Mechanical Advantage of a four bar linkage.

[racast5]

I'm doing a project outside of school and I need some help with the mechanical advantage of a four bar linkage. Ideally I want to have a torsion spring attached to the frontward most arm so that I can load the linkage and have it fling forwards. I want to use a servo to load the spring which i was going to attach to the backmost leg. Can someone point me in the right direction where I can find some equations for the transfer of torque/force between the legs? Ideally I want to put something like a 20-30 lb/in torque spring on the front end and so I need a servo powerful enough to load it. The case will likely be that the front leg is longer than the back leg while the top and bottom legs are roughly equal in length. I'm just getting started on this so sorry if it's a little not thought out but I was looking for some pointers.

 

[OldEngr63]

So, where is your analysis of the four bar mechanism? You need to start with the kinematics, and then you can easily use the method of virtual work to get the mechanical advantage. Show me what you have when you get that much done, and we can go from there.

Do you have a Theory of Machines textbook? Which one?