Roof Design
Roof Design
Roof:
- Roof has no of component inside like front roof rail, bow roof center roof, rear roof rail etc.
- The min thickness of roof is 0.75 mm.
- Depending on type and length of car no of bow roof varies. Bow roof are typically placed on flat surface of car.
- Rear roof rail connects body side outer and back door to roof.
- Front roof rail connects windshield glass, A pillar.
- Roof are to be designed based on roll over condition, for that roof crush test has to be carried out.
Front roof rail: -
- it acts as reinforcement for roof.
- Starting angle should be min 3 degree for ease of manufacturing.
- 5 mm length is kept to accommodate windshield glass as well as rubber reinforcement to accommodate at this location.
- Offset from roof rail is kept about 30 to 35 mm to satisfy visibility criteria.
- Length vary from 60 to 100 mm for maintaining head room clearance criteria.
- Min fillet radius of 3mm +thickness is kept for steel.
Rear Roof Rail: -
- It also has to be designed based on head room clearance and visibility criteria.
- All the reinforcement is attached to roof by means of mastic sealant or spot weld.
Position of bow roof can be checked and finalized based on heat distortion, snow load or roof crush test.
Roof crush is to be carried out after the manufacturing of roof.
Roof Design from Top: -
Roof Design with reinforcement:
Bow Roof Design:
Heat Distortion formula
W = 1.73x10^-3 x L+1.85x10^-8 x (R^2)/t + 1.10x10^-3 x l-2.68
Whereas,
L = Roof Length in X-Direction[mm](Roof dimension in 0-Y)
R = Roof curvature
R = 2(Rx*Ry)/(Rx+Ry)
Rx = X curvature
Ry = Y curvature
t = Roof plate thickness [mm]
l = Bow Roof Span [mm]
The condition to pass this test is given as,
OK<2.7mm<NG
From above value we can identify that roof curvature has to be modified by style design team.
Snowed Criteria:-