Abstract: A mobile crane intended for carrying heavy loads has a slewable upper chassis which is rotatably mounted on a carriage by a conventional rotatable connection and in order to transmit loads greater than the connection can withstand, there is an additional rotary mounting. The additional mounting comprises an inner frame with cantilever arms between the upper chassis and the carriage. The upper chassis is detachably bolted to the arms and the arms have rollers which run in a circular rail fixed to the carriage. The rail has a greater diameter than the width of the carriage to enable it to transmit the heavy loads and moments, but to keep the crane within the statutory width limits for transport by road from site to site, the parts of the circular rail which project beyond the sides of the carriage are detachable. When these parts are detached for transport, the rollers on the cantilevers engage with the remaining parts of the rail at the front and back of the carriage.