Roof Design

AIM:

TO DESIGN THE ROOF OF A CAR FROM GIVEN DATA AND ALL OTHER ENGINEERING COMPONENTS BY FOLLOWING GIVEN MASTER SECTION.

OBJECTIVE:

• THE OBJECTIVE OF THIS PROJECT IS TO DESIGN A CAR ROOF FROM THE GIVEN SURFACE DATA
• DESIGNING MOUNTING FEATURES AND SUPPORTING FEATURES LIKE DITCH AREA, BOW ROOFS, FRONT ROOF RAIL, REAR ROOF RAIL, CENTRE ROOF RAIL, RAINFORCEMENT ROOF RAIL.
• PERFORMING CURVATUR ANALYSIS STUDY FOR BOW ROOF POSITIONING AND HEAT DISTORTION STUDY
• PERFORMING SNOW LOAD CRITERIA FOR THE ROOF.
• PERFORMING DRAFT ANALYSIS FOR ALL THE INDIVIDUAL PARTS FOR MANUFECTURING FEASIBILITY.

INTRODUCTION:

A ROOF IS A PART THAT SITS ABOVE THE PASENGER COMPARTMENT, PROTECTING PASENGERS FROM SUN,RAIN, SNOW AND OTHER EXTERNAL ELEMENTS, IT ALSO PROVIDES SAFETY TO PASENGERS WHILE ROLL OVER.

DESIGN CONSIDERATIONS:

WE GET ROOF SURFACE FROM ROOF STYLING TEAM, FROM THE PROVIDED SURFACE WE START WORKING ENGINEERING FEATURES LIKE PROVIDING DICH AREA, DESIGNING FRONT ROOF RAIL, REAR ROOF RAIL, BOW ROOF AND CENTRE ROOF RAIL. WHILE DESIGNING THIS COMPONENTS SOME SAFETY STANDERDS ARE BEING FOLLOWED WHICH ARE MENTIONED BELOW.

• VISIBILITY CRITERIA
• HEAD ROOM CLEARANCE
• CURVATURE STUDY
• HEAT DISTORTION CRITERIA
• SNOW LOAD CRITERIA
• DRAFT ANALYSIS

ROOF COMPONENTS:

THERE ARE MAINLY FIVE COMPONENTS ARE USED FOR ROOF MAKING

• ROOF OUTER PANNEL
• FRONT ROOF RAIL
• REAR ROOF RAIL
• BOW ROOF
• CENTRE ROOF

IF THE ROOF IS HAVING SUNROOF THEN ONE MORE RAINFORCEMENT PARTS IS BEING ADDED INSIDE THE CENTRE ROOF RAIL.

ROOF OUTER PANEL:

ROOF OUTER PANEL IS THE MAIN PART WHICH PROTECTS PASENGERS FORM ALL KIND OF WEATHER CONDITIONS AND OTHER HARMFUL OBJECTS WHILE ACCIDENT.

IT IS THE MOST OUTER PART OF ROOF ASSEMBLY MOSTLY FOCUSED FOR ASTHETIC LOOK AND AERODYNAMIC DESIGN, IT DOES NOT HAVE ENOUGH STRANGTH TO PROTACT PASENGERS FROM ANY INJURY TO PROVIDE THAT STRANGTH OTHER COMPONENTS ARE INSTALLED BELOW THE OUTER PANEL.

THE OUTER ROOF IS GETS JOINED WITH BID PORTION OF CAR USING SPOT WELDING AT THE DITCH AREA OF ROOF OUTER PANEL.

FRONT ROOF RAIL:

THE NAME ITSELF SUGGEST THE FRONT ROOF RAIL INSTALLED AT THE FRONT SIDE OF THE ROOF PROVIDING STRENTH TO FRONT SIDE OF ROOD AND ALSO PROVIDING MOUNTING POINTS TO FRONT WIND SHILD.

WHILE DESIGNING VISIBILITY CRITERIA IS TAKEN IN COUNT FOR JOINING WITH THE WIND SHIELD THE FRONT ROOF RAIL IS BEING JOINED WITH THE BIW PART USING SPOT WELDING METHID AND USING RUBBER SEALANT IT JOINS WITH WIND SHIELD WHILE JOINING IT WITH ROOF OUTER PANEL ROBBER MASTICS ARE USED.

