Man's strength and ingenuity never cease to amaze. How in the world ancient builders transported and assembled the monuments of Stonehenge, for instance, mystifies modern generations. How today's experts move or tow the modern world's most massive structures can be even more amazing. Were war, famine or plague to wipe out civilization, perhaps surviving generations would look with wonder on some of our artifacts, too.
For us non-professionals, the most we'll ever have to tow is fifth-wheel trailers or maybe a few tons of cargo. And those who do have towing experience know that braking, turning and even parking become more complicated. If you think that's a pain, you should try towing a space shuttle down the road.
As engineers continue to build bigger and bigger structures, they also have to come up with more powerful vehicles and clever ways to tow them. Although some of these structures, like offshore rigs, were made to be moved, other things like buildings don't lend themselves as easily to moving. Each project poses its own challenges, and each involves things of monumental weight and proportions.
In the next few pages, we'll examine several marvels of heavy transportation. The first job involves a vehicle that moves around fine in outer space, but needs help getting around on the ground.
Towing Space Shuttles
A NASA space shuttle has to withstand a lot. It must hitch a ride on one or more enormous rockets for a dangerous launch, maneuver in Earth's orbit and then suffer through the intense heat of atmospheric reentry. And, as a reusable vehicle, it has to arrive safely on land to repeat the whole process again.
With all this to consider, you can bet engineers won't want to make these ships get around by themselves when they don't have to. Before launch, the orbiter -- with its entire rig -- weighs a gargantuan 2,250 tons (2,041 metric tons) [source: Boeing]. Moving this weight requires a Shuttle Crawler Transporter -- the largest kind of tracked vehicle in existence, according to NASA. This huge platform must carry a space shuttle from the assembly building to the launch pad using a 5,000-horsepower motor. "Crawler" is an apt name, however, as it moves the precious cargo a mere 1.24 miles per hour (2 kilometers per hour) [source: NASA].
Although the Crawler may not technically tow that prelaunch weight, the shuttle orbiter must be towed when it lands after its long, rugged journey back into the atmosphere. A 256-horsepower diesel tractor attaches a tow bar to the nose gear of the 121-ton (110-metric ton) orbiter for a two-mile (3.2-kilometer) trek back to the Orbiter Processing Facility. This tractor tows at speeds of up to 5 miles per hour (8 kilometers per hour). It's 16 feet (4.9 meters) long, 8 feet (2.4 meters) wide and can even tow up to 410 tons (372 metric tons) if needed [source: Dumoulin]. It also tows yet another vehicle that hauls the orbiter, the shuttle carrier aircraft -- a plane that transports the shuttle around the country and the world.
This towing marvel has to do with pulling a train. What's mind-blowing is how it was done. This tower pulled it off by the skin of his teeth -- literally. In 2007, a Malaysian man by the name of Rathakrishnan Velu pulled a train without the use of any towing vehicle -- he pulled it using his teeth.
This wasn't any miniscule train, either. He pulled a seven-coach train a distance of 9 feet, 2.2 inches (2.8 meters) along a track [source: Joshi]. Clenching a steel rope between his jaws and pushing against the tracks with his legs and arms, Velu pulled the train weighing 327.5 tons (297 metric tons), which is more than 2 ½ times the weight of the post-landing orbiter, if you're keeping track. This weight and distance secured Velu -- who is nicknamed "King Tooth" -- the world record for heaviest weight pulled with teeth.
Want to be like Velu? It'll take more than eating Wheaties -- he says he does jaw strength training every day in addition to other exercise. He chalks up his amazing talent primarily to meditation, however.
Planes, understandably, are primarily built for use in the air -- the ground is not their forte. It turns out that on the ground, it's often more economical to have a towing vehicle pull them. The development of heavier planes like the Airbus A380 -- the world's largest passenger aircraft -- requires more powerful towing capacity as well.
When looking at a Aircraft Tow Tractor vehicle, however, you may never guess it could pull the likes of the Airbus A380, which can weigh about 600 tons (544 metric tons) at takeoff [source: Airbus.com]. Although they're small, these tractors pack a punch. Like watching an ant carry 10 times its body weight, watching a small towing vehicle pull such a massive airplane is a fascinating sight.
Conventional tractors can pull planes by connecting a tow bar to the nose gear of the plane. Another method uses the aptly named towbarless tractor which, rather than using a tow bar, cradles and carries the front wheel of the plane. Because a TLT can actually lift the nose wheel of the plane, it causes less wear on the aircraft.
