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The Modern Antiquarian Forum » Stonehenge and its Environs » The bluestone debate |
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tonyh 247 posts |
Nov 19, 2008, 12:55
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sleeptowin wrote: i dont think you would get the push pull effect, the reason it does it with cars is because they are on wheels, i dont think a massive stone would jump forward as it started to move, it would just eventually start moving. though im probably wrong as ive never tryed to pull a rock. You don't need wheels for this effect. Dragging just about anything that has weight will give you the same result. A stone on a sledge will be slowed by varying ground conditions a ripple will run down the team of Oxen. The longer the Train the worse the effect.. Tony
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Steve Gray 931 posts |
Nov 19, 2008, 15:34
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tonyh wrote: You don't need wheels for this effect. Dragging just about anything that has weight will give you the same result. A stone on a sledge will be slowed by varying ground conditions a ripple will run down the team of Oxen. The longer the Train the worse the effect.. Tony You seem to be fond of taking one observation, extrapolating it to a different situation and then asserting as fact something for which you have no scienctific justification. If you consider one pulling unit (a pair of oxen, or a team, or whatever) attached by a single elastic rope to an object and strong enough on its own to overcome the limiting friction of that object then yes, there is an effect called resonance that will produce what you term the "push pull" effect. It's similar to an undamped spring. The resonance is further exacerbated by the fact that moving friction is somewhat less than limiting friciton. That's your one observation and it's quite correct at that level. However, there are several factors in my suggestion that you don't seem to appreciate. 1. There is considerable friction, which acts as a damping force, just like the old friction shock absorbers on leaf-spring cars. 2. There is considerable mass, so the forces required to alter the momentum of the system are very much larger. 3. I was talking about lots of individual pairs of animals each with its own rope attached to the stone. The force in any one rope is insignificant compared to the weight of the stone, so individually a rope cannot significantly influence the inertia of the stone and hence will not individually induce resonance in the whole system. 4. The combined effect of all the ropes will be a relatively constant force despite individual fluctuations. 5. Resonance will occur most readily if the relative frequencies of the puller and the object are similar. The resonant frequency of a system is inversely proportional to mass. The relative frequencies of an ox on a rope and a 40 ton stone on the same rope are so different that one will not tend to induce resonance in the other. If you doubt this try it. Get a group of say 10 friends each with a length of stretchy rope and tie them to a car with the handbrake partly on (to simulate dragging friction). If some of you begin to pull you will merely stretch your own rope and not achieve much. As the rest start to pull you will reach a point at which the car will begin to move forwards. At this point the combined pulling force has just overcome limiting friction, so the car will begin to move forward slowly. All you need to do now to keep it moving is to pull steadily and the car will follow you matching your combined walking speed. Nobody can go faster than this speed because they don't have the strength to speed the car by very much up on their own. Even if one of you starts messing about alternately tugging and stopping it won't have much effect for the same reason. On the subject of ropes, Nigel mentioned the Norwegian rope maker. My recollection of her rope was that it was about 5 cm diameter and had a breaking strain of around 4 tons.
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tonyh 247 posts |
Nov 19, 2008, 16:03
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But you had 50 teams of two oxen.. Do they stretch out in a straight line and have 50 different lengths of rope runing back to the sledge? or are the kind of fanned out so that the are not in each others way? Tony
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GordonP 474 posts |
Nov 19, 2008, 17:35
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I thought you might find the following of interest. This is taken from a paper presented to The British Academy by archaeologist Julian Richards and engineer Mark Whitby. "Whatever the precise route, the varied nature of the terrain, with undulating topography and potentially wet areas, helps dictate the approach to the development of a method of transportation. In this development a number of ideas were considered including the use of rollers, forming a timber cylinder around the stone and rolling it, Crabbing the stone along using levers and the use of ice as a medium across which the stone could be slid. The orthodox method using rollers to move the stones was considered but rejected. Subsequent experiments in moving the 10 ton lintel proved that it is a practical system, but has limitations. The direction of the stone is difficult to control on all but the most level ground and the method involves high risk as rollers have to be placed ahead of the moving object. As the load goes up, the system becomes prone to binding as the weight of the whole load will at times bear on only one or two of the rollers due to uneveness either in the rollers or in the ground surface. The latter can be overcome by running the rollers on a flat, possibily timber track, and the former by selecting rollers of a uniform diameter. However, directional control remains an issue, as any roller placed out of true to the track will cause the load to veer off.