REAR ROOF RAIL:

REAR ROOF RAIL IS A RAINFORCEMENT COMPONENT USED TO PROVIDE STRENGTH TO REAR SIDE OF THE ROOF, IT IS ALSO RESPONSIBLE TO PROVIDE MOUNTING POSITIONS TO BACK DOOR HINGE SO THET THE BACK DOOR CAN OPEN AND CLOSE WITHOUT HITING THE ROOF.

THE REAR ROOF RAIL IS BEING CONNECTED WITH BIW PART USING SPOT WELDING, IT GETS JOINED WITH ROOF OUTER PANEL USING RUBBER MASTICS.

CENTRE ROOF RAIL:

A CENTRE ROOF RAIL IS BEING INSTALLED AT THE CENTRE OF THE ROOF AND IS IS RESPONSIBLE TO CARRY LOAD WHICH IS BEING ACT AT THE CENTRE OF THE ROOF BASICALY IT HELPS TO CARY IMPACTS DURING ROLL OVER OR WHEN THE SNOW LOAD IS BEING APPLIED.

THE CENTRE ROOF RAIL IS GETS JOINED WITH ROOF USING RUBBER MASTICS. ITS SIDES ARE GETS SPOT WELDED WITH THE BIW PORTION.

BOW ROOF RAIL:

BOW ROOF RAIL IS A SUPPORTING COMPONENT WHICH HELPS TO PROVIDE ADDITIONAL STRENGTH TO ROOF IN BETWEEN CENTRE ROOF RAIL AND FRONT OR REAR ROOF RAIL, IT IS ALSO RESPONCIBLE TO CARRY THE LOAD OF SNOW AND TO WITHSTAND THE IMPACTS DURING ROLL OVER.

BOW ROOF IS ALSO GETS JOINED WITH OUTER ROOF USING RUBBER MASTICS AND SPOT WELDED AT THE SIDES WITH BIW PORTION SAME AS CENTRE ROOF

DEPENDING UPON LENGTH OF ROOF AND CURVATURE STUDY NUMBER RO BOW ROOF GETS VARRIED.

CENTRE ROOF RAINFORCEMENT:

WHEN THE ROOF IS HAVING SUN ROOF CUTOUT IT IS REQUIRED TO PROVIDE ADDITIONAL RAINFORCEMENT TO CENTRE ROOF RAIL.

THIS RAINFORCEMENT GETS JOINED WITH CENTRE ROOF RAIL USING SPOT WELDING PROCESS AND THEN BOTH THE COMPONENT ARE JOINED TO THE OUTER ROOF USING RUBBER MASTICS.

*ALL THE COMPONENTS ARE DESIGNED AS PER THE MASTER SECTIONS PROVIDED*

DRAFT ANALYSIS OF ALL THE COMPONENT:

FRONT ROOF RAIL:

REAR ROOF RAIL:

BOW ROOF 1:

BOW ROOF 2:

BOW ROOF 3:

CENTRE ROOF RAIL:

RAINFORCEMENT FOR CENTRE ROOF RAIL:

ROOF OUTER PANEL:

ALL PART GETS HIGHLITED IN GREEN COLOR IN DRAFT ANALYSIS WHICH STATS ALL PARTS ARE FEASIBLE FOR MANUFECTURING HOWEVER ON ROOF OUTER PANEL THE REAR SIDE HIGHLITED IN RED COLOR AS IT IS HAVING NEGATIVE 25-30 ANGLE ( AS PER GIVEN MASTER SECTION) WHICH MEANS IT REQUIRES TO FORM USING DIFFERENT TOOLING AXIS.

MANUFECTURING PROCESS:

AS IN AUTOMOTIVE INDUSTRIES CAR ROOF IS MADE OUT OF SHEET METAL BLANKING, DEEP DRAWING, PUNCHING AND BENDING PROCESS IS FOLLOWED TO MANUFECTURE THE PART.

FOR JOINING SPOT WELDING AND RUBBER MASTICS ARE USED, AT THE PORTION WHICH IS VISIBLE RUBBER MASTICS ARE USED TO JOIN WHEREAS AT PORTIONS WHICH IS GOING TO HIDE BY ANY HOW SPOT WELDING PROCESS TAKES PLACE. EMBOSSES ARE PROVIDED TO PARTS TO IMPROVE THE STRENGTH OF THAT PART AND CUT OUTS ARE PROVIDED TO REDUCE THE WEIGHT OF THE PART WITHOUT REDUCING THE STRENGTH OF THE PART.

