Creating perception of integrity in auto unibody...DIY methods? 1

[JamesMcD]

I posted this in the vibration/acoustics forum as well. I hope that's ok.

It seems like with each new model of car it is claimed to be some measure (30-40%) "stiffer" than the previous generation, laterally or longitudinally. For some cars, there are aftermarket parts to increase stiffness of the unibody, such as subframe braces and strut/shock tower bars. You can create your own as well, simple enough.

My question is this:
How would someone like me, who appreciates and desires "car stiffness", go about measuring vibration and noise in various places in the unibody? And furthermore how would I damp it out?

I am interested in both creating a perception of solidity, as well as actually increasing it. I do not want to use sound deadening products like that heavy tar paper the stereo guys like. I would rather go about it by reinforcing the structure to either make it stronger or change it's natural frequency(?)

You can tell I'm not entirely sure how to pose my question. I hope someone can give me some direction,

thanks.

-James

 

[GregLocock]

It is very difficult to improve the global properties of a unibody once it has been built. Typically the weak areas are the joints eg A pillar to header rail, and detailed faults in the way that the various beams transfer loads between each other. Bracing the strut tops to each other and back to the firewall is one obvious DIY possibility, the same at the rear of the car might work as well.

Other things you could try would be a roll cage with VERY good joints into the body (I bet this would be hard to do), and converting the rear seat-back into a rigid bulkhead.

I doubt that all of these together would result in a change of 5%, so I wouldn't bother!

Your perception of solidity is pretty much a function of the torsional stiffness of the body, which is also the most important for the ride and handling guys, so that's probably the best one to work on.

I'll answer your noise and vibration question in the acoustics/vibration forum. Cheers

Greg Locock