A robotic surgical tool includes an elongate shaft extendable through a handle, a drive cable extending along a portion of the shaft, and an actuation system housed within the handle and including an input stack having first and second ends. The input stack includes a drive input arranged at the first end, and an accumulator arranged between the first and second ends and including a differential body defining upper and lower redirect surfaces, and a redirect feature offset from the upper and lower redirect surfaces, wherein the drive cable is threaded through the upper and lower redirect surfaces and the redirect feature, and wherein actuating the actuation system rotates the input stack and thereby acts on the drive cable to cause one or more operations of the surgical tool.