xxjoeyxxeb Posted July 17, 2008 Share Posted July 17, 2008 Hey guys, I am working an internship and my project now is to design a rear lower control arm for a vehicle. The chromoly tubing has to withstand 6000lbs of compressive force. The length from bolt to bolt is 18.43". Column Design: I did Euler and JB Johnson column buckling equations and when solving for OD-ID I just assumed the more common 1-3/8" and 1-1/2" OD for control arm tubing. I get a little different answers from each way, but figure a wall thickness of .120" Threads Design: Then I have to figure out a thread callout, for the bung (12L14 material), to tap the inside of this tubing and still be able to withstand the force. I have been doing some calculations with 1-3/8" x 12 UNF thread. I haven't had any Design classes yet with threads so I'm not sure how to really go about this. I need to make sure the thread with withstand the force, and when the tubing is tapped, that it will not weaken the tubing to fail. Any help will help, whether it be links, equations for threads and forces, or just time taken out to help! Thanks, Joe Quote Link to comment Share on other sites More sharing options...
Phantom Posted July 17, 2008 Share Posted July 17, 2008 It's been a very long time since I've done this but, for starts, go to an Unbrako website. They make Grade 8 bolts and have the shear and tension/compression numbers you'll need for different diamters and threads. The weakest point in your assembly will be that small bit of threaded tubing that is not filled with the bolt. Keep that to absolute minimum and, since the bending and or shear moments really don't concentrate in that area, you should be fine. Not sure how to math that out but your prof should be willing to give you a little guidance there. Quote Link to comment Share on other sites More sharing options...
xxjoeyxxeb Posted July 17, 2008 Author Share Posted July 17, 2008 Thanks for that website. They had all the descriptions of their fasteners, but no equations or anything that could help lead me. I figured the last thread or 2 that doesn't get threaded would be the weakest point. Is it safe to take the cross sectional area of that threaded part and find the stress by F/A and if that is less than the stress allowable then that should be good? Quote Link to comment Share on other sites More sharing options...
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