MTS Series 247 Actuators - Manual (Page 30)

Series 247 Actuators 30
Spiral Washers
Installation
Spiral Washers
The optional Model 601 Spiral Washers are typically used to provide fatigue-
resistant connections between elements of the force train and to minimize the
effects of backlash. If the operating procedure requires changing of preloaded
force train elements such as the load cell or grips, the spiral washers must be
readjusted.
When cyclic loads below the tensile force level of the preload are applied to the
connections, the load is distributed between the surfaces of the spiral washers and
the stud in a ratio of the relative stiffness of the parts. The spiral washers have a
large surface area and therefore greater stiffness. They react to most of the load
and keep the stress in the stud below its fatigue runout level. In addition to
providing fatigue-resistant connections, the spiral washers also minimize the
possibility of backlash due to loose-fitting or worn stud threads.
The spiral washers are placed over the connector studs at each connection, and
adjusted to place a constant preload on the stud. The following procedures are
included in case spiral washers are needed in the application:
• “Installing Fixtures with Spiral Washers” on page 31
• “Removing Fixtures with Spiral Washers” on page 34
Force Train Components
Swivel Head
Spiral Washers
Connector
Studs
Actuator Rod
Upper End
Cap
Compliant
Material
Force
Transducer
Spiral Washers
Compliant
Material