Pietenpol-List: a question for the engineer types - 7075 aluminum thread
Posted: Wed Mar 03, 2004 12:48 am
Original Posted By: "Jack Phillips"
Done lots of reading online about thread pull-out force in aluminum but theequations make my brain hurt.Basically what I'd like to know it if I have a Piper Cub lift strut fork(1/2" - 13 thread I think) threaded into a 7075 aluminum block (approx70kpsi shear) about 1", what would it take to fail the threads in thealuminum and pull out the fork?My initial guestimate would say it would take at least 12,000lb..... Even5,000lb would do as some rough math shows each lift strut sees about 1400lbin a 4G load. Even with a safety factor of 3 that's only 4200lb..... butguestimates and probably's don't do much for you when your wing has foldedand you become a lawn dart.Who's got some engineering skills that could give me a more solid number oreven an opinion on whether I should use 7075 aluminum or 1018 steel block tothread this fork into. (I can't seem to find 4130 in .75 and 1" square bar)Maybe 7075 is a bad choice because of fatigue?Opinions!?DJ VeghN74DVMesa, AZwww.imagedv.com/aircamper________________________________________________________________________________
Done lots of reading online about thread pull-out force in aluminum but theequations make my brain hurt.Basically what I'd like to know it if I have a Piper Cub lift strut fork(1/2" - 13 thread I think) threaded into a 7075 aluminum block (approx70kpsi shear) about 1", what would it take to fail the threads in thealuminum and pull out the fork?My initial guestimate would say it would take at least 12,000lb..... Even5,000lb would do as some rough math shows each lift strut sees about 1400lbin a 4G load. Even with a safety factor of 3 that's only 4200lb..... butguestimates and probably's don't do much for you when your wing has foldedand you become a lawn dart.Who's got some engineering skills that could give me a more solid number oreven an opinion on whether I should use 7075 aluminum or 1018 steel block tothread this fork into. (I can't seem to find 4130 in .75 and 1" square bar)Maybe 7075 is a bad choice because of fatigue?Opinions!?DJ VeghN74DVMesa, AZwww.imagedv.com/aircamper________________________________________________________________________________