[Foster]

In the past I've built robots that have an arm made of 4 pieces of metal that form a parallelogram. The right side is fixed, and as the arm is raised the left side moves up, but stays parallel to the right side.

I've used the term 4 bar lift for this, but have heard others write/say "4 bar linkage". While I agree it's a 4 bar linkage, it is a single case. 4 bar linkages can have each bar be a different length. With different lengths, the motion is quite different. Which term is correct, or is there a better term / phrase to use.

Moving on to 6 bar linkages. When I Google these, an entire universe of really cool motion possibilities is shown. I've built 6 bar lifts, where it's two parallelogram 4 bar lifts superimposed over each other (the left vertical bar is the right vertical bar of the next linkage, the upper bar becomes the lower bar in the next linkage).

Lets go back to 4 bar for a second. There is a set of lifts where the bars cross (make an X). You see these in "high lift platforms". I've heard these referred to as "4 bar lifts" or in some cases 8 bar lifts, since there are 4 bars on each side. But then I've heard that stacking them makes that an 8 bar lift. And more stacking is a 12 bar lift.

So I'm looking for a little terminology help here. I'd like to be using the right terms (that mentor thing) to be understood / understand what others are trying to tell me.

I'm good if we limit these to moving in the same plane. I was watching a video of a "4 bar linkage" where the points can move in 3 dimensions and that appears to open up a much bigger can of worms.