[kieth]

I see all of the bracing and the addition of a flat piece of steel welded onto the flange of the frame (boxing) in a lot of hot rods. I think it looks great but do not know how much true strength that it adds to the frame of the vehicle.
When trying to make a big truck frame stronger and sometimes longer we keep these simple rules in mind.

1. do not weld on a truck frame .......reinforce and bolt it in.

2. if you cut and weld a frame do it on a angle (45 degrees) so it will not break when loaded (90 degree butt weld).....if we do butt weld, then we line the frame with another frame section, bolt it into place (inner glove) and make sure it goes well past the butt weld. (this spreads the load out away from the butt weld)

3. If you want to add ridigity to the frame make a frame section like the original (out of harder and thicker material if possible)-----do not weld on the frame

4. Only drill a hole in the web of the frame not the top or bottom flange...drilling a hole in the flange weakens the frame and if done the hole must be filled with a very tight fitting bolt or rivet so it helps keep the strength of the flange in tact....

5. Section modulus X material yield strength = RBM resistance to bend moment.

5a. 6" + 2.5 + 2.5 = 11" X 55000psi yield strength = 605,000 rbm

5b. boxing------------- 11" + 6" box X55,000 + 935,000 rbm (less the strength we took away welding it in....

5c. double framing 11" + 11" X 55000psi= 1,210,000 rbm


So here is what we are doing when we box a frame:

a. we make it prettier

b. we make it weaker by welding it in and loosing the heat treating of the frame where we weld it. this means if it is loaded heavily it will start to break at that weak point where it lost its strength.


If we really want to have a stronger frame adding full U shaped sections of frame material will add strength to the frame, these U sections can be welded together before they are installed and bolted into place. when we add U sections we are getting the benefit of the full length of the frame web and the frame flange.......this adds much more rigidity than boxing the frame and does not weaken the existing frame by removing the heat treating.....

Again not trying to start a war just trying to inform.......I do not build pickups for a living but I do build larger trucks (class 8 road trucks) and have been modifying them for 30 years...... Kieth

ps I think robnolimit has added some comments and techniques for adding rigidity to our truck frames, he did use tubing to reenforce where the loads get quite high during turning but he did say to use full channel U sections to reinforce the weak points in our truck frames. JMO Kieth