Review: Bachmann ‘Bubble Cars’
Pressed Steel Class 121 single car DMUs are the latest brand-new ‘OO’ gaugemodels to arrive fromBachmann. Employing its new low profile drivemechanism to clear the passenger compartment for seats and fittings, the Class 121 builds on the success of Bachma
Bachmann’s new Class 121 single car DMU is given a thorough inspection.
REPUTED to be the longest surviving first generation DMUs, the Class 121 has something of a following among enthusiasts which will make the brand-new ‘OO’ gauge model by Bachmann a popular choice for collectors and compact layout owners.
When unboxing the model, the first impression was that Bachmann has achieved the correct shape and character of the Class 121 ‘Bubble Car’. The roof is smooth, free of unsightly grooves that plagued earlier models of the Class 121 and the ‘Derby’ design cabs are as they should be with their three large windows. No motor intrudes into the passenger cabin or guards van area.
It’s an exciting representation of the 16 DMBS vehicles making up
Class 121 (there appears to be no plans to produce the 10 matching unpowered DTS vehicles at this time) intended for strengthening Thames Valley services and Western Region branch train operation in Berkshire, Avon, Devon and Cornwall to mention a few. Built by the Pressed Steel Company in 1960 and 1961, they lasted both in revenue service and as departmental vehicles
well into the Privatisation era including use of three relatively unmodified units (121027/029/031) by Silverlink on Marston Vale line services between Bletchley and Bedford until replaced by Class 150/1s in 2002.
As single car units, the Class 121s are equipped with a driving cab of the ‘Derby’ design at each end together with a guard’s van area and Standard Class seating for 65 passengers in two high-density saloons separated with a screen. Seating is in three-plus-two format accessed through slam-doors leading to each seating bay.
A four-character headcode box of the same type as Class 117s was fitted to the cab roofs, distinguishing them from the similar Class 122 Gloucester ‘Singles’ which bore destination boxes instead. The exhaust pipes fitted to the cab at the guard’s van end were excessively curved to clear them giving the Class 121 their unique character. Class
121s refitted for modern operations with Arriva Trains Wales and Chiltern Trains had the exhausts relocated alongside other modifications
to bring them up to modern standards.
Two 150hp AEC or Leyland engines linked to a mechanical transmission, one for each bogie, provided power for the 38t units. They were rated for a maximum operating speed of 70mph, although acceleration was not particularly good, particularly when paired up with a DTS. The units could be operated in multiple with other DMUs with the same blue square multiple working equipment including Class 117s. Side buffers are fitted together with screw link couplings and vacuum brakes.
Release of Bachmann’s brand-new ‘OO’ gauge model of the Class 121 consists of three models including an original BR green version with speed whiskers as No. W55027 (35-525); BR blue and grey as No. W55025 (35-526) and Network SouthEast
No. 55024 (35-527). They will be an excellent match for the forthcoming Class 117 from Bachmann which will share the same technical features.
Fine tooling is evident in the bogies including the springs and axle boxes. Footsteps are separate details alongside the flexible speedometer drive cable, a very ingenious touch.
Bodyshell
Four clips per side secures the singlepiece body shell to the chassis making it simple to remove for decoder fitting and detailing the interiors. Moulded detail such as door lines, window frames, commode handles, door hinges and door stops are fine in appearance and subtly represented. A barely visible dimple in each of the passenger doors represents the tiny opening for the door key. The roof is smooth and fitted with neatly tooled ridge dome ventilators of the correct size and position which were firmly seated on the roof except for one.
The four-character headcode boxes are correctly shaped and fitted with a blanking plate to suit the era of the review model. Small fittings also include various handrails adjacent to the cab doors, the distinctive exhaust clearing the headcode at the guards van end and cabs are correctly shaped.
Examining the bodyshell along its length on both sides confirmed that there is no sign of distortion, the rain gutter being as straight as one could desire. The correct cross-section profile is also apparent when making this check of the bodyshell. It sits squarely on the underframe with no sign of looseness or irregularity and no irregularities were seen in the roof.
The DCC interface socket is concealed in the brake van area of the model, yet some of the internal detail has been modelled. Note the LED boxes designed top illuminate the destination blinds and headcode box.
Room for passengers
A small but powerful can motor located under the floor (so-called low-profile) has allowed the interior to be modelled with the correct high-density three-plus two seating arrangement. Seats are correctly modelled in bench format with high backs in blue plastic. The dividing screen between the two saloons is modelled alongside the bulkhead separating the guards van from the passenger compartment.
Part of the guards van can be observed through the flush fitting glazing which is clear and flat across its surface. Little evidence of an edge to the outside of each glazing unit can be observed except when looking along the length of the vehicle, adding to the realistic appearance of the model.
Underframe and bogies
Below solebar level is a wealth of detail applied to the underframe including two modelled engines with their mechanical transmissions; exhaust pipes, radiator and fuel tank. The position of the underframe-mounted motor is not easy to see behind some of the underframe detail, where it is fitted to a cradle which does protrude belowunder the floor line.
Bogies are very fine looking models and are equipped with separate footsteps and brake shoes aligned with the wheels. When examining the speedometer drive linkage between the bogies and underframe, it took a second to realise that it is connected at both ends, yet flexible enough to allow the bogies to rotate to their maximum operating position. It does not interfere with the model’s operation on second radius curves – a nicely designed feature.
Wheels are fully concentric resulting in a smooth running model with no visible wobble. Split axle wheels are fitted to the unpowered bogie with end of axle or stub axle current collection. The powered bogie is equipped with traditional wiper pick-ups and blunt ended axles with the same black-painted wheels.
Drive train
A single can motor is fitted into a curved cradle which is moulded as part of the underframe floor. It is well concealed behind underframe features and not visible from normal viewing distances. It is connected to the bogie located under the guards van area with a short drive shaft which is mounted level with the underframe floor and therefore out of sight. Performance is smooth and with 190g of weight, was found to be capable of hauling a trailer car or a mail van or two without difficulty. When matched with the forthcoming Class 117, there will be sufficient power in both unit models for smooth and competent performance.
Advanced electronics
In common with the recently reviewed Class 159, electronics is becoming ever advanced in Bachmann models, and the use of the PluX22 decoder interface allows more lighting effects to be installed and controlled through a decoder. Through connections through the circuit board, together with a factory installed speaker, makes digital sound installation and full operation of all the on-board lighting effects simple to do, simply by plugging in the appropriate decoder.
For traditional analogue control layouts, there is a bank of miniature switches positioned under the unpowered bogie for selection of the desired lighting effects. Six switches
allow a measure of control of the interior lights, head and tail-lights alongside destination blind box lighting.
Livery and finish
The review model is finished as
No. W55025 in BR blue and grey livery which is neatly applied with level lining and neat printing of the number and legends. Whilst many Class 121s saw regular service on the Thames Valley route centred on London Paddington, Reading, Oxford and Newbury, some Class 121s saw service in the West Country. No. W55025 is labelled as set No. P125 as allocated to Laira. The destination blinds show Par and Newquay, a once common haunt of Class 121s
before
the introduction of Class 142 ‘Skipper’ units.
From its nicely detailed interior with driving cabs, guards van detail and interior partitions, to the delicate underframe, Bachmann’s Class 121 is a taste of what is to come with the Class 117 – clearly more thought is going into model design and how they operate. Assembly and finishing of the model is neat and clean, whilst the relatively simple assembly of single piece body clipped to an underframe makes both DCC simple and refinishing to a different unit (or conversion) straightforward to do. It’s the perfect branch train on one hand, but has potential for varied operation if a DTS trailer conversion is undertaken.