Modelling: Hunt Couplings

NEM-362 coupling pockets have done much to expand the coupling options for ‘OO’ gauge and 4mm scale modellers. Everything from Kadees to simple bar couplings that incorporate a compatible swallow-tail fitting can be used, assuming that the coupling box is

Amagnetic alternative to NEM-362 bar couplings for ‘OO’ gauge coaches is explored.

APRACTICAL alternative for the common but obsolete tension lock coupling remains to be agreed and engineered by the mainstream manufacturers for ‘OO’ gauge models.

The adoption of NEM-362 coupling pockets with their well defined specification seemed to be difficult enough, with Bachmann mounting them at the wrong height at the start and other manufacturers occasionally failing to apply the standard correctly for the height of the coupling box together with its position in relation to headstocks. Supplying a stepped shank tension lock coupling resolved the problem for coupling to other tension lock fitted models, but failed to address the needs of alternative NEM-362 compatible coupling systems – the whole point of the exercise in establishing such a standard. Based on experience, modellers would be excused in thinking that a new, more realistic working coupling system that fits NEM-362 for ‘OO’ gauge might be asking too much at this time!

It is left to smaller suppliers to tackle the problem of replacing the tension lock coupling with better ones from an operational standpoint. Perhaps themost annoying feature of tension locks is the slack in each couplingwhen coupled together, something onemight accept with some types of wagon, but not with coaching stock, and especially those used in push-pull and fixed train formation trains.

Manufacturers regularly include fixed bar couplings for NEM-362 boxes with coaches but they are rigid and make the reforming of train sets on the layout awkward to do. Coaches may have to be removed from the layout to couple and uncouple them, which can be a pain at best and will result in damage at worst.

West Hill Wagon Works (www. westhillwagonworks.co.uk) has come up with a simple idea using small but powerful rare earth magnets which offer some solutions, not only for coaches – their intended use, but wagons too, if the modeller is prepared to experiment a little.

Magnets are the key

Instead of a bar coupling with a swallow-tail fitting at each end, the Hunt Couplings are cast resin shanks fitted with magnets at the outer ends. When coupled together, they become what is effectively a continuous bar coupling that can be pulled apart with gentle pressure. The magnets are fitted in the end so the flat faces meet on contact, forming a strong bond, strong enough for most trains.

The opposite end of the coupling has a swallow tail fitting, or in the case of one type for Hornby HST Mk.3 stock, with a clip mounting for fitting to a model. Each pair of couplings making up one bar has magnets of opposite polarities, labelled ‘A’ and ‘B’, so this

Two lengths of coupling are available, designed to be used with NEM-362 coupling pockets in ‘OO’ gaugemodels. They are intended for Mk.2 and Mk.3 stock but have other applications too. A non-NEM coupling mount version is also available.

must be taken into consideration when fitting them. Turn a coach around in a train and the magnets will oppose each other. To account for inaccurately mounted NEM-362 coupling boxes, a

stepped version is also available. Each coupling is made up of a simple resin plastic bar which, when examined closely, appeared to have a slight bow in some of them. They should not be straightened as there is the chance of snapping the shank in two. Trials showed that the slight bowwas irrelevant though, as the magnets soon sought each other and coupled up with a smart click – there usually being sufficient slack in the coupling pockets to allow the shanks to take up the desired position.

Intended use

The first couplings in the range are designed for coaching stock including HST trailers and hauled stock fitted with NEM-362 pockets, such as Hornby Mk.2s. The tension lock coupling is removed and a Hunt Coupling inserted carefully in the coupling box. The adjacent similarly fitted vehicles couple up instantly on a layout as the magnets attract each other. Those models fitted with kinematic coupling cams will behave in the same manner as they would with a solid bar coupling. The appearance of the bar is considerably less visually intrusive than tension lock couplings.

Testing the couplings

Two lengths of couplings are available: a ‘standard’ length that will suit a non-kinematic coupling cam fitted model such as the Hornby Mk.2e and Mk.2f stock alongside the Mk.3s. This is also suitable for models expected

to operate over sharp curves down to second radius to avoid buffer and gangway locking.

The ‘close’ coupling better suits broad curves and models with close coupling cams. Testing showed that they performed in the same manner as solid bar couplings and a fair weight had to be hung behind the locomotive before any of the couplings disengaged. A standard length HST set presents little difficulty for the couplings.

Looking further afield

Clearly, the potential of using the Hunt Coupling withwagons used in block trains was not lost on the editorial team. A number were fitted to Bachmann BDAs and Dapol ‘Turbot’ wagons that would be operated in block rakes with a conventional coupling matching locomotive couplings on the outer wagons. The ‘close’ coupling type seems to be best suited to bogiewagons, which performed as well as the test

coaches. A rake of Accurascale four-wheel PCA cement tank wagons with frame-mounted NEM coupling pockets were tested with ‘close’ couplings. Being four-wheel wagons, it was expected that the couplings, designed for bogie stock, would be too rigid to cope with reverse curves over point work and sharp curves. Testing revealed that therewas enough movement in the NEM coupling box mount and the couplings themselves to allow them to be used in the PCAs and other fixed wheelbase wagons. Their use eliminated unrealistic snatching betweenwagons when tension lock couplings were fitted.

