There are plenty of decent helmets on the market that can protect your head in case of an accident. They are not always effective against small jolts that rattle the brain. Robert Knight’s BrainGuard helmet is two helmets in one. Its internal shell covers the skull and the top layer deflects the impact.
Here is how it works:
The outer shell of Knight’s football helmet is able to rotate about an inch relative to the inside shell, which is strapped to the head; this absorbs the dangerous torque that can cause permanent brain damage.
Rotation is made possible thanks to a strut mechanism. The above video shows how this clever helmet works.