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Manual WheelsManual wheels fall into two basic categories. The first-and by far the most popular-is the kickwheel, which is basically operated by kicking a very heavy revolving flywheel that is connected to the wheel head by a long heavy vertical shaft. The momentum of the flywheel provides the torque, or power, to permit throwing without unduly slowing the wheelhead.
Out of necessity, kickwheels are large and very heavy pieces of equipment (up to 300 lbs). Their design usually includes an integral adjustable bench seat. Most kickwheels are available with a motorized option, but it should be noted that this motorization is only used to help maintain momentum on a sporadic basis as needed, and must be manually activated and deactivated by foot while throwing.
The second type of manual wheel is a treadle wheel, whereby the foot repeatedly pushes a plate that returns automatically like an old-fashioned sewing machine. These wheels are rare and generally quite expensive, as there does not seem to be a mass market for them.
Electric WheelsElectric wheels are by far the most popular throwing wheels because of their ease of operation. A slight movement of the foot on a pedal precisely controls the wheelhead speed, allowing the potter to concentrate on throwing rather than the mechanics of the wheel. There are some differentiations in brands and models, but they all generally do what they are supposed to do in a satisfactory manner.
Specifications and features are all quite similar across the different manufacturers. For instance, most electric wheels feature l4-in. diameter wheel heads that can accommodate bat pins. Some smaller wheels have l2-in heads, but the size of the bat is what is really important, and all will accommodate at least a l6-in. bat. Most electric wheels feature a seldom-used reversing feature either as standard equipment or as an option, and all position the wheel head approximately 19 to 21 in. from the ground. Many offer leg extension options for stand-up throwing, and all have removable splash pans for ease of cleaning. Tabletop shapes and designs vary, but, as with the other features, differences are relatively minor in importance.
Speed ControlThere are three types of drive systems. Most electric wheels use the belt/pulley drive system, and speed is controlled via electric or electronic speed control of the motor by use of a foot pedal. A small pulley is located on the motor, while a large pulley is connected to the wheel head. A round, flat or vee-belt connects the two. Although belts can slip, occasional tensioning adjustment eliminates the problem easily. The technology is well tested, and wheels are generally very quiet and smooth. Differences from brand to brand are quite subtle, and preferences tend to be a result of what one has grown accustomed to as much as anything else.
Gear box/direct drive systems are very rarely used due to expense, loss of power to the gears and the difficulty of producing smooth speed changes.
The cone drive method was popularized by Shimpo in its older wheels. Torque is transferred from the moveable constant-speed motor to a small rubber-coated flywheel by a cone on the motor shaft. Speed is controlled by moving the motor so that when the larger diameter of the cone is running on the flywheel, the speed increases. This is mechanically efficient but requires more physical force to move the motor (with a pedal and/or a hand-operated lever), and it is not as smooth as electric or electronic motor speed controls.
Motors and PowerMotor sizes range from under 1/4 horsepower to 1 or even 1 1/2 horsepower. The power is necessary to ensure low-speed torque so the wheel head does not slow down while throwing. Smaller motors will not wear out or fail, but they may not be able to maintain their speed under severe low-speed strain.
Some manufacturers quote a clay weight capacity for their wheels, but this is somewhat misleading. First, some people throw more with muscle than finesse. Second, the further from the center of the wheelhead that the throwing or centering is done (as with large, flatter pieces), the greater the force of resistance and tendency to slow the wheelhead. Given the technology of today's wheels, 1/2 horsepower is adequate for 95% of potters for life. On a cone-drive wheel, 1/3 horsepower is comparable.
Editor's note: Reprinted with permission from Clay Planet. For more information, visit www.clay-planet.com.