BR Class 13 – Britain's Unique Master-Slave Hump Shunters

Historical Background and Context

The BR Class 13 emerged from a specific engineering challenge posed by Tinsley Marshalling Yard's opening in 1965. This state-of-the-art facility represented the centrepiece of Sheffield district rail rationalisation, designed to consolidate numerous smaller yards into one modern network yard handling 3,000 wagons daily. Officially inaugurated on 29th October 1965 by Dr Richard Beeching, former Chairman of the British Railways Board, Tinsley featured 50 main sorting sidings, 11 reception sidings, and sophisticated Dowty-manufactured computer-controlled retarders for gravity-assisted hump shunting operations.

The engineering dilemma was straightforward yet seemingly insoluble. Single Class 08 shunters, whilst ideal for general yard work with their short 8-foot wheelbase that prevented grounding on the hump's steep vertical curves, lacked sufficient power for efficient operations with heavy loaded wagons. Conversely, more powerful locomotives like the Class 20, with longer rigid wheelbases, risked grounding where the track profile rose sharply over the hump summit—potentially causing derailment or damage to the locomotive's underframe.

British Rail's solution, implemented at Darlington Works in May 1965, demonstrated characteristic pragmatism. Rather than designing entirely new locomotives, six existing Class 08 shunters were converted into three permanently coupled pairs. The slave unit's cab was completely removed, creating an unusual cabless locomotive that improved driver visibility from the master unit whilst reducing overall weight. Both units were ballasted beyond standard Class 08 weight to improve traction, effectively doubling tractive effort whilst maintaining the crucial short coupled wheelbase.

The timing of the BR Class 13's introduction occurred within the broader context of the 1955 Modernisation Plan, which allocated £1.24 billion (eventually exceeding £1.6 billion) to modernise Britain's railways. Large mechanised marshalling yards with automated shunting formed a significant component. However, the Plan contained fundamental miscalculations. By the late 1960s—merely years after Tinsley opened—road haulage was aggressively competing for wagonload freight traffic, the very type marshalling yards were designed to handle.

Converting existing locomotives proved cost-effective compared to designing new, more powerful shunters. The Class 08 was BR's standard diesel shunter—996 had been built between 1952-1962—making spare units readily available. Only three pairs were constructed, numbered 13001-13003 (originally D4500-D4502), reflecting both the design's highly specialised nature and limited requirement. They were built exclusively for Tinsley and never operated elsewhere, a specificity that would ultimately seal their fate when the yard's hump operations ceased in December 1984.

Design and Technical Specifications

The BR Class 13 combined two Class 08 diesel-electric shunters into a single operating unit through sophisticated multiple-working control equipment. Each pair comprised a master unit retaining its full driver's cab and controls, and a slave unit with its cab completely removed, creating the class's distinctive asymmetric appearance.

Individual Locomotive Numbers and Conversions

Three Class 13 pairs were created at Darlington Works in May 1965:

• 13001 (originally D4501): Master unit D4190 + Slave unit D4189, withdrawn January 1985, scrapped at Doncaster Works
• 13002 (originally D4500): Master unit D4188 + Slave unit D4192, withdrawn 1981, scrapped at Doncaster Works October 1983
• 13003 (originally D4502): Master unit D4186 + Slave unit D4193, withdrawn January 1985, scrapped at Doncaster Works September 1986

No locomotives found.

All three pairs entered service in May 1965, coinciding precisely with Tinsley Yard's operational opening, demonstrating the locomotives were purpose-built for this specific facility.

The Master-Slave Control System Explained

The control system represented elegant engineering simplicity. The master unit retained fully functional driver's cab equipment including direction switch, power controller, and brake valves operating its diesel engine, generator, and traction motors conventionally. However, the master also featured additional multiple-working control equipment transmitting electrical signals through inter-unit cables to the slave.

Despite having its cab structure removed, the slave retained its complete propulsion system: diesel engine, main generator, traction motors, and control circuits. Control panels remained accessible beneath the former cab floor area for maintenance. When the driver operated the power controller in the master's cab, electrical signals commanded the slave unit's traction motors to operate synchronously with the master's, meaning one driver simultaneously controlled both diesel engines, both generators, and all four traction motors delivering combined power to all twelve driving wheels.

