Materials 101 - What Are These Roll Bar Thingys?
Posted by SDR Motorsports on Feb 9th 2018
Here are some things about cage construction materials we have learned over the years that are often confusing or misunderstood:
Materials 101: There are many different materials that builders use to build cages. Here is a quick rundown of what is what....
CRERW: Cold Rolled Electric Resistance Welded. This is the most common and least expensive of the three we will talk about here. This tube is rolled into shape from a flat plate of steel and then welded creating a visible seam. This tube type is used here at SDR for connector tubes and non-critical bracing such as the V-bars in the roof area, dash bar, and the 1 inch bracing in the windshield and corner gussets. If your cage is built from this material it should be .120 wall thickness to maintain the same strength as .095 wall D.O.M. tubing wich we will talk about next. Also critical to strength when making a cage from this material is the seam placement during bending. Having the seam aligned with the inner or outer surface of the bend can lead to failure by causing the seam to rupture or split during an impact.
D.O.M.: DOM stands for Drawn Over Mandrel Steel. DOM Tubing is much more expensive and much stronger then CRERW. This DOM type of tube is often incorrectly referred to as seamless tubing. While it appears to be seamless because of its flash removal after the welding process it is also rolled and welded. This type of tube is most commonly used for structural products for its consistent ID and OD tolerances. DOM is also a very easy material to work with as it bends well and can be MIG welded with no heat treating or stress relieving needed. This is the material we use for all of the main structure of every SDR cage we build.
Chrome-Moly: Chrome-Moly stands for Chromium Molybdenum Steel is the "strongest" of the three materials we are discussing and also the most expensive of them by far. Not only is Chrome-Moly costly as a raw material it requires proper welding and stress relieving once it is welded to yield the strength it offers as a raw material. The argument of Chrom-moly versus DOM is a hotly debated topic and there never seems to be a clear winner. We believe that there is not enough strength benefits to outweigh the cost factor of a Chrome-Moly cage. But for those that have to have it, we can and will gladly build one for you.