I am pondering what material I wan't to use...I know 4130 is THE choise but how many of you have opted for the mild steel chassis???and how is it working for you??? Fabrication of 4130 weldments is not an issue I have done plenty of that...I am just building a play car to run at a local strip(3 miles away) with a smallblock/PG set up ....it may see the 9's ....maybee the 1020 tube is cheaper and easier to work with...right in line for this project, and if I remember I just have to upsize the tube...I need to download the latest specs before I buy material , but was just wondering how many people are building FED mild steel(1020) chassis...Thanks, Shawn
I have in the past use mild steel but it does add a lot of extra weight and does not like to flex (it Bends)so that is why I use 4130 now it has more flex but is much stronger and retain it memory.
I believe NHRA allows mild steel FEDs if they are certified slower than 7.50. SFI has the specs for these cars.
Thanks for the replys...I know about the flex issues...i have built several 4130 motorcycle chassis, and know about the proper fab methods....just wanted to know if there were many 1020 chassis...Shawn
You can use 1020 if you increase the wall thickness to compensate for the lower tensile strength. The only reason for using 4130 is to decrease weight without giving up ULTIMATE strength. Tensile is measured in pounds per square inch-thats pounds per square inch of cross sectional area. As long as the cross section of your 1020 at its tensile strength is enough to equal 4130 at a lesser crossection at a higher tensile you're in business.
When you consider the total cost of your finished dragster, the difference in price between the two alloys will be almost negligable. I would go with the 4130. The car will be lighter and faster. Best of luck with the project.
I find that trying to build with mild steel is more difficult. first you have to use .134 wall which cost more than CM, reason being not many places carry it and because .120 mild is only .114 , well below the .118 that is called for.Its heavier to work with. Sizing does not allow mild to telescope together. And at any time the spec could change to not allow mild in any dragster and you would have to do it all over again. The mention about anealing is not correct. In early sema spec. it was wrtten that "Even though welding CM with current welding techniques, the material loses some strenth,it has been determind that it does not signifecantly alter the structure and any procedure to normalize the area if done incorrectly would seriuosly compromize the weldment." I have built many Chassies and have worked on many others from current top builders in drag raceing and not one of them go thru that process.
I being a dinosaur build with mild steel right to the rule book. Why? Easy to find and easy for me anyway to work with. Strong. Weight difference to me is minmal. I could get better results by dieting off 100 pounds. But that is just me. it sounds like you areused to using Cm . I am not so for you whywould you not go the CM route. Have I ever been sorry i did not. ? Nope. But remember i dont know any better either. I tend to use the material I personally know I can do the best job with. I know I can weld mild steel well. I have no idea what would happen on CM. Someday I hope to find out. Don
two friends have feds with 1020 dom chassis and my altered is also have seen cages break off of a CM chassis but CM is lighter and my next chassis will be CM but I will not be welding it. the MS frames work well one fed (wb 160")went off the end of an outlaw track and bent the frt axle two years later the car still runs straight carrying the front wheels out of the hole
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