The permanently coupled configuration used reinforced drawgear capable of transmitting substantial pushing forces required for hump shunting. Large buffer plates helped counterbalance the paired locomotives and distribute loads. The coupling was fixed—units could not be easily separated for individual operation, reinforcing the locomotives' specialised nature.

Service History and Operations

The BR Class 13 locomotives operated exclusively at Tinsley Marshalling Yard throughout their entire service lives, from May 1965 until final withdrawal in January 1985. This geographical restriction reflected both their highly specialised design and the unique operational requirements that necessitated their creation.

Tinsley Marshalling Yard: Britain's Modernisation Showcase

Tinsley Marshalling Yard represented ambitious investment in Britain's heavy industry heartland. Located near Sheffield, immediately west of the M1 motorway, the facility consolidated Sheffield's cramped, piecemeal freight facilities. In 1961, one-tenth of Britain's rail-borne freight originated in the Sheffield district, necessitating this rationalisation into a modern "network yard" capable of handling diverse traffic flows.

The yard's sophisticated infrastructure featured gravity-assisted shunting modelled on large American rail freight yards. Incoming trains were split in 11 reception sidings, then propelled over the hump where individual wagons rolled down a slope and were automatically sorted into 50 main sorting sidings according to destination. Computer-controlled retarders either slowed rolling wagons before they coupled to others already on sidings or boosted wagons rolling too slowly—a technological marvel for 1960s Britain.

Hump Shunting Operations Explained

The Class 13's primary duty was propelling wagons over the hump for gravity sorting. Hump shunting is a sophisticated operation where locomotives push wagons up an artificial hill (the hump), allowing individual wagons or "cuts" to roll by gravity down the classification bowl into their designated sidings. The process requires precise speed control—typically operating at walking pace or slower—whilst maintaining sufficient power to overcome the gradient with loaded wagons.

Contemporary accounts describe the Class 13s operating at an extraordinarily slow, constant speed of approximately 1.3 mph whilst pushing wagons. The locomotives maintained this speed throughout shunting, rarely stopping if each cut was long enough to clear points before the next wagon was released. This rhythmic, patient operation characterised Tinsley's daily routine when handling 3,000 wagons.

Three Documented Operational Examples

Example 1 – Standard hump operations, 6th August 1974: Photographer Nigel Tout documented Class 13 No. 13003 propelling wagons over the hump at Tinsley Marshalling Yard. The photographs show the master-slave combination in typical nose-to-cab configuration, with the slave unit nearest the wagons. These images provide rare documentation of the locomotives performing their intended duty during the yard's operational peak period.

Example 2 – Unusual rail tour operation, 7th October 1978: In a remarkable departure from normal duties, Class 13 No. 13003 was used to haul a section of a rail tour from Rotherwood to Tinsley Yard on Saturday 7th October 1978. This represents one of the few documented instances of a Class 13 operating in a role other than hump shunting, demonstrating the locomotives' capability for light haulage duties when required, albeit at their restricted maximum speed of 15 mph.

Example 3 – Configuration modification, 1965-1966: Shortly after entering service in May 1965, operational experience revealed the initial cab-to-cab coupling configuration was impractical for driver visibility. All three Class 13s were reconfigured to couple master nose to slave cab within the first year, substantially improving driver visibility when propelling wagons over the hump. This modification demonstrates British Railways' willingness to adapt the design based on crew feedback and operational experience.

Withdrawal, Preservation, and Legacy

The BR Class 13 class became completely obsolete when hump shunting operations at Tinsley Marshalling Yard ceased. The yard's electrification was removed in 1981 with closure of the Manchester-Sheffield-Wath system. On 14th December 1984, the under-utilised Grimesthorpe Freight Terminal was severely damaged by major fire. Three days later, on 17th December 1984, Tinsley's arrival sidings and hump were closed, the sophisticated Dowty wagon control system removed, and the yard connections relaid to allow easier handling of block-load trains which now dominated rail freight.

The Class 13's unique master-slave configuration, designed specifically to prevent grounding on Tinsley's hump whilst providing sufficient tractive effort, meant the locomotives could not be economically redeployed elsewhere on British Rail. Their highly specialised nature and maximum speed of only 15 mph rendered them unsuitable for any other duty. Contemporary reports noted they were "not required elsewhere"—a damning assessment that sealed their fate.

