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Adding rigidity while restoring rusted metal

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Hi all! 

I thought some of you might like to see

the the reinforcement I’m working on to rebuild my rusted out rocker. I have the “slip on” rocker cover for asthetics, but the inside will be home made. 

I have prepared a vertical rib (14 gauge) which will go down the centerline of the rocker and serve as the surface for jacking the car, and where both the floor pan and slip-on rocker will weld to. Between the inner axial rib and inner rocker, I have welded in additional ribbing to resist shear (20 gauge). I will add additional 20 gauge ribbing between the axial rib and the outer rocker. 

Just an engineer geeking out. I’m sure there is a lighter, more efficient design but I’m having fun. 





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It is good you have the time and skill to do that!  One thing I have done on two of my 240Z cars is having beefing up the frame rails.  I do not mean the kits that are out there like the Bad Dog parts but instead more heavy duty boxed frame.  The first 240Z we did we welded a heavy gauge U shaped on the inside and underside matted together to form a true boxed frame.  That worked good but a lot of work and you had to take out all of the interior.  The next version on the second 240Z an already boxed heavy gauge metal was welded just to the underside.  This work was done by Dando's Automotive in Fremont, CA.  Both of these worked great as the cars are so much stiffer and stronger.  It actually saved my life see this post.  

You might consider also doing this as I think it is a great way to improve a street car for stiffness as well as safety without needing that extensive of a roll bar setup.  I am building a more crazy street car that already has a 9 point cage which I plan on doing this same frame rail upgrade.  My Red Z without any roll bars to me is about as stiff as my Z with a 9 point cage which is pretty cool...

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Hey thanks for the reply! I didn’t think anyone was interested 😂. I will look into what you did! 
smart to add the weight as low as you can. Moving the CG down by even half an inch will be noticeable when you corner hard. 

This is a race car so any additional rigidity without increasing weight is a win. You can use really thin metal (20 gauge) when under shear stress, so you don’t have to add a ton of weight if you are strategic about how you add it. Most of the rigidity I am adding is in the service of replacing rust, so the added time isn’t too bad when there isn’t much salvageable metal to start with.


also, my full race cage is holding the whole body together while I geeked out on the rocker. Without the cage or carefully choosing how you suspend the weight of the car, you could twist the frame and have a permanent body warp. I have seen some people temporarily weld bracing while rebuilding frame rails. 

here are some more pics and vids of my progress this weekend. I have only been welding for four months so it ain’t the prettiest thing. 






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  • 2 weeks later...
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Posted (edited)

Replacing passenger toe panel. Needed to reinforce the area just ahead of the passenger front vertical door Pilar, so I can cut out my rusted frame rail and tie rod box. I’m happy with the results :) 


needed this done so I can confidently finish the brake line and fuel line in the tunnel, since it passes the frame rail. Anyone else feel like one thing lead to another... to another... and soon enough it’s 6 months? 




Edited by AydinZ71
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Since the previous owner made the mistake of terminating the role cage tot he wheel well (and not the strut tower), I’m working on bridging across. I thought by using the wheel well skin as part of the bridge, I could use less metal overall. 


I think it needs a verticals flange too, since the tunnel will have tremendous force upwards. 


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