Keywords

1 Introduction

An All-Terrain Vehicle (ATV) is defined by the American National Standards Institute (ANSI) as a vehicle that travels on low-pressure tires, with a seat that is straddled by the operator, along with handlebars for steering control which can withstand harsh terrains. This paper provides detailed insight regarding the steering, powertrain, and brakes of the ATV. The vehicle is designed in a way to keep the cost minimum, with no compromise on driver safety, ergonomics, and durability of the vehicle providing the thrill factor. The design is such that it can sustain in all weather conditions and must be mobile in rough terrain. A special emphasis has been put on weight reduction [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20].

The design of the various components and assembly of the vehicle has been done using SolidWorks. It was made sure that the vehicle’s weight is kept as light as possible, along with adequate strength and rigidity. The design is highly based on dynamic analysis of components and stress analysis to still ensure safety under the unwanted situation when there is an existence of impact forces. It is made sure, that the fabrication is easy, and affordable [21,22,23,24,25,26,27,28,29].

2 Steering

Steering works as a guiding mechanism which is used by the driver to follow a desired course. In this buggy, rack-and-pinion (manual steering system) assembly has been used [30, 31]. The vehicle has under steer, for which negative camber and damper stiffness have been provided. Though written data shows under steer, it has been rectified. Rack is connected with the tie rods directly of length 15.09 inch using appropriate connectors. The steering ratio is 7:1. The steering angles are: 25.56° (outside wheel) and 40° (inside wheel). The two angles are found with the help of MSC Adams. Table 1 shows the steering assembly specifications.

Table 1 Steering assembly specifications
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Most of the components are custom-made, with the exception of steering wheel, dampers, and rack-and-pinion assembly. Knuckle is to be directly connected to the wheels and made of aluminum because of lightweight, heat resistance, and in case of dynamic loading, fractures will not take place. Tie rods are to be manufactured of stainless steel as it provides high strength (Fig. 1).

Fig. 1
figure 1

Characteristic of wheel motion with rack movement per unit time

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3 Powertrain

For the buggy, the following changes are shown in Table 2.

Table 2 The types of equipment change in ATV
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3.1 Engine

The engine considered is having Max power = 10 HP and Max Torque = 19.6 Nm@2600 rpm. By comparing the two, we have decided to go for CVT as our transmission because of the wide range of gear ratios and are easier to drive. As the terrain is tough the driver will have to change the gears very frequently to tackle the track, using a CVT removes that hassle and the driver is more focused on the track rather than just shifting to the correct gear.

3.2 Gear Reduction

To give the car the initial lift, an additional reduction is introduced which wil ladd to the acceleration. For that part, we are using a chain sprocket reduction as because it is easy to maintain, the ratios can be changed, during testing, if it is not suitable, more suitable according to the rear end of our buggy.

Also, since we are using CVT for the first time, a chain and sprocket are more feasible than a reduction through spur gears. First, we found the resistances with respect to ground that the buggy needs to overcome. The reduction required comes out to be 14:1. Moving on to the reduction design, since the ratio is high the reduction is completed in two steps where, it includes four sprockets and two roller chains. Sprocket N1 would be in axis with the output of the CVT and connected to sprocket N2 using a roller chain. Sprocket N3 would be in a compound with N2 and it would further be connected to N4, using a roller chain, onto the final drive. Referring to the sprocket manufacturers manual, the appropriate service factor was chosen for using a single strand sprocket with hub on both side sides considered that the car would travel at an avg. of 2600 rpm (for max torque). The variation in Tractive force is shown in Table 3. N1 = 23 teeth, N2 = 70 teeth, N3 = 17 teeth, N4 = 68 teeth, because of the design constraint the second reduction is carried out using smaller sprockets. The CVT is tuned to achieve a low ratio of 0.5:1 so that speed does not exceed above 60 kmph. Table 4 give the variation of speed and acceleration with respect to RPM.

Table 3 Tractive forces with respect RPM variations
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Table 4 Tractive forces with respect RPM variations
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3.3 Gear Torque Calculations

The gear torque calculations have been done to find the output torque provided by the engine at the wheels. The calculated amount of the torque is less than the rated torque of the engine which implies that the four sprocket arrangement will provide ample gear reductions to drive the vehicle. The rotational torque (Tr) can be calculated as

Rotational torque, Tr = µW cos αr

α = 30°; Tire size = 22” = 0.279 m = 279.4 mm

Tr = 0.3*293*9.81*cos 30*(0.1359) = 104.17 N-mm2

Mass moment of inertia, I = ½r2 W = ½*293*9.81*(0.279)2 = 11.18 N-m2

V = rω ⇔ 16.66 = 0.2794 ω; ɯ = 59.62 rad/s; ∝ = ω/t = 59.62/20 = 2.981 rad/s2

Iα = 11.18*2.981 = 33.32 N-mm.

Gear torque, Tg = Tr + I*α; Tg = 104.17 + 33.32 = 137.49

Since, ω = 2πN; N = ω/2 π = 9.49/s or 569.6 rpm;

Load power, HP = 2πNT = 7.32 HP

Therefore, Tg > Tr.

4 Brakes

The brakes were designed such that the vehicle stops in the least time and distance. Brakes are the most important of components, when it comes to the safety of the driver. Dual piston floating caliper would be used in our vehicle. This is primarily because it is effective with fewer prices, and even light-weighted [32–42]. Table 5 gives the braking specification [43–48].

Table 5 Braking specifications
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We have opted for Tandem Master Cylinder (TMC), the reason being that if a failure occurs in any of the linings, the remaining will still work and braking failure will be prevented. X-split arrangement would be used in our buggy. This is again because of the safety factor and if any of the brakes fail, the others would still work and bring the vehicle to halt. DOT 3 fluid is to be used in the brakes. It is a polyethylene glycol-based fluid and is commonly used in passenger vehicles. Its dry boiling point (205 °C) and wet boiling point (140 °C) is high and hence does not absorb moisture easily. It withstands high temperatures without getting boiled. SS 410 will be used as brake disc. The reason being that it has very favorable mechanical properties including high corrosion resistance and high strength.

5 Conclusion

After taking the design and calculation of the respective departments, the fabrication of an ATV was carried out and better results were achieved in all the departments, i.e., steering, transmission, and brakes department (Table 6).

Table 6 Vehicle comparison
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A better arrangement for the steering mechanism has been installed, thus improving the steering ratio of the vehicle and the SS for the steering column and aluminum for the rack-and-pinion has reduced the weight as well as given better results for the same. Similarly, CVT has been preferred over manual transmission as it proves out to be over efficient over rough terrain. In the brakes department, comparatively smaller discs have been used thus contributing to the weight issues and size constraint of the buggy, also improving the stopping distance of the vehicle.