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    Young's Modulus of Steel
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    Are there any techniques by which you could make you steel member of the chassis stiffer? As in, increase the modulus of elasticity ?
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    Re: Young's Modulus of Steel
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    Millenium Member nutz4sand's Avatar
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    Proper design and tube size will get you there better than worrying about that.
    Now that NOBAMA has PROVEN he is the absolute WORST president in the history of history Jimmy Carter can thank him for stealing the dunce crown.

    Lets hope the next guy repeals NObama care along with the rest of the stupid crap this blight on our windshield has done.
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    Re: Young's Modulus of Steel
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    Super Moderator minibajaman's Avatar
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    The modulus of elasticity is a property of steel and is not something you can change. However, the value does vary slightly among alloy steels; for example, mild steel (1018) has a value of 200 GPa, but 4130 steel has a value of 205 GPa.

    The only practical way to change chassis stiffness is with tube diameter and bracing. Using 1-1/4" OD tube instead of 1" OD results in a significant gain in bending stiffness and strength. Then proper bracing will keep flex to a minimum.
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    Re: Young's Modulus of Steel
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    No u misunderstood me. Thanks for the info though.
    We designed our chassis with 1" x 0.062" .. and this doesn't qualify with the stiffness calculation. We went with this as we had no other option an=t the end of the day and now we're in a bit of a fix. The only variables we have are E and I anyway. I is fixed according to our member so that's y i ask, is there any way to change the E ? Coz if not, we don't clear tech dude to the rules regarding tube strength.
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    Re: Young's Modulus of Steel
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    Senior Member Gotted's Avatar
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    1" x 0.062" tube is a light tube not to strong. Now if you change it to chromolly tube 1" x 0.062" you will have fixed the weak problem. Dont know what E means?
    "Imagination is more important than knowledge"
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    Re: Young's Modulus of Steel
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    Thats what tech inspection is for, to make everybody safe. Your supposed to read the rules BEFORE you build.
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    Re: Young's Modulus of Steel
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    Super Moderator minibajaman's Avatar
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    Quote Originally Posted by Vladmir123 View Post
    No u misunderstood me. Thanks for the info though.
    We designed our chassis with 1" x 0.062" .. and this doesn't qualify with the stiffness calculation. We went with this as we had no other option an=t the end of the day and now we're in a bit of a fix. The only variables we have are E and I anyway. I is fixed according to our member so that's y i ask, is there any way to change the E ? Coz if not, we don't clear tech dude to the rules regarding tube strength.
    I understand you used the wrong size tubing, and are now trying to figure out how to not scrap your frame. If the minimum is 1" x .120" wall thickness, there is no steel out there where 1" x .065" will ever be equally as strong. And as I said before, E is fairly constant for steel, so only I can be changed. What school do you go to or where is it located that makes it so hard to get a variety of tubing sizes?

    Quote Originally Posted by Gotted View Post
    1" x 0.062" tube is a light tube not to strong. Now if you change it to chromolly tube 1" x 0.062" you will have fixed the weak problem. Dont know what E means?
    The difference between mild steel and chromoly is not as great as you might think, and wouldn't help in this case. E is the symbol for Young's Modulus.
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    Re: Young's Modulus of Steel
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    I would say that unfortunately you need to manufacture a new frame. try speaking to a heat treatment specialist. They might be able to treat the frame to increase modulus. It would probably come at the expense of durability as i'm guessing that it would be brittle - NOT what you want for a chassis/roll cage. Most steel has a fairly standard modulus (as stated before). It is usually the tensile strength and yield strength that changes drastically, for example between mild steel yield is around 250 MPa, where as some high tensile steels its closer to 1200 Mpa. Much stronger, but it will still deflect a similar amount with the same load as the difference in elastic modulus is negligible.

    Another option, Increase the section modulus of each tube by welding some flat bar to the side of the tubes. It will end up heavy though, and that much welding will probably distort the frame a little. It would probably be less effort to weld a new frame from scratch.

    Good luck with it, realistically though, i think you might be up for a re-build. Sometimes the best and quickest option is to accept your mistakes and start fresh. So many times you will spend longer repairing a mistake rather than starting again from scratch
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    Re: Young's Modulus of Steel
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    Yea I dont know how you have specs if you cant get the material to meet them. You can stiffen any frame pretty easy. You just gotta throw steel at it. Thats gonna make you good and heavy to. If you saved enough weight using thin tube maybe it's a wash. But I doubt it saved that much at all compared to doubling up on main tubes or triangle bracing all over.

    Add some pics of what you built. Maybe it's open enough that it just needs more steel anyways. ahahaha
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    Re: Young's Modulus of Steel
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    J.M. Action Figure flyerrider's Avatar
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    If your time frame does not allow for building a new chassis, another option is to clam shell the tubes with thicker tube. 1.125" .065 wall tube clam shells 1" OD tube perfectly. Tube frame aircraft repairs are done this way. You see it a lot in Pitts biplanes with Spring gear conversions (they crack at the lower longeron above the gear) and Extra 300's at the tail wheel. There is actually a required service bulletin that needs to be complied with for the tail on an Extra 300 for this reason.

    Page 68 has the details of what I am talking about:

    http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2043.13-1B/$FILE/Chapter%2004.pdf
    Last edited by flyerrider; 09-23-2013 at 04:18 PM.
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