What Are Vertical Motors For?
First developed in the early 1920s by engineers from a small LA-based motor company called U.S. Electrical Motor, vertical shaft motors are a unique solution to the efficiency issues and the high cost that was associated with using horizontal pumps to tap into groundwater supplies. Originally, the above-ground pumps were used for irrigation in dry but otherwise agriculturally favorable climates such as California. They had right angle gear configurations and were powered by internal combustion engines.
Putting an electric motor on top of a pump eliminated the need for a mechanical gearbox (to provide torque) and external thrust bearings (for additional pump thrust). Less equipment meant a lower cost, a smaller size, easier installation, and fewer parts. The vertical pump motors also operate about 30% more efficiently than horizontal motors and are more durable and reliable for the pump application because they are specifically designed for the job and were also designed to withstand a wider variety of environmental conditions. Under these conditions, farming in California was able to flourish.
This innovation helped California become the top farming state in the United States despite its seasonal rainfall and dry summers. Today, vertical shaft motors are used for many applications, including turbine pumps, axial flow pumps, mixed flow pumps, and propeller pumps.
Solid Shaft Motors and Hollow Shaft Motors
Vertical pump motors come in two varieties with different construction features: either a solid shaft or a hollow shaft. A key difference between the two is the way that the motor is mounted on the pump; the solid shaft variety are attached to the pump shaft by externally mounted coupling while the hollow shaft variety are connected to an integrally mounted drive coupling.
Overall, hollow shaft motors have many advantages over their solid counterparts. No adjustable coupling is required for the VHS motor, so there is a reduced cost involved due to having fewer parts to purchase, repair, or replace. Additionally, impeller adjustments are made easier with the VHS's single-part coupling and convenient access to the top of the motor. Finally, VHS motors also have a lower profile, so no adjustable coupling is required in the discharge head and they are not as susceptible to reed critical frequency or vibration problems.