The Essex design was similar to the MIT designs by Mohammad Duralli, "Design of Small Water Turbines for Farms and Small Communities" TAP Report 76-1. In this analysis, the complexity of the blade shape is simplified by employing a short aspect ratio between the hub diameter and the throat diameter. This allows short stubby blades to deployed. The short blades approximate a straight airfoil. This eliminates the curvature required on longer blades, to achieve the correct leading edge and trailing edge angles, as a function of radial distance from the hub. 


Ted Larter and John Clements inspecting the new Essex installation at Franklin Falls Hydro circa 1984. Shortly before this day, Brooke Pennypacker and I were driving through and Ted was just lowering the turbine in place. We lent a hand and helped guide the unit on to the penstock flange. This unit gave reasonable performance. When Ted and John replaced the rope drive, cylinder gate machine, inside the mill building, Essex scaled the machine up. The stresses did not scale well and that unit proved to be most vexacious. Chris Krueger's units at Fiske Mill Dam have ongoing problems with blades shearing off at the hubs and temperature build up in the bulbs.

More of the Franklin Falls installation in Franklin, N.H.