nigelswift
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Re: Stone Shifting 3
Sep 02, 2003, 09:14
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Steve, if the thought behind your question was whether we’d be criticized for using modern tools I think it’s unlikely as it’s always accepted they were very sophisticated carpenters, on the basis of the carpentry techniques used on the lintels.
I have a flint drill bit that I found on the route of the stones outside Avebury, that’s perfectly efficient and leaves holes indistinguishable from a Black and Decker. I’ll let Gordon have it if he wants, and he can mount it on a handle and get a photo-opportunity using it on the day.
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Steve Gray
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Pre-shaped logs
Sep 02, 2003, 09:35
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Gordon, your orginal idea for the logs was to have a ripping taken off each side to make them of a uniform thickness and to give them a greater bearing surface. But, as you are aware, this is not likely to be historically accurate. As an alternative and because of the need to stabilise the tower you suggested that we notch out the logs so that they interlock with each other. This would be very time-consuming work and since the logs are likely to be of varying diameters, each joint would have to be tailored to the log it was mating with. This requires that the timbers are all sorted and numbered so they can be assembled in the correct sequence.
Suppose we just use raw logs and accommodate the inherent taper by laying them head to tail to maintain a level platform. We can easily make a plumb-line level out of primitive materials and use it to check that level is being maintained. If we find that one corner is a bit lower than another, we put the fat end of the logs to that corner for a layer or two. The weight of the stone would cause the surface of the logs to flatten where they meet and form a natural interlock. Raw logs would be much easier to insert into the crib than notched ones. If one or two of the logs below had twised under load, the notches might fail to engage properly and we'd be faced with making on site adjustments at a most critical time. We can still use birdmouth noggings as I suggested previously for the layers where the shoring props are attached. These are only required to take a compressive load, so they are self-retaining.
Speaking of shores, when I was talking about stopping the stone when it reaches vertical, the structure I had in mind is called a "flying shore". With a stop-log lashed to the top of the block, the shore would convert the rotational momentum into linear momentum in an upwards vertical direction. This would attempt to lift the stone back out of the ground, so we are using the stone's own weight to resist its momentum rather than brute force, which tends to smash things.
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GordonP
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Re: Pre-shaped logs
Sep 02, 2003, 18:04
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Hi Steve
Yes I know notching the logs would be time consuming but all this can be done before the event. If we use logs with an average diameter of say 6in and reduce the notched part to 4in, that is to say we take a bit off each side of the log just at the notched point we end up with a square section joint. If we make this joint loose enough to accomadate any of the logs we can tighten the loose joints with flying wedges. this would enable us to biuld the tower very quickly and the weight of the stone would hold it all together.
We can use the weight of the stone another way too. As we erect the tower when the need arises we can create platforms around the tower by inserting logs into the tower to form a canterlever platform complete with guard rails if necessary.
I'm still convinenced the stones were launched from the sloping side. I've been studying the film of the 4 ton experiment. At the time I didn't know about the sloping side of the hole, so dug my hole with four virtical sides but made it overbig just to be on the safe side. As the stone entered the hole at less than vertical the inside face of the stone catches the inside face of the hole stopping the stones rotation.
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treaclechops
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Re: Stone Shifting 3
Sep 02, 2003, 18:38
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Want a photographer?
treaclechops xx
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GordonP
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Re: Stone Shifting 3
Sep 02, 2003, 18:46
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Welome aboard
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treaclechops
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Re: Stone Shifting 3
Sep 02, 2003, 18:56
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:o) Splendid! I can be contacted at [email protected] if need be!
treaclechops xx
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Steve Gray
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Re: Pre-shaped logs
Sep 02, 2003, 22:33
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I had imagined that the overlap points of the logs would all be beneath the stone. That way there is no bending load on any of the logs and we rely entirely on the compressive strength of the timber, which is considerable and gives us a good safety margin. If we don't do this I would find it hard to provide convincing stress calculations unless we used stress graded timber (for which bending moments are known) and violate our historical integrity.
If the laps are all beneath the stone, I don't think we need proper joints. The logs cannot carry such a load on round surfaces without deforming into flattened contact areas, but if you really feel it is necessary, you could cut notches that have a 4" square bearing surface and a sloping shoulder on all 4 sides of the square. The slopes on the top of the log would go upwards whereas the slopes on the sides of the log would go down. As long as the angle is the same, all timbers will fit together perfectly regardless of the size of the log.
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Steve Gray
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Re: Stone Shifting 3
Sep 02, 2003, 22:38
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I think we need to start a personnel database (or a notebook if yhou prefer), Gordon, so nobody who's expressed an interest gets left out when the time comes. I'm new to TMA, Treaclechops, but I have seen a few others saying nice things about you. Welcome to the Stone Shifting Asylum.
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FourWinds
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Re: Stone Shifting 3
Sep 02, 2003, 22:49
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You haven't read all the posts then :-)
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Steve Gray
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Re: Stone Shifting 3
Sep 03, 2003, 01:44
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Hmm.. actually no, but do I deduce from your response that I should have detected an element of irony in the ones I did read?
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