A rotary motion transfer apparatus, such as a combine grain elevator, which includes first and second endless flexible members which may include belts and/or chains. Each flexible member is trained around a respective set of rotary members which may be pulleys, sheaves or sprockets. One rotary member from each set shares a common shaft and may, or may not, be in driving engagement with one another. The common shaft is mounted on an adjustment frame member that is linearly displaceable with respect to a main frame to adjust the tension in the first endless flexible member. A pair of idler rotary members are provided for tensioning the second endless flexible member and are mounted on a pivot arm which is mounted to the adjustment frame member for pivoting movement around a pivot axis intermediate the pair of idler rotary members. A lever is secured to the pivot arm, and spring means are attached between the lever and the main frame to bias the idler rotary members into engagement with opposite sides of the second endless flexible member with a substantially constant force over an adjustment range of the common shaft.
