1. Ordering 3-Wheelers:
-A- Short 3-Wheeler history:
We've all seen 3-Wheeler images. The Morgan Trike had two front steering wheels and a rear driving wheel. It was popular in England during the thirties:
Other 3-Wheelers appeared after the second world war. From left to right: The Messerschmidt with its roof opening like in older airplanes, the BMW Isetta that had a front opening door and two side by side rear driving wheels, and the Vespa delivery tricycle:
Nowadays, 3-Wheelers win most fuel economy competitions:
In fact, lots of 3-Wheeler vehicles have been developed over the years and can be found on the internet.
In north America and although many have heard about the T-Rex these last years, its obvious that there are few 3-Wheelers on the roads. So the first impression is to consider that 3-Wheelers cannot be as functional and competitive as conventional 2-Wheeler road motorcycles.
-B- A first question: Can 3-Wheelers be stable?
3-Wheelers ... only have three wheels. For many persons, they are thus non-stable and they present a risk of overturn in curves.
Curiously, it's taught in Mechanical Engineering, that only three supporting points are needed to hold an object against a plane, and that four supporting points give an over-static system (that has too many supporting points).
On the other hand, many may recall having overturned when they were young and riding their tricycle, at 'high' speeds ... Others may remember the off-road 3-Wheelers of the early 1980's that had a single front wheel and overturned easily when breaking while turning. This caused their elimination of the North American market.
Stability of 3-Wheelers was thus often questioned, resulting in the NHTSA (National Highway Traffic Safety Administration of the USA) mandating a workgroup to clear out the issue. This gave the DOT HS-806-093 report:
An essential conclusion of these report can be found on page 112:
This conclusion is easily understandable if a 3-Wheeler with two front wheels, such as to the right, is considered.
You can jump to section 4. Mechanical analysis of 3-Wheeler's stability, for a simple but more complete visual analysis and for a more detailed mechanical analysis.
So if the location of the center of gravity is adequate, a 3-Wheeler may then have a safety margin against rollover as good as for any 4-wheeler. Thus, any 3-Wheeler 'can' be stable on the road provided it's well designed.
Obviously, 3-Wheelers are not all well designed. Moreover, right from the start they are not created equal with their own specific component layout that does not always permit positioning the center of gravity correctly.
-C- Component layout of 3-Wheelers:
In the case of 4-Wheel cars, the general layout of the engine, the steering and the driving wheels has a dramatic influence on the potential of these vehicles. For example:
- A car with front engine, front steering wheels and rear driving wheels
has room up front for a larger engine and a fair weight up front for high speed stability on highways. Rear traction (or
propulsion) insures strong starting accelerations permitted by the bigger engine, since accelerations transfer weight at
the rear to insure the necessary ground traction. This front-engine/rear-drive layout thus lets cars like the Corvette
or BMWs accelerate fast while offering good straight line stability on highways.
It's the same with 3-Wheelers: Their component layout determines their intrinsic advantages and disadvantages, and they are far from being created equal. Thus, it can be very informative to order them in terms of their component layout.
-D- Ordering 3-Wheelers in terms of their component layout:
Click on the following links to examine this classification:
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