Description: A cantilevered wire hook of established geometry that interacts with an identical hook on the opposite vehicle.

Method of operation: The hook geometry is such that when stock is brought together the lower part of one hook over-rides the other establishing the link between the vehicles. Uncoupling is carried out by a vertical displacement of the hook. This disengages the hooks and on return to the nominal position the hook has relocated to the opposite side of the hook shank. Stock can then be propelled to a position remote from the uncoupler.

Uncoupling device: Early published details showed the hooks lifted by a ramp. Subsequent recent developments have allowed magnetic uncoupling. For this system electromagnets are recommended.

Modifications to stock: The modifications required to fit the coupling vary considerably from vehicle to vehicle depending on underframe detail. Generally provision has to be made to locate the fixed end of the coupling to the vehicle and provide some lateral location of the hook shank.

Fitting common to all stock?: The hook is common to all stock. It is not necessary to have a hook capable of displacement on a locomotive.

Compatibility with scale couplings: As originally proposed for 7mm use the hook was not compatible with scale couplings. The subsequent developments with magnetic uncoupling do allow its use with basic 3 link, but screw link couplings can impair operation.

Minimum recommended operating radius: 4 feet. Smaller radii can be used but will increase the overhang of the hook from the vehicle. This will be limited to the appearance of the gap between vehicles. Buffer locking will be a limiting factor to track geometry.

Instructions: The design of the coupler was first published by the Manchester Model Railway Society by the late Alex Jackson in 1949. It is also available in:

• This wiki
• Model Railways Handbook (Percival Marshall, 1965)
• Model Railway Journal issues 55 and 56 (Wild Swan)
• 7mm Modelling Part One, An Introduction by Gordan Gravett (Wild Swan, 1996)

Other Comments: Different sources quote some differing dimensions. With the magnetic uncoupling developments the wire diameter has been reduced from 24SWG to 28SWG and its cantilever length amended to suit.

Compiled by Bob Alderman