[T3] A new T-34 owner?

[Dave Hall]

Nice bit of analysis, John.  

I wonder what differences there are in the original VW mountings - the rear
outer has a large plate underneath, but I don't know what the ones going
into the tunnel, sill or C-post have.

Dave.
UK VW Type 3&4 Club
===================

-----Original Message-----
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of
jaransont3 at comcast.net
Sent: 01 July 2011 16:19
To: type3 at vwtype3.org
Subject: Re: [T3] A new T-34 owner?




> 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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