Silent Chain Design Considerations

A few silent chains are used in conveyors, but most silent ehains are used in high-speed drives. Shaft speeds of silent chain drives generally range from about 100 rpm to more than 10,000 rpm. The amount of power transmitted may be as litde as a fraetion of 1 hp or it may be more than 2,000 hp. 

The main design considerations for a silent chain to be used on a drive are the various tensile loads, joint wear, and link plate and sprocket wear. A consideration for silent chains with singlepin joints may be galling. 

Silent chain manufacturers have developed several joint designs to reduce chordal action and joint wear. These different designs can be classified into two broad categories. They may be single-pin or two-pin joints. Silent chains with two-pin joints are much more popular for power transmission. Silent chains with single-pin joints are more common for conveying and will be covered here briefly. Silent chains with two-pin joints will and be discussed more extensively. 

The size of the pins and the thickness of the link plates are roughly proportional to the pitch of silent chain, but these dimensions are not standardized as they are for roller chain. 

A silent chain with single-pin joints may be snbjected to all of the tensile loads that were described earher, but a silent chain with two-pin joints practically eliminates chordal action. A silmt chain with two-pin joints usually runs very smoothly. It is not affected mnch by traisile loads from chordal action or the types of vibration that are related to chordal action. Silent chains must have cralain tensile strength properties to withstand the wide range of tensile loads that may be imposed on Ih. The main strength properties that a silent chain must have are discussed below. 

---

This section reviews the general considerations for the design of roller, silent, engineering steel, and flat-top chains. The considerations differ as the functions of each type of chain differ. The specific design considerations for each class of chain will be covaed later. 

Link plate and sprocket wear is a consideration in designing silent chains. The link plates engage the sprockets instead of rollers, bushings, or full links. Excessive wear of the mating surfaces of silent chain link plates and sprocket teeth can cause erratic action and increase noise and vibration. 

Ultimate tensile strength is not a major consideration in the design of silent chains. Ultimate tensile strength is not to be used for selecting silent chains. There is no requirement for MUTS in ASME B29.2, and while silent chain manufacturers may have internal specifications for MUTS, they generally do not publish such values for their chains. 

Yield strength is not a major consideration in designing silent chains. Yield strength prevents the chain from permanently elongating when extremely heavy loads are applied to the chain. However, extremely heavy loads occur more often in low-speed drives, and silent chains are normally intended for high-speed drives. 

The fatigue limit is a most important consideration in designing silent chains. The lower-speed part of the power ratings for silent chains is based on a minimum fatigue limit. 

For the reasons stated earlier, link plate and sprocket wear are important considerations in designing silent chains. 

---