Firewall/Fender Truss for the KAKABOX:
After seeing the fender brace thread:
http://www.redpepper...e...st&p=191692 ...I thought this would be an easy, unobtrusive way to get a little more bending stiffness in the shock tower to firewall connection. By adding a gusset btwn the frame rail and the firewall, it will, at least in theory, stiffen (reduce the deflection) the frame rails cantilevered off of the firewall. This is a load path for some of the front end chassis loads that are reacted into the firewall bulkhead. Any stiffening in this area should provide some benefit in the handling performance of the front suspension by providing it w/a firmer platform, thus reducing geometry changes under load. This is the theory anyway.
But, also, if you're thinking of doing this mod, keep in mind that the frame rail you're stiffening is part of the front end's crush zone. By adding stiffness to this rail, in a front end collision, you could potentially cause more impact energy to be transferred into the cockpit. Anyway, just some thoughts to keep in mind if you're planning on doing this to your dd.
Anywhoooo, on w/the mod!
First off was the removal of the front fender inside liner where I was treated to a constant shower of debris word to the wise: wear safety glasses and keep your "pie hole" closed! After removing the liner and then the fender, I swept up the fallen debris and found that I had ~ 1 lb. of sand/leaves/pebbles hiding inside my fender!
I cleaned up under the fender and tacked on the liner to see the area I had to work with. Placement of the truss bars is critical for fender/liner clearance; I don't want the liner or the fender to rub on the truss.
I wanted to take advantage of the door hinge hard points, so, I made some hinge plates (.125" mild steel plate) that attach w/the oem hinge bolts. For mounting the plates, I used the two lower hinge bolts but only the lower bolt of the upper hinge. I didn't make that bolt common to the truss so that I can remove it w/o the door falling on the ground! The vertical member of the truss was welded to the hinge plates.
The truss is removable; a bolt on design was employed. The truss diagonal will connect to the lwr section of the vertical member and go up and fwd to the upper chassis section...I'll be using a bolted connection here, so I needed to add some "nutserts" to the upper frame rail. I need enough fasteners to ensure good load transfer; holes (5/8" dia) for the welded in 3/8" nutserts:
...this were located on a flat surface and there are doubled up sheet metal panels in this locn making it a stiffer place to weld in the nutserts. Here are the nuts welded in; the center one I've already filed down flat. All the welds were filed flat so that the bracket fits flush on the chassis:
Next up is fabbing the frame rail bracket. It's made from a 4.25 long section of a 2 x 2 x .125 mild steel angle...a quick paper template to capture the "nutsert" positions:
Then with some hack sawing, grinding, drilling, repeated mock-ups and lots of careful measurements to ensure that the bracket flange doesn't hit the inner fender (it did, so I trimmed it accordingly)...here's the frame rail bracket mounted to the chassis:
The diagonal member is welded to the lower portion of the door hinge tube and the frame rail bracket. An angle of 45* was chosen for the diagonal member. After a mock-up to ensure that the diagonal clears the fender liner (it does by ~ .25"), the diagonal is tack welded in place:
In order for the truss to be as close as possible and run parallel to the frame rail, I found I had to flatten slightly the frame rail's diagonal stiffening bead. Also, for the truss's horizontal member to connect w/the fender bracket, I had to cut away the lower portion of a sheet metal collector flange (three sheet metal panels are joined together to form a flange). This flange joint consists of three spot welds; I cut away the lower section leaving only two. I don't feel bad cutting out a spot welded portion as the lost area is more than replaced by the truss. Here's the area before flattening and clearancing:
...and after flattening w/a BFH and clearancing w/die grinder:
...to be continued next post...
Edited by kakabox, 12 March 2008 - 11:01 PM.
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