With the final concept design approved, the engineering team settled down to the task of producing detailed drawings for every individual component, on top of the major sub-assemblies such as the bogies, underframe and steel body frame.

Sadly, we didn’t have the advantage the railway had 20 years ago; we had no spare bogies, underframes or components. Every one of these parts had to be 3D modelled and drawn, right down to the individual parts that make up items such as hinges, door locks and light fittings.

Construction was to mimic the more recent PBR carriages manufactured in the 1990’s by Skilled Engineering, e.g. welded steel body frames, infilled with grooved plywood panels to give the impression of timber planks.

In addition, we needed to rationalise the amount to steel used to reduce weight and cost. Finite Element Analysis (FEA) software was utilised to work out where we could best make savings in both the body and underframe, whilst retaining the structural strength required of an operating railway.

During the design process, work was also carried out to assess the new carriages for DDA (Disability Discrimination Act) compliance, including consultation with an Accessible Tourism advisor. Modifications were incorporate to allow each NBHC carriage to accommodate 6 wheelchairs, increasing Puffing Billy’s total wheelchair capacity by 24. The option to add a hearing loop in the carriages has been considered, as well as the possibility of designing new access ramps incorporating shallow steps for those with low mobility.

Final detail design includes over 200 individual drawings, plus new or revised practice cards covering manufacture and maintenance procedures.

Initially we had planned to let a turnkey contract for 12 carriages, however it proved nigh-on impossible to find a company who could do this, so we split the project up into several smaller packages of work:

  • Bogie manufacture
  • Underframe Casting Package
  • Underframe and body frame manufacture
  • Seat, Door and Window package
  • Door & Window furniture package
  • Seat cushion & blind manufacture

Following final checking and sign-off of all the drawings, contracts were issued, and manufacture of the prototype began in mid-2017.

A constant flow of emails, phone calls and site visits over the ensuing months was followed, in early December, by delivery of the prototype carriage underframe and body frame. This was followed shortly after by the first 2 bogies.

On-site inspection against the design was passed with flying colours, and the bare bones of the carriage was soon transferred to Emerald to be fleshed out by the skilled team in the carriage workshops.