Withdrawal came swiftly. 13002 was withdrawn first in 1981 and scrapped at BREL Doncaster Works in October 1983. The surviving pair, 13001 and 13003, continued until the hump's closure, both withdrawn in January 1985. 13001 was scrapped at BREL Swindon Works in May 1985. 13003 lingered until September 1986 when it too was scrapped at Doncaster Works.

The Preservation Disaster

None of the three Class 13 locomotives survived into preservation. This represents a significant loss to railway heritage. The class was Britain's only purpose-built master-slave (cow-calf) diesel shunting locomotives—a configuration far more common in North America but extraordinarily rare in British practice. Their unique appearance, specialised operational role, and limited production numbers should have guaranteed preservation of at least one example.

The absence is particularly striking given that over 70-87 of the parent Class 08 design remain preserved on heritage railways throughout Britain, making Class 08 the second most numerous preserved locomotive class in the UK. The failure to preserve even one Class 13 means this unique chapter of British railway engineering exists only in photographic records and documentation—a gap in the national collection that can never be rectified.

Modelling Significance and Scale Replications

In a groundbreaking announcement on 3rd October 2025, Bachmann UK revealed the first-ever ready-to-run BR Class 13 model as part of their Branchline range. This represents a historic moment for British railway modelling, finally bringing this unique and obscure class to the mass market after decades of being available only through conversion kits. The announcement sent shockwaves through the railway modelling community, as few expected a major manufacturer to invest in tooling for a class of just three locomotives that operated at a single location.

Following hot on the heels of Bachmann's widely-acclaimed all-new OO scale Class 08 released earlier in 2025, the Class 13 shares the same mechanical and technological foundation whilst incorporating significant new tooling investment to capture the unique features of the master-slave configuration with unprecedented accuracy and detail.

Bachmann Branchline Class 13 – Revolutionary Ready-to-Run Model

Bachmann Branchline BR Class 13 (Catalog 35-945 and 35-946) represents the pinnacle of British diesel shunter modelling. Each Class 13 model comprises two motorised, fully-functional, highly-detailed units—the master and slave—both fitted with powerful five-pole motors with flywheels driving geared axles through metal gearboxes. All-wheel electrical pickup is complemented by Bach-Up Stay Alive systems in both units, providing DCC users with uninterrupted power to prevent stalling, light flicker, and sound cut-outs.

The engineering sophistication extends to the lighting system. Four user-configurable marker lights are fitted to each end of the pairing (master cab end and slave radiator end), controllable via microswitches located below the roof panels. The master features an enclosed cab light, whilst shunting light mode (one red, one white marker light) is selectable using microswitches or a single DCC function that activates shunting lights on both units simultaneously.

Prototype Accuracy and New Tooling Investment

Bachmann's investment in new tooling specifically for the Class 13 captures the unique characteristics with exceptional fidelity. The thick, deep bufferbeams fitted to both master and slave units are faithfully modelled, accurately representing the heavy metal plates added to improve adhesion. The slave unit's removed cab roof and front panels are precisely reproduced, with shortened side and rear sheets remaining. Within the former cab space, control equipment has been removed and replaced by access panels alongside the handbrake standard.

External details include antennas and aerials for signalling and radio systems, plus long vertical handrails on bonnet sides where radiator ladders were previously fitted. The multiple-working equipment requiring numerous pipes and cables to connect the pair is modelled faithfully and included in the accessory pack for optional fitting, along with bufferbeam infills to plug gaps in the deep bufferbeams for those removing standard tension lock couplings.

Precision moulded components, diecast metal parts, and etched and formed metal details combine throughout both master and slave units. Expert livery application employs advanced paint and print processes with authentic BR colours, logos, fonts, and typefaces.

Initial Release Versions and Pricing

The first Bachmann Branchline Class 13 releases depict:

• 35-945: No. D4502 in BR Green with Wasp Stripes livery (early 1960s period)
• 35-946: No. 13003 in BR Blue livery (1970s-1980s period)

Each version is available in three formats:

• Standard (DCC Ready): RRP £399.95 – Two motorised, fully-functional units with dual Stay Alive systems
• Sound Fitted: RRP £539.95 – Pre-fitted with two premium Zimo DCC decoders (MS450P22 sound decoder in master, MN330P22 loco decoder in slave), with sounds played through speakers in both units when wired connection installed
• Sound Fitted Deluxe: RRP £569.95 – As Sound Fitted plus Bachmann's revolutionary Auto-Release Couplings at each outer end for hands-free uncoupling controlled by single DCC function

Production is complete with delivery expected before the end of 2025. Given limited production quantities, early pre-ordering through Bachmann retailers is strongly advised. Fully decorated factory-finished models will be revealed during Bachmann's Winter 2025 British Railway Announcements on Wednesday 5th November 2025.

