26 1 8 Chapter 22 



dimensions shown in figure 22-31. In making the green pallet parts, an effort 

 was made to use only high-quality lumber insofar as possible. Each pallet 

 contained 28.6 nominal board feet of lumber. 



Sixty-nine tough hardened-steel pallet nails were used in assembling the top 

 deck and 42 in the bottom deck. They were pointless, 3 inches long, 0.120 

 inches in diameter, and had four helical flutes. Pallets were assembled from 

 green lumber and nails were hammer driven as shown in figure 22-3 1 . 



Pallet weight. — Pallet green weights when assembled ranged from 93 pounds 

 for yellow-poplar to 128 pounds for cherrybark oak and averaged 1 13 pounds. 

 At test, the pallets (deckboards and stringers) had dried to approximately 12 

 percent moisture content and ranged from 53 pounds for yellow-poplar to 88 

 pounds for mockernut hickory, with an average of 72 pounds (table 22-13). 



Specific gravity. — Data from each deckboard and each stringer of each of the 

 1 10 pallets tested, indicated that specific gravity of the deckboards averaged 

 0.66, and ranged from 0.36 for yellow-poplar to 0.95 for mockernut hickory 

 (based on weight and volume when ovendry). Stringer specific gravity ranged 

 from 0.40 for yellow-poplar to 0.94 for mockernut hickory, and averaged 0.68 

 (table 22-13). 



Pallet stiffness under static load. — The pallets, when equilibrated to an 

 average moisture content of approximately 12 percent, were static tested for 

 stiffness, i.e, for their deflection when loaded in 200-pound increments, for a 

 period of 2 minutes, up to a total of 2,000 pounds. Pallets undergoing test were 

 supported at each corner on 2-inch by 2-inch supports and top-loaded at pallet 

 center point with a hydraulic jack through a spherical seat to a 9/16-inch-thick, 

 12- by 14-inch steel plate with width and length parallel with pallet width and 

 length, respectively. Pallet deflection was measured at the pallet's center direct- 

 ly under the load, and at the center of the pallet's ends and sides. 



Average pallet deflections, after application of the 2,000-pound concentrated 

 load for 2 minutes, were as follows (table 22-13): 



• At pallet center — Average of 0.69 inch with range from 0.50 for scarlet 

 oak to 0.95 inch for post oak. 



• At midpoint of pallet ends at the 13/16-inch end deckboard — Average of 

 0.39 inch with range from 0.28 for scarlet oak to 0.56 for post oak. 



• At midpoint of pallet sides at the outer 1-%- by 3-y8-inch stringer — 

 Average of 0.30 inch with range from 0.21 inch for northern red oak to 

 0.41 inch for post oak. 



To arrive at an index of stiffness, average deflections observed at these five 

 locations in the five pallets of each species were summed; an average index for 

 all 22 species was determined and species expressed as a percentage of this 

 average (fig. 22-32). Among all 22 species, Shumard oak and northern red oak 

 performed best and post oak poorest; the poor showing of post oak was attribut- 

 able to cupping of bottom leading-edge deckboards, causing significant deflec- 

 tion with application of the first 200-pound load increment. Among the six non- 

 oaks of Species Class C, mockernut hickory and white ash performed best and 

 hackberry poorest. Among the five hardwoods of Species Class B, yellow- 



