Whether you are building a car for the demolition derby or you are looking to add support for an off-road rig, a roll cage is the best way to do it. Metal tubing and steel plates are the strongest and most durable component options for a roll cage, but crafting the cage from these materials will require you to weld the components together as well as weld the cage in place inside the vehicle. Those welds are a crucial part of the structural integrity of the cage, so they need to be done properly. Here's a look at the welding steps required for your roll cage and some tips to get it right.
Base Plate Attachment
The base plates serve as the core foundation for your roll cage. Each of the cage legs, or tube structures, will weld to these plates to keep the cage secure. Before you can do that, though, the base plates must be securely attached to the inside of the vehicle.
For proper structural integrity, you'll want steel plates for the base plates. Aim for fairly large squares, and make sure that the steel is thick enough to hold up to both the welding and the structural support.
The rear roll cage baseplates should be welded to the floor pans in the floorboard behind the front seats, or in the floor pan of the cargo area, depending on how large you're making the cage. You'll typically need to mold the plates to the shape of the floor pan because those floorboard sections are typically ridged and somewhat curved. You need the plate to sit perfectly against the floorboard with no gaps. Then, once it's positioned correctly, tack weld it in place so that it doesn't shift. Tack welds are just small, quick welds to hold something where it's at.
Once the plates are tacked into place, it's time for a full weld. You'll want to work around the entire perimeter of the plate, ensuring a smooth, even bead all the way around. Don't move too quickly or you'll have weak points in the weld that could give out. By that same token, you don't want to move too slowly because the floor pan of the vehicle is usually thin sheet metal and you may burn through it if you stay in one place for too long.
Assembling The Tubing
Each component of your roll cage's tubing will need to be welded together as well. Sometimes, it's easier to assemble this in the vehicle instead of trying to place it after it's been welded together. Start in one front corner and work your way back, then around to the other front corner, or you can start in a back corner and do the same.
Support the first piece of tubing with zip ties or a helper holding it in place up by the car's roof. Position the base of the tubing on the base plate and tack weld four points around the tubing. Then, you can go back and do a proper weld all the way around. Like before, you're aiming for a continuous, strong weld with no gaps, bubbles, or other flaws. Repeat this all the way around, welding the tubing to the base plates and the connecting bars.
If you don't have the experience to create solid, quality welds, reach out to a welding service near you. The professional step is worth it for the structural integrity of your cage.