CURVATURE STUDY OF THE ROOF:

THE CURVATURE STUDY IN CAR ROOF DESIGN CHECKS IF THE ROOF BOW PASSES THE HEAT DISTORTION CRITERIA AND SNOW LOAD CRITERIA.

IN THIS STUDY MAINLY TWO CONDITIONS ARE ANALYSED THEORITICALY WITH SOME MINOR CALCULATIONS.

• HEAT DISTORTION CALCULATION
• SNOW LOAD CALCULATION

HEAT DISTORTION CALCULATION:

HEAT DISTORTION IS A TEMPERATURE AT WHICH THE METAL GETS SOFTEN AMD GETS DEFORMED UNDER CERTAIN LOAD.

THIS STUDY IS USED TO PREDICT THE TEMPERATURE AT WHICH IT GETS SOFTEN UNDER CERTAIN LOAD AND ALIVATED TEMPERATURE, BY ANALYSING THIS WE CAN AVOID BENDING OR DAMAGE TO ROOF BY PROVIDING BOW ROOF AT SPECIFIC LOCATION.

TO PREDICT BOW ROOF LOCATION A FORMULA USED WHICH MENTIONED BELOW

BOW ROOF PREDICTION FORMULA:

W = [1.73 x 10^(-3) x L] + [1.85 x 10^(-8) x (R^2)/t] + [ 1.10x10^(-3) x l] - 2.68

Where,

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]

JUDGEMENT CRAITERIA

OK<2.7

HERE WE HAVE THICKNESS OF ALL COMPONENTS IS 0.75 SO T = 0.75 FOR ALL CALCULATIONS

HERE IN THE EQUATION THERE ARE SOME VALUE WE NEED TO FIND OUT TO FIND THIS VALUE FOLLOWING STEPS ARE FOLLOWED:

• START A NEW SKETCH
• DRAW A LINE IN Y DIRECTION AT THE CENTRE OF ROOF (O-Y LINE)
• NOW OFFSET THE LINE FOR 300M AT DOWN SIDE (-3 - Y LINE)
• OFFSET -3Y LINE FOR 100 MM BOTH SIDE
• NOW DRAW CENTRE LINES FROM ALL THE BOW ROOF, CENTRE ROOF RAIL, REAR AND FRONT ROOF RAIL
• DRAW LINES IN CENTRE BETWEEN TWO RAILS EG. FRONT ROOF RAIN AND 1ST BOW ROOF, 1ST BOW ROOF AND CENTRE ROOF RAIL AND SO ON
• OFFSET THIS CENTRE LINES FOR 100 TO 200 MM BOTH SIDE
• PROJECT THE SKETCH ON ROOF OUTER PANEL
• MARK POINTS ON EVERY INTERSECTION
• USE CURVE ON SURFACE OPTION TO JOIN 3 OF THEM POINTS AND MAKE CURVES
• MEASURE THE RADIUS OF THIS CURVES
• THE CURVES IN X DIRECTION GIVES VALUE OF RX AT THE INSTINCT
• THE CURVES IN Y DIRECTION GIVES THE VALUE OF RY AT THE INSTINCT.

*CURVES IN RED COLOR ARE RY AND CURVES IN BLUE COLOR ARE RX*

AFTER GETING ALL THE VALUE SUBSTITUTE THEM IN ABOVE'S EQUATION

SR NO.	BOWS	RX	RY	R	I	L	T	R^2/T	W	OK / NG
1	FR & 1ST	4987.293	2393.054	3234.227	525.130	2033.4	0.75	13946965.71	1.6734	OK
2	1ST & CTR	4499.374	5698.473	5028.426	234.304	2033.4	0.75	35118150.05	1.7452	OK
3	CTR & 2ND	4016.806	9672.239	5676.2	300.139	2033.4	0.75	42958995.25	1.9626	OK
4	2ND & 3RD	3300.339	11799.866	5158.017	300.096	2033.4	0.75	35473520.81	1.82	OK
5	3RD & RR	2942.302	14223.499	4875.954	86.599	2033.4	0.75	31699905.53	1.51	OK

FROM THE TABLE WE CAN SEE THET ALL THE VALUE OF W IS < 2.7. WHICH STATES THET ALL THE BOW ROOF ARE LOCATED AT RIGHT PLACE AND THE DESIGN IS SAFE FOR HEAT DISTORTION CRITERIA.

