Find posible lengths for the linkages in this hood mechanism

2. Prismatic 3. No-Prismatic I. Clock Spring Mechanisim

Solution

solution:

1)here hood mechanism is similar to slider crank mechanism with additional spring for generating restoring force in system due to springs potential energy to return its own position when hood lock is unlocked.

2)for synthesis of slider crank mechanism ,we must know displacement of slider and length of mean position of slider to pivot of crank.

3)let consider ABC as mechanism with

L2=AB=crank

L3=BC=connecting rod

L1=AC as fixed link between slider mean position and pivot A.

4) here displacement of slider is from C\' to C\'\'

l(C\'C\'\')=length of displacement

as we know slider maximum displacement is twice the crank length,hence we can write

crank length=AB=L2=C\'C\'\'/2

4)here if minimum and maximum displacement position of slider is C\' and c\'\' is known then for knowing length of another two link

we have choose any point as pivot pointA and draw circle of radius equal to L2,

then we have to extend pivot line along horizontal direction and at suitable distance as per space limitation mark point as C\' and after distance of 2L2 again plot C\'\' along same line as it represent slider displacement.

then draw arc from point C\' such that it will cut circle at 180 degree angle and another arc from point C\'\' with same distance mark on circle ,if it cuts circle at 0 degree angle then this length of arc is length of connecting rod.

l(BC)=length of arc at 180 degree to circle from point C\'.

5)now we have to find length of fixed link and which is given by

AC\'=min. dispacement=L3-L2

AC\'\'=max. displacement=L3+L2

L1=AC\'+AC\"/2=L3=mean displacement of slider

6)for given slider if obliquity ratio is not given then length of slider is given by above method from just slider displacement as above and we get length L1,L2,L3

7)where stiffness of spring is decided on the basis velocity of system and force applied at the end of link AB.