Updated ‘O’ Gauge ‘Rat’ from Heljan



Time to read

6 minutes

An impressive Class 25/3 joins the Heljan Class 25/1.

THE Class 25/3 sub-class was the final development of British Railways’ Sulzer Type 2 Bo-Bo family, which began in 1958 as a ‘pilot scheme’ batch of 20 Class 24/0 locomotives for evaluation by BR and resulted in a total of 151 Class 24s entering traffic.

Class 25s followed the same basic design, but with a four-character headcode box above the cab and an uprated Sulzer 6LDA engine. A number of design changes took place during the production run of Class 25 locomotives, including the redesign of the body shell to clean up its appearance (locating bodyside ventilation grilles to the roof shoulder) and removing the front gangway doors.

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By 1965, evolution of the design came to a close with the introduction of 80 Class 25/3 locomotives numbered Nos. D7598-D7677 (nos. 25248-327 under TOPS). They were built for freight duties and consequently not fitted with a train heating boiler and water tank. It is in this guise that Heljan has produced its late Class 25, a design that remained in traffic until 1987 and was a reliable and competent locomotive. Changes in traffic patterns, together with the introduction of new heavy freight locomotives, saw the demise of the Class 25, which were a popular locomotive with enthusiasts.


A very good rendition of the Class 25/3 body shell has been created by Heljan, including the all-important face of the locomotive with its curved cab and gently raked window panel. Windows are well shaped and of the correct size both on the front and sides of the cab, affording a good view of the cab interior.

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Shoulder grilles are fine toolings, as are the roof panels – some of which are picked out in cream to represent translucent GRP material. Smaller fittings added to the body shell include etched radiator and boiler compartment grilles, whilst etched blanking plates for the bodyside footsteps and the boiler grilles are supplied for fitting by the modeller. Flush glazing is neatly applied and clear enough in the cab to have a good view of the driving controls, driving desk and the detailed rear cab bulkhead.

Several small points arise from examining the bodyshell assembly. The recessed window frames have prominent ‘rivets’ that are not obvious on the full size locomotives, and the cab roof headcode box extends further back along the cab roof, relative to the cab side windows, than it should. Nonetheless, with its finely tooled details, particularly on the cab front, and overall excellent proportions, the Class 25/3 body looks great from any viewing angle.

Underframe and bogies

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A great deal of work has been into replicating the heavy-looking bogies of the Class 25 family – and to good effect. In addition to bogie sideframes, with their deep section moulding resulting in a good level of relief, the bogies are fitted out with footsteps and other small details, all of which are neatly attached. Wheels are of the correct size, but do not feature the weight-saving holes of the full size locomotives. They are nicely turned and exhibited no sign of wobble during testing of the review model.

Another key area for Class 25/3s is the underframe and this is a lovely piece of modelling too, with the correct underframe tank arrangement. Again, the components are of the correct shape and add to the character of the model, particularly when viewed from a low angle. Numerous pipe runs and other small details are fitted to the underframe, the tank and bogies, enhancing the highly detailed appearance of the model.

Drive mechanism

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Two can motors, each fitted with a large brass flywheel, sit at the heart of this model providing a great deal of tractive effort. Both motors are centrally mounted end to end on the chassis frame and linked to the bogie gear towers through a well engineered drive shaft assembly that is securely fitted.

Both motors were well balanced compared to each other, resulting in smooth operation throughout the speed range when the model was run in both directions. The four-axle drive, combined with a weight of 2110g, provides sufficient adhesion for hauling long trains, something the full-size locomotives were asked to do regularly, particularly with Saturday-only summer trains.

The model has a third, albeit much smaller, motor mounted in the roof to drive the cooling fan, which is controlled through a small circuit board. A potentiometer allows the speed of the fan to be set and the use of a separate motor rather than a band drive linked to the drive system ensures that the fan rotates in the correct direction and at a constant speed regardless of the direction of travel.


As supplied, the Heljan Class 25 is fitted out to run on conventional analogue control. Current collection is through wiper pick-ups acting on all eight wheels, with leads connecting the bogies to the circuit board. The circuit board is mounted on top of the motor frame and has screw terminals for decoder installation. A secondary circuit board controls the cooling fan and directional lighting is fitted throughout.

Choosing the right decoder for this model is important because of the likely power consumption of the paired can motors in such a heavy model. Current draw is likely to be high on starting a train from a stand, particularly if the model is being put through its paces with a heavy train. Its impressive hauling power will allow a long train to be hung behind it, but such performance will make high demands on a decoder.

For this model, avoid the temptation to save money by fitting a decoder intended for ‘OO’ gauge,
even though smaller ‘O’ gauge models can be fitted with higher-rated but less expensive ‘OO’ gauge decoders. The Heljan Class 25/3 is a bit of a brute and needs a decoder to match!


With a recommended retail price of £525.00, the Heljan Class 25/3 is excellent value for money for an ‘O’ gauge ready to run model of its level of specification, particularly compared to the cost of building a brass kit of a similar type of model. It an excellent representation of the Class 25/3 despite a couple of small points, some of which can be corrected by a keen modeller. Its assembly is neat and robust, whilst performance is faultless, making it an impressive package overall.

Models like the Heljan Class 25/3 will do much to fuel the growing enthusiasm for ‘O’ gauge modelling. The relatively small size of the Heljan ‘O’ gauge ‘Rat’ makes it ideal for modellers wanting to try ‘O’ gauge for the first time. At 355mm over the buffers, it is small enough to fit a compact layout equipped with a handful of wagons, but has presence too for its small size.

As more accurate off-the-shelf ‘O’ gauge wagon models emerge from Heljan and Dapol, ‘O’ gauge layout building is becoming a more realistic proposition for modellers who find themselves with too little time to kit-build rollingstock.


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