Examining the Science behind Bicycle Performance
This is a brief look at the stress and stiffness effects of chainstay bridges. I applied the horizontal torque load from pedaling to my beam FEA model with and without a chainstay to compare stiffness. The FEA shows about a 5% increase in stiffness with a chainstay.
However, there appears to be no significant change in stress levels. Real stress levels would be sensitive to local stress concentrations at all joints and corners, so it is difficult to definitively say that there is no difference. The FEA stress plots below give a general sense of the stress patterns under pedaling loads.