Car Question fellas...

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Ok guys that fabricate a lot...I have a question for you.  I have a vette that I built a cross member for out of 1.5" square tubing.  But the car is VERY low to the ground and because my exhaust sticks a little below the floor of the car I had to build a drop down section in the middle to clear the exhaust and then back up again to hug the bottom of the car.  So basically the crossmember is very tight to the floor on the sides and then is lowered by about 2-3" in the middle.  Anyways I do not like this design, since it hits the road and anything on the road if conditions are right, or pulling out of an uneven surface it will touch as well.  Nothing serious, but enough you can hear it.  I want to build another out of round tube, or even solid tube and have a fab shop bend it for me..the span is about 51", so what size tubing or solid rod would you recommend I use.  FIxing it to the sides is not a problem, as I can utilize the same principle I am using now that works fine.  THanks.Regards,Best Times with 434 Naturally Aspirated Vette60 - 1.261/8 -  6.37@ 107.25 MPH 1/4 - 10.08 & 134.9MPH1/4 - 9.60@144MPH
Reply:How thick is the square tubing? I would say go down a size for round and up a size in thickness if you need clearance.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:Remember the old crossmebers? They where flattened round tube, or a roll formed shape like a stretched "u" or "w", very low profile. Could you buy an old x-member and modify it?For more clearance, could you pass the exhaust pipe through, rather than under the crossmember?Maybe make a "window" or "tunnel" through the crossmember out of round tube, pass the exhaust pipe through this.
Reply:Originally Posted by denrepRemember the old crossmebers? They where flattened round tube, or a roll formed shape like a stretched "u" or "w", very low profile. Could you buy an old x-member and modify it?For more clearance, could you pass the exhaust pipe through, rather than under the crossmember?Maybe make a "window" or "tunnel" through the crossmember out of round tube, pass the exhaust pipe through this.
Reply:Originally Posted by ski_dwn_it...I built a cross member for out of 1.5" square tubing.  But the car is VERY low to the ground and because my exhaust sticks a little below the floor of the car I had to build a drop down section in the middle to clear the exhaust and then back up again to hug the bottom of the car.  So basically the crossmember is very tight to the floor on the sides and then is lowered by about 2-3" in the middle.  ..it hits the road and anything on the road if conditions are right..., or pulling out of an uneven surface it will touch as well.  Nothing serious, but enough you can hear it.
Reply:I'm thinkin' a couple of 3/4" square tubes that run parallel to one another.This would gain you about 3/4" clearancedo you have a picture of your curent setup?Don't talk about it, Just do it!
Reply:Might be better to chop out the floor, move the offending section of exhaust up, then repair the floor with new glass and resin.WeldingWeb forum--now more sophomoric banter than anything else!
Reply:The tranny cross member in the 'Hoss is only 3/4" tubing..Tranny crossmembers do nothing more than hold up the tailshaft..Its against the rules but 1/4" wire cable is more than enough to do the job...Just as long as you have solid motor mounts with a tourque bar..Or engine plates front and rear then little is needed to hold it up..Lou has a "footbrake" car he races also..'68 Coronet..440 Automatic..Engine plate in the front and just the stock tranny crossmember in the back.Car runs hi 9's.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:The vette has no mid or front plate, so its holding the trans and motor up.  Not a LOT of weight as the majority is on the motor mounts, but there is an appreciable amount.  I will try to get some photos today of what I have currently.  I do not want to have to cut the car apart to do this.  Thanks for the help....Best Times with 434 Naturally Aspirated Vette60 - 1.261/8 -  6.37@ 107.25 MPH 1/4 - 10.08 & 134.9MPH1/4 - 9.60@144MPH
Reply:Here is what I have to work with fellas.  The crossmember in there now works but with the street tires is pretty low as you an see.  On the near side it looks like I could have moved it up higher, which is correct, but on the other side the way the header are, it just barely misses.When I race it, I have 30" tall rear tires compared to 26" on the street and 28" tires in the front - so I get some relief.  Even with it now doing about 28" wheelies to the bottom of the front tires it never hits.I need something that gives me some more ground clearance on the street.  What do you think would happen if I used ~1" tubing and ran some 1" wide, by .25 thick steel strips along each side of it.  Sorts like an H beam rod with the middle being the tube......SOme of you guys that do more fabricating migh have some pretty crafty ideas.....lets hear them.  Thanks a lot.Best Times with 434 Naturally Aspirated Vette60 - 1.261/8 -  6.37@ 107.25 MPH 1/4 - 10.08 & 134.9MPH1/4 - 9.60@144MPH
Reply:I would do a 3/8 flat MS with two bumps in it...almost like a flattened W. I've done it on a few GM cars.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:Originally Posted by MicroZoneI would do a 3/8 flat MS with two bumps in it...almost like a flattened W. I've done it on a few GM cars.
Reply:Originally Posted by MicroZoneI would do a 3/8 flat MS with two bumps in it...almost like a flattened W. I've done it on a few GM cars.
Reply:Originally Posted by denrepFor more clearance, could you pass the exhaust pipe through, rather than under the crossmember?Maybe make a "window" or "tunnel" through the crossmember out of round tube, pass the exhaust pipe through this.
Reply:Twisting angle so the point is down is the same as 3/4 tubing...3/4" tubing is stronger than twisted angle....Back to square one......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:SKI - like this: ...or this: John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:Your current idea is correct, just flip it and use 3/8" plate bent in a W for your car...John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:^similar to what i was thinking, however, i think that he has too many clearance problems running it as an "M"a "W" may work though....
Reply:Thanks fellas....I did some experimenting with a piece of 1" square today....its seemed pretty rigid...held me with very little flex at 220lbs and a span of 53".  I ordered a piece along with about 300 dollars of other stuff for my other project I have going.  I also looked at my fathers vette and his exhaust is above the floor - his is stock so for those cars a straight across design would work fine.  I will give the 3/8 a shot for mine and see how it looks/clears.  Thanks again for the ideas.Best Times with 434 Naturally Aspirated Vette60 - 1.261/8 -  6.37@ 107.25 MPH 1/4 - 10.08 & 134.9MPH1/4 - 9.60@144MPH