We have seen that the simplest one-DOF linkage is the fourbar mechanism. It is an extremely
versatile and useful device. Many quite complex motion control problems can
be solved with just four links and four pins. Thus in the interest of simplicity, designers
should always first try to solve their problems with a fourbar linkage. However, there
will be cases when a more complicated solution is necessary. Adding one link and one
joint to form a fivebar (Figure 2-19a) will increase the DOF by one, to two. By adding a
pair of gears to tie two links together with a new half joint, the DOF is reduced again to
one, and the geared fivebar mechanism (GFBM) of Figure 2-19b is created.
The geared fivebar mechanism provides more complex motions than the fourbar
mechanism at the expense of the added link and gearset as can be seen in Appendix E.
The reader may also observe the dynamic behavior of the linkage shown in Figure 2-19b
by running the program FIVEBARprovided with this text and opening the data file
F02-19b.5br. See Appendix A for instructions in running the program. Accept all the
default values, and animate the linkage.