Need help designing rear seat braces

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Discussion Overview

The discussion revolves around the design and effectiveness of rear seat braces for a Buick Grand National, focusing on the materials and shapes used for rigidity. Participants explore the implications of using round hollow versus flat bars, as well as alternative modifications like roll cages.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks opinions on whether round hollow or flat bars would provide better rigidity for rear seat braces.
  • Another participant suggests that tubular structural members are generally stronger than flat or solid ones, particularly for resisting bending.
  • There is a proposal to consider installing a roll cage instead, as it may provide greater safety and stiffness, despite requiring more work.
  • A later reply emphasizes the importance of using tubing for bending applications and offers advice on bending techniques to avoid weakening the material.
  • Participants discuss the practicality of the proposed brace design, noting that it is simpler to install compared to a roll cage.

Areas of Agreement / Disagreement

Participants express differing views on the best approach to enhancing rigidity, with some advocating for the use of tubing while others consider the practicality of flat bars. The discussion remains unresolved regarding the optimal design choice.

Contextual Notes

Participants do not reach a consensus on the superiority of one design over another, and there are varying opinions on the necessity and complexity of alternative modifications like roll cages.

usfz28
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I have a Buick Grand National. There is a company that sells a kit that consist of 4 bars connected in the back seat area of my car. http://img.photobucket.com/albums/v625/BrockBlackZ/braces1.jpg" . I wanted to get your opinions on what you think would be better for rigidity (round hollow or flat bars)and also does this design look good? or could it be improved? Everybody that has one of these says they notice the car is much stiffer and handles better. Just one of those things that I have been thinking about during classes.
 
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Man... I've gone through a lot of car mods and I've never seen that one before. Why not install a roll cage instead? It wouldn't be too much more work, and it could save your life as well as stiffen up the ride.
To answer your question, though, most structural members are tubular because they're a lot stronger than rods or the straps that you show. The flat or solid ones are fine for tensile loading (stretch), but useless for resistance to bending. If you reinforce them enough, they'd probably work for what you want, but the tubes would be guaranteed to.
I'd still weld or bolt 2 or 3 inch steel tubing to the frame and run it inside the perimeter of the body instead, though.
 
Well they did include this on the high performance GNX... The roll cage would require a lot more work where as you just have to cut 4 pieces of tubing and bolt them in (holes already exsist). I was just wondering which type of shape was stronger
 
Okay. In that case, use the tubing. If bending is required, use a mandrel or at least fill the thing with sand before bending. That minimizes any 'crinkling' that would weaken it. If you want the ends flattened as in the picture, keep that section as short as you can. It's also a good idea to put washers under both the bolt head and the nut to distribute stress better. Good luck with it.