Which Scale Coupler?

There are several "scale" couplers that have been used on S scale models:

• Kadee HO scale couplers - especially #5
• Kadee O scale couplers
• Kadee S scale couplers (802/808)
• SHS 01295 couplers
• Sergent Engineering S scale couplers

Kadee O scale couplers have the advantage of being able to couple to themselves, Kadee S scale couplers, and AF compatible couplers. They have been used as a "more prototypical" coupler on some cars where most of the layout remains AF compatible couplers. Otherwise, they are considerably oversized for S scale. They allow automatic coupling and automatic or manual uncoupling by magnets, and they support "delayed uncoupling", but only with themselves. When used with AF compatible couplers, they only reliably couple or uncouple manually.

Kadee S scale couplers (802/808) are the most popular "scale" couplers in S scale at this time. Depending on which dimension you check, and which coupler your prototype car used, they are typically somewhat oversized for S. They allow automatic coupling and automatic or manual uncoupling by magnets. They support "delayed uncoupling". They have considerable "slack" in them, which is very noticeable when there are several cars in a train. 802 are black, 808 are rust colored. They come unassembled. Coupler boxes are included.

SHS 01295 couplers look and operate similar to the Kadee 808. The knuckle is slightly smaller, thus closer to scale. They allow automatic coupling and automatic or manual uncoupling by magnets. They do not reliably support "delayed uncoupling". There is much less slack in the couplers as compared to Kadee 802/808 (a plus in the eyes of many modelers). They have a smaller coupler box, thus will sometimes fit where there is not enough room for an 802. They are only supplied rust colored. They came pre-assembled (a BIG help)! The knuckle is .045" lower in relation to the mounting surface of the coupler than is the Kadee 802/808. This makes it ideal for the SHS open top hoppers and ore cars and SW-1/SW-9 locomotives. Other applications may require a bolster shim.

Sergent Engineering Couplers were designed for the best possible scale appearance while still allowing operation. They have to be uncoupled manually by using a small magnet above the coupler, then pulling the cars apart. They will not couple unless the knuckle is open. Sergent couplers come unassembled. Coupler boxes are not included, but a good article on building inexpensive coupler boxes for the Sergent couplers can be found in the S/Sn3 Modeling Guide, Volume 8/Issue 5, pages 19-21. Sergent couplers are still relatively rare in S scale.

Like everything else in life, there are tradeoffs! Most modelers will probably find the Kadee 802/808 or the SHS 01295 the best choice. These can be used interchangeably with the following provisos:

• Don't use 802s unless you paint them. Rust and black couplers look funny together.
• If you need/want delayed uncoupling you may have to fiddle with the 01295s
• 01295s have slightly smaller holes for mounting screws. If you mount them on S Scale America tank cars, you'll need to drill the mounting holes slightly larger
• The coupler box for the 802/808 is larger, so it won't fit everywhere an 01295 will (like on SHS Ore Cars)
• The 01295 knuckle is .045" lower in relation to the mounting surface than the 802/808. Use the one that gives the best alignment.
• The 01295 knuckle height is a scale 11.6" vs the 802 at 12". There is a good discussion of prototype and model sizes here.
• 802/808 has excessive slack. If it bothers you, you can add a small piece of 3/64" styrene rod inside the centering spring (inside the coupler) to limit it somewhat.

My approach has been to stock both 808s and 01295s, and to use the one that fits best in a specific application.

As usual, all comments/criticisms/corrections or additions are welcome!

Part 3: Step-by-step instructions