Thanks. That is pretty much in line with what Al came up with so it is probably accurate. Considering that the load is shared between two lap belt bolts plus the cable that is attached to the shoulder harness I should break well before the bolt.
Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Matthew Elder Sent: Friday, October 29, 2004 9:28 AM To: KRnet Subject: RE: KR> bolt shear strength / Axle size [long] Brian, Actually I think most seat belt bolts are sized for 20g for shear. Not so much for flight maneuvers as much as a "hard landing" (aka nose first)... You can get a good idea of shear strength of any section with the following formula: Section area * .577 * tensile strength.... The .577 I know applies to steels, but I'm still looking around to see if it applies to ductile materials other than steel (aka aluminum). Anyone that might know, chime in so I can stop my hunt. (distortion-energy theorem if you want to look it up) So for a bolt (round section) you get: (radius ^ 2) * 3.1415 * .577 * tensile strength Example: AN-3 Bolt (3/16in dia) 0.09375^2 * 3.1415 * .577 * 125000psi = 1990 lbs I used 125000psi because that was the number I got from the Spruce catalog on the bolt tensile. It will vary based on the material you use, but all you have to do is look it up. Spruce lists that number as "minimum tensile" so where Wicks got the 2125lb figure, may be that the 125000psi number is conservative. I'm sure "AN" bolts aren't all made from the same materials... There are probably 2 or 3 acceptable ones that they make them out of, and it would depend on who made them. Spruce lists 4037 and 8740 with the 8740 being the most used. Don't forget to add a safety factor and of course you must keep in mind the amount of shear planes.... Also, you can forget about the bearing area on the surface you are transferring the load to... Just make sure you have enough bearing area to transfer the load without over-stressing the supporting material. Matt Brian Kraut <brian.kr...@engalt.com> wrote: Thanks Al. You must have the early version of the catalog they had at Sun N Fun. The newer one they did for Oshkosh has the pages a little different and I can't find it there. I will dig out my older one. I guess that 12 Gs on my seat belt bolts is plenty strong enough. Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Allen Wiesner Sent: Friday, October 29, 2004 12:02 AM To: KRnet Subject: Re: KR> bolt shear strength / Axle size ------------------------------------------------- Matthew Elder Orangeburg, SC http://www.infinigral.com/melder _______________________________________ to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
