Four-Stringer Wood Pallets Save Dollars By Decreasing Buckling of Gallon Cans

Pallet studies were made in large commercial canneries and store-houses in central California, where large gallon-size cans containing fruit or vegetables were often stacked as much as 20 feet high on 3-stringer western softwood pallets and moved in several stages by fork-lift. In this handling, many cans, particularly the larger ones, were critically damaged by buckling, and often had to be sold at approximately half price. Because of the magnitude of these losses, amounting to hundreds of thousands of dollars per year, several alternate types of pallets were considered. The 3-stringer pallets commonly used, with nominal 2 by 4 (1-5/8 by 3-5/8) stringers supporting 7 nominal 1 by 6 (3/4 by 5-1/2) boards for decking, were found inadequate, by test as, well as by theory, for handling and storing the large, heavy, number 10 cans. After considering several types of improvement, it appeared that simply adding an extra stringer would be most effective as well as economical. The original 3-stringer pallet deck boards, when fully loaded, were bent badly and over-stressed between and over the stringers, causing tilting of the cans and increased bending stresses of the deck-boards, often above the elastic limit of the western softwoods generally used, and occasionally above the ultimate stress. Four stringers were recommended as being the most favorable improvement, and were tested in comparison with the 3-stringer pallets, using 25,088 cans. Reducing the unsupported deck-board spans between stringers tripled the effective load capacity and quadrupled the stiffness of the deckboards, reducing deflections and tilting, and cutting down the number of badly buckled cans by more than 50 percent. Addition of an extra stringer would lead to a saving, over a period of 5 years, of more than $20 for each additional dollar invested in the fourth stringer.

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