Sprat & Winkle AC4 Couplers, My Sn42 / Sn3½ Coupler Standard

Part of preparing the second hand ALY wagons for my layout is the installation of the suitable couplers.

For most modelling QR in Sn42 / Sn3½, the classic hook and 3-link couplers appear to be the most popular followed closely with the Kadee HO couplers being a close second.

Non-delay couplers, Sprat & Winkle AC4/1

I started modelling S scale with  hook and 3-link couplers as they looked brilliant and are prototypically correct, but they were very fiddly to use with a shunting layout and I had a lot of buffer lock issues, even with the large 900 mm radius Peco points. So after some experimenting, I decided to do things differently and go with the Sprat & Winkle couplers. These couplers may not be to everyone's liking, but they work well for my needs.

Example of medium length wagons, being pushed through a "S" curve, showing how the Sprat & Winkle coupler prevents buffer lock issues.

Sprat & Winkle couplers come in delay and non-delay uncoupling options. I prefer the non-delay version for wagons and the delay version on the locomotives.

Non-delay version of coupler on a wagon, Sprat & Winkle AC4/1

Delay version of coupler on a locomotive, Sprat & Winkle AC4/3

I have set up the Sprat & Winkle coupler on one end of each item of rolling stock. This has the disadvantage of making the rolling stock direction, but as my layout has no locomotive turning capability, this is not a problem for me and I keep the classic QR hook on the other end for compatibility with wagons that only have the  traditional hook and 3-link couplers installed.

Traditional hook installed on one end for compatibility with traditional 3-link couplers.

Once painted black the Sprat & Winkle hook and wire is not as obvious and blend into the wagon.

Uncoupling of the  Sprat & Winkle coupler is with a simple magnet mounted in the centre of the track, under the sleepers. The magnet pulls down the soft iron links and opens the coupler. The couplers do not appear to be affected by Kadee uncoupling magnets.

Coupler over a uncoupling magnet. I use Jaycar  LM1614, 20 x 15 x 5 mm heavy duty magnets with 6 magnets in each packet.

My installation method, a short description:

1. I use a Jig 12.6 mm high to mark the correct centre height of 12.7 mm on the buffers of both ends.
   

   

   I use a fine tipped pen to mark height on buffers to show drilling height of 12.7 mm above the rails.

2. Drill a 0.5 mm hole in the ends of buffers
3. Bend some 0.5 mm wire to fit between the buffers

   

   Tip: Use a spare bit of wire in second hole to assist getting the correct spot to bend the wire.

   
   
   
   
   
   
4. The wire should fit, without pushing the buffers out of alignment
   
5. The buffers that I use are out of soft white metal, so I like to press the wire into the buffer so it sits flush with the buffer head

   

   Pressing wire into white metal buffer. For plastic buffers, I use a sharp  blade to  cut a "V" in the buffer end for the wire to sit in.

   
   

   

   Making the wire flush with the buffers will allow closer coupling and looks better. 

6. Once you are happy with the wire between the buffers, use some CA super glue to keep it in place, only a fraction is needed (A sharp tooth pick is useful for applying the glue)
7. Add a wire to the other end between the buffers
8. Build up a pad for the coupler to be mounted on 12 mm wide. I like the pad to be about 0.5 mm lower than the coupler wire.
9. To make life easier, I have made a Jig for the Sprat & Winkle coupler hook, so they are can all be installed a the correct distance from the coupling wire

   

   1.5 mm spacer

   
   

   

   Jig in place ready to drill 0.5 mm holes 

10. Drill the 0.5 mm holes for the Sprat & Winkle hook

    

    After the first hole is drilled, I place a length of wire in the hole to help keep the Jig in place for drilling the second hole.

    
11. With about 40 mm of 0.5 mm brass wire, bend it to make the pivot for the Sprat & Winkle hook
    
    
    
    
12. Prepare the Sprat & Winkle hook, as per the instruction at http://www.modelsignals.com/couplings_frame.htm . At this stage it is easier to add the soft iron wire loops for the magnetic uncoupling

    

    For now, I use two soft iron wire loops for uncoupling. 
13. Install the Sprat & Winkle hook. I like to have the hook set up with a slightly up angle.

    

    No need to off-set the hook as described in the Sprat & Winkle instructions.  At rest the bottom of the soft iron wire loops sit about 1 mm  above the rail tops.

    

    Coupler mounted lower than buffer wire, this allows for better up and  down movement of the hook over  uneven track work .

    

    Completed couplers. Wagon in now ready to have some under body details installed and a patch up coat of paint.

    
    
14. You should now be ready to test the wagon.
    
    

Happy modelling!