With straight fingers in a splice, there is always one point in a belt where at least 50% of the cords are cut. Since the polyurethane in the belt has very little contribution to the splice strength, it is impossible to ever get more than 50% of the original tensile strength with a straight finger splice.
With a tapered finger splice, the cords are interrupted on a more random basis, and there is never a line across the belt that has more than 1/3 of the cords cut. In some cases, there are significantly less than 1/3 of the cords cut. With the Gates Mectrol tapered finger splice, some belts have tested as high as 95% of the original tensile strength.
Even Tapered Fingers are Limited
Since the tensile strength in the splice area is dependent upon the urethanes’ ability to pass the forces from one cord to another, adding cord results in exceeding the ability of the urethane to transmit these forces.
A clear example of this is AT10. A tapered finger splice in AT10, yields approximately 50 to 55% of the original tensile strength. However, the same splice in ATL10, which has a much stronger cord, is no higher than that of regular AT10. This means that we actually only get about 40% of the original tensile strength. There is a distinct point in every belt where the welded urethane at the splice area is the weak link.
The Tapered Finger is a Superior Splice
Straight Finger Splice
At one line across the belt, 1/2 of the cords are cut
Tapered Finger Splice
At any one line across the belt, no more than 1/3 of the cords are cut