More on Gussets and triangulation

Brian Tecklenburg - Monday, March 05, 2012

When building a RZR Roll cage, the general advice is to gusset any single point intersection. This means an un-triangulated span. This is to help strengthen the joints, reinforce the welds, and honestly, it's cheap insurance. Why not triangulate every termination? well some places triangulation interferes with the function, or look of a cage. For example not everyone wants a triangle truss running corner to corner in their windshield, or where they get in and out of the car. But, there are some good reasons to add gussets here instead of triangulating with full size cross members. First we need to explain a little bit about triangulation to help us explain. Triangulation, by definition means the formation of a plane into triangles or division a plane into triangles. in the context of roll cage building, it means using a beam (in our case a tube) to support a plain diagonally. This doesstrengthens a cage section in a number of ways. First, it reduces the overall length of a beam. This reduces the total leverage on that member. In other words, if i have a 4 foot wide cage, but I put one triangle support in the middle, I now have 2, 2 foot sections of un supported leverage. This makes each piece more resistent to failure. Second it converts a point load bend failure force into a tensile compression expansion force (see diagram).As you can see in the diagram, fully crossing a gap at 45's is probably the strongest you can make anything. That said, it is not always practical. For example a full cross brace in both directions is not very convenient for say a door gap. Also sometimes there are suspension and engine parts that you can't go through, and therefore have to go around. This is where you use gussets instead. Gussets help convert forces to take advantage of how materials are the strongest also in the case of a roll cage, compression and tensile forces. They, however run in corners, to brace the torsion of a cage. A slightly different method, but the same basic result. Gussets also increase the welded surface are in the case of a plate gusset, in the case of a tube gusset, they create a separate joint, requiring a multiple failure at one point to produce a significant cage failure. So this is the reasoning as to why large openings, which cannot be properly triangulated need gusseting. Essentially there are two principles that govern the use of cross braces or gussets. First, take advantage of materials in their strongest manner (for steel tensile and compression forces) and second, make your cages potential failure points as redundant as possible.

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