Use in block rakes of wagons (or block sections within a longer train) is an interesting consideration given that the couplings are priced at £12.95 for 10 pairs, which compares well with alternative systems that could be used to replace tension lock couplings to make operation of a rake of wagons smoother. A block rakemay not need to be taken apart very often but the Hunt Couplings make the job quite straight forwardwhen reforming trains in the fiddle yard. Part blocks of wagons within a longer train allowing it to be divided up in a yard using an operational coupling at the outer ends of a section could be considered, in a similar manner as the ‘jumbo’ trains of Mendip stone are divided or combined at Acton.

A shorter shank version would

be welcomed for those wagons and passenger stock with NEM coupling pockets fitted beyond the headstocks, such as the Dapol ‘Turbot’. It is possible to modify the couplings to shorten them and secure them into NEM pockets. Take care when filing shanks so not to breathe in any of the dust.

Future developments

The face of both the ‘A’ and ‘B’ polarity couplings in a coupling pair are flat, making the resulting bar quite rigid, although experiments have shown they can work with fixed wheelbase wagons. Would replacing one of the magnets with a round one provide some further flexibility? Would such a change cause problems with the strength of the bond?

Another consideration for the manufacturer would be to produce a shorter length coupling for wagons such as the Dapol Turbot, in which the coupling box extends beyond the headstocks. Both the close and standard Hunt Couplings resulted in too large a gap between the wagons. The same was true when the couplings were used in a Hornby 2BIL EMU model to replace the solid bar coupling.

Finally, the needs of ‘N’ gauge modellers spring to mind. NEM-355 pockets are increasingly common in ready-to-run ‘N’ gauge stock, together with close coupling cams. A Hunt Coupling to suit ‘N’ gauge bogie wagons and coaching stock could be developed, with a narrow shank and NEM-355 compatible fittings. Would a sufficiently small magnet be available? It’s food for thought! Clearly, the potential for the concept is large and would have many applications if developed beyond the current range intended for coaching stock.

If you decide to have a go with the Hunt Couplings for any purpose other than the intended coaching stock, buy a pack of 10 pairs to experiment with before committing to any more. At £12.95, some experimentation to adapt them for other applications is certainly not going to be expensive and could be very rewarding.

A pile of abandoned tension lock couplings lies to the side of the track after being removed fromAccurascale PCA cement tank wagons in favour of Hunt Couplings. Despite being four-wheel wagons with frame-mounted coupling boxes, the PCAs worked well with Hunt Couplings when tested through 36in radius curves.

The manufacturer’s intended use for the Hunt Coupling is coaching stock including HornbyMk.2 and Mk.3 stock. Hornby Mk.2f stock has NEM coupling pockets mounted on the bogies, making the choice of length important to avoid gangway and buffer lock on the layout’s sharpest curves.

The standard coupling is shown in this view. The couplings have ‘A’ and ‘B’ sides as the magnets are polarised. The shank of the ‘standard’ version is 13mm long, including the magnet, but excluding the swallow-tail fitting.

The choice of coupling length will be determined by the need to prevent the gangways and buffers from locking when the coaches negotiate curves.

There is definitely a need for a coupling with a shank shorter than the 9mm of the ‘close’ type for models with kinematic coupling cams, such as the Hornby 2BIL, amodel that uses a bar coupling between the two vehicles making up the train.

A combination of ‘close’ and ‘standard’ coupling produces a coupling gap of 3mm to 4mmdepending on the slack in the coupling boxes.

At 6mm to 7mm, the widest gap between the gangways is achieved with the ‘standard’ coupling fitted to both coupling boxes.

There is sufficient clearance to negotiate curves down to 30in when used in wagons such as the PCA. Note that the coupling boxes are correctlymounted in relation to the wagon headstocks. The economical price of the couplings makes them an ideal choice for inner couplings in block trains.

Experiments with fixed wheelbase wagons such as the Accurascale PCA cement tank wagon were undertaken and with considerable success. The ‘close’ type was used to replace tension lock couplings in a block train, removing the excessive slack between the wagons when tension lock couplings are used.

Bogie wagons operated in fixed rakes or blocks ofwagons within rakes benefit from the Hunt Coupling. The difference between the ‘close’ and ‘standard’ couplings are clearly visible in this view. Some wagon models would benefit from a coupling with a shank of 4mm to 5mm in length.

The ‘close’ couplings fitted to the Hornby Mk.2f produces a coupling gap of 1.5mm to 2mm depending on the slack in the bogies and coupling boxes. This is only suitable for very broad curves.

A side view of the couplings clipped into the bogie-mounted NEM coupling pockets of the BDAwagon.

The couplings in action in Bachmann BDAwagons working over on 36in radius curves.