Roof Design

DESING AND DEVELOPMENT OF CAR ROOF AND ITS REINFORCEMENTS.

AIM:-

To create an assembly by developing the essential flanges for the outer roof and creating the reinforcements for the given roof styling.

DESCRIPTION:-

An automobile roof or car top is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements.

In later years, many variations on the automobile roof developed.These include:-

• Convertible roofs
• Hardtops
• Roof modules
• Sunroofs
• Targa tops
• T-tops
• Vinyl roofs

For this challenge the hard roof top is created with the help of given Class A skin data. Along with the outer hard roof top ,different types of roofs will be created as per the design guideliness and functional requirements.

Requirements for the roof design:-

• Design requirements of the roof.
• Functional requirements.
• Types of roof and its functionality.
• Roll over test regulation and requirements.
• Methods to increase the strength.
• Joining techniques.

Design requirements of the roof:-

The roof designs were classified into different types with respect to the budget of the car, according to the market and people. Here i am going to develop a hard roof top with the help of given Class A skin data.

FRONT ROOF OUTER:-

The above image is the mastersection data for the outer and inner front roof rail.

Using wave geometry linker extracted the roof outer surface and untrimmed it to make a continous surface without hole.

Created the flanges for the outer front roof rail with the help of law extension and taken values as per the mastersection data. This is the place where the windshield glass and its rubber flange will be joined. The values given in the mastersection are as per the design consideration mainly the visibility criteria for the driver and passengers with respect to that the front roof rail flange length is given and the angle for the flanges which is for the manufacturing feasibility and the visibility criteria.

REAR ROOF OUTER:-

The inclined angle of 25 to 30deg is given for the clearance for the backdoor opening and the angle depends as per the industry standards.

With the help of bridge curve and studio surface created the connecting surface between the two flanges.

Created the outer rear roof rail with the law extension and values as per the given mastersection data.

Fillets value provided as per the given mastersection data.

DRAFT ANALYSIS REPORT OF OUTER FRONT AND REAR ROOF RAILS:-

Some areas are not clearing the draft analysis because of the inclined area and created the law extensions as per the mastersection which will be associated with the backdoor opening angle.

FRONT INNER ROOF RAIL:-

The front inner roof rail which acts a additional strength to the front outer roof and it also has a major role in fixation of lamps and certain additonal things. The 32mm offset distance from the outer panel is defined as per the head room clearance of the driver and passengers and also for the visibility criteria. The offset value differs according to the industry requirements. The minimum draft of 7deg is provided for the manufacturability of the product.

The gap for the mastic is given in the rear side of the front inner roof rail as per the mastersection and in the front side both the roofs are spot welded together.

Offseted the flange from the outer panel and created the offset in face to make a trim for the front roof flange as per the given mastersection value and the top surface of the roof is offseted to 32mm as per the mastersection these values will varies according to the industry standards.

Created the law extension to connect the bottom surface of the front roof inner with the flange. With respect to the tooling axis every law extension is created in positive draft direction in the required places.

Fillets are applied as per the mastersection data

Embosses are created to increase the strength of the inner front roof rail and mountings are created for the fixations of rear view mirror , head liner and lamps.

Mirrored the front roof rail with respect to the xc plane and sew it together.

Thickened the front roof inner towards up side facing the outer roof with the value of 0.75mm.

DRAFT ANALYSIS OF INNER FRONT ROOF RAIL:-

REAR INNER ROOF RAIL:-

Taken the extract of the rear roof outer using wave geometry linker and offseted to 10.7mm as per the mastersection data. After that created a law extension with a positive draft angle to connect both the surfaces together and trim it of to make a corner. Extended the surface as per the given mastersection data.

The offset value which is considered with respect to the head room clearance and visibility criteria it varies with respect to different industries.

With the help of law extensions, created in positive draft angle flanges for the inner rear roof rail.

Created embosses and mountings in the inner rear roof rail similar to the inner frot roof rail, which is used for headliner fixations and lamp fixations.

After mirrored the sheet and created an mounting emboss in the centre. Trimmed the sharp edges with the help of bridge curves.

DRAFT ANALYSIS OF INNER REAR ROOF RAIL:-

The inner rear roof rail is clearing the draft analysis of minimum value 7deg as per the design rule and stamping process for manufacturing.

CENTRE ROOF RAIL:-

The centre roof rail is located in the centre side of the roof if the outer roof is more flater and it provides strength for the roof outer and in some higher end vehicles sunroof is provided in the roof so the roof rail also designed accordingly. The mastics in the centre roof itself also increases the strength of the component.

