Are Sergent Engineering couplers compatible with my 18" radius curves?

Yes. The minimum radius is controlled by the amount of side play the coupler has within its draft gear box. Sergent Engineering's EC87 couplers fit into existing coupler pockets.

Therefore rolling stock equipped with Sergent couplers will not require curves any broader than with conventional HO scale couplers. Traditional knuckle couplers that incorporate centering springs require a large gathering range in order to successfully couple on a curve. The gathering range of a coupler indicates the amount by which the couplers can be misaligned and still successfully hook up.

Couplers that use centering springs need lots of gathering range because the springs push the couplers out of alignment on curves. The gathering range of Sergent Engineering couplers is about half that of conventional knuckle couplers, but since there are no centering springs to push the couplers out of alignment, curves aren't a problem. Alignment of Sergent Engineering couplers before a tie is a manual operation, ... more.

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