Drive Selection Steps

Below you will find the detailed steps for selecting chain and sprockets in a power transmission application. This process can be time consuming and Ramsey offers a PC based Drive Selection program as an alternative. To access the program you an click Computer Program and then provide some basic contact information.

To access a two page form summarizing the information needed during drive selection, click here.

Drive Selection – Step by Step

Drive selection consists of choosing the appropriate chain and sprockets for the space, loads, and speeds involved. Often more than one pitch and width will work in a given situation. In such cases one may choose two or three possible selections and base the final choice on factors such as cost, stock availability, ruggedness or space availability.

Information Needed

  • Type of power source and application
  • Shaft center distance(CD)
  • Shaft diameters and keyway sizes
  • Power to be transmitted(W)
  • RPM of shafts(N1=faster shaft speed, N2=slower shaft speed)

Follow These Steps

  1. Choose a service factor(SF) from the Service Factor table.
  2. Compute the design horsepower(Wd) by multiplying the power to be transmitted(W) by the service factor.
  3. Use the speed of the faster moving shaft(N1) to make a tentative pitch selection(p) from the chart.
  1. Select the number of teeth in the small sprocket(Z1), making sure the sprocket can accommodate the shaft diameter. See maximum sprocket bores in sprocket tables.
  2. Use the following equations to calculate the required chain width(Cw). If the required chain width is not readily available it may be necessary to go to a wider chain or a larger sprocket.
Table of R Values
3/8″ 1/2″ 5/8″ 3/4″ 1″ 1 1/2″ 2″
RPV (SG) 1.5 1.8 na 1.6 1.5 1.1 1.0
RPV (CG) 1.5 1.8 na 1.3 1.2 1.1 1.0
RP .922 1.0 1.0 1.0 1.0 1.0 1.0
  1. Select the large sprocket (Z2) by multiplying the number of teeth in the small sprocket by the desired shaft speed ratio. Z2 = Z1 x N1/N2
  2. Compute the chain length (Click Chain Length for instructions). If the computed length is fractional, round off to the nearest whole number of pitches. An even number of pitches is always preferable to an odd number of pitches which requires an offset section. If an offset section is required it will be necessary to increase the width of the chain by 25% to account for the offsets reduced tensile strength. Note: offset sections are not available for RPV chain.
  3. Compute the new center distance (Cd) for the rounded off chain length. The following formula provides an approximate center distance. When fixed center drives are used or extremely accurate center distance is required consult Ramsey.
  1. Select a method for lubricating the drive:
    Forced feed lubrication will provide optimum results and is recommended whenever chain speeds exceed 2500 ft/min. Drip or bath type lubrication may be acceptable at lower speeds. Additional information on lubrication is given in the section describing lubrication. Also, if the drive will not operate inside a housing, a chain enclosure is recommended.
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