Attention: TDR Forum Junkies I hear country singers are good with pick-up frames
It may be prudent to find a donor frame to get frame sections that match the current frame. (or call up toby keith, he carries frame sections around with him, I hear.
) Careful attention needs to paid to joint geometry. A vertical weld will cause a significant stiffness discontinuity on the tension side of the joint. A longer, angled joint spreads the stress across a greater length, hence greater cross section for load carrying through the joint, and reduces the chance of stress concentrations at weld terminations. Once the sections are installed, the gusseting mentioned above would prevent general bending weaknesses when applied properly. The harder one to address is torsional bending and then identifiying mode shapes and frequencies at which they happen. I'm not trying to throw out a bunch of engineering lingo but you will be changing the stiffness of the "system" and there are lots of details to consider. By matching the overall bending and torsional stiffness without adding too much mass, little things like drones, boom, door jamb pinching, and other NVH maladies will be minimized.
Basically, the engineers try to have the first natural frequency of their system (frame, front axle, suspension, rear axle, engine mounting, body mounts, etc) out of each other's operating range. An axle housing might be at 8Hz, a frame at 10Hz, and so on. By changing the frame, it may now be at 12Hz if you really throw the beef at it or at 8Hz if the added mass does nothing for stiffness. If it falls to 8hz, then the frame will be excited at the same frequency as the axle housing. This is not a terribly bad thing unless it happens a lot or the excitation turns into noise, wear, or other bad things.
Having a professional service perform the work would be a smart way to go in this case.
GWBourne said:
It may be prudent to find a donor frame to get frame sections that match the current frame. (or call up toby keith, he carries frame sections around with him, I hear.
) Careful attention needs to paid to joint geometry. A vertical weld will cause a significant stiffness discontinuity on the tension side of the joint. A longer, angled joint spreads the stress across a greater length, hence greater cross section for load carrying through the joint, and reduces the chance of stress concentrations at weld terminations. Once the sections are installed, the gusseting mentioned above would prevent general bending weaknesses when applied properly. The harder one to address is torsional bending and then identifiying mode shapes and frequencies at which they happen. I'm not trying to throw out a bunch of engineering lingo but you will be changing the stiffness of the "system" and there are lots of details to consider. By matching the overall bending and torsional stiffness without adding too much mass, little things like drones, boom, door jamb pinching, and other NVH maladies will be minimized. Basically, the engineers try to have the first natural frequency of their system (frame, front axle, suspension, rear axle, engine mounting, body mounts, etc) out of each other's operating range. An axle housing might be at 8Hz, a frame at 10Hz, and so on. By changing the frame, it may now be at 12Hz if you really throw the beef at it or at 8Hz if the added mass does nothing for stiffness. If it falls to 8hz, then the frame will be excited at the same frequency as the axle housing. This is not a terribly bad thing unless it happens a lot or the excitation turns into noise, wear, or other bad things.
Having a professional service perform the work would be a smart way to go in this case.
