Quote:
Originally Posted by csangster
Good evening,
Let me first say that I am extensively impressed with this build thread and all of the modifications. I have been wanting to build a Javelin just like this, and yours is one of inspiration..........very nice.
In a small effort to help make sure you build goes off well, I feel compelled to tell you that the above strength calculation is incorrect (I am a registered Professional Engineer and I perform these types of calculations for a living).
You are mixing your strength numbers when performing this calculation.
If you are trying to determine the load carrying capacity of your fastener in shear, you need to use the shear strength of the material, not the tensile strength. These are two entirely different measurements. The good thing is you can look on a website called MatWeb, find the material in question and it will give you nearly everything you need to know about that material, CTE, yield strength (tensile and shear), ultimate strength (tensile and shear), thermal conductivity......the list goes on.
The next thing you are missing is your factor of safety. You need to carry a factor of safety on your design to cover anything that you may not have thought about or considered. Generally, you can pick a factor of safety from 1.1X all the way up to 16X or more.........it just depends on how much risk you think you can take. For a suspension component, a factor of safety between 2 and 4 is a good place to start......the Carroll Smith's book that was mentioned earlier will have a better guide for selecting the factor of safety for your application.
As far as single shear vs. double shear is concerned, the shear strength of the fastener is what it is, when the fastener is in single shear, you are loading only one shear plane in the fastener, when the fastener is in double shear, you are loading two shear planes, thus doubling your strength of the fastener in shear.
While you are looking at shear strength of the fastener, keep in mind that the fastener is also stressed in bearing, you will need to make sure that the bearing surfaces don't have too much stress in them and causing plastic deformation of the fastener or the suspension components.
Additionally, the above calculations are all static calculations and do not apply to dynamic load cases. Sometimes you can increase your factor of safety if you are unable to properly calculate the dynamic stresses in a joint.
Dynamic stresses are important because they can cause failure by fatigue of the material, not by failure at the ultimate strength.
I'm rambling too much, I just wanted to make sure you taking everything into consideration for your build so something doesn't break on you and give you headaches later.
Again......very impressive and inspirational build.
Cheers,
Chris
|
Thank you very much for the information and the nice words. I am going to have to research this a bit more. I believe that the Lateral Dynamics 3 link uses 5/8" bolts with 5/8" hole and 3/4" shank, so at least I know that set up is tested and works.
Thanks again,
Jon