By Joel Haywood
There is quite a bit of talk about welding brackets and such to the frames of trucks. Where the thought that the frames were heat treated came from is a mystery. I do believe it was a German thing years ago.
When welding on the truck, please note to disconnect the battery and unplug any modules that your truck may use. Just disconnecting the battery is not enough. The electrical system on your truck is very sensitive to spikes, hence the use of fuses and breakers. A welder uses a lot more amps than the system is used to seeing. You could end up frying any one of the modules. Not a good thing if you’re just making a small patch job. It’ll make the frustration level increase. Also check for harnesses and lines running inside the frame channel. Make sure that these are moved out of the way of the welding. A melted harness or a broken brake line would be bad. Fuel lines tend to be bad when heat is applied to them. Can we say Darwin candidate?
Since older truck frames are made up of two parallel C-channels, running front to back, there is not very much stiff ness to just the C-channel alone. The added cross members, be it bolted or welded, are what is going to give those channels the stiffness your truck needs. A majority of the forces are up and down on the C-channel. A good example of what cross members will do is to take an extension ladder and try to twist it. Now take that same ladder and remove all the steps except for two, one at either end. Now twist it. Can you say twizzler? A lot of the new trucks these days are coming with Boxed sections, which are by far better than the C-channel design as for stiffness. There are a lot of things that can be done to the C-channel to make it stiffer. Another thing to note is that frame flex is not a good thing. It may look neat in a picture, but your frame may not like it. Eventually leading to the frame failing and cracking in two, or collapsing.
Now on to the good stuff! You can weld to the frame but the quality of the weld depends on the welder and the dude behind the mask. Say you want to weld on new leaf spring hangers to the rear of the frame. Welding all around the bracket would be recommended to ensure that nothing can get behind the plates to rust them out. Try to avoid sharp corners, radius or chamfer all corners if possible. This will allow you to weld continuously around the part. If you’re extending the hanger down then adding a cross member is good. Remember the twisting thing? Add an arm like that and your going to accentuate the problem of C-channel twist and possible cracking leading to a failure. Consider another thing when welding, “Will this have to come off at some point in time.”
Welding a bracket solid then having to remove it is a PITA. So watch when doing this.
Please consider the following when welding brackets and brackets to the frame. Welds are not good in tension or compression. Ideally a weld will serve best if in shear. Same goes with bolts. Having a weld is shear will be 3 times stronger than a weld in compression. Tension weld we all know what happens to them right? POP and that’s it.
So to sum things up in a nut shell:
- Welding to the frame is possible but the quality depends on the person doing the welding.
- Consider if the bracket may have to come off at one point in time
- Radius or chamfer any corners to allow continuous welding around the bracket.
- Shear welds are your friend, tension and compression welds should be kept to a minimum
- Disconnect any electrical components (i.e. Battery, ECU’s) before welding to the vehicle.
- Extra cross members are a good thing, but keep them light weight; a 7” x 7” boxed cross member is not a good thing.
Happy designing and welding.~TRS