**3. The concept of electric go-kart**

For working out creation of the concept, it was assumed that the eKart design should be a simple four-wheeled vehicle with rear-wheel drive, using advantages of an electric drive. The key advantages of the electric drive are the compact size, power-to-weight ratio, high torque of the drive, and the ability to provide almost identical output parameters (speed, power, and torque) [18].

The ability to provide identical driving parameters like ICE go-kart has also become the basis for vehicle chassis design. It was assumed that for the simplicity of the eKart, a tubular flat frame without suspension element will form the chassis.

In the eKarta project, it was decided to use the compact dimensions of the electric motor. It was assumed that each wheel of the rear axle would be driven by a separate engine. This solution will allow to vary the speed of the inner wheel and the outer rear axle while cornering. This will help to achieve better stability with a similar balance of eKart versus the ICE go-kart [15].

The use of an electronic differential is an advantage of the electric motor to provide the same or better driving performance. In the case when the ICE go-kart is moving in a turn with rigidly join left and right wheel by rear axle, forces a large understeer as the inner wheel moves at a higher speed than that vehicle trajectory and the outer wheel moves at a lower speed than the trajectory. Thanks to the torque vectoring correction of independent rear axle motors, eKart handling will be neutral. Disconnection of rear axle wheels and powering them by separate motors make possible to adjust its settings so that, depending on the track, the effect can be configured under or above the steering.

According to the assumptions, the following solution was proposed.

eKart chassis is ICE go-kart chassis with two modifications shown in **Figure 9**.

The first modification marked 1 in **Figure 9** is the additional rear axle support to the left side of the chassis. Support is symmetrical longitudinally to the existing double supports on the right side, in a way that the rear axle can be divided into two components.

Since in the ICE go-kart support of the rear axle on the right-hand side are at the same time structural parts of the engine mounting, modification marked 1 in **Figure 9** will allow the installation of separate motors for both wheels of the rear axles. At the design stage, it will be determined whether the motors are located ahead of or behind the rear axle of the vehicle; as

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eKart will be equipped with electric motors of different power depending on the age category. There can be also different kinds of motor cooling, air cooled and liquid cooled, depending

Potential position of batteries is also shown in **Figure 11**. It was indicated to ensure the best balance of eKarts. The position of the batteries must at the same time ensure maximum protection due to poisoning or burns in case of damage. The position of the batteries has been proposed in places least exposed to other eKarts and track elements (barriers) during the

illustrated in **Figure 11**, both variants are possible.

**Figure 10.** Rear suspension elements of Kosmic MERCURY MY15 [16].

**Figure 9.** Sketch of modification of the ICE go-kart chassis for the eKart construction.

on its power.

The second modification marked 2 in **Figure 9** is the division of the rear axle into two independent elements. Because the rear axle in ICE go-karts connects its fulcrum points (shown in **Figure 10**, marked 2), it is also the structural component of the rear frame of the vehicle. In the ICE go-karts, the rear axle has different stiffness parameters so allow to adjust the rear traction of the vehicle. The traction of the rear axle of the eKart will be adjusted by strut bar between the inner axle support points (not present ICE go-karts) and the spacer between the outer support points (solution in go-karts marked 2 in **Figure 10**).

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**Figure 9.** Sketch of modification of the ICE go-kart chassis for the eKart construction.

Based on battery capacity QB (6), we analyzed the options for designing eKarts for each category, within the limits of the maximum mass of the drivetrain system and the battery. We took into consideration the energy density of today's most efficient Li-ion battery technology (250 Wh/kg) and the technology expected in 3 years time (350 Wh/kg). The analysis is shown

For working out creation of the concept, it was assumed that the eKart design should be a simple four-wheeled vehicle with rear-wheel drive, using advantages of an electric drive. The key advantages of the electric drive are the compact size, power-to-weight ratio, high torque of the drive, and the ability to provide almost identical output parameters (speed, power, and

The ability to provide identical driving parameters like ICE go-kart has also become the basis for vehicle chassis design. It was assumed that for the simplicity of the eKart, a tubular flat

