Monday, June 25, 2007
Saturday afternoon, 4 of my camp mates joined me for the first raising of the full tower. We succeeded in standing the tower up but not without breaking a stave and then breaking a few more on the trip down. I learned a lot about the forces being applied during erection and have a few modifications to make before the next attempt.
The first point of failure was a stave on the horizontal triangle connecting the first and second section. When the tower is in its upright position these triangles are in tension - but when the tower is being raised they were subjected to compression forces that proved to be too much for these thin members. In addition, the contact points of the vertical sections apply an eccentric loading to the triangles that ultimately caused the stalks to crush and fail when loaded in compression. I have an idea about how to correct the problem that I will implement in the next build.
Another aspect of the raising that needs some improvement is the gin pole. We opted for a single pole this time instead of the intended "A" frame, not surprisingly it turned out to be a little unstable. I'll make sure the "A" frame model is ready for the next raising.
A big thank you to David, Mark, Brad, Matt and my wife Jenny for helping move this process forward.