Different classes, and different types of racing, often have different rules with regards to what material roll cages and chassis must be made from. There are also differing opinions on which is best. We’ve heard lots of arguments both ways, and in this video Tim McAmis explains both materials and some of the arguments for one vs the other. We all know that Mild Steel is heavier than 4130, because it must have a thicker wall to come close to the same strength, but there are other distinctions as well.
And it goes beyond the material itself, but also to the way that they are handled in a chassis. Mild steel can be either MIG or TIG welded, while 4130 requires TIG welding according to most sanctioning bodies.
Check out the video below.
He says “very” a lot, but 4130 is not “very” strong and mild steel/1018 “very” weak when you look up actual charts. Chrome moly material has around 1/3rd higher tensile etc. psi for a given mass with the significant penalties of increased hardness and decreased weldability. Bottom line is, for components that may only represent a fifth or less of a vehicle’s total weight is it’s appropriate where saving a small amount is worth significantly increased cost, such as when you want to fly through the air in a plane or run eights or quicker like with the type cars he’s selling. Otherwise, choosing to use it is mostly bragging rights or overkill.
because the mild steel needs to have thicker walls to equal the strength of the CM tube, the mild steel tube is actually STIFFER than CM. That’s sometimes an important consideration too.
I’d like to see them address docol along with the other two
I think it depends on if your doing a full tube chassis or simply building a 12point onto an existing frame. TIG welding .065 chrome moly onto steel plate is tricky, overheating CM is easy to do when trying to get the penetration into the steel plate. This was a study that we tested to see the tensile strength afterward on a tension instrument.