chrome moly

[dirt fox]

about how much weight differance on a roll cage

[petermanbuilt]

I won't venture a guess to the weight savings as every chassis is different, and there are too many variables to consider.

4130 steel (chromoly) has roughly the same weight density, or pound per cubic inch, as standard 1020 (DOM). Basically a 1 foot piece 1.5"x0.95 wall tubing weighs roughly the same whether it is chromoly or DOM.

The weight savings is there because when done correctly, chromoly is stronger than DOM. The Ultimate Tensile Strength (Breaking Point) of 4130 is higher than that of 1020 steel, which allows for the use of thinner wall tubing. Less metal, less weight.

I can get some hard numbers for the Yield and Ultimate Tensile strength from one of my engineering books if you want that.

Another consideration is that DOM is easily MIG welded, Chromoly should be TIG welded and normalized.

Personally, i would use DOM, because of the ease of use and cost. There are more important places to try and save weight on your race car.

[Driver88]

You are also supposed to preheat chome before welding. Besides that I have read minimum wall thickness and amount of bars is regulated also many tracks also have a minimum weight so I doubt it would be worth the added trouble and cost.

[SRXSRULE]

It addeds up more then you think. Many rules state wall thickness for the main cage uprights, halo, and door bars. After that you can build them as thin as you want. If you do all of the other bars you can save 40-70 lbs on the car. I built a Crome moly car in 08 and it was very light, BUT the issue I ran into is that it didnt like to bend. The mounts would just snap off close to the welds. The hood pins, body mounts, passenger door bar mounts, etc.. would just break off from contact that with DOM would just bend. Eric

[zeroracing]

I have fixed many modifieds and late models that where made from chromoly. Save your money and go with DOM. If your not an expert welder you will have cracking problems at welds. The car will tend to be more brittle. I have seen bars completely shear off on brand name cars, chromoly is a dangerous tubing to use if your not careful.

Most street stocks have such a high minumum weight I do not see much of a gain, take the money you save and buy more motor or tires.

Go with DOM it will cost less to build, last much longer and be safer.

[dirt fox]

thanks for the info

[stockcar5]

i agree..my stockcar weighs 2400lbs without driver or lead and we have 2950 weight rule. chromemoly is a sales gimmic imo.

[hogracer3d]

Our super has 1" 4130 from the firewall foreword since 08, no pre heat, stick welded with mild steel rod, did stress relieve

No cracks, no problems whatsoever, and saved 40 lbs in weight from doing it

http://i63.photobucket.com/albums/h136/hogracer3d/100_49921.jpg

[4bangerhotrod]

the biggest think to chromemoly is to be stress relieved. if you dont stress relieve it will crack, usually at the heat line. when you stress relieve a weld it rearranges the molecular structure of the metal and makes the metal one. like there was never any welding done on it.