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Steve Gray 931 posts |
Nov 19, 2008, 20:20
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tonyh wrote: But you had 50 teams of two oxen.. Do they stretch out in a straight line and have 50 different lengths of rope runing back to the sledge? or are the kind of fanned out so that the are not in each others way? Tony It doesn't matter, the principle is the same. I would imagine practicalities might dictate a mixture of the two. Bear in mind that I only posed this as a question, not as a fully-fledged theory.
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tonyh 247 posts |
Nov 19, 2008, 20:38
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Steve Gray wrote: tonyh wrote: But you had 50 teams of two oxen.. Do they stretch out in a straight line and have 50 different lengths of rope runing back to the sledge? or are the kind of fanned out so that the are not in each others way? Tony It doesn't matter, the principle is the same. I would imagine practicalities might dictate a mixture of the two. Bear in mind that I only posed this as a question, not as a fully-fledged theory. You mean it would not work.. That's OK.. So do I.. Tony
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nigelswift 8112 posts |
Edited Nov 19, 2008, 21:10
Nov 19, 2008, 21:07
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Steve Gray wrote: It doesn't matter, the principle is the same. I would imagine practicalities might dictate a mixture of the two. Quite. There has to be a limit to the length of a train. The American hauliers obviously found no difficulty with hitching those pairs in series but anything longer presumably starts to get unwieldy so having more than one train seems the obvious solution. And I agree, there's no question of a ripple effect.
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Steve Gray 931 posts |
Nov 19, 2008, 21:12
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GordonP wrote: I thought you might find the following of interest. This is taken from a paper presented to The British Academy by archaeologist Julian Richards and engineer Mark Whitby. "Whatever the precise route, the varied nature of the terrain, with undulating topography and potentially wet areas, helps dictate the approach to the development of a method of transportation. In this development a number of ideas were considered including the use of rollers, forming a timber cylinder around the stone and rolling it, Crabbing the stone along using levers and the use of ice as a medium across which the stone could be slid. The orthodox method using rollers to move the stones was considered but rejected. Subsequent experiments in moving the 10 ton lintel proved that it is a practical system, but has limitations. The direction of the stone is difficult to control on all but the most level ground and the method involves high risk as rollers have to be placed ahead of the moving object. As the load goes up, the system becomes prone to binding as the weight of the whole load will at times bear on only one or two of the rollers due to uneveness either in the rollers or in the ground surface. The latter can be overcome by running the rollers on a flat, possibily timber track, and the former by selecting rollers of a uniform diameter. However, directional control remains an issue, as any roller placed out of true to the track will cause the load to veer off. Yes, I've read that before (quite a long time ago). As you may be aware Julian Richards was at Foamhenge and took a great interest in our project. He was especially impressed with Gordon Heeks' glass axe. I had a long chat with him on the day and later we corresponded by email about these very topics. One of the ideas that came up was that a variable workforce may have been employed with a smaller number of men moving the stones over the easier sections of the route and a larger force being assembled as and when needed for the difficult parts. However, Nigel's picture clearly dispells the myth that oxen are too difficult to handle in large teams and illustrates that they could easily have been a viable force for moving large stones by dragging them (probably on a wooden sled to avoid pecking) without rollers. A sufficiently large team might even provide their own supply of lubrication en-route. ;o)
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Steve Gray 931 posts |
Nov 19, 2008, 21:22
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tonyh wrote: You mean it would not work.. That's OK.. Having no further technical arguments to bring to the table you are reduced to "misconscrewing" [sic]
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tonyh 247 posts |
Nov 19, 2008, 21:27
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LOL.. You and Me know.. Give it up Man. Do You really what to do this point by point.. I have no problem with You.. But if You insist Tony
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