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As I tried to make clear: slinky action is intrinsic to the centering action of Kadee's and MicroTrains' designs of semi-scale split couplers. If you want to avoid it, you must prevent the coupler's longitudinal motion in the draft gear. This requires a solid pivot, or a dynamical equivalent.
I do not see how to achieve a solid pivot with these couplers, but I have not given it much thought. Jim Vail's heavier spring approach, which you brought up, should allow working of short light trains without much slinky action. However this approach puts more centering thrust on the couplers and makes it harder to open them when coupling.
Kadee's original centering design for their K and MK series couplers was dynamically similar to that in the 714. In the later production of these, they provided a short wire stub that fitted into the spring. This limited the amount of spring compression to the minimum needed for coupler swing, thus minimizing slinky action, without quite eliminating it. This might work for the 714s.
MicroTrains took up this matter as N-scalers moved toward prototype length trains. Their initial solution was a T-shank design with the spring inboard, followed by the reversed 714 style with the spring outboard. Both eliminate slinky action when pulling, by pulling the coupler against solid stops. But both are subject to slinky action when pushing. This is apparently the price of producing couplers that will couple reliably against the very light rolling resistance of N scale cars.
Total elimination of slinky action requires fixed coupler pivots. At this time we seem to be limited to the Kadee "scale" knuckle couplers, which are still oversize for circa 1900 designs, and Sargents' truly scale couplers.
Does anyone know of other alternatives?
On 10/12/2018 12:37 PM, Mark Kasprowicz wrote:
That makes sense. Is there a solution for it John?