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Frame Rail Question


Guest Crispy Chicken

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Guest Crispy Chicken

Hello everyone, I'm about to do front and rear frame rails in my 73 z. I've decided to do 2.5x2.5 for the front rails and 2x3 for the rear. What I can't decided is what gauge steel to use. I've seen a lot of people use .083 14 gauge 2mm and I've seen people use up to .130 10 gauge 3.25mm. At what point is it over kill? 14 gauge seems like it would be fine.

 

I guess one big determining factor will be weight. Any advice or info will be greatly appreciated. I know there are a lot of knowledgeable people on this site. Thanks

 

Derek

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Guest Crispy Chicken
It also depends on how mutch power you think you're going to put to the road in that car and how heavy the drivetrain.

 

Built single turbo Ls1. Maye over 1000hp to the ground on the highway. At some point or another...

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With my project, I decided that for any tubing which will have suspension pickups attached to it I would go with .095'' at a minimum. Depending upon the amount of triangulation in your frame design and your method for attaching any pickups, you may want to run thicker wall tubing.

 

If you're talking about rockers, .083 should be fine but you might want to go with .120 just to avoid the possibility of any distortion when putting a jack under there.

 

If you're going to have that absurd amount of power, adding 15 pounds to the car by going with .120 as opposed to .083 will certainly make no difference.

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Roll cage tubing for a Z is spec'd at .120" wall for a 1.5" OD tube. That's designed to take the full weight of the vehicle in a 80 mph impact. 1,000 ft. lbs. of torque ain't poop compared to that kind of load.

 

Since you are building something with 2" and 3" tube you can reduce wall thickness by about 40% and still retain similar strength. .083" wall tubing should be plenty strong. Remember, you're not building an off-road truck or a forklift.

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Guest Crispy Chicken
Roll cage tubing for a Z is spec'd at .120" wall for a 1.5" OD tube. That's designed to take the full weight of the vehicle in a 80 mph impact. 1,000 ft. lbs. of torque ain't poop compared to that kind of load.

 

Since you are building something with 2" and 3" tube you can reduce wall thickness by about 40% and still retain similar strength. .083" wall tubing should be plenty strong. Remember, you're not building an off-road truck or a forklift.

 

 

Thanks a lot John!! Good info...

 

Derek

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I went the overkill route but I don't have a cage, just a rollbar. I would agree with John that 14 gauge (.083 wall) should be sufficient. I used 2 1/2" x 2 1/2" x 3/16" for the frame rails and 3" x 1" x 0.12" (11 gauge) for the subframes.

 

Here is the subframes.

subframes.jpg

 

Here is the subframe to frame rail and yes a gusset to the TC bucket was added later.

frame%20to%20sub.jpg

 

If you make it to Orlando your more than welcome to check it out but the car is headiing for storage this Saturday for probably 4-6 weeks until I get settled into a new house.

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  • 4 weeks later...
Guest Crispy Chicken

Ahh, went with 120 wall, hell with it. Here are some pictures.. Still gotta add plates on the inner side.

 

After looking at the old front rails. I'm glad they came off..

 

icky doo doo

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5HqtGAOxDABtL0Z0KX2Zq03LftnKr2qk0280.jpg

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i have a question.

why haven't i seen pictures of custom built front subframes? Is it hard to do? or am i missing something here?

 

I figure that if someone were to make new frame rails for the entire car, doing a subframe that is better than the stock stamped metal could be a good idea, no?

 

Or do i have to be the first to do so, without borrowing parts from another car.?

 

EDIT: and yes, those floor pans and frame rails are exquisite =)

 

something along the lines of what i will be doing in the following months, over the winter.

 

my car is in dire need of subframes and floors, but i figure i'll just do the front as well, and now possibly a subframe as well, but i need my RB engine first.

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ummmmm.... did you not see all the pics posted on this thread? Ive seen several pics in different threads showing the subframes replaced. Im finishing my front subframe and hoping to order rear rails in the next couple of weeks. What started out as a "finished by Halloween" project, turned into a "finished by thanksgiving", now its a "finished by the end of the year" project. I hate everyone on this site for all their good advice and great ideas. I think the "while im there" bug is highly contagious.

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