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Structural stability: Since the shell is being made out of Carbon Fibre, it will be a Single structure, that would be molded. This will provide more rigidity to the structure to bear high dynamic loads and the shell is intact to the chassis throughout the period of operation.

 

• Ease of fabrication: Since the shell is being made out of carbon fibre, a mold would be required to manufacture the same and hence manufacturing the shell would be easier in this case.

• Space optimization: Having the cross-sectional area optimized and restricted, the way out for maximum space is to increase the length of the pod and hence keeping weight reduction, cost-cutting and every other bit in mind, the needful has been done.

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The use of I-section is preferred over H and C section beams as their torsional rigidity is less than that of I section.

 

The I-section is symmetric about both the axes making it a more torsionally rigid structure and can take great amount of loads and distribute it evenly on both the axes.

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Dry Ice Cooling

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We are implementing the dry ice cooling method for cooling of battery packs.  This is a potential method to cool down the heat generated by the battery pack because dry ice sublimates at - 78.5 degrees Celsius at standard atmosphere conditions.

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Stability System

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Purpose of the stability system:

• To increase the surface area of contact between the I-track and the pod for maximum stability.

• To provide the necessary friction and help prevent slip.

• To provide, better traction control.

• To prevent the pitching and yawing motions of the pod.

 

Design of the system:

• The design has been made keeping in mind the efficiency, compactness and the easy assembly with the chassis. It has simple geometric features which would be made from easily attainable stock materials.

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Suspension System

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Active air suspension system is being employed in our pod for the following reasons:

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• It increases the ride comfort, by minimizing the jerk.

• It is more efficient than the conventional suspension system.

• It is lighter than the conventional suspension system.

• The stiffness of the air bellows can be widely varied by fluctuating the pressure inside the air bellows.

• A default height, maximum deflection and minimum deflection can be set as per the requirement.

• It doesn’t require dampers to dampen the unwanted vibrations, reducing the vibrations of the pod in case of an encounter with an obstacle.

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Components of Air Suspension System

 

An air suspension generally has two basic components. They are; “air supply & regulation ” and “air bellows”.

 

• Air supply & Regulation:

The air supply and regulation system consists of an air cylinder. Electronic control Unit (ECU), air valves and air lines. The air cylinder outlet is be controlled by the ECU which allows us to vary the stiffness of each air bellow. The valves are to be electronically controlled to allow the passage of compressed air to the bellows.

 

• Air bellows:

They are simple rubber bladder that holds air. The system contains 4 air bellows. The 2 pair of air bellows would be would be attached to the chassis and the skis at an angle of 28.7 degree such that the axis of bellow and wheel are collinear so that the load is transmitted uniformly to the ground via the wheel. The working of Active Air Suspension has been explained in a flowchart manner in the following slide.

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Vacuum Compatibility Test

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• The shell is pressurized from inside and external conditions are taken to be at a pressure of 868.74 Pa.

• The shell is then placed into a cylindrical section with the above parameters.

• The test is performed successfully and a conclusion is drawn for the same.

• We observe that all the systems involved in the test are safe to use in vacuum conditions.

• The shell does not collapse and protects the internal components from any sort of damage.

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Payload Capability

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The Chassis of the pod has been built considering a factor of safety 11.36 with the material being Carbon Fibre IM 10. The Chassis would be able to bear a load of approximately 350 Kg with a factor of Safety 4. The propulsion system though would be able to propel a load of 200 Kg with the given set of motors currently used.

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Skis

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Skis play a major role in the mounting of the wheel and the suspension system.

 

• The presence of skis prevents the formation of different oscillation frequencies in the wheels. So, there could be only two possible different frequencies which the wheel will come across in its entire run.

• We subsequently decrease the degree of freedom of the wheels as well as allowing only longitudinal rotation.

• Each ski has two wheels placed in the front and rear. Two skis with a total of four propulsion wheels will propel the pod at the speeds of 120m/s. 

 

Application:

• To hold the wheel in place and prevent its lateral movement.

• To prevent side slip and turning of the wheel.

• To connect the suspension system with the chassis

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Wheels

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The propulsion of the pod at high speeds would only be possible if there is right amount friction present between the tires and the aluminium track.

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• At angular velocity as high as 15,000 R.P.M or 1570.7963 radians/second, there ar chances of the efficiency going down due to inadequacy in friction between the two surfaces. Henceforth for the pod to run efficiently on the aluminium track there needs to be an optimized amount of friction between the two surfaces, also at such high angular velocities the material of tire wears out sooner.

• At such velocities a lot of heat energy is also released due to the interaction of the two surfaces. Henceforth a material which can withstand at such a condition needs to be chosen.

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Viton rubber is one such fluoroelastomer which can withstand temperatures as high as 380-degree Celsius

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Experimentation: The samples of Viton rubber were collected and tested before they were actually employed for the same. Sample of Viton rubber was coated on an Aluminium 6061-T6 pin and was tested against the test track material(Aluminium 6061-T6) on a tribometer.

 

•  Aim: To find the frictional torque between Viton Rubber and Aluminium 6061-T6

• Apparatus required: Tribometer, Viton rubber samples, Aluminium 6061-T6 pins, Aluminium 6061-T6 disc, Loctite superglue, M4 countersunk screws, Emery Paper- 220, 400, 600 and 800.

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Transient Structural was performed on the wheel in order to validate and rectify the design using Ansys 18.1

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