Update on the Helmet

I've been trying to work on this project every week now but this weekend i ran into trouble with the next step which is the teeth with will come out past the lips. I could have made this simple for myself by having the teeth run on rails like the lips do but i wanted them to come out at an angle and this is the result.

To get the square section to come out into and angle without colliding with itself I'm using a four bar linkage and this drawing is plotting the circle the outer arm will rotate around. If you can see the two right angles with corners on the circle those are the respective positions of the teeth in the open and closed position. There was some complex trig i could have tried but decided that doing a functional drawing like this was easier for me due to being less abstract in my thinking.