A linkage comprises a first rounded end providing a complimentary profile configured to mate with an inner radius of a loop element in a first drawbar spring, and a second rounded end opposite the first rounded end. The second rounded end provides a complimentary profile configured to mate with an inner radius of a loop element in a second drawbar spring. The linkage is configured to be positioned between the loop element in the first drawbar spring and the loop element in the second drawbar spring such that the first rounded end is mated with the loop element in the first drawbar spring and the second rounded end is mated with the loop element in the second drawbar spring to mechanically couple the first drawbar spring in series with the second drawbar spring.