In the eKarta project, it was decided to use the compact dimensions of the electric motor. It was assumed that each wheel of the rear axle would be driven by a separate engine. This solution will allow to vary the speed of the inner wheel and the outer rear axle while cornering. This will help to achieve better stability with a similar balance of eKart versus the ICE go-kart [15]. The use of an electronic differential is an advantage of the electric motor to provide the same or better driving performance. In the case when the ICE go-kart is moving in a turn with rigidly join left and right wheel by rear axle, forces a large understeer as the inner wheel moves at a higher speed than that vehicle trajectory and the outer wheel moves at a lower speed than the trajectory. Thanks to the torque vectoring correction of independent rear axle motors, eKart handling will be neutral. Disconnection of rear axle wheels and powering them by separate motors make possible to adjust its settings so that, depending on the track, the effect

in **Figure 8**.

116 Green Electronics

torque) [18].

**3. The concept of electric go-kart**

frame without suspension element will form the chassis.

can be configured under or above the steering.

According to the assumptions, the following solution was proposed.

eKart chassis is ICE go-kart chassis with two modifications shown in **Figure 9**.

right side, in a way that the rear axle can be divided into two components.

outer support points (solution in go-karts marked 2 in **Figure 10**).

The first modification marked 1 in **Figure 9** is the additional rear axle support to the left side of the chassis. Support is symmetrical longitudinally to the existing double supports on the

The second modification marked 2 in **Figure 9** is the division of the rear axle into two independent elements. Because the rear axle in ICE go-karts connects its fulcrum points (shown in **Figure 10**, marked 2), it is also the structural component of the rear frame of the vehicle. In the ICE go-karts, the rear axle has different stiffness parameters so allow to adjust the rear traction of the vehicle. The traction of the rear axle of the eKart will be adjusted by strut bar between the inner axle support points (not present ICE go-karts) and the spacer between the

**Figure 10.** Rear suspension elements of Kosmic MERCURY MY15 [16].

Since in the ICE go-kart support of the rear axle on the right-hand side are at the same time structural parts of the engine mounting, modification marked 1 in **Figure 9** will allow the installation of separate motors for both wheels of the rear axles. At the design stage, it will be determined whether the motors are located ahead of or behind the rear axle of the vehicle; as illustrated in **Figure 11**, both variants are possible.

eKart will be equipped with electric motors of different power depending on the age category. There can be also different kinds of motor cooling, air cooled and liquid cooled, depending on its power.

Potential position of batteries is also shown in **Figure 11**. It was indicated to ensure the best balance of eKarts. The position of the batteries must at the same time ensure maximum protection due to poisoning or burns in case of damage. The position of the batteries has been proposed in places least exposed to other eKarts and track elements (barriers) during the

• Wheelbase 1050 mm • Battery mass 23.2 kg

track, 8–12 m wide, clockwise direction (**Figure 13**).

assembly of eKart is presented.

**Figure 13.** Short track of Tor Łódź © circuit.

**5. Tests of eKart**

**Figure 12.** Assembly of eKart.

The construction of the eKart was realized in cooperation with car enthusiast student club from Faculty of Mechanical Engineering of the Technical University of Lodz. In **Figure 12**,

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The purpose of the test was to verify the concept and the design assumptions in experimental research. Test run was conducted on the Tor Łódź circuit in Stryków, Poland 596 m short

Test runs were carried out on November 19, 2016, air temperature 11°C and atmospheric pressure ~ 992 hPa. The surface at the start of the tests was wet, while the test surface was mostly wet.

**Figure 11.** Potential position of the main components of eKart.

crash. The proposed battery position at the rear of the vehicle is located between the rear axles and is protected by a rear bumper, and lateral side seats are secured with side chassis, aerodynamic elements, and a bumper. The front battery compartment is located at the fuel tank of ICE go-kart. The advantage of rear or side mounts is the distance to the motor, while the advantage of the front position is a better eKart static balance.
