The Simple Math
The first thing is, that a crash with a Spinal Injury only happens occasionally.
Maybe once or twice a season at a given track.
Sometimes you don’t hear about it because the driver walks away with adrenaline masking the pain until later when pain persists and a visit to the doctor or ER confirms a compression fracture.
The math of an occurrence is simple by example, if you toss a Nickel in the air enough times,
eventually it will land on it’s edge.
Random chance will determine when. Could be the first toss or the two hundredth.
So every once in a while, during a crash, the car lands flat on the frame bottom and that’s when the driver’s spine is compressed against the well constructed, rigid seat bottom.
The chance of it happening to you, is an unknown, but when it does happen to you, it’s 100%. Impact Math
To understand the Impact problem and the solution, the math is pretty simple. And to keep it simple, the important concept is the -relationship- between the crash energy and the impact forces. Here’s the formula: E/t = F
Energy divided by time equals Force. Crash Energy can be best understood as the speed of motion of the car.
If a car is stationary, it has no energy and as you know it’s pretty hard to get hurt sitting in a car that isn’t moving. But once the car is moving, it takes force to stop it.
Normally when you stop the tires from rolling (with the brakes)
there is a force created from the tire to the track. This force stops the whole car because everything is firmly connected together.
You, as the driver, feel this force as your body tends to keep moving while the belts hold you back. You feel the force of the belts against your body and you become part of the car. The belts are connected to the car frame and all the parts of the car are connected to the tires, it’s all the same force.
Now the amount of force you feel from the belts depends on how quickly you
stop. Hit the brakes harder, you stop quicker and you will feel more force... but the car
doesn’t stop immediately, it slides to a stop over time and distance.
This stopping time (or distance) is the key to how strong the force will be.
If you hit the wall head on and stop instantly, you know that the force
will be much higher and knock the wind out of you.
So the amount of force you feel from the belts depends on how quickly you
stop and the math is pretty simple.
E/t = F. Energy of motion, divided by the time it takes to stop, equals the Force.
When the force is high because the duration is short, we consider that an Impact Force.
The situation with Spinal Injury is that in a frame bottom impact, the frame
and seat stop dead... and if you are in the car, so do you.
The duration is very, very short. The car goes from dropping at the speed caused by
gravity, to zero, in much less than 1/10th of a second. It happens so
fast that you can’t really catch it on a normal video frame at 30 frames per
second (1/30th of a second).
Now the primary direction of force that causes the injury is vertical down
because that is the orientation of your spine. So think of an arrow
(vector), straight down the back of the seat, with the point against the
bottom. This is the force (vector) that is the problem and it is the
alignment of your spine in the seat.
The force is created when the seat stops and your body is still in motion
but has to stop because the seat bottom holds you from traveling any
Your body fortunately has some squishy parts between the bones
of the vertebrae that can absorb about 10 times your body weight in force
(10Gs) but at about 14Gs the bones come together and can be cracked or
break or be crushed.
And that’s when they call in the helicopter to get you to the hospital in a hurry!.
So back to the math. Here’s what it comes down to...
The Energy of motion divided by time equals Force.
As an example, and we’ll leave out the Joules and other units and conversions
to keep the relationship simple...
1. 1000 / 1 = 1000
If you have 1000 units of energy and stop over a duration of 1 second it will
create 1000 units of force.
2. 1000 / 0.1 = 10,000
If you have 1000 units of energy and stop over a duration of 0.1 second (one tenth)
it will create 10,000 units of force.
(frame bottom impacts can actually stop faster than 0.1 seconds making even larger impact force!).
3. 1000 / 0.2 = 5000
If you can double the stopping duration to 0.2 second (two tenths)
the force will be reduced to 5000 units ! ...cut in half !
So the point is that, if you can add just 1/10th of a second to the already
short impact duration, you can make a BIG reduction in the force.
You can see that because the stopping duration is so short in a frame
bottom impact, that the force gets really big,
AND because the stopping duration is so short,
it doesn’t take much added time to make a big reduction!
The material in the CRASH PAD provides the SPACE needed to lengthen the
duration, plus it has a very unique resistance during compression that is
the same throughout compression to slow your motion evenly (very important) ,
AND it doesn’t bounce (very important).
The CRASH PAD uses the material that tested best for the US Military to
reduce spinal compression forces in vertical down forces in the seat.
So the thicker the material the better. More space means longer
compression time and lower forces.
Now that you know how and why, it’s your decision of what to do.
We created the CRASH PAD for ourselves and used the best material we could find.
If there was something better, we'd use it.
Then after a few bad crashes of our own, we decided to make it available for all racers.
See these simple seat inserts at the pages below:
http://www.802solutions.com/crash-pad-products/ for complete CRASH PADs
http://www.802solutions.com/802sam-shock-absorbing-material/ for raw material you can put under your existing upholstery.