[T3] A new T-34 owner?

[jaransont3 at comcast.net]

> I'm sure they are, but presumably no more than the wearer experiences, 
> since 
> the wearer is the one exerting the force on the mountings, due to their 
> momentum?  I wonder what force a human body can survive.  I think I read 
> 20g 
> deceleration was quite normal in a collision, which would require a pretty 
> substantial force (250lb x 20 = 5000 lbf?  That matches your figures quite 
> well, Jim.   I normally work in newtons, so I hope I've not made a silly 
> error). 

A 35mph front crash into a fixed object generates approximately a 25g decceleration!  The number can be much higher at higher speeds, depemnding on what you hit.  Federal Motor Vehicle Safety Standards (FMVSS) require testing at 25g front impact, 20g rear impact and seat belt pull testing at 16Kn (3500lbs) on both the lap and shoulder belts simultaneously.  This means the outer fixed end of the belt sees about 7000lbs of load in this quasi-static test. 



Assuming that 7000lb load acts on a two inch square plate and the floorpan is 0.050 inches thick and mild steel with a Ultimate strength of 50 ksi and thus a shear strength of 38 ksi. 



7000lbs / (0.050" x 2" x 4) = 17.5ksi.  



That is a factor of safety of just over  2 and assumes that the plate is pulled straight up through the floor.  The reality is that it will likely twist and only load one edge of the plate significantly.  Taking that into account, you probably only have a bit over 2" of the perimeter of the plate doing much for you rather than the full 8".  That means the local stress in the floorpan is something like 56ksi...so much for that factor of safety. 



This is one of the reasons I went with the reinforcement and attachment method that I did. 



John
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