Graphical Four Bar Linkage question

[jojosg]

Homework Statement

In a four-bar mechanism, the length of crank AB-15 mm, length of coupler BC-40 mm. length of rocker CD-30 mm, and length of frame DA=45 mm. Graphically determine the following.(1)The throw yof rocker CD,
(2)The maximum value of pressure angle a., and(3) The time ratio.

Relevant Equations

nil

Did I do mine correctly?

 

[Lnewqban]

How the instantaneous position of the mechanism can be determined from the description?

 

[haruspex]

Homework Statement: In a four-bar mechanism, the length of crank AB-15 mm, length of coupler BC-40 mm. length of rocker CD-30 mm, and length of frame DA=45 mm. Graphically determine the following.(1)The throw yof rocker CD,
(2)The maximum value of pressure angle a., and(3) The time ratio.
Relevant Equations: nil

View attachment 371186
Did I do mine correctly?

I find your diagram illegible. If I expand it at all it becomes very fuzzy.

 

[jojosg]

I find your diagram illegible. If I expand it at all it becomes very fuzzy.

 

[haruspex]

I don’t fully understand your diagram. It looks like you have superimposed three states in one picture:
1. Joint B is down to the left from A, with AB and BC at 180° to each other.
2. Joint B has been rotated so that angle CAB is 180°-134°=46°.
3. Joint B is further rotated so that ABC form a straight line.
The throw, then, would be the change in angle of CD from position 1 to position 3.
So what is position 2 and where does the 134° come from? I see no basis for it in the question text.
I agree with your 55° (well, 54 point something).

 

[jojosg]

I'm also not not sure about 134 degrees. I'm not sure how to measure pressure angle

 

[haruspex]

I'm also not not sure about 134 degrees.

You must have written it for a reason. Where does it come from?

I'm not sure how to measure pressure angle

What do you mean by a "pressure angle"?

 

[jojosg]

You must have written it for a reason. Where does it come from?

What do you mean by a "pressure angle"?

For the 134 degrees I drew the case where link AB and link BC are coincident and fold together. The I measured the angle between AB original position to the folded position which gives me 134 degrees. Maximum pressure angle occurs when the transmission angle is minimal, typically at extreme positions of the linkage. Thats what I think it is.