should compliment 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.

Below are the most popular ranges of cranes 3 – 24 ton meter and the minimum recommended vehicle GVM

For technical advice, pricing, vehicle load charts, etc. please contact us 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.

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