Conversion Kits – Still Relevant for Budget-Conscious Modellers

Whilst Bachmann's ready-to-run model represents the ultimate solution, conversion kits remain viable for budget-conscious modellers or those seeking alternative liveries and numbers not produced by Bachmann.

Niu Models (NIU2033) – BR Class 13 Conversion Kit: This 3D resin-printed conversion kit (OO gauge/4mm scale) works with both Bachmann and Hornby Class 08 models. The kit includes complete conversion parts designed from British Rail reference drawings. Requires intermediate to advanced modelling skills for cab removal, filing, and painting. Total project cost including two donor locomotives: £130-£240.

RT Models – Class 13 Bufferbeam Conversion Kit: Partial conversion kit comprising etched nickel silver and whitemetal castings (OO gauge/4mm scale). Provides bufferbeams and major components but requires significant scratchbuilding. Suits advanced modellers comfortable with extensive fabrication work.

Scale Availability and Market Impact

OO Gauge (4mm scale): Bachmann ready-to-run models plus Niu Models and RT Models conversion kits available

N Gauge (2mm scale): No ready-to-run models or kits currently available

O Gauge (7mm scale): No ready-to-run models or kits currently available

Bachmann's decision to produce the BR Class 13 demonstrates remarkable confidence in the British railway modelling market's appetite for obscure prototypes. The class represents one of the rarest subjects ever tackled by a major ready-to-run manufacturer—only the three-strong GWR 4700 Class 2-8-0 produced by Heljan in 2013 rivals the Class 13 for limited prototype numbers. This announcement sets a precedent that even the most specialised, short-lived classes can achieve commercial ready-to-run production if engineering ingenuity and prototype significance justify the investment.

Models

Unique Modelling Tips and Layout Integration

The BR Class 13 offers distinctive operational possibilities for model railway enthusiasts willing to embrace the unique characteristics of hump shunting operations. Authentic integration requires understanding both the prototype's operational patterns and practical compromises necessary for model railway layouts.

Realistic Hump Shunting Operations

Class 13 locomotives operated at an extraordinarily slow, constant speed of approximately 1.3 mph whilst pushing wagons over Tinsley's hump. This glacial pace, maintained consistently throughout shunting operations, created a rhythmic, patient operational character fundamentally different from typical model railway operations where locomotives race around circuits at unrealistic speeds.

For modellers, recreating this requires careful DCC programming. Set CV3 and CV4 (acceleration/deceleration) to very high values (200+) for gradual speed changes. Set CV2 (start voltage) low (around 10-15) and create a custom speed table via CV67-94, concentrating adjustment on the lowest speed steps. Most importantly, set CV5 (maximum voltage) to around 50-60% of full to prevent models ever exceeding realistic hump speeds.

Appropriate Rolling Stock and Period Accuracy

Tinsley handled predominantly coal and mineral traffic from Yorkshire's industries. For authentic consists, model:

• BR 16-ton mineral wagons (diagram 1/108 welded and 1/109 riveted)—the most numerous type 1951-1979
• 21-ton mineral wagons (diagram 1/107 unfitted, diagram 1/110 riveted)
• Coal traffic from Yorkshire coalfields to power stations and industrial users
• Steel traffic for Sheffield's industries
• Mixed freight requiring classification

Accurascale, Peco, Dapol, and Bachmann now produce excellent ready-to-run 16-ton and 21-ton mineral wagons in multiple variations. For period accuracy (1965-1985), model unfitted wagons with Morton brakes, showing heavy weathering from coal loading and rust from impacts during shunting operations.

Weathering Techniques for Shunting Duties

Class 13s and their Class 08 counterparts showed distinctive weathering patterns from constant yard work. Characteristic features include heavy rail dust and grime around bogies and underframes, oil staining around engine compartments, paint damage from coal and mineral wagon impacts, exhaust staining above engine vents, faded paintwork from constant outdoor exposure, rust streaks particularly on the slave unit's modified cab area, and brake dust accumulation on wheels and frames.

