What Happens When You Fall Without a Helmet:
If you were to take a fall from your horse and land on your head without a helmet, your head which would contain a great deal of kinetic (in motion) energy would strike the hard ground and a good deal of that energy would then transfer back to your head in a great shock to your brain. Hard ground is a poor energy shock absorber, but rather more of a shock reflector.
This would be like hitting a telephone pole with a baseball bat. The pole can’t absorb the kinetic energy of the moving bat, so the pole reflects the energy back into the bat and back up your arms. This is what you don’t want to happen when trying to prevent a head injury. You want the energy to leave your head and move into the ground at a rate that the ground can absorb it at.
Neither your head or the ground compress very well and therefore the impact energy is transferred from your head to the ground over a very small amount of physical displacement, or movement. This rapid deceleration of your skull hitting the ground means that your brain which is floating in a fluid can slam into the inside of your skull and become bruised, resulting in a concussion.
How a Helmet Works:
Helmets are made up of a hard outer shell and a firm, but compressible inner liner normally made from polystyrene. The outer shell is designed to stay in shape in a fall and not deform upon impact. This causes the energy of the helmet contacting the ground not to be focused on a small local area of the helmet, but to be spread out over the entire surface of the helmet where it contacts the ground.
Between your head and the hard outer shell is a polystyrene foam layer. This layer is designed to compress at a predetermined rate when the helmet strikes the ground. This compression rate is designed to decelerate (slow) your head at a rate that doesn’t cause your brain to strike the inside of your skull. This is similar to an airbag in your car. It inflates just before you hit it and then deinflates as your body presses into it, thereby slowing your forward motion so you don’t slam into the steering wheel. Additionally, the force of your head upon the foam compresses the foam and this converts the kinetic energy of your head into mechanical energy (compressing foam) and then into heat which is quickly dissipated.
Accidents:
Once a helmet has been used in an accident and the inner liner of foam has become compressed in even a small amount it must be replaced or rebuilt with a new foam liner, or next time there will be less non-compressed foam to absorb the energy and the shock to your head will be greater.
Aging:
The materials that make up a helmet over time can become compromised due to daily use, ozone and other environmental forces causing them to become weakened. Old helmets should be replaced, or they could fail when called upon.
The kids came today and about 10 - 12 of them had the new helmets (different brands) that were “fitted” at the tack stores for them. All I have to do is take ahold of the brim and push or pull a little and they swing up or down.
