Design of backdoor

CAR BACK DOOR DESIGN

Aim: To design back door of car using given outer class 'A' surface.

What is back door of a car?

A door which is located at the rear side of a car which gives access for the boot space to store luggage, spare wheel etc.

These doors can be operated manually or electric powered. In most of the luxury cars door is electrically operated.

Types of doors based on working position,

1. Top Mounted Door
2. Side mounted Door
3. Bottom Door

Design Considerations for a Back Door-

• Rear Visibility for Functionality and Safety.
• Boot Space and Accessibility.
• Type of Backdoor Opening (For individual vehicle requirement).
• Fixing and Support Structures like Hinges and Gas stays.
• Mounts for Wiper Motor, Back Lights/Tail Lamps and Other Wiring loops.
• Fit and Clearance (For Assembly and Aesthetically looks).
• Strength Of Backdoor (Require in collision).

The components designed in this project are:

1. Back Door Outer Panel

2. Back Door Inner Panel

3. Hinge Reinforcement LH and RH

4. Gas Stay Reinforcement LH and RH

5. Wiper Motor Reinforcement

6. Latch Reinforcement.

The above components are shown in the below image

Back Door Outer Panel:

Outter panel is the styling surface of the backdoor.Glass for rear visibility is mounted on the outter panel upper.Rear lights are also mounted on the outter panel upper.

Number plate is mounted on the outter panel lower.Spot welds and other manufacturing process should done only on the inner panel because the outter panel is the styling surface which should not have any scratches or welds .Because it affects the style of the car which leads to bad impression on the customers.

Back Door Inner Panel:

Car backdoor inner panel is made of either steel or alumminium.Most of the luxuary car's inner panel are made of aluminium because of is properties.But the cost of aluminium is high.

	STEEL	ALUMINIUM
PARTS	Parts are stamped	Parts are casted
REINFORCEMENTS	Necessary	Can be neglected
THICKNESS	Constant	Can be Varied
COMPONENTS	More	Lessin number
WEIGHT	More	Lighter
COST	less in cost as compared to Aluminium	More as compared to Steel

Cost of aluminium is more as compared to steel .TO easiy understand , the cost of aluminium for inner panel is higher than the cost of all parts of backdoor together.

Bechmark between companies who are using steel and aluminum inner panel

Wiper motor , latch reinforcements,hinge reinforcements and gas stay reinforcements are mounted on the inner panel of the backdoor only.

Hinge Reinforcement LH and RH:

Hinges support the weight of the whole backdoor.Hence, the reinforcements must be provided there too.The emboss is designed in such a way that the hinges should operate freely.The hinge is connected to the rear roof of the car.

Gas Stay Reinforcement LH and RH:

Gas stay is used to lift the backdoor automatically.There are two types of gas stay one is semi-automated and another one is fully automated.In semi automated type the back boor needs little force to lift after that it lift the backdoor automatically.In fully automated , it has power spindle which lift the backdoor automatically.

Wiper Motor Reinforcement:

Wiper is used to to wipeout the rain water falls on the backdoor window.It is actuated by the motor which is mounted on the inner panel.Due to the vibration and heat created by the motor .the inner panel where the motor is mounted gets deform and the parts attached to the motor starts to vibrate which leads to poor NVH.So we have to provide the reinforcement where the wiper motor is placed.

Latch Reinforcement:

At bottom of the panel , reinforcement and emboss are given to accomodate the latch and striker assembly.Generally key operated or automatic remotly controllable mechanism is used to keep the door open or closed.The actuators , recivers and other electronic devices are mounted on the inner panel only.

Hemming:

Hemming is the metelworking process in which a sheet metal edge is rolled into itself.The outter surface of the panel is rolled 2 or 3 times over the inner panel.In first roll the panel is bent slinghtly,and in the second roll the shhet matel is rolled even more and in the last roll it completely fits or covered the inner panel.There must be a 0.2mm gap between outter and inner pannel in both upper and lower side.

Relief:

Draft Analysis:

Draft analysis of inner panel is carried out through the tooling direction only.Only the green areas are acceptable and i worst cases yellow regions are accepted but the blue and red regions are never accepted.

The draft angle for aluminium casted panel is 2 to 3 degrees is enough but if it is steel then the angle is more than 7 degrees.

In this project i considered it as steel and used 7 degrees as draft angle and direction is choosen as tooling direction which is the deep drawn direction.

Conclusion:

As per the objective the backdoor is designed for the given panel.