TrotBot's Linkage Dimensions
As shown below, TrotBot has an 8-bar linkage (without adding the heel/toe linkages)
Below is a simulation of TrotBot's linkage with the heel and retractable toes added, using non-LEGO dimensions. The LEGO version of the heel/toe linkages are an approximation, and have a bumpier gait than what is simulated below.
The diagrams below can get crowded and confusing, so the linkage is presented in two stages, starting with TrotBot's bar lengths without the retractable toe. Please note that the triangle's bottom right angle highlighted in pink is not 90 degrees, but is 109.475 degrees.
In case the 109.475 degree angle of the triangle above is confusing, below is the same linkage using a 90 degree angle instead, while shortening bar B7 from 3 to 2.83 and connecting it one unit below the crank to bar B10.
Below are the bar and joint numbers used in the TrotBot's Python code, which can be downloaded here:
Next, the retractable toe is added: