In technical terms, Jacking Load Shoes are load-compensating skid shoes, designed for use with a hydraulic skidding system to increase the system's load capacity, versatility, and load support.
In practical terms, they may just be the best idea in heavy load moving that you've never heard of. Read on to learn more about how Jacking Load Shoes work, and how they can facilitate some very heavy, very challenging moves where other solutions may not be available.
In a typical jack and slide operation, the load rests directly on steel skid shoes, ideally with a compressible material like rubber or wood in between to help distribute the weight and avoid point-loading. For most operations, this setup works great and nothing further is needed. For certain jobs though, some additional support is needed: for example, if the load is extremely heavy, large and fragile, sensitive to tilting, and/or with uneven weight distribution. This is where jacking load shoes may be an ideal solution.
The concept behind jacking load shoes is simple, but powerful- each skid shoe supporting the load has a heavy-duty hydraulic cylinder inside it, so the lift points can be individually raised and lowered with precise control. This arrangement unlocks several capabilities:
· The load’s horizontal level can be fine-tuned
· The load can be raised or lowered as needed to navigate clearance restrictions
· The load can be precisely distributed across all support points, and prevented from wobbling
(Photo) 200 feet underground, a 670-ton tunnel-boring machine (TBM) is being assembled directly onto a set of four Hydra-Slide JLS250 Jacking Load Shoes. The HT500 skidding system is ready to slide the TBM into its final position as soon as assembly is complete.
Credit: PSC Crane & Rigging, Piqua, OH
Let’s take some time to talk about load distribution. In engineering terms, a load resting on four points is considered statically indeterminate, meaning it’s not possible to know for sure how much weight is on each point. As the load moves, it’s probable that it will wobble to some extent, causing one or more points to become completely unloaded, and potentially causing one or more points to become overloaded.
As an analogy, think of a four-legged table, perhaps at a restaurant- sometimes you’ll come across one that’s relatively stable, but more often than not it’s wobbly until you wedge some napkins under one leg. It’s a bit of a silly analogy, but quite accurate! Now imagine if you could remotely raise or lower each leg of the table independently- it would be much easier to balance. That's what the hydraulic lift cylinders inside jacking load shoes allow you to do. Furthermore, the hydraulic cylinders are usually connected to one another in three groups, forming a three-point suspension. A system in three-point suspension is analogous to a table with three legs instead of four- and a three-legged table will never wobble, even on a rough surface.
The jacking load shoes also have pressure gauges on each lift cylinder, to provide a direct measure of the amount of load on each point. To summarize: supporting a load on jacking load shoes ensures that the load is always supported and cannot wobble, and it also allows the rigging crew to locate the load's center of gravity and fine-tune the load distribution.
For some additional background information, you can find our full rundown on hydraulic skidding systems here.
Get in touch to discuss your specific situation with us - we love to explore solutions for the most challenging moves.
