Monday, September 24, 2012

Werner Von Braun and the Civic

Several years ago I made a trip to Alpena, Michigan to meet and speak with Besser Company.  They make machines and equipment to mass-produce concrete products, such as masonry blocks.   They are global leaders in the industry.

I met with an engineer, and tried briefly to explain my ideas.  He interrupted me, and brought in the Vice President.  I began to try to explain my ideas to the Vice President, but he also cut me short.
“Can you give our President a ride to Ann Arbor tomorrow?”
I was taken aback.  Isn’t one of the Lear jets available? I stupidly wondered.

“Sure!”  I said, “I’d be happy to.”
I picked up Mr. James Park at his house, having spent the previous 24 hours cleaning my Honda Civic as best I could.  We began our 4 hour drive, and spoke.  It was the very point of the whole thing.  He is an easy man to talk to.

I described how I thought this masonry system could be used, in various applications.  I went through one application after another.  “What else you got?” he kept asking.
I didn’t want to seem silly or crazy, or goofy; I’m the guy proposing triangular block already.  But I said it anyway.

“Lunar blocks.  Like on the moon.  The cost of sending materials from earth is too great, we should use what’s there, and with robots, this block system would…”
He interrupted by laughing.   He laughed heartily and deeply.  Uh-oh, I thought:  I’ve gone too far.

He then explained his laughter. 
Every year Besser would create a special limited edition hardbound leather book of general interest, and would send this book to their very valued customers, as a sign of appreciation.  One year the subject of the book was Rocketry.  One particular customer of Besser happened to be friends with –none other than- Werner Von Braun, the father of modern rocketry. 

Werner Von Braun was so taken with Besser’s book on Rocketry that he sent them a letter, in which he assured them that when man built on the moon, they would do so in something like the masonry manner which I had just suggested, and that it would be done on Besser equipment. 
We both had a good laugh in my Honda Civic, with Werner Von Braun grinning in the back seat as we pulled into Ann Arbor.


Thursday, September 6, 2012

Corrugations and ribs in a masonry arch

In a masonry roman arch (or round arch) the arch may be viewed as a horizontal half-cylinder.   The arch is subject to stresses from gravity which are represented by a catenary thrust line, as discussed several times on this blog (here, here and here).   Various techniques may be employed to strengthen the round arch against the thrusting forces of its catenary load.

A cylinder may –in turn- be seen as a shell structure, as also discussed several times on this blog.  An arch as a shell structure is seen as a curved plate.  A plate may employ various techniques to provide it with greater flexural rigidity. 

Flexural rigidity, or increased structural stiffness, may be achieved by providing corrugations in the plate.  Corrugations are defined as a series of parallel ridges or furrows.  One example of this which most people are familiar with is corrugated cardboard. 

Corrugated  paper (also called pleated) was patented in England in 1856 and was used as a liner for tall hats; tall hats which are nothing more than cylinders. 

Another example of cylinders being made stronger by corrugations are the tin cans which employ corrugations to give them greater rigidity.

As I discussed earlier in this blog, I have developed triangular block to make cylinders and arches.  There are two types of triangular blocks used to assemble into a cylinder, or section of cylinder, or arch.  I call these two types of blocks “flat” and par” because one has a flat top, and the other has abutting edges which are parallelograms. 

Each of these blocks has a “tilt” to it which departs from the vertical.  If the triangle which describes these blocks is lower and wider (more obtuse of a triangle) then the amount of “tilt” or departure from vertical is increased.  If the triangle which describes these blocks is taller and skinnier (more acute of a triangle) then the amount of “tilt” is decreased.

The tilt or “leaning” of the triangular blocks used to assemble a cylinder have the effect of introducing corrugations, or ribs into the arch.  These corrugations or ribs have the much desired and beneficial effect of increasing the flexural rigidity and strength of the resulting arch.  The effect is the same as the corrugations in a tin can, as shown above.  The structure is made much stronger and more robust to any applied force; whether it is gravity, wind loads, hurricanes, tornadoes or impacts.

This feature is a simple artifact of the design of these block, it is something of a “happy accident.”  Thus masonry arches made with corrugations are much stronger, more robust and better than a simple, rounded arch.