Catheter actuators providing a mechanical advantage are disclosed. The actuators include a pull wire arm guide plate and a drive wheel attached around the pull wire arm guide plate and pivotable relative to the guide plate, the drive wheel comprising at least one thumb boss for pivoting the drive wheel about a drive wheel axis of rotation. The drive wheel mechanically engages at least one pull wire arm slidably mounted in a pull wire arm channel in the pull wire arm guide plate. A mechanism transfers drive wheel input into longitudinal motion of the at least one pull wire arm. The mechanism may include, for example, a pin pushing against a bendable pushing member riding in an arcuate pin groove in a top surface of the guide plate, or a pin pushing against a surface of a cam arm pivotably mounted on the top surface of the guide plate.