Unless you live in a houseboat or trailer, you may never think about moving your house -- or the building where you work for that matter. But structural moving is getting more common as technology makes it easier. The process of moving these enormous structures requires a good deal of planning and hard work -- not to mention some heavy-duty towing power.
If you've read How House Moving Works, you know that it involves digging down to cut openings into the foundation and inserting steel beams. These beams are lifted by hydraulic jacks placed underneath them. When lifted the beams are lifted, movers can place wheels on the ends. At this point, a towing vehicle pulls it to its new location, which might be miles away.
Some structures might have to be moved in sections, but some large buildings can be moved intact. The Guinness Book of World Records recognizes the Fu Gang building in China as the heaviest building ever moved intact. Movers were able to pull this 16,689.43-ton (15,141-metric ton), 111-foot (34-meter) tall building 116.86 feet (35.62 meters) [source: Guinness World Records].
Towing on the Water
Some of the heaviest towing jobs don't happen on land but on water. Tugboats, like the tractor vehicles that pull airplanes, must push or even pull vehicles several times their size. Not only do these jobs involve towing some of the heaviest vehicles and structures, but they also involve towing the longest distances.
Towing cables, called hawsers, run underwater from the stern of a tugboat on one end to the bow or front of the towed structure on the other end. These cables equip tugboats to pull wrecked ships, barges and even oil rigs from one place to another.
Take the Adriatic LNG terminal, the first offshore liquefied natural gas terminal. It weighs more than 300,000 tons (272,158 metric tons) and needed four tugboats to tow it 1,700 nautical miles (3,150 kilometers) an average speed of 4.4 knots (8 kilometers per hour) to its permanent location -- a process that took about three weeks [source: Edison].
To learn more about towing, and read about the heaviest buildings ever moved, browse the links on the next page.
Torque versus horsepower: Which of these two measurements is more important when you tow? Learn the difference between them and see which is more important.
- Airbus. "Aircraft Family -- A380 Specifications." Airbus. [Oct. 22, 2008] http://www.airbus.com/en/aircraftfamilies/a380/a380/specifications.html
- Airports International. "Towing the big jet: now that the Airbus-A380 has begun to flex its wings, the competition for orders between the tow-tractor manufacturers is greater than ever." Airports International. Nov. 1, 2005. [Oct. 22, 2008] http://goliath.ecnext.com/coms2/gi_0199-5012414/Towing-the-big-jet-now.html
- Airport-Technology.com. "TBL 600 Towbarless Aircraft Towing Tractor Handles A380 Aircraft." Airport-Technology.com. Nov. 8, 2007. [Oct. 22, 2008] http://www.airport-technology.com/contractors/apron_clean/douglas/press1.html
- Boeing. "Space Exploration: Space Shuttle Backgrounder." Boeing. Last updated Oct. 2006. [Oct. 22, 2008] http://www.boeing.com/defense-space/space/hsfe_shuttle/docs/shuttle_overview.pdf
- Braden, Twain. "The Handbook of Sailing Techniques." Globe Pequot, 2003. [Oct. 22, 2008] http://books.google.com/books?id=z6GMZP0Wh40C
- Dumoulin, Jim. "Launch Control Center." GlobalSecurity.org. Last updated April 17, 2008. [Oct. 22, 2008]http://www.globalsecurity.org/space/library/report/1988/sts-lcc.html
- Edison. "First Offshore Regasification Plant in the World Lands to Italy." Edison. Press Release. Sept. 20, 2008. [Oct. 22, 2008] http://www.edisongroup.eu/edison/site/en/pressroom/index.html?&uri=/shared/press/ir/ n20settembre2008.html
- Guinness World Records. "Heaviest Building Moved Intact." Guinness World Records. [Oct. 22, 2008] http://www.guinnessworldrecords.com/records/science_and_technology/buildings/heaviest_ building_moved_intact.aspx
- Huffman, Alan. "Take It Away." New York Times. Feb. 1, 2007. [Oct. 22, 2008] http://www.nytimes.com/2007/02/01/garden/01moving.html?pagewanted=1&_r=1&partner=rssnyt&emc=rss
- Joshi, Vijay. "Malaysian man pulls train with teeth." Boston.com. Aug. 31, 2007. [Oct. 22, 2008] http://www.boston.com/news/odd/articles/2007/08/31/malaysian_man_pulls_train_with_teeth/
- NASA. "Astronomy Picture of the Day: The Shuttle Crawler Transporter." NASA. March, 4, 2002. [Oct. 22, 2008] http://apod.nasa.gov/apod/ap020304.html