The offset value's for the centre roof rail is given as per the given mastersection data and some of the values are assumed.

The law extension were more than 7deg due to the manufacturability of the roof rail which will clear the minimum draft angle of 7deg.

After offseting the surface using offset in face option to create the edge line of the surface and trimmed to the required distance

The overall length of the centre roof rail is with in the given mastersection data limit.

The centre roof flanges are filleted to avoid sharp corners and the fillet values are taken as assumed value as there is no specific data given in the mastersection data.

Trimmed some portion of the centre roof rail and extracted the outer flange from the roof outer then offseted it.

Trimmed the outer flange with respect to the centre roof rail distance and created through curve mesh between the centre roof rail and outer flange, then sewed it together. All the curvatures are coming tangentially.

Extended the flange and trimmed it with the centre datum plane then mirrored it using the centre datum plane.

After mirrored the geomentry joined it using sew command.

DRAFT ANALYSIS REPORT OF CENTRE ROOF RAIL:-

BOW ROOF RAILS(1&2):-

The Bow roof's are created to increase the strength of the outer roof by providing support to the roof outer.

The bow roof is created with the given mastersection data and offseting the surfaces with the assumed own values as there is no specific values given in the mastersection. Fillets are also given accordingly. The outer flange of the roof outer is extracted and trimmed with the datum planes in the bow roof edges and created a through curve mesh tok join the bow roof and the outer flange of the roof outer which is the same procedure used to create the centre roof rail.

Created sketch for the mastic cutout in the Bow roof rail which will reduce the weight of the Bow roof and the mastic will increase the strength locally.

Extended the sheet and trimmed with the centre datum plane , then mirrored with respect to the centre datun plane after that sewed it together.

The created Bow roof rail is thickened about 0.75mm in the upward direction.

Both the Bow roof rails are created with the same above mentioned methods.

DRAFT ANALYSIS OF BOW ROOF'S:-

The draft analysis is showing that the Bow roof is clearing the minimum of 7deg.

HEAT DISTORTION CALCULATION:-

The heat distortion test evaluates the ability of a car roof to maintain its physical structure without deformation under elevated temperature conditions. Car roofs are exposed to sun at day time. The strength of the roof by analysing its curvature. Especially the Bow roof position with respect to that the heat distortion values wiil change or we can modify the distance of the bow roofs accordingly.

Here we are going to calculate the heat distortion of the car roof using the heat distortion formulae:-

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]

Judgment Condition

OK< 2.7

Created a sketch for the heat distortion calculation.

Created a line from the centre origin point of the WCS datum plane and to the bottom side created an another line for 300mm distance from the origin point. Then offseted the bottom side line 100mm on both sides.

Created points at the edges of the inner and rear roof as well as Bow roofs over the origin line. With the points on each roof on both sides created a midpoint between those two points.

From the midpoint created a line and offseted to 100mm on both sides.

The lines which is intersecting the bottom created lines from these perpendicular lines created points for the curvature study which will be Rx and Ry.

Where the distance between the Roof inner ,Bow roofs are the Bow roof span value for each cases.

The Judgement condition is satisfied for the heat distortion which all the (W) values are below 2.7.

SNOW LOAD CALCULATION:-

Snow load criteria is used to predict the withstand capability of the roof of the car during snow fall. It is a study that checks the durability of the roof for the snow load conditions and also its capability has to restore to its original position after the snow is cleaned/removed.

Snow Load Prediction Formula

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

Note: The Qr value given over here is correct. There was a typo error in the formula given in the video.

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

Judgment condition

Qr ≥ 3.1

250 ≤ s ≤ 380

With the help of lines which is previously created for the heat distortion , created points in the centre juction of two lines which is perpendicular to each other.

Projected the edges and created point over the junctions of the line and the projected edges.

To find the value for ly, moment of inertia is calculated by creating the closed cross section sketch of the thickened Bow roofs and Centre roof by using intersection curve option.

Bow Roof1:-

Centre Roof Rail:-

Bow Roof rail2:-

Judgment condition

Qr ≥ 3.1

250 ≤ s ≤ 380

Some values are not satisfying the condition, so for the additonal strength roof emboss is created accordingly

DRAFT ANALYSIS OF ROOF OUTER:-

FINAL ASSEMBLY OF ROOF OUTER:-

Google drive link:-

https://drive.google.com/file/d/1C6TRRUKmn5Qtwr51ilUWcTpTyQnq8zB-/view?usp=sharing

Due to size of the compressed file i'm unable to upload it , so i've given the link for the Roof assembly file for the project. Kindly take a look at it.