Tower Crane are also characterised according to their mounting configuration. They are available as static bases, rail-mounted units and mobile units.
Static bases -There are three main types of static bases.
In-situ base – The crane is mounted on special corner angles, frames or an expendable tower section, cast into the concrete foundation block.
On own base – The crane is mounted on its own base section or chassis which, without wheels and travelling gear, but with ballast, stands on a concrete base.
Climbing base – The crane is supported by the structure which it is being used to construct, and to which it is attached by climbing frames and wedges. The height of the cranes can be extended as the height of the structure increases by means of climbing supports attached to the frames. Climbing support can be metal ladders, rods or tubes. A climbing crane may be mounted initially on a fixed base and its support be later transferred to climbing frames and supports.
Rail-mounted units – The cranes are mounted on a chassis frame which is supported on rail wheels. The wheels are usually double flanged. When all wheels are removed, some tower cranes can be used as static-based cranes
Mobile units – The mobile mounting configuration consists of truck-
mounted, wheel-mounted or crawler-mounted units.
Truck-mounted tower cranes – Tower cranes mounted on truck or lorry chassis are available. It is essential that this type of crane has its outriggers extended. The outriggers should be securely set up and level on its jacks when handling loads.
Wheel-mounted tower cranes – These are not normally self- propelling and may be moved by towing by a suitable vehicle. They are provided with stabilizers or outriggers and jacks which should be set (and the wheels either removed or raised clear of the supporting surfaces) before commencing erection or lifting operations.
Crawler-mounted tower cranes – There are two principal types of crawler bases used on this type of tower cranes. One is a twin- track type which is mounted on one pair of crawler tracks. The crane requires outriggers to be extended and jacks set when handling loads. The other is the straddle-type which is mounted on four widely spaced crawler tracks, each of which can be adjusted to height. Both types of tower cranes should be set firm and level when handling their rated safe working loads. In general, they do not have the same freedom of mobility as for example crawler-mounted mobile cranes. Reference should be made to the crane specification and to the manufacturer regarding conditions under which these machines may travel in their erected state.