Apply weathering as tinted matt varnish (Humbrol matt 29 dark earth and 33 matt black mixed). Dab off flat panels with kitchen paper, leaving colour in corners and recesses where dirt naturally accumulates. Reference photographs from Nigel Tout (1974) and other period sources show Class 13s typically carried moderate to heavy weathering by the 1970s, reflecting Tinsley's intensive daily operations with 3,000 wagons.

Layout Design for Class 13 Operations

A functional hump yard requires substantial space. In OO gauge, a minimum 16-20 feet length is necessary for arrival sidings (3-4 tracks, 5-6 feet each), the hump with its approach gradient (5-10% recommended for gravity operation), a classification bowl (8-12 tracks minimum, though Tinsley had 50), and departure sidings (3-4 tracks). This represents a significant commitment unsuitable for smaller layouts.

Compressed alternatives better suit typical home layouts:

• Compressed yard: Represent arrival, hump, and 4-6 classification tracks in 8-10 feet, capturing the essence without full prototype complexity
• Inglenook shunting format: Use Class 13 for classic shunting puzzles within limited space (8-10 feet)
• TMD scene: Model Tinsley depot area with stabled Class 13 and maintenance activities, avoiding complex track arrangements
• Fiddle yard operations: Use Class 13 for switching whilst representing off-stage classification through fiddle yard manipulation

Finally

The BR Class 13 represents a fascinating footnote in British railway history—ingenious in conception, successful in solving Tinsley Marshalling Yard's specific operational challenge, yet ultimately a victim of the rapid decline in wagonload freight traffic that rendered large classification yards obsolete within a generation. The class's complete extinction without preservation makes these locomotives particularly compelling subjects for railway modellers seeking to recreate vanished aspects of Britain's railway heritage.

For model railway enthusiasts, the BR Class 13 offers unique operational possibilities and distinctive visual appeal. Whilst conversion from Class 08 models requires intermediate to advanced skills, the resulting locomotives provide a centrepiece for 1960s-1980s freight-focused layouts that no ready-to-run model can deliver. The patient, methodical operation at prototypical 1.3 mph hump shunting speeds creates contemplative operating sessions fundamentally different from typical fast-running operations.

The class embodies lessons about over-specialisation in locomotive design. Built for one location and one duty, the three BR Class 13 pairs could not be redeployed when their singular purpose ceased to exist. This inflexibility—combined with the broader structural decline of wagonload freight as road transport captured market share—meant withdrawal was inevitable. The locomotives' 20-year service lives, whilst respectable, were far shorter than the 40-50 years many diesel classes achieved, and dramatically shorter than the Class 08s from which they were converted, many of which continue operating on heritage railways today.

For railway historians, the BR Class 13 epitomises the ambitious but flawed 1960s Modernisation Plan. Tinsley Marshalling Yard—with its computerised wagon control, gravity-assisted hump, and sophisticated infrastructure—represented substantial government investment that never achieved anticipated returns. The yard operated below capacity from inception, its expensive automation rendered obsolete by containerised and block-load trains requiring no intermediate marshalling. The Class 13 locomotives, custom-built for this facility, shared its fate.

The absence of any preserved example represents a regrettable gap in Britain's railway heritage collection. Whilst over 70 Class 08s survive on heritage railways, the unique master-slave configuration cannot be experienced by future generations except through photographs, documentation, and the dedicated efforts of model railway enthusiasts who continue to build and operate these distinctive locomotives in miniature. The BR Class 13 remains a compelling subject for modellers—rare, unusual, historically significant, and a permanent reminder that not every chapter of railway history survives into preservation.

Frequently Asked Questions

How many BR Class 13 locomotives were built and where?

Only three BR Class 13 locomotives were created, numbered 13001, 13002, and 13003 (originally D4500-D4502). All were converted from existing Class 08 shunters at British Rail's Darlington Works in May 1965 specifically for hump shunting operations at Tinsley Marshalling Yard near Sheffield. No additional examples were built.

What made the BR Class 13 different from a standard Class 08?

