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I have almost perfected the art of underestimating the time required to complete a task. I carefully considered each step in the process of erecting a carport and allocated what was clearly adequate time for every task. I then summed these times, and decided I could complete the job by taking two days of vacation. AJ came to help, and we spent the two vacation days, plus two weekend days, and are only about 80% complete. There is a psychological condition called, "delusions of grandeur." I wonder if it applies to this situation...
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I actually needed another week before having AJ come, but his spring break was fastened to the calendar pretty securely. I only had two trusses completed, and the pieces for the third one cut when he arrived. |
| Welding a truss is pretty much a one person job, so he worked on setting the support poles in the ground. Each post (a 2-3/8 inch, schedule 40, steel pipe) is 13 feet in length. We dug holes approximately 18 inches deep, and then, using a fence post driver, drove the pole another 6 to 10 inches down (the ground slopes) before setting them in concrete (80 lbs. per post). |
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AJ purchased a leveling device (perhaps called a plumb level [not to be confused with a strawberry level]) designed specifically for this purpose, and it turned out to be very functional. |
| Using that, plus a line level and a couple of pieces of string, we got the posts aligned with each other, plumb, and the tops level. |
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Most of my construction looks rather "haphazard" (to put it kindly), but these supports turned out very well, and I'm quite pleased with them. |
| The truss supports are constructed out of channel and angle iron. I was in a hurry and didn't spend a lot of time making sure that what I designed was what I fabricated. As a result, the end product is not exactly as I would make it if I were to do it again. The channel is too shallow such that the weight of the trusses (at least some of them) sits not on the channel iron (made of 1/4 inch steel and secured to the post by 8 inches of welding), but on the angle iron (made of 1/8 inch steel). The result is that if the truss were to buckle and sag in the center, the rotation could tear the relatively thin angle iron and peel it off the channel. The solution (that doesn't include hours of grinding) is to tie the top of the truss to the support post, such that that rotation cannot occur even if the truss buckles. There are a number of ways to accomplish that, but none of them are particularly esthetically pleasing... |
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At this point in the construction, the structure is prone to harmonic vibrations. That is, if you push then pull on it with the right rhythm, it sways with some degree of vigor (and continues to sway long after cessation of the motive forces). To counteract this tendency, I plan to run bracing between the poles where they stick up higher than the roof (if the bracing were below the roof line it would be in the walkway). The two obvious options are to build three "Xs," one between each adjacent pole, or to construct a single "X" spanning all four poles. Which of the two designs will provide the greater stability is not intuitive. Any thoughts? |
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We managed to drop two of the trusses while installing them. One suffered no damage, but the second deformed, with a section of rebar that runs along the top of the truss buckling between two of the nodes. It was relatively easy to hammer it back straight, and reinforce it with two additional pieces of rebar, but the fact that it failed gave me pause... I think I am wishing I had used #4 (1/2 inch) instead of #3 (3/8 inch) rebar. Isn't this a pretty weld? The web gives the density of snow as being between 5.2 and 20 pounds/ft3. Assuming six inches of snow with a density of 15 pounds/ft3, the roof will probably, at some point, be called upon to support a static load of around 2430 pounds, or 607 pounds per truss. If you include the weight of the 800 pound roof (probably over estimated), that final figure rises to 807 pounds per truss. AJ and I parked our combined 400 pounds in the center of the span and bounced, with no deleterious effect (although it did deform perhaps an inch or so). Is 400 pounds bouncing in the center of a span equivalent to 800 static pounds distributed across its' width? I'll let you know in a year or two... |
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I purchased the "I" beams off craigslist, and took all the gentleman had. After bring them home, I did a quick eyeball measurement, and drew up the roof plans. This is the amount I had left over. Occasionally, I get lucky. |
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We had a number of grass fires started by the molten metal/slag spatter from the welding process. Most of them would hardly burn, but there were a couple of times when they took off with vigor. One of those time, AJ hollered for me to get the camera but, fortunately, I chose to get the hose instead. When you are wearing a welding helmet, it is difficult to see a fire. You usually feel it, smell it, or hear it first. |
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AJ suffered two falls while working on this project, but fortunately wasn't injured by either. One was from the rack on the pickup into its bed, and the other was off a stand while lifting a truss (which by some minor miracle, didn't land on him). I'm glad he wasn't hurt, but images like this might make a person wonder how he was so lucky. |
| I enjoy welding, which may be the reason I undertake projects like this, but I think I may have over done it this last week. I'm tired, but I'm pretty sure that feeling will pass... |
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A couple of months back, I acquired a spot welder. I chose the 220 volt model, because it would weld thicker materials. I wired up a 220 V circuit, and then haven't gotten back to experimenting with it. Other than watching robots welding automobiles on TV, I have never seen one work, nor know any of the theory. But, when we tried it out, fastening pieces of perforated angle iron together, it seemed to work quite well. Still, I have qualms about the strength of the welds. So much to learn, so little time... |
| I'm soooo close and I really want to finish this project, but one thing after another seems two be keeping me form getting back to it. Give me patience, Lord, but hurry... |
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