Keep Things Moving, Part II

   As I noted in last month’s installment, most shops start out with lots of brawn to move their stone around, but there are alternatives to brute force in doing the job.
   Some friends in Ohio – Jerry and his partner Craig – are really doing their research in setting up their shop, They’re looking at the employing overhead or jib cranes to make fabrication life a little easier on them. What they’re quickly realizing is that, by using cranes to move slabs and/or pieces of stone around in their shop, they’ll be able to start out with a smaller staff, and greatly increase the safety factor in lifting stone.
   Their biggest interest, with possibly just the two of them at the start, is having a one-person capability of moving big pieces of stone around in the shop. This can be done if either an overhead or jib crane enters the picture … and vacuum-lifting devices become an integral part of the overall assembly.
   Let’s look at cranes first. The ideal setup is a large monster crane – commonly known as a bridge or overhead crane – stretching across the width and traveling the entire length of a shop. I’ve been in many shops that have an overhead crane, and the common denominator in this type of system is that the shop was designed around the installation of the crane.
   If you’re designing the shop, it’s much easier to incorporate the overhead crane, because supports need to be engineered into the structure of the building. Typically, the track along which the bridge travels must support not only the weight of the crane unit, but also the load being carried. Basically, for a heavy-duty overhead crane that can lift bundles of 3cm stone, you’ll need a unit with copious amounts of mojo … and that will cost lots of money.
   Don’t get discouraged, though, because there are alternatives. There are overhead cranes that can be installed after the building has been erected, and there are many types of overhead assemblies that can work in an existing situation.
   Some of these types of overhead cranes have a slightly lower weight capacity, since you’re retrofitting the unit into an existing structure with weight limitations. Determining factors here for installing an overhead crane are the available width for the bridge, the type of structure you’ll put the tracks on and the building’s foundation size. Most companies that sell overhead and/or jib cranes can send their own engineers to your shop to evaluate its crane-readiness, or refer you to a structural engineer.
   Don’t be disappointed if, in the end, you’re not able to put in an overhead crane. There is another alternative: the jib crane.
   Many more shops use jibs rather than overheads, due to the jib’s lower cost and versatility. I’ve also noticed that, in the last three years, the cost of a decent sized jib crane came way down from pre-2000 levels.
   Jib cranes can be strategically placed in your shop in order to service more than one machine. You can have a jib crane placed at your saw station; it can lift a slab off of an A-frame positioned to hold all of the slabs for the day’s cutting. Once a slab has been cut up into individual pieces, each piece can be lifted off of the saw table by the same jib crane, and be placed on a rolling worktable, or an edge machine that would be within reach of the jib crane. Remember that jib cranes can be ordered with a service radius of 90°, 180° and even 270° travel. This factor makes jib cranes a great alternative when the cost of an overhead crane is just out of the question.
   This is why it’s so important to do your research when planning the workflow pattern of your shop, and plan for one or more jib cranes to be placed in your shop immediately – or in the future. Keep in mind what I said about planning – now or in the future.
   Here’s a tip if you really want to install one or more jib cranes – but your budget requires you to wait until you have the dough on hand to buy the cranes. Pick out the make and model you want to buy, and immediately get the manufacturer’s specs for installation.
   There’s a lot more to installing a jib crane that Liquid Nails® and some mounting bolts. Most jib cranes require a deep footing of solid concrete, and don’t think you can get away with drilling some holes in your existing 4” concrete-slab floor and inserting 6” bolts.
   Most jib cranes require that you dig a pit – on average 2’-3’ square by 4’-6’ deep. This big hole is filled with concrete and, while the concrete is still wet, 3’- to 4’-long threaded J-bolts are inserted into the mix. About 2”-3” of the threaded ends are left sticking up out of the concrete so that when everything is dried & cured, you’ll have a structurally sound base for mounting your jib crane.
   So, for your prep work, decide where the cranes will be set, cut the existing concrete slab out, and dig the pit as if you’re going to pour the concrete right away. (If you’re putting drainage trenches into your new shop area, this is also a great time to dig out the bases for your cranes – since you’ll already be cutting the existing concrete slabs for the trenches.) Then make a ¾”- or 1”-thick hatch cover to be secured down over the jib-crane pit.
   Cover the hatch cover with a waterproof membrane coating, and reinforce the underside with 2×4 or 2×6 studs, so your employees can walk on the covers if need be. When you’re ready to buy your jib cranes, the bases for them will be ready.
   Whether you have an overhead crane or any number of jib cranes, the business end of the lifting is a two-part system of vacuum lifter and electric chain hoist. Check with the manufacturer of the crane for the recommended weight capacity of chain hoist in relationship to the carrying capacity of the crane itself.
   Keep in mind that I am not an engineer (if I had it to do over again, my major in college would have been “engineering,” not “pre-med” and “English”), but it seems to me that the “more-is-better” concept comes into play here. For a dead load of, let’s say, 6 tons max, I’d use a crane with an 8- to 10-ton capacity, with a chain or cable hoist with the same weight capacity. If you don’t max out your equipment’s capability, your equipment will perform longer and better.
   There are many excellent vacuum-lifting assemblies; most will require compressed air in order to operate, although a few models have an electrically operated vacuum system. A vacuum lifter will likely need to be tethered to your existing air system.
   I prefer a lifter with a built-in tilting mechanism allowing a slab to be picked off an A-frame and laid flat on a saw bed. Some vacuum systems offer the tilt feature as an option; some have it as a standard feature. Some systems even have a rotational feature that makes loading a large piece of cut stone into a top-feed line-edge polisher a lot easier that trying to muscle it into position.
   With upcoming trade shows this fall (the second annual ITSS in Las Vegas, and the ever popular StonExpo 2003 in Atlanta) you’ll have plenty of opportunities to inspect all of the latest and greatest cranes, vacuum lift systems, chain and cable hoists, and other ways to get stone around the shop.
   With all of these aspects of material handling in proper use, you could actually fabricate an entire kitchen all by your lonesome – I’ve done it myself – and you can definitely keep things moving in your shop.
   Until next month – Happy Fabricating!
   Kevin M. Padden operates KMPadden Consulting in Phoenix.

This article first appeared in the September 2003 print edition of Stone Business. ©2003 Western Business Media Inc.