Fraidy Cat Racing

1994 Jaguar XJ12


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Calling degreed engineers

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1 Calling degreed engineers on Wed Oct 05, 2011 4:26 pm

This email I got from a customer is over my head. I will continue to work on it, but if one of you is bored and can help, please do.





The discussion that took place between Garrick and my co-worker leading up to the defined 1800 psi at 1.0 min stroke is below.



The item impacting the material will be the head of a frangible bolt, in Joel’s application below he had the opposite end of the bolt. Unlike Joel’s application I need a thru hole in my absorber to pass cables thru limiting my surface area to portion of the bolt head’s outside diameter.



The Surface Area is 1.095 in2

Velocity at impact is 75-90 ft/sec (in my calculations I’ve been using 85 ft/sec) at time=.0004 sec

Weight of impacting items: 1.142lbs



To calculate the force on impact I used the conservation of momentum such that R = [W/g (Vfinal-Vinitial)]/time

The Kinetic Energy I calculated using 1/2W/gV^2

Calculating the displacement as: Force *displacement = KE and displacement=KE/Force



My depth/height of impact absorbing material can change, Currently it is sized with OD = 2.7”, ID=2.06”, Thru hole dia = 1.688”, depth/height=1.535”. The OD could possibly grow but not significantly



I need to verify that the form factor of my absorber using 1800psi with 1”min stroke will sufficiently dissipate the energy and crush the material.

I look forward to hearing from you.

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