These two separate helms from Austria are worth the time to examine, in only to clearly get an idea of the "form" of a real helmet.  They are salets with visors of course, very heavy ten guage or heavier, though it is a little hard to see that from behind the glass!
        These helms are for jousting.  The wearers were up on a horse.  Way up there.  Take a look at the second picture...how narrow the frontage is.  How narrow the eye slot is.  How sharp and defined a keel it has.
         What can we learn from this?  Well, among other things, we can learn that any serious impact on the "nose" would rock the helmet up.  Pushing the helmet back would cover the eye slot. 
         But.
         A more over riding question would of course be "Why have two parts, a top part (salat) and a bevor.  Would this not risk a lance head being shoved under the helmet?" Well, when you consider that they would employ a Grande Guard to prevent that eventuality (sometimes), they clearly didn't worry themselves about it too much.
         My thinking is that they were prepared to lose the salad if it got hit hard enough...better to lose the armour than to break your neck.  But that does not explain the popularity of a helmet form which you can get a lance head under!
         I may have to revisit this line of thinking...perhaps some of my readers have an idea or two on the subject.


 Oh, and the one below?  Well, I just had to include the most beautiful helm in the collection!  Click on it to see it in all its glory!