Hello hornists of the world

Bit of an odd request if that's OK. I am a 3D artist in the middle of modeling a cheap student edition Sterling French Double Horn. It's going well so far, but I'm about to hit a virtual brick wall when I get to the thumb lever that operates a bar that pushes around the 4th rotor valve (I think this is the one that changes 'sides' ?). I have lots of reference photos, but they are too low res, and I just can't visualize how the mechanism works for that one lever. Does the bar rotate towards the valve, and if so, how is downward motion on the thumb key translated into transversal bar rotation ? Or does the whole bar move right and not rotate at all, in which case, how does the valve change states via that linkage ?

Lastly, I can see where the valve end of that bar attaches, but not what connects the other end of it to the instrument - in my ref pics it looks like it's not attached to anything other than at the valve end, and that can't be right, can it ?

Here's my reference... http://luminetrics.net/blog/horn-reference/

Forgive my ignorance; I am a muso like you guys, but I'm in the piano department, and really don't know my horns well enough. But most grateful for any help at all with this.

Thanks

CBR

Well, I can't see everything but the bar just rocks, the pivot point comes out from the second finger key. So you squeeze the thumb valve and the bar on that end moves toward your hand and the other end of the bar moves away turning the valve. The valve end is just basically hanging in air not attached. Exactly how they translate the motion on the thumb key to the bar, I cannot see and do not know.

<Added>

Better scratch that, I believe the bar rotates but I can't see how exactly the motion of the thumb key is changed into the rotational movement.

Thank you for taking the time to look at that for me - I do agree with you that the bar most likely rotates toward the rotor valve. I can imagine a mechanism for rotating the bar that involves the section of it near the thumb lever having a small cog profile, which might match up with a similarly toothed underside of the crescent shaped metal that protrudes from the lever itself. But my reference shows that the crescent piece is smooth on both sides, so however it works, it's not that !

As it happens, I've been able to model that to the point where it looks great, even if its physics don't necessarily make sense, but it would nice to get it 100% right, so if anyone knows how we get that bar rotation from depression of the lever, please do let me know !

Many thanks

CBR