Helmet and shield design
A facemask is designed to stop a projectile from directly hitting the face or head but it just transfers the energy to your head which absorbs the energy and rattles your brain around.
What is needed is a method of stopping the projectile before it hits the shield, but the only example I have seen is on display models of lathes, never on one being used in a shop.
For the face shield there should be a system of attachment to the head that is solid, easily removable, comfortable and most importantly that spreads the energy (as yet undefined) of the hit over a period of time rather then the almost instantaneous time of the hit.
The head band of the shields such as Uvex mask I have seen and used are almost worthless for this last requirement. See a prior post of mine is this thread.
A baseball weighs 5.25 oz (0.149kg) and is 3” (76.2mm) in diameter and a hockey puck weighs 6oz (0.17kg) and is 1” (25.4mm) thick by 3” (76.2mm) diameter
Both have been measured at 100mph (44.7 meters per second).
Using E=1/2 m*v (squared) this gives an energy of 0.5*0.17*44.7*44.7=170 Joules for the puck.
This is greater then a riot helmet shield specification. I did not find a hockey or baseball specification on a quick look at Google.
A Catcher's mask: ( From Wikipedia) (To protect the face, much of the side of the head, and, often, part of the throat. In recent years, catchers have begun wearing masks similar to those worn by ice-hockey goaltenders. The hockey-style mask typically includes a section which protects the top of the head…
Since the catcher and goaltenders mask have to stop a well defined size and shape projectile they can be wire cages. As woodturners we never know the size, shape or even the weight or maximum velocity of the projectile. Some guesses after the fact are available. See Lynne Yamaguchi writings.
The idea of mating a riot shield to a hockey or catchers mask per Odie is not so far fetched an idea as it is made out to seem. The problem is a method of attachment that allows the full force of the blow to be transmitted thru the padding to the head without failure.
This would be a specialty item with minimum demand as most of us would not want to take that perfect cut that puts us in harms way.
Stu
If you Google Ballistic Helmets specifications to see what is offered in helmets or look at NIJ Standard for Ballistic Helmets - National Criminal Justice ...at
https://www.google.com/url?sa=t&rct...hxgTGxUV55MeIog&bvm=bv.75097201,d.cWc&cad=rja
you will see a basic method of testing, not an actual spec.