[TheForge] Mechanics of Stonehenge

[GRAF]

Bruce Freeman wrote:
> The one flaw I saw in this video was that he moves monoliths on a
> cement surface by placing a couple pebbles under the monolith and
> rotating first on one, then on the other to get net linear motion.  It
> is not clear how he could apply this technique over soft earth, though
> the demo of the barn moving might have been one such.  (Not clear how
> that barn was constructed to enable to be moved like a monolith.)
>   

I'll bet that there was a fair amount of skeletal work done before 
jacking it up.
Concrete on soft earth or flat stones set in flat earth or on movable 
sledges would be my guess. Stepping stones if you will.

> I just went through my collection of "ancient engineering" books to
> find a technique I've read about.  Unsuccessfully.  So I can't give
> you a source, but I can give you another hypothesis, apparently based
> upon relics from Egypt, IIRC.  Apparently, excavations found what
> could be described as large (6'+) millstones that were not quite
> millstones.  So the hypothesis was that these stones were placed one
> over another and could then pivot fairly easily around a center shaft
> because they touched only near the shaft.  It continued that two booms
> projected away from the center shaft in such a manner that they'd
> rotate with the upper stone (I don't recall details).  These two booms
> were held at an angle above the stone (like, 60+ degrees to
> horizontal) and connected at the top with a rope, from the center of
> which rope a rope was dropped to the top stone.  Call this the "center
> rope".  From the end of each boom, a rope was dropped.  One of these
> held the load, the other the counterweight sling.
>
> So you get a rope around your monolith and hook it up to one of the
> boom ropes.  Now load small stones up in the counterweight sling until
> you have an equal mass on both booms.  Pull down on (or hang a weight
> from) the center rope and the load and counterweight both are lifted
> from the ground a small amount.  At this point, using oxen hitched to
> a beam extended radially from the 'millstones', rotate the upper stone
> on the lower 180* and you've moved your load by the distance between
> the tops of the two booms.  If you have a chain of these cranes in a
> series, you can move loads continuously and the counterweights
> oppositely.
>
> Note that since the counterweights are smaller stones, they could, if
> necessary, be loaded up on a sledge and moved back for reuse.
>
> One neat thing was that you could take the two "millstones", stand
> them on edges and put a beam between them and you've got wheels.
> Place the other beams across them, hitch up the oxen, and you can move
> your crane to the next work site.
>
>   
Something on this order might have application for a temporary crane for 
moving things around the yard or shop.
Gotta go get the sketch pad, now.

Mike Graf