Abcd is a four link mechanism ,ad is fixed link . ab =30 ,bc=50,cd=60,ad=70.what is mechanism?
Answers
Given,
ABCD is a 4 link mechanism,
AD: fixed,
AB = 30, BC = 50, CD = 60, AD = 70.
To find,
Type of mechanism.
Solution,
Here, it can be seen that link AD, which is the largest link (∵ AD = 70), is given to be fixed.
Now, AB = 30, which is the shortest link, will work as a crank, since it will be able to rotate completely and make full revolutions.
This can also be verified using Grashof's law, which states that, "for a four-bar linkage system, the sum of the shortest and longest link of a planar quadrilateral linkage is less than or equal to the sum of the remaining two links, then the shortest link can rotate fully with respect to a neighboring link".
That is,
(s + l) < (p + q),
where,
s = length of the shortest link,
l = length of the longest link
p and q = lengths of the remaining two links.
So, here,
(30 + 70) < (50 + 60)
100 < 110
So the condition is satisfied.
Hence,
AD is fixed, and,
AB is acting like a crank,
so, the link BC is a coupler, and,
CD will work as a rocker.
Thus, it will be a crank-rocker mechanism.
Therefore, the 4 link mechanism ABCD will be a crank-rocker mechanism.