Mechanism analysis - Linear to arc motion 1

[GarethMcGrory]

Hello all,

I currently am looking at a mechanism which I know provides a slightly non linear output at one link which is then amplified at the shorter link. Please see attached JPEG of the mechanism.

In essence there is a linear input (Input actually moves through a small arc) at the left hand side which drives the longest link by 15° either side of vertical. This in turn drives the shortest link by approximately 90°.

I know this is a version of a 4 bar linkage; however can the output from the shortest and longest links be linear the way it is being driven? Or does the input have to drive the mechanism at the base point pivot, for this to be the case?


The amplified non-linearity at the shortest link is undesirable for my output.

Any help or suggestions here would be grateful

Regards
Gareth

 

[drawoh]

GarethMcGrory,

You should be able to model this action using parametric 3D[ ]CAD like SolidWorks. It should not be particularly difficult to program this with a spreadsheet.

--
JHG

 

[GarethMcGrory]

Hello Drawoh,

Yes I have drawn this with a CAD sketch and understand the mechanism. however where the mechanism is being driven, will the output of the 2 links always be non linear, as it is linear to arc movement?

Does the input need to occur at a base point rather than pushing at a point along the driver link?

 

[jlnsol]

GarethMcGrory,

I checked the mechanism in mechanism software. The red line is input angle between 66.43 and 90 degrees versus time at x-bar running from 0 to 1 second (a straight line)
The purple line shows the output angle of the short bar 4 which is a curve.
So the amplification is not linear as you already stated.