Mar 31, 2008

Cool (re)construction!

I'm in awe. This man shifts huge blocks of concrete weighing many tons - alone, without fancy tools or machines. He's reconstructing Stonehenge in his backyard. Get a fun physics lesson from Wally Wallington:

(Via Boing Boing.)

PS: Can somebody please explain the "two small rocks" method? I'm not clear on either where the pebbles are being placed, nor how it's helping him move the block. (Max?)

UPDATE: Max came through for me! Check the comments! Thanks, Max!

5 comments:

Sparkling Red said...

I saw this guy on TV. I don't fully understand his methods either, but he's very impressive.

Keera Ann Fox said...

I love his creativity and know-how. I hope somebody explains his technique to me.

max said...

PS: Can somebody please explain the "two small rocks" method? I'm not clear on either where the pebbles are being placed, nor how it's helping him move the block. (Max?)

Hi! Winter SAD! Connection problems for about a week now. Sorry for slowness. (Took 2 hours to get the video to load.)

Roughly: on the video on the web site, he's got the big block balanced on a board. When you balance something large like that on something small, you've massively reduced the friction involved. That is, not only is a big weight hard to move because of inertia, but also because of friction (friction is the bigger problem). Coefficient of the friction of the two surfaces involved times the total surface area will give you the amount of energy required to overcome the friction. If you dramatically reduce the surface area involved while the coefficient of friction stays the same, the energy required to overcome the friction is massively reduced. That just leaves the inertia involved, but without friction eating up the energy, you can just keep applying force to it and it'll keep moving. So that big stone kept spinning, but the board underneath makes a godawful wailing noise as the energy from the remaining friction is converted to noise.

Whether you use a rock or a bord, the principle is the same; unfortunately, he's got the physics wrong. The big block (in the video, on his web site) is the lever. The board underneath is the fulcrum. (Another way of looking it, is that he's made the equivalent of an axle (the board/rock) and a wheel (the stone). Same principle.

The two rock method is the same thing with two (probably three, actually) rocks. You have the stone balanced on two rocks. You would then lift at one end so it was balanced on one rock and swing it 180 degrees onto the third rock. It's still on two rocks, but it has moved. Then you take the rock you left behind and move it around to the other end of the stone, balance it on the third rock and swing it around onto the relocated first rock. Now the stone has moved again.

And that probably doesn't make any sense - but if you take a big long book, and three small things (like spools of thread, or dice, or something like that) and balance the book on two of them (spool one and spool two), you can push down on one end of the book, and swing it 180 degrees around until it rests on spool two and three. Then you move spool one to other side (in the direction of travel) and repeat, so now the book is balanced on spool three and spool one. It should have traveled one full book length at that point.

The technique really isn't undiscovered, so much, since I've done similar crud with engines and crap out of neccessity. It is impressive because no one has tried to recreate Stonehenge before. That's pretty cool.

There's a Nova episode, BTW, from back in the 90's I think, where they tried to recreate the various building techniques involved in assorted ancient monuments.

max
['I hope that at least sorta explains it.']

Keera Ann Fox said...

Yeah, that did. Even tried the book experiment. Thanks!

max said...

Cool!

max
['It helps if you have moved big heavy objects around before.']