Roof challenge

REPORT- Roof Design

1. OBJECTIVE-
   • To design the roof outer, Front roof rail, Bow roof rails, Rare roof rail.
   • To calculate the Heat distortion critecria and snow load criteria.
     
     
2. ROOF AND ROOF PARTS-
   
   
   1. ROOF-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.
      
      
      
   2. ROOF RAILS-Roof rails run along the length of the vehicle's roof. Their purpose is to provide an attachment point for crossbars and other devices designed to secure loads carried on the roof of the vehicle. Roof rails are attached to the vehicle's roof by feet or other mounts.
      
      
      
      1. FRONT ROOF RAIL-Front roof rail is at the front side of the roof what takes a important prt in roof assembly for givvinge strength to the front portion of the roof.
         
         I designed this with proper dimenstion and gap considerations according to the master section provided.
         
         
      2. BOW ROOF RAILS-Bow roof rails are the strengthening features in roof assembly. These are for givving the most of strength to the roof and the mountings(cabin light, wiring) are also fitted with bow roof rails. Here I designed three bow roof rails and I gave min of 5mm distance between the Bow roof rails and the roof for the mastics.
         
         
         
      3. CENTER ROOF RAIL-Center roof rail is assembles basically with the B-Pillar, approximately at 50% or middle of the roof. It gives the strength in the middle portion of roof. And reinforcement is added with center roof rail because it takes the main role against the bending of the roof.
         
         
         
      4. RARE ROOF RAIL-Rail roof rail is mounted in the back or rare side of the roof. It is mounted with the outer roof flange using mastics. It is for strengthening the rare side of roof. I designed it with proper dimensions and also I did some embosses for giving more strength to the roof rail.
         
         
         
3. DRAFT ANALYSIS-As we know for sheet metal we have to give min of 7degrees of draft. Draft analysis is to check that draft angle if it is proper or not. If the part is showing green then the draft for 7mm is proper if it is in red then it should be moidified.
   1. FRONT ROOF RAIL DRAFT ANALYSIS-
      
      
      
   2. 1st BOW ROOF RAIL-
      
      
      
   3. CENTER ROOF RAIL-
      
      
      
   4. 2nd BOW ROOF RAIL-
      
      
      
   5. 3rd BOW ROOF RAIL-
      
      
   6. RARE ROOF RAIL-
      
      
4. PREDECTION FORMULAS-
   
   
   1. HEAT DISTORTION FORMULA-Heat distortion is nothing but heat genereted by the load which is calculated for the outer roof rail. If W is less than 2.7 then it is ok. In my design there are five sections, and I calculated this for the all five sections.
      1. 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

         Judgment Condition

         OK< 2.7

         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]

      2. Results-
         
         
         
         
   2. SNOW LOAD CRITERIA-Snow load formula is measured actually the weight of the accumulated snow on the roof. If the load exist the the roof should bare the load and constructed like that.
      1. 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)

         Judgment condition

         Qr ≥ 3.1

         250 ≤ s ≤ 380

         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

      2. Results-
         
         If the Qr is greater than or equal to 3.1 then it is ok.
         S is also shoud be less then 300 but in my design for all sections it is wrong.
         
         
5. SECTION MODULUS-
   
   
   
6. CONCLUSION-As the value of S is greater than 300 then We have to manage the position of roof rails.