2620 



Chapter 22 



poplar and black tupelo performed best, and sweetgum poorest. Yellow-poplar 

 and black tupelo, both species Class B woods, had less deflection than white 

 oak — which had deflection average for all 22 species. 



Impact rigidity of pallets. — After static test, and while held at approximate- 

 ly 12 percent moisture content, the pallets were suspended by one corner, and 

 released by a solenoid-operated mechanism to drop from a height of 40 inches 

 (between lowest pallet corner and the impact surface) onto the smooth surface of 

 a massive concrete block. This procedure was repeated 12 times, always drop- 

 ping the pallet onto the same pallet comer. The changes in length of each of the 

 four pallet diagonals — between marks near the four comers of both pallet top 

 and bottom — were recorded after each drop. No major failures occurred except 

 on one sweetgum pallet where the impacted end of a bottom deckboard 

 fractured. 



Table 22-13 — Weight of 48- by 40-inch nailed hardwood pallets of 22 species, specific 



gravity ofdeckboards and stringers, and pallet deflections at five locations resulting from 



a 2,000-pound concentrated load applied for 2 minutes to the center of the top deck while 



the pallet is supported at the four corners (Data from Stern 1978)' 



p^jlgj Specific gravity^ Deflection 



Species weight^ Deckboards Stringers Sides'^ Ends^ Center 



Pounds Inch 



Ash, green 69 0.63 0.61 0.28 0.37 0.65 



Ash, white 71 .63 .65 .25 .35 .57 



Elm, American 64 .58 .61 .34 .40 .79 



Elm, winged 80 .74 .75 .30 .37 .64 



Hackberry 65 .56 .61 .34 .49 .83 



Hickory, mockemut 88 .86 .88 .22 .35 .55 



Maple, red 72 .61 .63 .34 .46 .78 



Oak, black 81 .73 .73 .32 .39 .72 



Oak, blackjack 81 .72 .77 .29 .49 .82 



Oak, cherry bark 78 .73 .75 .31 .35 .65 



Oak, laurel 72 .75 .72 .32 .34 .69 



Oak, northern red 76 .66 .72 .21 .34 .51 



Oak, post 80 .72 .78 .41 .56 .95 



Oak, scarlet 77 .70 .68 .26 .38 .62 



Oak, Shumard 77 .74 .72 .22 .29 .51 



Oak, southern red 71 .64 .69 .23 .37 .61 



Oak, water 76 .70 .72 .28 .33 .59 



Oak, white 84 .77 .80 .33 .39 .69 



Sweetbay 57 .51 .54 .37 .36 .83 



Sweetgum 61 .54 .58 .33 .44 .82 



Tupelo, black 62 .54 .57 .29 .42 .69 



Yellow-poplar 53 .45 .43 .29 .40 .65 



Average 72 .66 .68 .30 .39 .69 



'See figure 22-31 for pallet design; each value is the average for five pallets. 

 ^At approximately 12-percent moisture content. 



■^Based on weight and volume when ovendry; each value is the average for five pallets based on 

 data from each stringer and each deckboard of each pallet. 

 '^Midpoint of the sides at the outer edge of the outer stringer. 

 ^Midpoint of the ends at outer edge of the 13/16-inch end deckboard. 



