Picture Perfect

[Yoda]

Martee wrote:

Here are my pics: Horizontal Hinge Action Horizontal Plane of Motion Hinge Pin Vertical (Perpendicular) to the Horizontal Plane Vertical Hinge Action Vertical Plane of Motion Hinge Pin Vertical (Perpendicular) to the Vertical Plane Angled Hinge Action Angled Plane of Motion Hinge Pin Vertical (Perpendicular) to an Angled Plane

Okay, Martee. Terrific pictures! I've edited the captions in your Quoteabove and they are now "picture perfect!" They will help everybody alot.

Now, in your PM, your thought was that the vertical hinge action (#2 photo)requires a Horizontal pin. And I can clearly see where you are coming from: Thepin is aligned horizontally if you view it only in relation toitself. Clearly, the pin is horizontal.

But...here's the key:

We're not looking at it that way! We're looking at the pin in relation toits associated Plane of Motion. In this case, that is the vertical planeof motion. And relative to that plane, the pin is vertical, or touse your very good word, perpendicular, to the vertical plane of motion.[As a matter of fact, 'perpendicular is so good that I'm going to edit my postto use it instead of the 'at right anges' to. Same thing, of course, but bettersaid.]

So, no matter which of the Three Basic Planes of Motion is illustrated,the hinge pin is always vertical to its associated plane:

-- Vertical to the horizontalplane;

-- Vertical to the vertical plane;

-- Vertical to the angled plane.

The pin is never horizontal to any one of the three planes. It is alwaysvertical! All you do to achieve any one of the three basic planes of motionis to mount the hinge pin vertical to the plane of motion desired.

Do you see it now? This is a really important point because pretty soonwe'll be learning to use our Flat Left Wrist to duplicate the motionof a hinge by keeping it vertical to one of these threebasic planes.

Thanks again for the pictures. They're great.

We're on the right track now!