SNOW LOAD CRITERIA ANALYSIS:

Qr = [Iy x t2] / [α x s x [(Rx + Ry)/2]2 x 10-8]

Where,

α = My x Lx2 x 10-12 , My = Y(Ly-Y)

t = Roof plate thickness [mm]

Ly = Distance between the front and rear roof Rails on the Vehicle along with 0Y[mm]

Length of Roof panel with the center point between Roof rail Front /Rear as the front and rear reference point.

Lx = Distance between the Left and Right end of the roof on the Roof BOW [mm]

The width of the roof panel is exposed on the surface.

Y = Distance front Front Roof Rail to Roof BOW[mm]

s = Distance for which Roof BOW bears divided load [mm]

s = L1/2 + L2/2

Iy = Geometrical moment of inertia of Roof BOW (Y cross-section )[mm4]

Rx = Lateral direction curvature radius of roof panel Y cross-section on Roof BOW [mm]

Roof panel curvature Radius of the Length Lx in Front view

Ry = Longitudinal Direction curvature radius of the Roof panel X cross-section on Roof BOW [mm]

Roof panel X curvature radius of length s in Side view

JUDGEMENT CONDITION:

Qr ≥ 3.1

250 ≤ s ≤ 380

SNOW LOAD CRITERIA CALCULATION

MEASURING THE MOMENT OF INERTIA FOR THE BOW ROOF AND CENTRE ROOF, FOR THAT WE HAVE TO TAKE THE INTERSECTION OF THE PART AT THE CENTRE PLANE AND THEN PROJECTING THE INTERSECTION ON SKETCH PLANE THEN USING INERTIA ANALYSIS WE CAN FIND THE VALUE OF MOMENT OF INERTIA

WE WILL CONCIDER MINIMUM MOI TO CALCULATE SNOW LOAD CRITERIA.

BOW ROOF 1:

CENTRE ROOF RAIL:

BOW ROOF 2:

BOW ROOF 3:

CALCULATION FOR FINDING MY:

MY= Y(LY-Y)

SR NO.	BOW ROOF	Y	LY	MY
1	FRL - BR1	663.1	2033.4	908645.93
2	FRL - CRL	979.9	2033.4	1032324.65
3	FRL - BR2	1362.4	2033.4	914170.4
4	FRL - BR3	1737.3	2033.4	514414.53

FROM THE VALUE OF MY WE CAN FIND VALUE OF α USING THE FOLLOWING EQUATION

α = MY * LX^2 *10^-12

AFTER THAT WE CAN FIND VALUE OF QR FROM THE FOLLOWING EQUATION

QR= [IY*T^2]/[α*S*[(RX+RY)/2]^2*10^-8

SR NO.	ROOF RAIL	IY	α	L1	L2	S	RX	RY	T	QR	OK / NG
1	FRL - BR1	2145	1.118	663.1	316.8	489.95	2404.20	2502.51	0.75	36.59	OK
2	BR1 - CRR	4368	1.22	316.8	382.5	349.65	3470.62	6115.66	0.75	55.15	OK
3	CRR - BR2	1954	1.052	382.5	329.9	356.2	4158.98	9378.47	0.75	6.402	OK
4	BR2 - BR3	1956	0.58	329.9	246	287.95	2933.04	13454.57	0.75	9.812	OK

HERE BY CALCULATING THE VALUE OF QR WE CAN SEE ALL THE VALUES SATISFY THE JUDGEMENT CONDITION, ONLY THE S1 VALUE (489.95) IS EXIDING THE CRITERIA THE REASON BEHIND THAT IS DUE TO SUN ROOF THE GAP BETWEEN FRONT ROOF RAIL AND ROOF BOW 1 IS HIGH TO IMPROVE LOAD CARING CAPACITY OF THIS ROOF A ADDITIONAL RAINFORCEMENT IS ADDED INSIDE THE CENTRE ROOF RAIL.

CONCLUSION:

THUS AS PER THE HEAT DESTORTION CALCULATION AND SNOW LOAD CRITERIA CALCULATION WE CAN CANCLUDE THAT THE DESIGN IS GOOD TO GO FOR MANUFECTURING.