DG couplings are the go-to choice for many 2mm scale modellers. They offer hands-free uncoupling to represent realistic train movements, and when built and adjusted with care, they deliver smooth operation and close coupling. This guide covers the complete process: assembling the couplings, building a simple soldering jig to make the work easier, and fine-tuning the finished product for consistent results on any layout.
Why DG Couplings Work So Well
- They allow realistic shunting without visible hands or tools.
- The design is mechanically simple yet reliable when set up correctly.
- Close coupling is possible without derailing on tight curves.
- Proven in exhibition conditions, where reliability is essential.
Making a Soldering Jig
The joint between the steel dropper wire and the phosphor bronze loop is the trickiest part to make consistently. Holding the parts steady while soldering is the key. A jig makes this easy, ensures repeatable results, and avoids burnt fingers.
Materials:
Aluminium plate (approx. 35 mm × 25 mm)
Aluminium block for fixed side
Aluminium block for removable side
Brass rod for locating pin
12BA countersunk screws
Small self-tapping screws (for feet)
Construction Steps:
Base Plate – Cut from aluminium; its size isn’t critical, but 35 mm × 25 mm is a good starting point. Aluminium resists solder sticking.
Fixed Block – Cut a 45° groove underneath to hold the tail of the dropper wire. Drill two holes through with a No. 62 drill, tap the base 12BA, open the holes in the block with a No. 55 drill, and countersink them.
Chamfer – File a small chamfer beside the groove so the other end of the dropper wire can sit flush with the block’s face.
Removable Block – Make it a snug fit against the fixed block. Drill a tight ‘interference fit’ hole for the locating pin through both blocks clamped together. Ream the base plate hole slightly for clearance, then drive the brass pin into the block.
Feet – Fit small self-tapping screws to the underside so the protruding locating pin clears the workbench.
Loop Recess – File a shallow recess in the removable block to clamp the loop firmly against the dropper wire.
Using the Jig
Make the steel dropper with a 45° bend.
Slide the tail into the groove in the fixed block, with the short end in the chamfer.
Fit the removable block in place.
Position the phosphor bronze loop in the recess so it aligns with the dropper.
Apply flux (e.g. Carr’s Green Label).
Touch briefly with a hot, tinned soldering iron. The aluminium won’t take solder, so the joint can be lifted out easily.
Remove the removable block to release the loop.
If desired, curve the tail of the dropper slightly for better clearance over embedded track.
- Fine-Tuning for Reliability
Free-Moving Flaps – Before fitting, file a tiny notch on either side of the flap tongues so they pivot freely.
Flap Length – Trim so they just cover the hooks.
Burr Removal – Smooth away any sharp edges that could obstruct the loop.
Loop Length – Shorten slightly (around 4.5 mm) to achieve closer coupling while still taking 24 in curves.
Buffing Plate Strength – Reinforce the right-angle bend with a small fillet of solder. Slightly turn back the ends to help on tight curves.
Buffing Plate Height – Critical for smooth coupling. Aim for 4.5 mm above rail top. Make a height gauge from metal, plastic, Tufnol, or Perspex, and use it for every coupling.
Level Loops – Ensures the loop passes cleanly over the opposing one rather than “butting”.
- Preventing Loop Interference
On layouts with a traverser or sector plate and no turntables, you can fit a loop at only one end of each vehicle and keep stock the same way round.
If you prefer turning trains, keep all loops level and untwisted, and ensure they rest on the buffing plate rather than being lifted by the dropper’s solder joint.
- Closing Notes
DG couplings have been refined over time and remain the first choice for 2mm modellers who value operational realism. With a simple jig, careful assembly, and consistent adjustment, they can give years of trouble-free service, even under the demands of exhibition running.
https://www.youtube.com/watch?v=rwnrcuMdl5w
https://www.youtube.com/watch?v=b_3OOoGteTI
More Information
- Adams, Laurie. “DG Couplings: Variations and Reflections.” The 2mm Magazine, Aug. 2017, p. 74.
- Cox, Andrew. “Solderless DG Coupling Loops.” The 2mm Magazine Feb. 1992, p. 16.
- Dearnaley, Nick, and Peter Whitehead. “DG Couplings.” The 2mm Magazine, Oct. 2000, p. 62.
- Mallott, David. “DG Couplings.” The 2mm Magazine Feb. 1989, p. 1.
- Mallott, David. “Coupling Loop Postscript.” The 2mm Magazine, Apr. 1989, p. 21.
- Robinson, Bill. “Reflections.” The 2mm Magazine, Dec. 1991, p. 93
- DG Couplings Mallott, David 1989 Feb 1
- Coupling Loop Postscript Mallott, David 1989 Apr 21
- Reflections Robinson, Bill 1991 Dec 93
- Solderless DG Coupling Loops Cox, Andrew 1992 Feb 16
- DG Couplings Dearnaley, Nick & Whitehead, Peter 2000 Oct 62
- DG couplings:variations and reflections Adams, Laurie 2017 Aug 74