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When an aircraft wheel touches the stationary runway at high speed, great force from the forward direction suddenly pushes on the tires and landing gear. The widely used vertical shock absorber, known as an oleo strut, is unable to buffer this forward shock. This results in smoking and severe wear of aircraft tires on landing. Therefore, in contrast to automobiles, expensive aircraft tires need to be replaced frequently, adding considerably to maintenance and transportation costs. We first presented new technology for solving this problem during the international conference 2001WAC, and in further detail in 2003WAC. We proposed a new type of landing gear that uses a crank element to absorb horizontal shock from the forward direction. The next focus of attention was the problem of increased weight, resulting from introduction of the crank element. Computer simulations using a basic model of the landing gear showed a 62.1% decrease in the maximum bending moment.

The moment at which a wheel of a landing aircraft touches the ground, the wheel meets great resistance to forward motion. As the undercarriage absorbs almost none of this longitudinal impact, the tire begins to smoke, while the oleo strut undergoes spin up and spring back. Most people are unaware that this phenomenon represents the technological limits of current suspensions. For the wheel to absorb forward impact, it must be given longitudinal stroke. We have created a new type of undercarriage, containing a crank element and adequately gives the longitudinal stroke (1),(2). We clarified the new undercarriage with basic dynamical analysis and computer simulations using an aircraft model with 1 degree of freedom. This simulation showed that when given specific freedom of circular motion, the wheel will accelerate in two stages after landing. Consequently, the sliding friction work on the tire is reduced by a maximum of about 47.4%.

The author proposes a new principle of suspension system. First, a new shock isolation method prevents sudden sharp jolts and enables a body to continue in motion as before, by transforming linear motion into circular motion. This method reduces abrupt deceleration and impact force. Next, we examined the gravity spring action of a pendulum as a new vibration isolation method. Because the pendulum generates longitudinal vibration, it has isolation effect against the longitudinal vibration input. Application of this new principle to aircrafts, automobiles, motorcycles, and even to bicycles and wheelchairs, overcomes the limitations of current technology. This study focused on two as-yet-unresolved safety problems of aircraft undercarriages. One is acceleration impact on the wheels; the other is collision with an obstacle on the runway.

A new suspension system based on the functional movement of the human knee joint has now been developed, utilizing torsion spring as restoring force. The main characteristics of this new suspension mechanism are the application of spring force to both the vertical and longitudinal directions, and the elimination of high energy loss hydraulic, and friction dampers from the suspension system. This suspension was successfully used in the 1995 Race Across America trans-continental bicycle race, completing the grueling trip with no mechanical trouble and with a significant reduction in physical damage and stress to the rider.

To reduce the shock and improve the safety when a motorcycle has a front collision, the authors have created a new suspension system using a crank element and have demonstrated its usefulness. For this purpose, a test motorcycle was made by installing this system on an ordinary motorcycle with an engine displacement of 125 cc. A pulling type impact test apparatus was made to collide the test motorcycle against an obstacle. The shock absorbing characteristics of the suspension system were investigated systematically. The result shows that the impact load on the motorcycle decreased by approximately 30% when compared with ordinary motorcycles, and that the inclination of the motorcycle in a collision was significantly reduced.

In two previous papers, the authors proposed a new type of isolator for shock and vibration and conducted a collision experiment with a new bumper system using the new isolator. This paper is a study on the suspension characteristics of the isolator. In the new suspension system, a crankshaft acting as an isolator swings around the center of the front wheel. The body of the vehicle is mounted on this crankshaft. When an obstacle on the road causes a horizontal shock to be applied to the vehicle, the crankshaft swings around the wheel center and reduces the shock. This swinging mechanism is designed to greatly reduce the stiffness of the suspension system in the longitudinal direction. It is, therefore, expected to improve suspension characteristics. We performed an experiment on a motorcycle which verified that the suspension characteristics were improved as expected.

In the automotive field, safety has become a world-wide issue along with energy and the environment. In an effort to propose a shock isolator based on a new principle, the authors have formulated an idea of isolating and reducing shock by transforming rectilinear motion into circular motion. We call it a swinging unit. According to its principle, it is a shock isolator, not absorber. In the first report, we described this transformation of motion and gave an analysis of the fundamental characteristics of the swinging unit. This time, we prepared a new bumper system composed of the swinging unit and two oil cylinders. An experimental vehicle model was made and the new bumper system was installed in it. Then, an experiment was conducted using the vehicle model to verify whether the new bumper system is effective in reducing shock. The experimental results show that the new system is effective. The cost may be the main factor in deciding whether it will be used in practical applications.

In the automotive field, safety has become a worldwide issue along with energy and the environment. In an effort to propose a shock isolator based on a new principle, the authors have formulated an idea of isolating and reducing shock by transforming rectilinear motion into circular motion. We call it a swinging unit. According to its principle, it is a shock isolator, not absorber. In this report, we described this transformation of motion and give an analysis of the fundamental characteristics of the swinging unit. One of the main components of the swinging unit is a disc which rotates around a pin. This pin is inserted through the disc at a point distant from the center of the disc by an eccentric radius e. Our experimental results showed the unit is effective in reducing shock and an eccentric radius is a dominant factor in this shock reduction.