How to Plan How Much Steel You'll Need for a Sculpture
Kevin is looking at a hemisphere covered with chalk marks that will be the basis of a large sculpture for a commercial development. The new sculpture is based on his smaller Street Urchin contemporary art sculptures. They range in size from Punks, which are as small as an inch in diameter with their Mohawk hairdos (see them on the Web site), to about 18" in diameter. This Street Urchin sculpture will be 5 feet in diameter.
Kevin is starting with a 12" diameter hemisphere with about an 1/8" wall, so it has some strength to it.
With the smaller sculptures, he'd cut a lot of solid metal stock and smooth off the ends with a bench grinder so people wouldn't stab themselves, then start welding. If he needed more spines, he'd just cut and grind more steel stock.
Because these spines will be 24 - 18" long, Kevin needs to figure out how much metal he'll need to buy. So he called the steel yard to find out what they had in stock in 1", 1-1/12", 1-3/4", 2" or something similar. He is looking for pipe with approximately 1/8" wall. The man at the steel yard said they had 1", 1-1/4" and 1-1/2" pipe in stock.
That means that the hole saws Kevin is using as templates are just about right, although they measure on the inside of the saw, not the outside. To determine approximately how many spines he'll need, he starts with the largest hole saw, sets it on the hemisphere, and uses it as a pattern to draw a chalk circle. He moves the hole saw around the hemisphere, drawing circles and distributing what will become the largest spines. Next he uses the 1-1/4" hole saw to draw and distribute that medium size spine, and then he follows similarly with the 1" hole saw to fill out the hemisphere. This gives him a pretty good idea of how much steel to buy.
He came up with 51 feet of 1-1/2" pipe. If the spines are 2 feet long - although some of them will be shorter - he'll need 80 feet, because the pipe is sold in 20 feet sections. He needs 40 feet of the 1", and [EDITOR'S CORRECTION:] 100 feet of the 1/1-4".
Once he has his pipe, to terminate it, he can "orange peel" the steel by cutting slices, bending them over, and welding them solid, then grinding them all smooth. Or he could just buy hemispheres to match the diameter of the pipe, weld them on, and grind their edges smooth.
Kevin didn't just use solid metal stock for the spines instead of solid metal stock primarily because of weight. The sculpture will be shipped to Florida, and who wants to ship all that extra solid steel? The exponentially higher weight also might overload the hemisphere.
Kevin has also been thinking about how to lift the artwork, too. His current idea is to weld a nut to the hemisphere itself, to which a 1-1/2" threaded pipe - which he can buy or make with his tap and die set - with a lifting ring can be screwed. Once the sculpture is in place, the lifting ring spine substitute can be replaced with the decorative spine that belongs there, which is simply screwed into place and snugged up.
Now that Kevin has his shopping list, he'll call the steel yard, which will send over a truck with a load of pipe on it.
Kevin says you'll be able to watch the sculpture develop on his Web site, after which it'll be crated and shipped to the Florida development, Harbourside Place. Kevin points out that the sculpture will probably weigh several hundred pounds, so he'll probably have a base on the sculpture that can be bolted to the crate, that can then be used to secure the artwork on the site.
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