Megalithic Engineering Techniques: Experiments Using Axe-Based Technology
Osenton, Clifford J., Antiquity
Many theories have been proposed about the methods used in prehistoric megalithic engineering, usually in the form of modern civil engineering methods imposed on to megalithic construction. For example, methods proposed in the 1950s (Atkinson 1956: 98-117) depict an image of mass labour using modified prewar lifting technology. In later testing in the televised series Secrets of lost empires (Page 1996), the means used took advantage of modern engineering techniques for the erection of concrete blocks, although they were manually pulled upright. More recent field trials have used a combination of prehistoric and modern technologies.
Clearly, however, ancient methods would have been limited by available resources and any modern technology would be likely to exceed these. It is likely that the prehistoric communities would have had access to little more than broad-bit stone axes and would have worked `by eye' rather than using calculations, compensating for errors as work progressed. Thus any use of modern construction technology is likely to produce a result incompatible with the archaeological record.
Our objective was to replicate megalithic construction techniques to produce a result as consistent as possible with the archaeological record. For this we used only round timber, processed using axes and working by eye, without calculations. Using these techniques we hoped to extract an irregularly shaped 3-tonne bluestone, load it on to a sledge, transport it approximately 200 m and erect it vertically.
Field tests showed that mature hard wood trees can only be worked by axe when the wood is green. For example, oak heartwood is difficult to fell, whilst ash is easier, but both will split when green. Hornbeam can be worked when green, but cannot be split. All hard woods are difficult to work with steel-edged tools when dry. Soft woods and willows would have been easier to work using flint axes and they would also have been strong enough for most megalithic construction work.
A problem to be overcome is that when round wood is split lengthways and faced, the finished surface becomes convex as it dries, making the length unstable when used for stacking and hard to re-face. This could be overcome by selecting suitable timber types and cutting joints directly into larger green round timbers, similar to the techniques used for pit props in deep mining.
Ash, elm or sessile oak provide the longest and strongest timber, which would have been suitable for sledge runners to carry 50 tonnes or more. Green soft woods have also been tested under weights of 10 tonnes. Wood for rollers would have been selected for its roundness, giving strength and lightness. Harder woods may have only been needed when moving stones for the larger megaliths. Where available, coppiced ash would provide suitable levers. Wych elm could have been used for stacking timber and hornbeam or oak for wedges.
Three replica dolmens were constructed, each having a 5-tonne capstone, being built by two men, with a lift ratio of 100:1 (FIGURE 1). Experiments showed that by lifting the stone along three axis lines near the point of balance (FIGURE 2), a 5-tonne capstone could be lifted to a height of 1 m by one man using a wooden lever, thus giving a ratio of 5 tonnes per man. The technique was then refined to a point where two men were able to erect a 4-tonne standing stone, one using a wooden lever whilst the other stacked (FIGURE 3). Further tests, lifting a 6-tonne stone along two axis lines, upgraded the technique to give the lifting efficiency required using wooden levers to raise stones of 100 tonnes, where large lifting crews of 200 men could not be assembled in the limited space.
Erection of standing stones
A large stone circle was built using manual lifting techniques …
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Publication information: Article title: Megalithic Engineering Techniques: Experiments Using Axe-Based Technology. Contributors: Osenton, Clifford J. - Author. Journal title: Antiquity. Volume: 75. Issue: 288 Publication date: June 2001. Page number: 293. © 2008 Antiquity Publications, Ltd. COPYRIGHT 2001 Gale Group.
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