If you're doing a full ladder frame, differential displacements between corners would work fairly well for design, just remember to keep the design displacement small...very small...or you'll end up with an over-designed frame ;)

Smaller braces, however, would be very difficult with displacements; you've got three translational degrees of freedom, and no information about their motion corresponding to vertical motion at the wheel.

Sidenote: When auto companies do physical chassis tests (when full FEA runs aren't enough), it's really cool. They use laser doppler vibrometers to track the underside of the car while it is sitting on four actuators. Neat stuff, those laser doppler vibrometers.

i think my wife has one of those laser dobbler vibrometer 2000s in the night stand next to our bed.... u mean i can use that thing to check the stiffness of my frame too!?!?

Yeah the laser vibrometers are fun, were using two of them for a vibrations study to reduce noise in gearbox boxes. Stupidly expensive.

But stupidly cool, too.

lol, its an amazing piece of equipment eh? lol

Why not just buy some racing beat chassis braces? They're relatively cheap seems like they work well.

does it make you jealous....??

Who would be jealous?

hahahah na, she uses that, gives me more time to work on my car!

shipping for one....getting stuff here isnt hard just a little pricey.

HA....i found a pic of the autoexe one....im quite certain mine wont look that fancy but function over form

http://adrenalineracing.com/images/NB1.jpg

Man that's sick. You could reproduce that almost exactly using rubing is you were so inclined. I might have to take advanced welding just so I have a designated class period to build my new mani/dp and some braces like those.
Makes me drool just thinking about it.

there's no way in hell those braces WON'T make a big difference. They've essentially closed up the entire "open" area on the underside of the car. Too cool.

Oh shit that is SICK!

btw where in the world are ya? I know shipping up here kills too but sometimes u gotta bite the bullet.

the car is in the cayman islands...im kinda inbetween there and england (university).

i want to do a diy version of the autoexe stuff, ijust need to get the car running on the TEC so i can leave it with my friend to put it on a lift and get that shit done as he has the time.

If I were you, I'd make a hybrid of that example and the FM butterfly. From that pictures, it looks like it ties into the floor. I'd attach to the "frame rails" as well.

Here's a page off the old SebringMiata.com (I keep a mirror of it on my server):

http://ww2.lightweightmiata.com:8080...ans/page3.html

(BTW, John's car is the one that got me started on my Red Beast project)

If you can put one together, I'll buy it.