New Jaso Low-Top Tower Crane Lifts Up to 52.8 U.S. Tons
June 10, 2020 – Tower crane manufacturer Jaso has unveiled its second-largest low-top tower crane, the J800.48.
The new model is second only to the J1400 that Jaso introduced last year. It is part Jaso’s Low Top series of tower cranes that are designed for heavy-duty operations and feature a short tower head.
Jaso says that the clearance height of its Low Top cranes is essentially the same as those of flat-top tower cranes. That’s because flat top cranes need deeper jib and heel sections to match the strength provided by the short but sturdy jib tie Jaso uses on its low-top models.
Furthermore, says Jaso, using a strong jib pendant eliminates the problems generated by deflection, whereas the jibs of flat-top cranes typically need more steel to achieve the same stiffness.
During erection, the section with the pendant attached is lifted in one piece with the first two sections, forming an extremely short 75.5’ jib. The rest of the jib can be assembled in 8.2’ sections to reach the 262.5’ maximum jib length.
These 8.2’ jib intervals give the J800.48 great versatility, which can be beneficial when several cranes are operating in the same area.
The crane’s modular counterjib can be assembled to one of four lengths, depending on the length of jib being installed. The shortest counterjib tailswing is 61.0’. The longest tailswing, which comes from using all four counterjib sections, is 91.9’.
The new J800.48 can free stand to 241.5’, working with single reeving and using standard tower sections that have a cross section of 7.1’x7.1’ and are 18.4’ long.
Using stronger TSP20-5.6 sections, which have the same 7.1’x7.1’ cross section, allows maximum under-hook heights of 333.7’ with the 75.5’ minimum jib length, or 296.9’ with the 262.5’ maximum jib length.
A new feature offered on the J800.48 is the ability to mount different trolleys for different capacities. The ST-SR trolley has single reeving, a maximum capacity 26.4 U.S. tons, and 4.5- ton capacity at the tip of the 262.5’ jib.
The ST-DR trolley uses double reeving, has a maximum capacity of 52.8 U.S. tons, and can lift 3.6 tons at the tip of the 262.5’ jib.
The special SR trolley is designed to work exclusively with simple reeving for higher load capacity at the jib tip. It has a maximum capacity of 26.4 U.S. tons and can lift 5.6 tons at the tip of the 262.5’ jib.
The standard hoist motor is 150 hp, and the optional 180-hp motor gives a maximum line speed of up to 492 fpm. In addition, the hoist winch comes with a grooved Lebus drum designed especially Jaso. It holds enough rope for a 1,492’ hook height when the crane is using single reeving, and up to a 908’ when the crane is double reeved.
Optimized component sizes and weights make transportation and assembly easy. The complete crane can be transported in standard 40’ containers, so there’s no need for open-top or flat-rack units. Low component weights minimize axle loads and enable the crane to be assembled by a smaller mobile crane.
The J800.48 has been designed to delivery the reach and capacity needed by new construction technologies and building systems. On the one hand, for PPU loads, which generally call for lifting 19.8 to 23.2 U.S. tons at a 131’ radius on a 196.9’ jib, the performance of the J800.48 is excellent.
The same is true for the PPVC (prefabricated prefinished volumetric construction) system, which requires lifting 38.5 to 44 U.S. tons on shorter jibs, says Jaso.
