Marion 8750 Dragline (now Bucyrus International)

Problem: To turn the massive weight of this dragline requires a large gear and 16 drive pinions. There are 4 of this model of dragline in the world and early on it was found that there was not enough clamping force holding the segments down.

The gear is made up of 24 segments, all bolted to the base in a circle with 22 long, highly torqued studs. There was no solid retainer and some of the segments would slide back out of position which caused gear tooth misalignment and subsequent segment damage. The manufacturer, at great cost, had already replaced 28 segments under warranty on this machine alone and had to find a permanent solution soon.

Solution: Superbolt®, Inc. was approached to provide a bolting system that would both increase the clamping force and elasticity of the joint without having to modify the existing segments.

Along with the use of high powered Superbolt® tensioners on the top and Flexnuts on the bottom, Superbolt® designed and manufactured studs that had a yield strength of 155,000 psi. The studs were easily fit into the existing segments and tightened to 105,000 psi stud load using 1/2" air impact wrenches and hand held torque wrenches to confirm the torque. While substantially increasing the clamping force per stud, the flexing action of the Superbolt® tensioner and flexnut reduced stress concentrations in the threads, doubled the elasticity of the joint and distributed the load out to a larger area away from the bolt hole.

Marion (now Bucyrus International) has purchased the Superbolt® solution for the 3 other machines, putting to rest an expensive bolting problem.

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  Multi-jackbolt tensioners installed.