Caught in the Crab's claws
'The crab', a new cryo magnet transport vehicle, starts work at CERN. Produced by the ESI group of EST division and built in Finland, it has the job of transporting LHC magnets in buildings SM18 and SMA18.If you see a huge crab scuttling around building SMA18 don't be afraid! It is the new Cryo Magnet Transport Vehicle produced by the ESI group (Engineering Support for Infrastructure, EST Division) for CERN's LHC project and built by Finnish Company ROCLA. This orange vehicle, nicknamed 'The Crab', is perhaps the strangest piece of equipment used for the construction of LHC magnets. It will start work at the end of this month.
The crab will be used to transport LHC cryo-magnets and their components in the assembly and preparation building, SMA18, and test building, SM18. It has many capabilities that will allow CERN staff and contractors transport magnets between the two buildings and to locate them in the right position on the test beds.
The crab in action during its first tests on 8 February.
How does the crab manage to do this? It is a serious crab: almost 10 metres long, 3.5 metres wide and nearly 3.5 metres high. It is battery powered and it can reach 4 km/h - reduced by a factor of two when the vehicle is under load. It is driven by remote control with two operating steering modes of all the wheels - parallel and anti-parallel - which provide excellent manoeuvrability.
By semiautomatic or manual control, the crab can be driven from different buildings and it can also move on magnetic tracks embedded in the floor of buildings SMA18 and SM18. These tracks are parallel to the test beds where magnet components have to be assembled and tested. Thanks to these tracks the crab can move in the right direction with an accuracy of few millimetres, using sensors that are placed on the small wheels under its four legs.
The vehicle has been programmed to reach the test beds and put the magnet in the right position, with a precision of 1 millimetre. The maximum it can carry is 37 tonnes.
The new vehicle at work as a shuttle between buildings SM18 and SMA18.
The crab provides different types of handling options depending on the equipment to be transported; the longest magnets to be transported (17 metres) are supported at four different points, preventing deformation.
Thanks to several electric motors situated in different parts of the vehicle, it can move the magnets in the horizontal and vertical planes and can also tilt them along their longitudinal and lateral axes.
In this way the vehicle operators can transport six types of equipment: the cold mass, the vacuum vessel, the assembly of the two (called a Cryo-Dipole), and three different types of arc quadrupoles called Short Straight Sections.
When the different components arrive outside building SMA18 they are carried inside by the crab. Then they are installed on the assembly beds where they have to be checked, prepared, and assembled. When ready they are carried by the vehicle to building SM18 and installed on the test beds. After the test, the magnets will again be transferred to SMA18 where they are either prepared for temporary storage or for final installation in the tunnel.
