How Three-wheel Cars Work

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Three-wheeled cars have been around for a very long time, even pre-dating the Patent Motor Wagen design. For instance, in the 15th century Leonardo da Vinci created sketches of a primitive, three-wheeled car that was propelled using a wind-up mechanism similar to a clock. And French engineer Nicolas Cugnot created a large, tractor-like vehicle in 1769 that used a three-wheel design and was powered by a steam engine.

As the world moved into the 20th century, three-wheelers gained in popularity as low-cost, lightweight vehicles -- that is, until about the late 1920s, when cars generally started going more along the four-wheel track. 

But after World War II, things changed once again. In war-torn countries like England, France, Germany and Japan, gasoline and mechanical supplies were scarce, but people still needed a way to get around. In many cases they couldn't afford full-sized, four-wheel cars or those cars simply weren't available and a motorcycle was far too small to meet their needs.

In postwar England, Bond Cars Ltd. found success in making small, three-wheel cars powered by single-cylinder motorcycle engines. These small cars proved popular among motorcyclists looking to protect themselves from the elements, and as an added benefit, the car didn't require an automobile driver's license. In addition, their ability to achieve more than 100 miles per gallon (42.5 kilometers per liter) was extremely helpful at a time when fuel was expensive and supplies were scarce. Bond Cars continued to make three-wheelers well into the 1970s.

BMW began selling a three-wheel version of the colorful, egg-shaped Isetta micro car during the 1950s. Again, the three-wheel variant of this car was extremely popular in Great Britain, because they could be driven there with a motorcycle license. In Japan, car companies like Daihatsu made three-wheelers that became popular as taxis, light trucks and other utility vehicles. Again, many were small and powered by inexpensive motorcycle engines. England's Reliant Robin, a fiberglass micro car, was made off-and-on for more than 30 years, and arguably remains one of the most iconic three-wheelers of all time.

But where do three-wheel cars fit in today? While it's true that there are far less of them around now than in the 1950s and '60s, modern examples include the electric CityEl, the performance-minded Can-Am Spyder and numerous exotic concept cars from companies like Volkswagen and Peugeot.

So, three-wheelers are more common than many people may think. In the next section, we'll find out about the many different ways three-wheeled cars are designed.

A three-wheel car is, by design, basically a triangle shape. Depending on where the passengers sit, the location of the engine, and the placement of other critical mechanical components, this means the car either has two wheels up front and one in the rear or two wheels in the rear and one up front. The engine can drive the single rear wheel or the two rear wheels, and the steering can be done either way as well.

Having one wheel up front and two in the back is known as the delta configuration. Karl Benz's creation followed this setup, as did the Reliant Robin. The original three-wheeled Mazda automobile, the Mazda-Go, was configured this way to allow for a pickup truck bed in the back.

The benefit to the delta setup is its inherent low cost. Most cars set up this way have the engine driving the rear wheels and leave steering to the front one. It's relatively easy (and inexpensive) to build a steering setup with only one wheel.

The second type of three-wheeler setup is called the tadpole or reverse trike. The opposite of the delta, this formation has two wheels up front and one in the back. This setup is the basis for the speedy Campagna Motors T-Rex, as well as the exciting Volkswagen GX-3 concept vehicle.

Tadpole designs are much more stable than the delta setup because the back wheel drives the vehicle while the two wheels up front are responsible for steering. There's also an aerodynamic benefit, since the vehicle is shaped almost like a teardrop -- wide and round up front and tapering off in the rear. This allows air to flow easily over the vehicle's bodywork.

The tadpole design is becoming more and more favored among auto designers for its stability, aerodynamics and ability to house a fuel-efficient engine. In fact, a number of current hybrid and electric concept vehicles use a three-wheel setup along these lines. As cars get more eco-friendly, you may be seeing more and more three-wheelers on the road than ever before.

On the next page, we'll examine the advantages behind having a car with fewer than four wheels.

Whenever gasoline has been scarce or expensive, three-wheel cars have been there to provide people with the efficient transportation they need. Many of the early three-wheeled vehicles ran on motorcycle engines and they were great at sipping fuel, while also providing the storage space, seating and protection from the elements you can only get from a car.

