Roof challenge

ROOF DESIGN CHALLENGE

Automobile roof plays an important role such as protecting occupants in case of rollover and also function to shield occupants from sun or rain. While the roof is part of the styling surface of an automobile, its inner structures include components such as:

1. Front Roof Rail
2. Bow Roof(s)
3. Centre Reinforcement
4. Rear Roof Rail.

The structures listed above provide support to the roof and serve as reinforcement. There are certain considerations that determine the number of structures used which include:

1. The flatness of the roof
2. The length.

Generally, the length of the roof of a vehicle determines the number of bow roofs to be attached.

COMPLETE ROOF ASSEMBLY

The structures of a roof assembly are located at specific positions to support the roof outer panel.

FRONT ROOF RAIL

The front roof rail is critical in the design of the roof as it is the component that supports the windshield. In the design of the front roof rail, the driver's visibility and headroom must be considered.

BOW ROOF(S)

Depending on the design and strength requirement of a roof, more than one bow roof can be designed and inserted in the roof design. Basically, roofs with flat surfaces tend to be weak and then require bow roof(s) for support.

CENTRE REINFORCEMENT

Some designs might be created with a combination of a bow roof and a center reinforcement. The bow roof on this is attached to the inner surface of the roof using mastic seals for better reinforcement.

REAR ROOF RAIL

This is located at the rear of the roof where the tail-gate is mounted. In the design of the rear roof rail, the rear passenger's headroom is taken into consideration.

ROOF OUTER

This is the part that is directly visible to the onlookers. The length and the curvature of the outer roof determine the number and the sequence of support that is required.

ROOF SECTION

ROOF DESIGN CONSIDERATIONS

In the design of a roof, certain factors are taken into consideration:

1. Heat Distortion Criteria
2. Snow Load Prediction

Heat Distortion Criteria:

In other to determine the heat distortion criteria, certain points are created on the surface of the roof. The radius and length of these points are measured.

Heat Distortion Values

s/n	BOWS	Rx	Ry	R	I	L	t	R*2/t	W	OK/NG
1	FR/1st	5729.6	2186.4	3165.03	306.5	2028.4	0.75	13356553.20	1.41	OK
2	1st/CTR	5029.4	5971.2	5459.98	522.9	2028.4	0.75	39748508.80	2.14	OK
3	CTR/2nd	3977.1	10588.2	5782.28	423.9	2028.4	0.75	44579682.66	2.12	OK
4	2nd/RR	3237.1	14881.2	5317.49	435.9	2028.4	0.75	57700933.20	2.01	OK

Snow Load Prediction

Certain intersection points are created on both the x, y, and OY axis of the roof. These points are measured, including the length of the roof and the distance between the bow roofs and the rear roof rails.

Snow Load Prediction

BOWS	Rx	Ry	Lx	Ly	Y	iy	s	My	a	t	Qr OK/NG
FR/1st	4778.28	2278.54	1154.04	2028.4	402.18	237.34	498.54	654033.16	0.9	0.75	2.39 NG
1st/CTR	3575.42	5873.95	1096.37	2028.4	594.89	74.09	542.80	852780.77	1.03	0.75	0.33 NG
CTR/2nd	4276.92	11089.51	1065.67	2028.4	490.71	57.28	495.20	754559.86	0.86	0.75	0.13 NG
2nd/RR	3933.05	3933.05	1050.73	2028.4	499.69			763881.09	0.84	0.75

According to the calculated values of Qr, the roof is not satisfying the Snow Load Prediction in any of the areas, so an emboss will be created on the outer surface of the roof.

OUTER ROOF WITH EMBOSS

Embosses are created for better rigidity and to compensate for areas that are susceptible to deformation.

SECTION MODULUS STUDY

This study determines the strength of a structure before manufacturing. This is to determine how the structure will perform and if the structure is strong enough. The study is performed on the bow roofs and the center reinforcement.

front roof rail study

bow roof one modulus study

center reinforcement study

bow roof two study

rear roof rail study

bow roof one draft analysis

bow roof two draft analysis