Gardening Articles: Care :: Tools & Equipment
The Inside Scoop on Shovels (page 3 of 4)
by David Lyon
Early studies of shovel design efficiency in coal mining concluded that shovels should have short handles and that shovelers could work at about 21 scoops per minute, moving loads of 11 to 24 pounds. Of course, these studies also suggested that the best position for shoveling was to kneel--appropriate perhaps in a mine hole but rarely for gardeners.
About 10 years ago, when industrial engineer Andris Freivalds, a professor at Pennsylvania State University, studied design efficiencies of shovels, he provided scientific support for common practice. He tested square versus rounded blades, short versus long handles, weight of shovels and varying degrees of lift. He measured energy expenditure by analyzing gas composition of the subjects' respiration, looked at compression forces in the lower back and gathered the diggers' subjective ratings of perceived exertion.
We'll skip the detailed data and complex mathematical analysis and get straight to Freivalds's useful recommendations for "the design of the common, all-purpose shovel." They're also good guidelines for buying a shovel. He suggests a lift angle of "approximately 32 degrees," which compares favorably with the standard 37 degrees. Lift of 48 degrees reduced back strain considerably because the subjects could stand up straight, but the material kept falling off the shovels when they went to move it. Freivalds also found a long handle far superior to a short one for scooping and moving earth from one spot to another because it promoted upright posture.
He recommended a "large square-point blade for shoveling" and a "round-point blade for digging." The square blade carries a larger load, whereas the rounded blade presents a more efficient cutting surface. The traditional square blade of a spade may derive from its historical use as a tool to cut peat, sod or soft garden soil, none of which provide much resistance to the blade.
Based on his studies, Freivalds also recommended minimizing weight without sacrificing too much strength or durability. In his sand-shoveling task, the hollow-back construction allowed subjects to work longer with less fatigue.
When you apply Freivalds's recommendations to the classic American shovel, it passes the test as an excellent all-purpose tool--the best choice if you're going to get by with just one. But certain tasks go easier with specialized tools, which is why manufacturers produce dozens of designs in varying grades.
Two variations on the shovel and spade are especially handy. Sometimes called floral or border spades, they're simply scaled-down versions of the garden spade. My border spade, for example, has a 5- by 9-inch blade, compared with a standard 7- by 12-inch model. It's especially useful for tasks in cramped quarters, like digging perennials among overgrown shrubs. The border spade is also a good fit for gardeners who tire quickly using larger versions. Another useful variation is the ditch or irrigation spade. It has a long, slender blade and a short handle--perfect for digging narrow trenches.