The Megalith Movers Prehistoric Engineering
Blog 22nd August 2015    Last week we made some progress in our thinking as a result of a strange dream, this week has been different, this week progress has been made by day-dreaming. By Monday we had decided to abandon the bottom part (the tilted lifting platform) and extend the straight lifting tower all the way to the ground but we would also move this tower towards the plinth as far as we could, thus reducing the amount we would have to extend it. Steve and myself had this job completed by the end of Tuesday's work session.    I awoke early Wednesday, and started day-dreaming. I was thinking about something Steve had said when we were tilting the completed tower, so that the top of the tower was parallel with the underside of the obelisk. I was pushing the tower towards the plinth, and Steve was the other side of the tower preventing it going too far. “I could hold the tower at this angle with my little finger, I can feel it wanting to tip back to you,” said Steve. “Yes, that's because we built the tower the same shape as an obelisk, the extra weight at the bottom means that an obelisk wants to stand upright at a certain angle.” I replied.    The day-dream continued. If the obelisk wants to stand upright at a certain angle, we will have to be careful once the obelisk reaches something like seventy degrees, as it might rock forward violently and over-balance onto the land beyond Steve's garden. I began to think in terms of some kind of restraint. About an hour later I was still daydreaming, but no longer about restraint. My thoughts had changed track without my being conscious of the change. I was now thinking about cantilevers. If I can build a cantilever at the base of the obelisk, I can lighten the load we have to lift. My thoughts accelerated: If I can lighten the load, then I can reduce the load until the obelisk is perfectly balanced between the load (the top of the obelisk) and the cantilever, meaning theoretically I could erect the obelisk with one hand at this point.    I began to think about building a cantilever at the base of the obelisk. By the time I arrived at Steve's place, I had a plan roughly sketched out in my mind and was bubbling over with enthusiasm. Ewan had already arrived and was in deep conversation with Steve. Not wanting to interrupt I contained my enthusiasm and rolled myself a cigarette, while I waited for the conversation to reach its conclusion.    Eventually I had my chance and I outlined the plan to use a cantilever, it wasn't well received. Steve was doubtful we could lift the obelisk from this angle, as a cantilever is almost the opposite of a lever and Steve was by now a great fan of levers. I persisted, demonstrating by arranging timbers in cantilever fashion on the base end of the obelisk. Steve still objected saying, “You'll break the timbers at the point where they overhang with the amount of weight you're talking about.” “Not if we balance the overhang with the same weight on the other side, the entire weight will still be on the right side of the balance point of the obelisk and we will have made the heavy end of the obelisk heavier still, thus making the light end lighter by comparison and the obelisk will want to become self-righting sooner, and we can make the overhang stronger by corbelling the timbers at the point of the overhang.” “Well it can't do any harm to give it a try.” Steve replied.    We spent the rest of the morning building the cantilever. By the end of the shift Steve was more enthusiastic about possibilities of the cantilever, while Ewan remained apparently unconvinced, but Ewan's strong point is his understanding of computers, not engineering.    By Thursday morning I had refined my ideas about how to construct the cantilever. The previous day I thought that we would have to reduce the weight on the cantilever as the obelisk rose, otherwise the speed of the erection would accelerate and become uncontrollable. Now I thought otherwise. Steve was slowly beginning to like the idea of the cantilever and by the end of the shift was more enthusiastic, though still concerned about our losing control. We removed the timbers we had put in place, rearranged them, and fastened them to the obelisk with windlasses. As we added more layers of timber, corbelling them out over the end of the obelisk, we fastened them in place with more windlasses. Soon we had run out of rope for the windlasses and were fast running out of timber. We called a halt for the day. Tomorrow we should have a delivery of more timber I had ordered previously for the tower, we would now use this for the cantilever, and Steve said he would buy some more rope.    That evening I continued to think about the cantilever. I realised that the cantilever was more or less self- controlling. Once we had added enough weight to the cantilever end of the obelisk, the obelisk would be perfectly balanced. Add just a little more weight, and the balance is tipped in favour of the cantilever, and the obelisk will start to rise. The speed of the erection will depend on how much extra weight is added, and as the obelisk rises the process becomes self-correcting, because the cantilever shortens automatically with every degree the obelisk rises, and the overhang will hit the far side of the plinth, preventing further movement when the obelisk is upright.    I sent Steve an email cancelling the next days work session, I wanted more time to think about what we were about to do. Steve replied, saying that he too had to cancel due to some family business in the morning, which he had to attend to. Joe had the builders in at home, demolishing and re-building his girlfriend's house, so would be unavailable also. Ewan was busy on his computer, and Sean was on holiday down south, after which he had to attend a course in the Philippines, to do with his work.    Next week we may succeed. We may fail again, or it might take longer to tip the balance. We shall see soon enough. << previous blog page next blog page >> To read & post comments click here return to top of this page

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