How do you make a magnetic crane?

The electromagnet is a separately-sold accessory, and adds to the array of c ontrols in the operator"s cab ( Kwan Yin- patroness of Crane engineers!)- well one more arm might be needed to conn the magnet hoist- to turn it on and off. The usual type is a (Doughnut) or circular magnet-which is of course electromagnetic- and requires a separate power line, geneator, etc which would take up space in the the cab and in the case of the generator, the body structure of the crane. They have been around since the early l900"s but have their limitations- stainless steel is non-magnetic , for example, they also generate heat and are fairly heavy for lifting power. so it goes. the Roaring junkyard in Williamsport, PA used one on a thirties vintage crane on the back of a Mack truck ( this customized). They had three generations of cranes in that yard- one old Steam, in the back- the gas truck mounted one just described, and a then, spanking-modern Lorain yellow Diesel truck c rane.