The CCR's are kinda fuzzy, since they are written around 3/8" bolts for 20lb plates...
If I'm going to mount 135# of ballast (rectangular plates), how many fastener's do I need to run and what size? I'm going to be drilling them and want to make sure they are properly secured. I'm thinking two grade 8 1/2" bolts.
Here are my nerdy engineering thoughts:
A 1/2" grade eight coarse thread bolt has a tensile breaking strength of 21,300. According to the Maximum Distortion Energy Theorem, to convert to shear breaking strength, multiply by .577 This gives 12,290 lbs per bolt, or 24,580 lbs total bolt strength.
A conservative approximation for a "worst case" crash with a concrete barrior at 150mph would be approx 80g (3 ft compression impact in 135 milliseconds from 150mph to zero, assuming linear deceleration), so the 135 lb plate stack will weigh 10,800 lbs during the impact.
Therefore, if I run the two bolts as mentioned above, I will have a factor of safety of approx 2.27.
Should be plenty, right?
Bookmarks