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A new 0.9-liter 4-valve-per-cylinder liquid cooled engine was developed for 1984 model motorcycles. This new engine was optimized from the standpoint of performance, durability, and weight efficiency. Semi-Flat slide carburetors, high compression ratio, relatively short stroke and large valves were employed. This engine was upgraded every other year with changes in displacement. Induction system, exhaust system, and valve train. This paper describes, from the viewpoint of the designer, the evolution of the 4-valve liquid-cooled engine from the 1984 to 1988 models. In that evolutionary process we employed: (1) semi-down draft carburetors with smooth air ducts, (2) a computer-aided intake and exhaust port design and manufacturing system. (3) individual rocker arms. (4) a cool air intake system. (5) lightweight pistons. (6) angle -controlled tightening of connecting rod bolts.

A waterjet propulsor has come to be used more popularly for high speed watercrafts such as personal watercrafts. The most difficult problem for designing the waterjet system is that a tradeoff is required to properly determine the best parameters for the waterjet pump and subsequently the best overall propulsion system. This paper presents the design method and performance improvement of the waterjet propulsor used for personal watercrafts. The authors have clarified the performance of the individual component in the waterjet propulsor and improved the component efficiency empirically, and established the method to estimate the thrust and power characteristics of the propulsor on board from the component test results and other design parameters, which enables the optimization of the waterjet system.

Motorcycle configurations, such as CG (center of gravity) location, have come to be fixed to the current ones by trial and error since motorcycle was born. Generally motorcycles' ratio of CG height to wheelbase is relatively higher than four-wheel cars'. We have analyzed the optimal motorcycle CG location with relatively simple formulas, which we have derived to calculate the maximum acceleration with three performance limitations and calculate the maximum speed and the shortest time to run through a course. The results show that the calculated speed is significantly close to actual sport motorcycle's and that the optimal CG locations for various courses are bounded in a certain limited area which is near actual sport motorcycle's.

The Japanese Quiet Short Take Off and Landing experimental aircraft named ASKA was developed and flight tested during 1977 till 1989. The control system hard and software were examined by the functional mock-up with using the actual hardware. The small longitudinal limit cycle was observed in the closed loop test when the Pitch Control Wheel Steering software was on in the mock-up testing. In this paper, first, the method to analyze and to expect the limit cycle based on the describing function was shown. The limit cycle was induced due to the nonlinearities in the automatic control mechanism. The nonlinearities in the hardware were examined to make the model to simulate the system on the computer. The method was shown effective to predict the limit cycle in the mock-up. Second, with using the flight measured dynamics, the limit cycle was concluded as on border line between existing and not, which coincides with the actual flight result.

In line with the increase in the output of motorcycle engines, there has been an increase in incidents of the seizure between shift fork and gear because of the increased thrust force. We designed a test method that uses actual shift forks to simulate actual sliding conditions, then used that test method to evaluate the feature of the shift fork sliding and the different shift fork surface treatments. The shift fork slid against the gear not as surface contact but as tilted contact. We selected the candidates from the view that the surface treatment of the shift fork contact surface to give it higher seizure resistance when in tilted contact is required. We evaluated chromium nitride thin film, diamond-like carbon thin film, molybdenum sprayed coating, and sulphonitriding, and molybdenum sprayed coating exhibited the highest seizure resistance. The conformability plays a significant role in the sliding between the shift fork and the gear.

The rocker arm has a function to lead the cam shaft rotation to the valve operation. There are cases when damages are caused due to abnormal wear at the sliding part, causing certain problems. Authors classified the wear phenomenon, and realized a systematic analysis on the possible cause of the damage. As a result, it was revealed that the damage was of two types, and to prevent the hard wear, it is effective to apply shot peening before plating. The prototype rocker arm was test under various lubricating conditions, thus actually confirming that the occurrence of wear was largely reduced.

Electroimpact and Kawasaki Heavy Industries (KHI) have produced a new riveting process for the forming of Briles type rivets in Boeing 777 and 777X fuselage assemblies. The Briles rivet is typically used for fuselage assembly and is unique in that it has a self-sealing head. Unlike conventional headed rivets such as the NAS1079, this fastener does not require aircraft sealant under the head to be fluid tight. This unique fastener makes for a difficult fastening process due to the fact that interference must be maintained between the hole and fastener shank, as well as along the sides of the fastener head. Common issues with the formed fasteners include gapping under the fastener head and along the shank of the fastener. Electroimpact has employed a host of different technologies to combat these issues with Briles fastening. First, Electroimpact’s patented “Air Gap” system allows the machine to confirm that the head of the rivet is fully seated in the countersink prior to forming.