In addition to hosting smaller engines, the triangular shape is more aerodynamic than a boxy car, meaning it can achieve better fuel economy simply from its body design alone.

They also offer far more safety than motorcycles. While smaller than cars, many of them have enclosed bodies with seatbelts and windshields, keeping the driver and passengers protected from outside impacts.

A three-wheeled car's small size -- plus the inclusion of a powerful engine -- can mean exciting performance as well. The F3 Adrenaline, a three-wheel vehicle from TriRod, is made of carbon fiber and boasts a powerful V-Twin engine. Because it has three wheels, it's built much lower to the ground than a typical motorcycle and that lower center of gravity gives it incredible handling characteristics.

Keep in mind that three-wheelers are also much more stable than their two-wheeled cousins. You don't have to worry about learning to balance a three-wheeler or putting your foot down to keep it upright when the vehicle stops. The vehicle's triangular base means it can support itself, and they also don't have the uncomfortable seating that characterizes motorcycles.

Also, in many countries, a three-wheeler is treated as a motorcycle for licensing and title purposes. Many drivers like this because they can own a three-wheeled car without going through the trouble of getting an automobile driver's license.  

We've looked at some of the advantages three-wheeled cars have over vehicles with an even number of wheels -- now what are the drawbacks?

While a three-wheel car often combines the advantages of a car and a motorcycle, they also carry the weaknesses of both. How so? First, let's look at the small size. There have been very few large three-wheelers throughout automotive history -- most of them end up being subcompacts or motorcycle-sized vehicles.

That means you won't see too many three-wheelers with large engines, and despite the high-performance of some models, most of them haven't set the world ablaze with their speed. For example, the Reliant Robin could only muster 0 to 60 miles per hour (0 to 96.6 kilometers per hour) in about 16 seconds. Another point to remember is they aren't quite as agile as motorcycles can be.

Because of their smaller size, three-wheelers don't offer the seating and storage options you see in most four-wheel cars. They may be large enough for some people to use to get around town, but a small three-wheeler won't meet the needs of a large family with a lot of people or cargo to haul.

One of the main problems with three-wheel cars is instability. Anyone who's ever ridden a tricycle knows how easily they can tip over. That's because many three-wheel designs -- in the delta configuration -- are simply more prone to tipping over than four-wheel cars are. Three-wheeled cars, with one less wheel to provide support, carry an increased possibility of roll over in a corner. However, this instability can be reduced by choosing a three-wheeler with a tadpole setup -- two wheels up front. Cars that follow this pattern have proven to have greater cornering ability than the delta setup, which is why nearly all new three-wheel designs have gone this route.

We've weighed several of the strengths and weaknesses of three-wheeled vehicles. Next, let's look at what it takes to own one, including prices and laws regarding them in different areas.

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Are three-wheeled cars street legal? In most cases, the answer is yes. But it's always smart to look into your local laws before buying one, just to be sure. In the United States, three-wheel car laws vary from state to state. They're typically classified as motorcycles, and drivers have to be licensed as a motorcycle rider to drive one. Motorcycle insurance is usually a requirement, too. And because three-wheeled cars are considered a motorcycle in most states, you can even drive them in the commuter lane.

You have plenty of options if you decide a three-wheeler is more your speed than a motorcycle or a compact car. One route to go is to buy a classic three-wheeler, like a Morgan three-wheeler, a BMW Isetta, a Reliant Robin or a Bond Bug from classified ads or on a site like eBay.

If you want something a little newer, there are many ways to go, too. Especially since three-wheelers are becoming increasingly popular as 'green' vehicles. If you want something that offers more speed than Earth-friendliness, consider the Campagna Motors three-wheeled T-Rex. It has a 200 horsepower engine in a body that only weighs 1,040 pounds (471.7 kilograms). This offers a stunningly fast three-wheel automobile that, at $50,000, can put supercars that cost four times as much to shame [source: Campagna Motors].

If you decide to go the three-wheel route, know that you aren't alone. Millions of people use these vehicles around the world every day as their main source of transportation or as a just-for-fun way of getting around town. And with the advantages they present to electric, hybrid and other eco-friendly car designs, it doesn't look like they're going away anytime soon.

To read more about three-wheel cars and other related topics, follow the links on the next page.