The last bit i will say about material, is that you should shop around. bottom line is, it really just depends on the design, how you truss it, etc. for NON proprietary members of the cage (aka, not the main roll hoop) you can use 0.083 thick tube, or some other thickness. a well designed cage with "expensive" material can be safe and possibly close to the cost of a poorly, overbuilt cage with shit material. That being said, you will benefit THE MOST from a well designed cage, as opposed to going with the cheapest material. that is to say, 1/8" larger diameter in this case allows about 12% weight savings over 1.5" tube. larger diameter tube is stronger than its smaller diameter equivalent.
SHOULD ROLL CAGES BE BUILT WOTH TUBES OR PIPES EVOM FULL SIZE
for huge full size trucks, 2.0" is recommended. for smaller, lighter street vehicles, 1.5" is very common.
for off road rigs that are typically in the 2,500-8,000 pound weight range, you will not use smaller than 1.75" for proprietary members of a roll cage. the only reason someone should justify using chromoly is if budget is not a factor and they are trying to save literally as much weight as possible. it will be less prone to cracking due to stress over time, which means it will be more reliable 5 years from now. ill put it this way: if you plan to keep the truck for years, use mild steel. long story short, chromoly rigs are designed with a life span in mind. before you make the argument of "bro, my buddy mig welded a chromoly cage and it didn't crack" I urge you to check out the links that go into detail about tube choice, and proper welding procedure for metals. this is not nearly as critical with mild steel as it is with chromoly steel. you SHOULD be stress relieving all welds. High carbon content is stiffer, and thus more prone to cracking compared to mild steel. cons to this are typically the longevity and processing (welding). **Chromoly steel tube: its about twice the cost of the mild steel DOM, and about 40% stronger, which means you can use thinner wall tubing and effectively have a lighter vehicle. this is typically what you would find any reputable shop using for a non race oriented vehicle. (during the process it "eliminates" the seam. **DOM tube is made FROM HREW, but goes through an additional manufacturing process. I repeat if you're going to spend the time and money, do it right the first time and never have to worry or second guess it. Again, its cheaper than DOM but also weaker given the same cross sectional area. **HREW is steel TUBE that is seam welded. for the same "basic" level of safety, you are using more tube, which will weigh down your rig, and somewhat offset the cost of the pipe-which is its ONLY advantage. its a cheap alternative but imo if you're spending the time and money on a cage, do it "right"- meaning NO well respected shop will suggest that you use schedule 40 pipe to make a roll cage, or any structural component. pipe has different manufacturing tolerances, AND its weaker than TUBE given the equivalent cross sectional area.
pipe is not an interchangeable term for tube. see links at the end for more info and other threads In order to keep this from becoming another huge in depth thread on tubing, ill try to touch on all the points here in one response and keep them as concise as i can. Hi guys, former FSAE design lead here, (ive also worked with a few guys from the BAJA SAE team at our school). DOM CARB tubing A-513 (or equivalent) see reasoning below: TLDR: use 1.75x0.120 DOM mild steel tubing (1018 or 1020 alloy (1026 is even better, but not as available and more expensive)Ī.K.A.
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