PRELIMINARY DESIGN OF AMPHIBIOUS CRAFT

Firdaus Bin Mahamad, Ab Saman Abd Kader Universiti Teknologi Malaysia, Skudai, Malaysia

E-Mail: firdaus_mahamad@hotmail.com

ABSTRACT

This work is to present conceptual design of an amphibious craft that has great reliability and terrain capabilities. This craft is designed to operate like ATV (all-terrain vehicle) that can travel at extreme environment with a suspension system designed to move on uneven surfaces. The difference is, this craft has amphibious capability that can travel both land and water, where practical ATV can’t do. In this work consists the calculation that involves in determining the center of gravity, hydrostatic force, wheel size, engine power, stability assessment and initial costs for development an amphibious craft. Finally, it is proposed that this concept can be improved in the future because it has the potential to be applied in Malaysia as a recreational craft or craft that can be used for patrol and surveillance by the authorities.

Keywords: amphibious, roller craft, stability.

1.0 INTRODUCTION

Tourism industry in Malaysia has been traditionally concentrated and promoted towards international markets since its infancy stage in 1960s. Until todays, the tourism sector has grown tremendously and has been ranked the second largest foreign income earners behind manufacturing in 2000 and its subsequent years [Tourism Malaysia, 2003]. Despite the importance of alluring more and more international travelers to visit Malaysia, the domestic front cannot be overlooked for their vast benefits and numerous untapped potentials. After a string of crises that effect international arrivals on recent years, the domestic tourism industry in Malaysia started to be given priority by the Malaysian government.

One of the activities of the tourism sector is extreme sports has grown extensively today. This sport involves driving ATVs in the appearance of challenging terrain, for example in the forest and coast. Tourists can enjoy the beauty of nature through this activity. As we know, Malaysia consists of a variety of unique

terrain, which consists of mangrove swamps, lakes, rivers and others. But in this situation, ATV vehicle have a problem through the river and swamp areas, because, ATV unable to float on water with small and heavy wheel. So the solution needs to be done by introducing a vehicle that is capable of amphibian through swamps and rivers without any problem. This vehicle is capable to drive at terrain area and also on water which other ATV can’t do.

2.0 AN AMPHIBIOUS VEHICLE

An amphibious vehicle (or simply amphibian), is a vehicle or craft, that is a means of transport, viable on land as well as on water – just like an amphibian.

This definition applies equally to any land and water transport, small or large, powered or unpowered, ranging from amphibious bicycles, ATVs, cars, buses, trucks, RVs, and military vehicles, all the way to the very largest hovercraft. Classic landing craft are generally not considered amphibious vehicles, although they are part of amphibious assault.

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6.0 STABILITY

Intact stability, height of the center of gravity, and static stability diagram of a multi-hull ship are determined by the space and weight distributions. Metacentric height, as an index of transverse stability, can vary within a wide range from the value typical for conventional ships to values by an order of magnitude higher than that. Static stability diagrams an also vary greatly. Usually, stability puts no constrains when designing the multi- hull ships [V. Dubrovsky et al., 2001].

The essence of stability calculations is finding the force couple between buoyancy and weigh. This is the moment of force which a stable craft develops to counteract the overturning moments arising from external forces. From the configuration of the body, KB = 10cm, KG = 83cm. Then, GM = 132cm. The craft has positive stability for the Meta center in above the center of gravity (Figure 6).

Figure 6: Craft roll motion

7.0 DESIGN SPECIFICATION

The design specification of an amphibious craft is the result for this project. The design specification will be including all aspect about an amphibious craft that has been got from analysis before. The design specification of an amphibious craft is show in Table 7.

Table 7: Developed an Amphibious Craft Specification

CHARACTERISTICS SPECIFICATION Capacity Single seat, one

person. Overall length 2652mm Overall width 3363mm Overall height 1741mm Wheelbase 1832mm Gross vehicle weight 243.02 kg Drive system Shaft Front Suspension Independent,

Double Wishbone, oil-damped, spring preloaded, 5 way adjustable.

Rear suspension Independent, Double Wishbone, oil-damped, spring preloaded, 5 way adjustable

Front brakes Dual disc, hydraulically operated

Rear Brake Sealed oil-bathed multi-disc

Steering type Skid Steering System

Drive type 4-wheel drive Transmission Automatic × 2

speed with reverse and diff-locked 4WD

Wheel size Front: Diameter: 0.70m Width : 0.56m Front: Diameter: 0.70m Width : 0.56m

Max. speed 50km/hr.

M

BK

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8.0 DISCUSSION

This project is focusing on the preliminary design that including the hydrostatic calculation to determine the optimum size of wheel for an amphibious craft. The design structural is the design of the modified chassis from original dune buggy chassis that involved component design consideration. The weight and center gravity of craft is also calculated in this project in order to do stability assessment to know whether that craft is save or not when travel through water. And finally cost estimation of this project was calculated to get the initial cost in fabricating this craft.

This proposed projects that can be continue by next project student for their future project in prototype model development. In this project there is still several aspects that can be improve or upgraded in the future. Such as, for wheel design should doing further research in undershot water to improve the performance of wheel propulsion and power estimation.

9.0 CONCLUSION

Overall, this design had been successful in its main objective which is to produce an amphibious craft. The main basic concept that had being selected to be used in this kind of study for development an amphibious craft is cylindrical shape of wheel and with modified buggy chassis. This concept is more practical based on the selection technique used during the design process. From the design, wheel size was calculated based on hydrostatic calculation to estimate the buoyancy size that need for support an amphibious craft.

In case chassis design, the chassis design was taken from original buggy chassis and some modification for new chassis in order to suit an amphibious craft design requirement. Meanwhile, for material selection

had been done by using light weight material and can wind stand from surrounding environment. Drive system used in this design is 4 wheel drive system and for steering system is skid steer system. This system was being selected because of its high efficiency during moving and maneuvering on water.

Finally, an analysis for stability assessment by using basic stability for multi-hull method, based on data and information from the wheel design. The outcome of the analysis for the design was the value GMT is positive and adequate initial stability.

Therefore, as a conclusion, the design for an amphibious craft had been successful produced thus fulfilling the criteria, objective and primary target of the study.

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