Here are some details on flaring holes. The ideal situation is where this method provides a drop in mass yet remains stronger than before it was worked. However, flared holes should not be situated where there is stress on the surface. It can be located elsewhere where stress is required.
This idea came to me as I explored ways to make holes on sheet metal to make it lighter. Quite obviously, if the manufactured product has a small thickness, making holes would reduce its stiffness and rigidity. It is also questionable whether the reduction on thin sheets are worth the effort in trying to save weight.
When we look at areas to lighten, we would also need to take into account the loss of this rigidity. This means torsional forces causes material failure. Such was what had happen in the racing scene may years before. The race officials then banned the holes if it was not designed into the production. Steel material would need considerable amount of force to cause it to break. Front bumpers for many years have been intended to be broken and not just dent. A snap of a known material size is equivalent to the accidental forces. Flanging or belling reinforce the strength of that material simply by cold working the holes. The shape of the flange itself is not important. What does effect is the stressing of the material increases its strenght. Much like Reinforced Concrete. The bars are actually strained to increase its rigidity.
This article reminded me of the wooden tools that I used to see when I was in Secondary school. Its quite odd to find such tools nowadays. As the world moves on to machined manufacturing, we loose knowledge on proven skill based method of steel working. I used to think of using the mechanical draw method to make these flanges. This article showed me of the die method using hardwood to form metal which remains an option to me.
Continuing my interests in car up skirts photos, I peeked into one of the anticipated design from a french automaker; Renault. The car that makes my heart aflutter is the Alpine concept car.
If you look at the broadside it was supposed to be as close as possible with the 2012 Renault Megane and its iteration from Renaultsport.
Like many arm chair browsing artist, I used major search engines to find some pictures of the frame of the current production car against that of the concept car.
What you see is totally different. While the production car is mostly pressed metal plates welded or screwed together, you see it differently on the concept car. The concept is all bits of tubes held together by either welding or brazing and perhaps glue.
The ‘Cup’ chassis is prevalent with anything with Megane RS sitting in the middle. While searching for more tell-tale pictures, it seems that the hatch chassis is lighter by 25kg. But of course the bhp on the RS blown 4 pot is double that of the undisclosed name for the normal 4 pot on the pedestrian hatch/sedan Megane.
But the different chassis in engineering used is a well known subject. It is definitely cheaper to produce tubular skeleton if you only making a handful. Pressed plate chassis is only economical when there is volume to consume the production. You cannot discount the fact that when you do change from one offs to volume, there is bound to be trade offs. In this case it is stiffness. Something has just got to give. The tubular cage is indeed a method used to meet intent; marketing. While the pressed steel chassis is one for the real world. The majority of commuters do not need the stiffness that enthusiasts yearn for.
No one would even think that this will even go into production as a commuter car. This is after all; an Alpine. If you think the RS models were rare, this will be rarer still.