Several elements affect the structure of eutectic silicon in hypoeutectic aluminum alloys [1, 2, 3, 4]. Among them, calcium has been investigated to a lesser extent compared to the typically used sodium and strontium. In order to enhance the thermal fatigue strength of a small engine, the morphology of eutectic silicon in hypoeutectic aluminum-silicon alloys is controlled by the addition of calcium. In addition, the castability and mechanical properties are investigated. Hence, samples containing different amounts of calcium are prepared at different cooling rates during solidification. The results revealed that, with the increase in the calcium amount and the cooling rate, eutectic silicon exhibits a fine morphology in cross-sectional images. Particularly, with the addition of at least 62 mass ppm of calcium in a specific range of cooling rates, refined eutectic silicon is obtained.

Owing to the recent developments in sensors with reduced size and weight, it is now possible to install sensors on a body of a motorcycle to monitor its behavior during running. The analysis of maneuverability and stability has been performed based on the data resulted from measurements by these sensors. The tire forces and moments is an important measurement item in maneuverability and stability studies. However, the tire forces and moments is difficult to measure directly, therefore, it is a common practice to measure the force and the moment acting on the center of the wheel. The measuring device is called a wheel forces and moments sensor, and it is widely used for cars. The development of a wheel forces and moments sensor for motorcycles has difficulty particular to motorcycles. First, motorcycles run with their bodies largely banked, which restricts positioning the sensors.

We developed the motorcycles based on RIDEOLOGY (Ride + Ideology) concept. In the past, the “Ride” was studied by a sensory evaluation with actual driving. However, the recent progress in numerical analysis, there have been developed driving simulators. It allows more quantitative measurement in a sensory evaluation. Therefore, we also developed a riding simulator specialized for motorcycles. In order to develop such riding simulator, there are some technical challenges for motorcycles. First, we need to reproduce roll motion height of motorcycles. Compared to four-wheeled vehicles, motorcycles have a higher center of rotation. Second, we need to reproduce vehicle motion control by rider’s changing body position. A rider controls vehicle’s lean by shifting his center of gravity. Therefore, it is necessary to construct a measurement system of rider’s body position. Third, we need to improve senses of speed and reality.

In order to improve the fuel efficiency and the operating performance of motorcycles, there is a need to reduce their weight. Magnesium, which is the lightest of the various metals currently being used and has a high specific strength, has the potential to satisfy that need. We conducted a study to clarify the weldability and strength characteristics of, and the most suitable surface treatment for, extruded magnesium alloys and rolled magnesium alloys. Based on the stress analysis by the finite element method, we designed a magnesium swing arm and produced the prototype swing arm by pressing hot rolled AZ31 magnesium alloy plates and welding them. The prototype is about 10% lighter and has higher torsional rigidity than a conventional aluminum swing arm.

Fuel-efficient motorcycles are essential for energy conservation and environmental load reduction. To achieve low fuel consumption, reducing the weight of the body parts of the motorcycle is important. This study focuses on reducing the weight of the swingarms, a relatively heavy body part. However, reducing the weight of swingarms is challenging owing to the low flexibility in their shape because swingarms are conventionally made of multiple pipes and casting parts welded together. Therefore, we utilized the integral casting technology and examined a new light weight shape. However, creating a new shape manually is difficult. Thus, we examined a new shape using the shape optimization technology, which has been recently used in additive manufacturing. The shapes fabricated using this technology are generally complex and difficult to manufacture by casting. Therefore, we adjusted optimization condition with casting.

In response to design requirements for lower weight and higher output, the motorcycle engine cylinder block has evolved from a cast cylinder block to an aluminum alloy cylinder block whose bore walls are surface-treated for wear-resistance. Hard-chromium plating, nickel-compound plating, and the like are in wide use as the wear-resistance surface treatment method, but spray technology has recently been attracting attention because of less impact on the environment, superior initial running-in performance and good oil retention. We have been applying a unique spraying method called wire explosion spraying to those models with a special need for wear-resistance surface. In this report we describe our wire explosion spray technology. With the aim of improving the bond strength of the sprayed coat, we studied the effects of the collided particles' form on bond strength in the wire explosion spraying conditions.

“ASKA” developed by National Aerospace Laboratory (NAL) is a quiet, short take-off and landing (QSTOL) research aircraft adopting upper surface blowing (USB) concept as a powered high lift system. To achieving sufficient STOL performance by augmenting stall angle of attack and roll control power, blowing BLC technique was applied to the outboard leading edges and ailerons.Supplied high pressure air to save the BLC piping space,the BLC system which was fit for use of high pressure air was developed. The BLC system, in which BLC air is discharged by a series of discrete jets from small drilled holes (0.8 ∼ 3.0 mm in diameter) arranged in a raw, is one of the unique features of the aircraft. In this paper, the summaries of aerodynamic development of the BLC system are described except for the air piping system.