tower with trapezoid sides
Sunday, August 10 2014
I was all by myself at the house today, so I took some recreational pseudoephedrine, did some web work, and spent much of the afternoon building the five-foot tower I am making from pressure treated lumber. I've made three similar towers in the past, but those have always had the overall shape of a box, with right-angle corners and lots of diagonal angle-bracing. I wanted to make today's tower trapezoidal in all elevations. Trapezoids are less likely to tip over when pushed from the side, which is a bonus for a water tower subject to possibly-strong winds. Also, after making that small stool for Celeste the kitten, I've discovered that trapezoidal shapes require significantly less angular bracing to stay rigid. While the slope of ths sides of Celeste's stool had been 10 degrees off of vertical, for the tower I was making today, the slope of the sides would be no more than five degrees off of vertical. I figured with such a small slope, I'd be able to flex the two-by-four legs in their most-flexible dimension the amount necessary to achieve the 5 inches of distance their feet would need to have from where they would have needed to be in an absolutely orthogonal design. In the other dimension, of course, the two-by-fours couldn't be flexed much at all, so they had to be attached to the platform at the correct angle. Since the process of bending the legs out by five inches each would require a lot of force, I supplemented the deck screws with carriage bolts at the attachment sites of all four of the legs.
It turned out that I'd overestimated the flexibility of the two by fours along their most-flexible dimension. Instead of being able to flex each leg by about 5 inches, the best I could do was 2.5 inches. So the tower ended up being much more orthogonal in the east and west elevations than it was in the north and south elevations. I was delighted to discover that even with such slight slopes of its legs, the tower was completely solid without any angular bracing at all, though I'll probably add some if only for decoration.
Meanwhile Oscar keeps showing signs of greater and greater adjustment. Today I saw him exploring down in the brush and saplings just east of the house (the region into which Celeste fell when she toppled off the side of the east deck). He scampered away when he saw me looking at him, suggesting he either didn't recognize me in that context or he thought he was being busted for wandering off too far. Oscar was apparently down there deliberately, because he returned to the house soon thereafter.
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