The jaw is hinged via tube and rod and works by bumping your chin. The movement is flawless for silent movement but does voice sync decently as your chin moves when you talk.
This head has no fan but when I add one it goes in the muzzle where that little triangle of firm foam is (helps keep the soft foam of the muzzle in in its proper shape) I have the fan blow up into the top of the muzzle with the nose end blocked off so it blows only out the face side of the muzzle, I then create a deflector in front of your nose to keep it from blowing in your eyes/on your nose and to direct the air across your cheeks and around your neck.
The only parts that actually touch you are the back of the jaw, the hat and sometimes part of the neck. Your nose, most if not all of your neck, cheeks and ears are left untouched allowing airflow, minimizing the amount of sweat that gets soaked into the head, and creates a less claustrophobic feel (honestly I cannot stand a head made on a balaclava, makes me freak the heck out and I have to take it off)
The one disadvantage to my method is making the inside look clean, with a balaclava head the inside is instantly lined but with my method I have exposed foam to cover up. I like to make the whole inside black so there is no exposed foam distracting your vision from the inside, I then sign and date the piece decorting the inside and adding a character name if I am given one <3
The neck opens in the back and you simply slide your face in, which also allows one with glasses to get the head on without messing up their specs (I myself do wear glasses btw) The neck closes via strong rare earth magnets an thus practically closes itself.
The neck connects from the ears back with the sides of the neck being taller than/behind the cheeks and the front of the neck gets pulled under your chin, this allows one to "pop the top" as in lift the face up like a welding helmet allowing you to take a quick breather or browse a vendor table without fully de-heading, you can even set the inside of the face on top of your head to be hands free if need be but ideally you'd hold onto it to keep the chin flap out of your face lol. Now if a kid rounds the corner while your top is popped it is super easy to slide it back down.
With realistic eyes I like to do huge mesh tearducts that go both at the corner of the eye and under the eye, normally working in the mesh as a black marking around the eye,. In this case this head has excellent forward and peripheral vision with minimal blind spots. You can also glance down through the mouth to manage stairs and not tripping over small children.
Now as for WHAT head this is.... I'll show you soon
I finally got to meet Tycho this past weekend, and he was kind enough to let me see your "head work" close up, in addition to the cooling add ons that he did. I was very impressed!! The jaw movement when he talks is perfectly synchronized with his voice..
I look forward to when you start working on my commission, and think your idea of neck vision with the "bump jaw" mechanism you describe here would be perfect!!