Kinematics of a Ram-R

Simple Ram-R Example


The Ram-R is a similar to an RRR Dyad, but one of the Parts extends. Also, you only need two Parts in the kinematic-chain.

The Ram-R uses the Motion-Path FB.

The Motion-Path FB adds a Motion-Point to a sketch-element (CAD-Line) in one Part.

We join the other Part to the Motion-Point with a Pin-Joint.

We add a wire from a Motion FB to the Motion-Path FB so that the Motion-Point moves,

The Red Arrow in the image shows the Motion-Path of the Motion-Point along the CAD-Line of one of the Parts.

How to Add a Ram-R


1.Add a Part1s-red

The Part is a Free Part.

The Part has three Degrees-of-Freedom


2.Add a Pin-Joint between two Points

The Pin-Joint removes two Degrees-of-Freedom.

The Part has one Degree-of-Freedom


3.Add a Motion-Path FB

Select the CAD-Line.

The Motion-Path FB adds a Motion-Point1s-red at the start of the sketch-element to which you add the Motion-Path FB. The Motion-Point is coincident with the Origin at the start of the CAD-Line. It is also coincident with the Pin-Joint.

The Part is a still a Free-Part


4.Edit the Motion-Path FB

The Ram-P does not usually work when the Motion-Point1s-red is at the Origin of the CAD-Line.

Note: If the Motion-Point is at the Origin of the CAD-Line in the first Part, then the second Part would need to have a length exactly the same as the distance between the two Pin-Joints in the Base-Part. This is kinematically impossible.



5.Add a Part and Pin-Joint

This Part is also a Free-Part



6.Add a Pin-Joint between the new Part and the Motion-Point1s-red

The kinematic-chain is now kinematically-defined chain.

It is a Ram-R

See Video below

Video of RamR Dyad.


Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd