Forum SubscriptionsSubscriptions DigestDigest Preferences   FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups  RegisterRegister FAQSecurity Tips FAQDonate
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log in to websiteLog in to websiteLog in to websiteLog in to forum 
Warning: Make sure you scan the downloaded attachment with updated antivirus tools  before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.

how the Egyptians moved pyramid stones and large statues

Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> Engineering Marvels
View previous topic :: View next topic  
Author Message
Dr. N. Subramanian
General Sponsor
General Sponsor

Joined: 21 Feb 2008
Posts: 5434
Location: Gaithersburg, MD, U.S.A.

PostPosted: Fri Aug 07, 2015 7:26 pm    Post subject: how the Egyptians moved pyramid stones and large statues Reply with quote

Mystery about how the Egyptians moved pyramid stones and large statues -Solved!

photo credit: Schematic from the tomb of Djehutihotep depicting the transport of a colossal statue. Notice the person standing by the statue’s foot is pouring water over the sand right in front of the sled / Wikimedia

Ancient Egyptians had to pull massive statues and pyramid stones weighing 2.5 tons on large sleds across the desert -- without any modern mechanical device. Now, new research shows how adding a small amount of water to sand significantly reduces the sliding friction -- a clever trick that allowed the Egyptians to cut the number of workers needed by half.

To make a good sandcastle, you don’t use dry sand. By adding water, the grains stick to each other, and your castle holds its shape. Same thing with sand transportation: Adding water reduces the sliding friction of any object moving over the sand. With the right amount of dampness, water droplets bind the sand grains together.

An international team led by Daniel Bonn from the University of Amsterdam tested the sliding friction of dry and wet sand by pulling a weighted sled across the surface in a tray. With dry sand, a heap would form in front of the sled, hindering its movement. And as they added water, both the force needed to pull the sled and the amount of friction decreased. As the water made the sand more rigid, the heaps got smaller and smaller until there was no obstacle forming in front of the moving sled.

Their experiments revealed that the required pulling force decreased proportional to the stiffness of the sand. When water was added, capillary bridges arose; these small water droplets act like glue to bind the sand grains together. With the right amount of water, wet desert sand is about twice as stiff as dry sand, allowing the sled to glide far more easily.

“I was very surprised by the amount the pulling force could be reduced -- by as much as 50 percent -- meaning that the Egyptians needed only half the men to pull over wet sand as compared to dry,” Bonn tells the Washington Post. Pictured here is the lab setup: A pile of sand accumulates in front of the sled when it's pulled over dry sand (left), but not with wet sand (right).

But just like with sandcastles, too much water isn’t good either. Water saturation is accompanied by a decrease in stiffness. With very high water contents, the capillary bridges (which used to act like a glue) start to merge and disappear, and the sliding friction increases again. It’s a delicate balance. "If you use dry sand, it won't work as well, but if the sand is too wet, it won't work either," Bonn tells LiveScience. "There's an optimum stiffness." The ideal amount of water falls between 2 and 5 percent of the volume of sand.

The answer had been staring us in the face for a long time. In a wall painting from the tomb of Djehutihotep (schematic above), you can see a worker pouring water on the sand in front of a sled that’s carrying a colossal statue. The sleds were little more than large wooden planks with upturned edges. “Egyptologists had been interpreting the water as part of a purification ritual," Bonn says, "and had never sought a scientific explanation.”

The work was published in Physical Review Letters last week.

Where we encounter friction?
The design methodology of storage structures  like Silos/Bunkers/tanks storing bulk materials, is very different from the conventional water or liquid storage structures-one of the main differences between designing the storage structure for solids V/s liquids is that: for solids you have to deal with forces exerted by friction.

Friction also creates a lot of flow problems. For example: If hopper walls are not smooth and steep enough, there will be more resistance to flow of the material at the walls, which might lead to funnel flow and subsequently problems like arching, rat holes, segregation occurs (see Ref.3). Also, depending on a material, their friction behavior changes depending on moisture content, shape, size etc.

The concept of the friction is very simple, yet sometimes counterintuitive, understanding this simple phenomenon is sometimes tricky.

1. http://www.iflscience.com/physics/mystery-how-egyptians-moved-pyramid-stones-solved
2. http://www.omafra.gov.on.ca/english/engineer/facts/08-057.pdf
3. http://www.ct.upt.ro/suscos/files/2013-2015/2C08/L20_Silos%20and%20tanks.pdf
4. https://www.linkedin.com/pulse/friction-atul-kulkarni-p-e-?trk=hb_ntf_MEGAPHONE_ARTICLE_POST
Back to top
View user's profile Send private message
Thankful People
1 user(s) is/are thankful for this post.
Display posts from previous:   
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> Engineering Marvels All times are GMT
Page 1 of 1


Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum

© 2003, 2008 SEFINDIA, Indian Domain Registration
Publishing or acceptance of an advertisement is neither a guarantee nor endorsement of the advertiser's product or service. advertisement policy