The BR Class 13 comprised two Class 08 shunters permanently coupled in a master-slave configuration. The slave unit had its cab completely removed, creating a distinctive asymmetric appearance. This configuration doubled the power output to 700-800 hp and tractive effort to 70,000 lbf whilst maintaining a short coupled wheelbase necessary to safely traverse the hump without grounding—solving a critical operational challenge at Tinsley.

Why were the Class 13 locomotives only used at Tinsley Marshalling Yard?

The BR Class 13 was purpose-built exclusively for Tinsley's specific operational requirements: sufficient power for hump shunting heavy loaded wagons whilst maintaining a short wheelbase to prevent grounding on the steep hump profile. Their highly specialised design, maximum speed of only 15 mph, and permanently coupled configuration made them unsuitable for redeployment elsewhere when Tinsley's hump operations ceased.

What happened to all three BR Class 13 locomotives?

Tragically, none survived into preservation. 13002 was withdrawn in 1981 and scrapped at Doncaster Works in October 1983. 13001 and 13003 were both withdrawn in January 1985 when Tinsley's hump closed. 13001 was scrapped at Swindon Works in May 1985, whilst 13003 lingered until September 1986 before scrapping at Doncaster Works. The complete extinction of this unique class represents a significant loss to railway heritage.

Are there any ready-to-run BR Class 13 models available?

No ready-to-run BR Class 13 models have ever been produced by any manufacturer. The only option for modellers is conversion from two Class 08 models using specialist kits. Niu Models offers the most comprehensive conversion kit (NIU2033) for OO gauge, whilst RT Models produces a partial kit requiring significant scratchbuilding. Total project cost including two donor locomotives ranges from £130-£240.

How fast did the BR Class 13 operate during hump shunting?

The BR Class 13 operated at an extraordinarily slow speed of approximately 1.3 mph during hump shunting operations, maintaining this constant glacial pace whilst propelling wagons over Tinsley's hump. The maximum design speed was only 15 mph, though normal operations rarely exceeded walking pace. This patient, methodical operation characterised the locomotives' entire working lives.

What was the master-slave control system and how did it work?

The master unit retained its full cab and controls, whilst the slave had its cab removed but kept its complete propulsion system. Multiple-working control equipment in the master transmitted electrical signals through inter-unit cables to the slave. When the driver operated the power controller, both diesel engines, generators, and all four traction motors responded synchronously, meaning one driver controlled all twelve driving wheels from a single cab position.

Could the Class 13 master and slave units be separated?

No. The BR Class 13 pairs were permanently coupled with fixed, reinforced drawgear designed to transmit the substantial pushing forces required for hump shunting. The units could not be easily separated for individual operation, reinforcing their highly specialised nature. This inflexibility ultimately contributed to their rapid withdrawal when Tinsley's hump operations ceased, as they could not be economically redeployed elsewhere.

What livery did the BR Class 13 carry?

The BR Class 13 initially carried BR green with wasp-stripe warning panels. Following introduction of the TOPS numbering system in the early 1970s, they were repainted into BR blue with full yellow ends and received their 13001-13003 numbers. Photographs from the 1970s and early 1980s show them in BR blue with varying degrees of weathering from intensive yard operations.

Were there any other master-slave diesel locomotives in Britain?

No. The BR Class 13 was Britain's only purpose-built master-slave (cow-calf) diesel shunting locomotive configuration. Whilst common in North American railroad practice, this arrangement was extraordinarily rare in British railway engineering. The concept was never repeated after the Class 13's limited success, making these three locomotives truly unique in British railway history.

Why did Tinsley Marshalling Yard close so soon after opening?

Tinsley opened in 1965 at the peak of wagonload freight optimism but faced immediate competition from road haulage. By the late 1960s, containerised and block-load trains were replacing traditional wagon-by-wagon freight that marshalling yards were designed to handle. Economic decline in the 1970s, closure of Yorkshire industries, and British Rail's shift away from wagonload freight rendered Tinsley under-utilised within years. The hump closed in December 1984, just 19 years after opening.

Can I build a BR Class 13 model in N gauge or O gauge?

Currently, conversion kits are only available in OO gauge (4mm scale). No N gauge (2mm scale) or O gauge (7mm scale) kits exist. Advanced modellers could theoretically scratchbuild Class 13 models in other scales using two donor Class 08 models, but this would require extensive research, prototype photographs, and considerable modelling expertise. The limited market and extreme specialisation make commercial kit production in other scales unlikely.