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Railroads Produce Less Ground Friction Than Motor Vehicles
First, think about some simple physics. A turning steel wheel in contact with a steel rail reduces by 85-99% the amount of rolling friction than a rolling rubber truck tire has in contact with an asphalt or concrete pavement. [Nice, Karim, How Tires Work, HowStuffWorks.com, http://auto.howstuffworks.com/tire4.htm] The train wheel’s reduction in friction over a car tire is even greater. Much of a car’s gasoline bill goes into bending and wearing out tires. Feel your tires after a trip. They are hot, and that heat was produced by repeatedly bending them and rubbing them on the road. Car or truck tires flatten into four “footprints” as each meets the pavement when the wheels turn. The tire sound made at highway speeds is mostly a consequence of tires quickly compressing against the pavement and decompressing as they spin. Auto drivers paid for the gasoline to bend, unbend, and re-bend those tire thousands and thousands of times. Truckers pay in diesel.
Heat is also produced when the tires wear out the road and the roads wear out the tires. Heat is a form of energy, and all that heat in you tires is wasted energy for which every car and truck driver pays dearly. Even on a cold winter day surrounded by frigid air which is continually extracting the waste heat, tires still get hot to the touch. Steel wheels and steel rails bend imperceptibly and wear very little compared with the plainly visible bending of tires on pavement.
The footprint of a truck tire on pavement approaches one square foot. There are 18 of these on each truck. The footprint of a steel wheel on a steel rail is about the area of a dime. There are only eight of these and the rail car is carrying many times more weight.
Think of rolling a small rubber ball on a level roadway. Depending on the initial speed you give it and on the true levelness of the roadway it will roll some distance and stop. Think about rolling a steel ball bearing on a level steel plate. The ball bearing would roll on and on and on. The amount of friction experienced by the ball bearing is trivial compared to the friction experienced by the rubber ball.
In addition to being a significant waste of energy, the rubbing of tires on pavement is also a significant source of pollution. Every time you replace your tires because they are wearing out, all the rubber that was on the tire when it was new, but has disappeared thousands of miles later, has been ground off in minute particles that have fouled the air and water. Once these particles are freed of the constant friction against the pavement they do not continue to disintegrate at the same rate they did when on your vehicle. These particles stay in the environment just like a discarded tire will endure for years. You are basically buying new tires so you can grind them up into particle sized pollution. Once you have ground off enough of the tire tread, you head for the tire store and buy some more.
The energy used to drive a train is primarily devoted to torque, turning the wheels. There is far less loss to friction and heat compared with truck and car tires. Rail infrastructure can withstand heavier loads. (Even where legal weight limits are followed, it would take thousands of cars to equal the damage to highway infrastructure of a single truck [cite].) Electrify the train and even greater efficiencies in locomotion are obtained. And regenerative braking sends electricity across the wires to power another train up a grade rather than wasting the energy as heat as when a car or truck brakes.
Less Air Friction, Too
Trains run like bicycle racers--Highway vehicles need to leave one car-length between them for every 10 miles per hour of speed. Each vehicle must independently fight air friction which may be more than you think. Stick you hand out the car window at 60 mph and feel the force exerted on the small surface of your hand. Multiply that surface area by hundreds to represent your car or around a thousand times to represent a truck, and you can imagine the amount of energy expended by your vehicle’s engine just to push aside the air in your way.
Bicycle racers ride very close together so that all the others use the air draft started by the first cyclist. Race car drivers also clearly understand and use the energy efficiency of “drafting” the car ahead. Trains of long cars all linked close together all ride in the draft of the locomotive greatly reducing air friction drag. That means trains require less energy to move their proportionate volume and weight because of aerodynamic design and operation.
When the Steel Interstate is constructed, the dual track, smoothed curves and removal of grade crossings will allow smoother train operation and consistently faster speeds. Steel Interstate freight trains will encounter fewer stops and starts than trucks. It takes much less energy to maintain a fixed speed than it does to accelerate. Every time a truck or car driver brakes, he or she throws away energy that must be bought again with more fuel.
Trains also run on much flatter grades than cars. Railroad tracks are constructed with minimum slopes compared with the hills found on most highways. Train tracks are even much flatter than slopes on Interstate highways. Steel Interstate trains will be electrified and will employ regenerative braking systems to convert the energy from braking into electricity rather than waste heat as in typical auto and truck braking systems. In this way electric locomotives act like hybrid automobiles, except that the power they generate goes immediately back into the power grid where it can assist a different locomotive climbing a grade, a more efficient use than storing the power in a hybrid car battery.
Energy Savings Realized by Steel Interstate Technology
Transportation researcher Alan Drake notes that diverting "freight from trucks to electrified double stack container trains trades roughly 20 BTUs of refined diesel for 1 BTU of electricity."[Drake, A., An American Citizen’s Guide to an Oil-Free Economy: A How-To Manual for Ending Oil Dependency With valuable bonus information on Saving Our Economy, Our Planet and Strengthening Our National Security, unpublished manuscript, 2010, copied with author’s permission.]
The relatively modest energy required to electrify and expand the railroads, the 20 to 1 improvement in energy efficiency and the long life of the infrastructure gives some truly astounding energy saved on energy invested (ESoEI) numbers. Some rough calculations show ESoEI can approach 1,000 to 1.
As the supply of energy becomes a growing problem, getting close to a 1,000 to 1 payback, or even a 50 or 20 to 1 return, will become essential economic strategies. By comparison, boiling tar out of sand has about a 4 to 1 energy returned on energy invested (ERoEI) and corn ethanol has less than 2 to 1 ERoEI return.[Ibid]
It’s difficult to precisely measure ultimate wheel strength beyond the maximum load each wheel is rated for. The load ratings of steel and aluminum wheels can be all over the place. A wheel with a higher load rating is typically heavier than a wheel made of the same material with a lower load rating.
Forged aluminum wheels are by far the strongest and lightest wheels available. However, their cost can be prohibitive for most off-road enthusiasts. Also, there are not a lot of forged wheels available, so the designs are limited. Forged aluminum is generally reserved for extremely large diameter wheels and racing applications.
If you frequent rocky areas, you’ll likely want to find aluminum or steel wheels with lots of material around the wheel beads. The wheel bead is where most wheels are damaged off-road, especially when running tires at lower trail pressures. Aftermarket wheels with extra thick bead areas and imitation beadlock designs are usually better protected than standard wheels. Avoid spun aluminum wheels for off-road use. They feature a lightweight design, but there is often not a lot of material in the bead area to help fend off rocks.
It’s not at all uncommon for a wheel to be damaged when driving off-road. Higher speeds combined with rock impacts are the main reason for wheel damage in the bead area. The good news is that nearly any wheel can be repaired, no matter how bad the damage is. Of course, steel is far more malleable than aluminum.
In many cases, a temporary trail repair can be made to the bead of a steel wheel by pounding it back into shape with a large hammer. Aluminum wheels can be beaten back into shape to some degree, as well. However, cast aluminum is far more brittle than steel, making it more likely to crack during a hard trail impact or repair. Because of the brittleness, bent or cracked aluminum wheels should only be repaired by a professional or replaced.
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