Kinematics of a Ram-P

Simple Ramp-P Example


The Ram-P is a similar to an RRP Dyad, but one of the Parts extends.

The Ram-P makes use of the Motion-Path FB. The Motion-Path FB adds a Motion-Point to a sketch-element (CAD-Line) in one Part.

The other Part is joined to the Motion-Point with a Pin-Joint.

motion-values are given to the Motion-Path FB by Motion FB.

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

How to Add a Ram-P


1.Add a Part1s-red

The Part is a 'Free' Part.

It has a blue Part-Outline

A 'Free' has three Degrees-of-Freedom


2.Add a Pin-Joint between two Points

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

The Part now 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.

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.

Why? It becomes clear later.


5.Add a Part and Slide-Joint
6.Add a short Line1s-red to the Sliding-Part


7.Add a Pin-Joint1s-red between the short-line in new Part and the Motion-Point1s-red

The kinematic-chain is now kinematically-defined chain.

It is a Ram-R

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 that is exactly the same as the distance between the two Pin-Joints in the Base-Part. This is kinematically impossible.

See Video below

Video of RamP Dyad.



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