Wednesday, January 9, 2008

A Physical Maximum for Vehicular Speed=55 KmpH

The time is now to begin the process of transforming the world of automobiles. As a world of people, we have to agree that 55 kilometers per hour will be the maximum attainable speed that any motor vehicle on the public highway or roadway, will physically be able to attain. Why such a sloooow speed?

The slow speed of 55 kph (or, 34 miles per hour) will enable all vehicles to attain superb, excellent mileage. Want tangible proof? Peruse this link:

Check out the "2007 results" link. The winning entry got 1541 miles per gallon!!
If a "normal car" with normal accouterments got one-tenth of that mileage, it would be a "breakthrough". Yet it is very possible. The winning cars in the SAE contest are very efficient at cutting through the air, the largest component of force needed when traveling in a vehicle from "A" to "B". Air resistance to "moving through space" goes up exponentially as the speed increases. By restricting all cars to a maximum of 34 mph (55 kph), a lot of energy will be saved in not pushing aside so much air. In fact, I'm speculating that if cars that could not exceed the 55 kph limit went into production for a few years, I think a mileage of 400 miles to the gallon would be routine! Why? Weight.

Beyond the aerodynamics, the other killer of efficiency in internal-combustion-powered-vehicles is weight. Is it any wonder all the "SUV"s of the world are only getting between 15 and 24 miles to the gallon? Heck, in 1987, my own 1986 Toyota Camry I consistently got 38 miles to the gallon, on long freeway jaunts, traveling at 65 miles an hour?? What changed??

Weight. All the "car columns" profiling the latest and greatest cars tout "top speed" and "0-60", but usually downplay the weight. That is because SUVS routinely weigh two tons! So if cars are used 85% of the time to haul one person, the situation becomes one where a vehicle weighing 4000 pounds is used to haul around a 200 lb. human (more or less). Isn't this absurd, when a bicycle weighing 25 pounds can haul around the same 200 lb.?

So, what's with all the weight? Speed. If you are the manufacturer and your little compact can hold 800+ pounds of people plus 100 more in luggage, your compact better be able to stay on the road, stop, and get on a freeway, so you have overbuild the suspension for that max load, the brakes, the power steering, the airbags for a high speed crash, the rollover protection, ...all because the compact CAN go down a steep mountain road, fully loaded at 85 mph! For safety at high speed, you need more weigh. More weight means beefier components ...on and on it goes.

A car that cannot physically go faster than 34 miles per hour; why, that car can meet all possible performance tests with thinner lighter tires, which need less braking, less power steering (if any is even needed) and less structure for rollover, and probably no airbags. Even the glass windows would weigh less; polycarbonate could be used.

A car of current, average size and weight traveling at a constant 60 miles per hour needs about fourteen horsepower to maintain that 60 miles per hour. Fourteen horsepower!! Why do we have 400 horsepower muscle cars?? Because we are addicted to the sense of acceleration. Cars with sluggish acceleration don't sell.

How much power would be required to hit the 34 mph top speed? Let's be generous and say a whopping ten horsepower would give us brisk acceleration in a lightweight car. A single occupant vehicle would need maybe four horsepower to run all day at 34 mph... maybe less. Can you imagine how small that engine could be? You'd never have to "leave your car at the shop". Heck, if your car engine completely blew apart the AAA rescue vehicle could bring you another engine, stick it in, take the bad one away, and you're on your way! Oil change? You'd simply unscrew the reservoir/filter, and screw on a new reservoir/filter.

Except for Interstate Highway travel, most people would not even notice that they could not go faster than 34 mph.

1 comment:

King of the Road said...

Argh. I have no problem discussing your proposal rationally but please get the math and terminology correct. Drag DOES NOT increase exponentially with speed, I see this error in so many places I had to make a blog post on the subject. It increases as a power law, specifically (approximately, all else being equal, i.e., incompressible, inviscid flow, etc.) as the second power of speed. "Exponential" has a well-defined meaning.