Table O-11-Strength and Dimensions for Wood Ram Props
Size of timber, inches1 | Square inches in cross section | Minimum allowable crushing strength parallel to grain, p.s.i.2 | Maximum static load within short column range3 | Safety factor | Maximum recommended weight of forging hammer for timber used | Maximum allowable length of timber, inches |
4 * 4 | 16 | 5,000 | 80,000 | 10 | 8,000 | 44 |
6 * 6 | 36 | 5,000 | 180,000 | 10 | 18,000 | 66 |
8 * 8 | 64 | 5,000 | 320,000 | 10 | 32,000 | 88 |
10 * 10 | 100 | 5,000 | 500,000 | 10 | 50,000 | 100 |
12 * 12 | 144 | 5,000 | 720,000 | 10 | 72,000 | 132 |
1 Actual dimension.
2 Adapted from U.S. Department of Agriculture Technical Bulletin 479. Hardwoods recommended are those whose ultimate crushing strengths in compression parallel to grain are 5,000 p.s.i. (pounds per square inch) or greater.
3 Slenderness ratio formula for short columns is L/d = 11, where L = length of timber in inches and d = least dimension in inches; this ratio should not exceed 11.
29 C.F.R. §1910.218