Digitising a Spitfire
02 April 2012
A 3D digital scanning specialist has captured the very essence of the last airworthy Spitfire MkIIa. The digital data was used to create a model of the aircraft for architect, Norman Foster's collection.
Creating a model replicating every detail of one of the most iconic pieces of aviation history is no small task. That’s why Amalgam Fine Model Cars asked Surrey-based Physical Digital, a specialist in optical scanning and design, to spend three days at RAF Coningsby scanning the last airworthy Spitfire MkIIa that flew sorties in the Battle of Britain during World War II. The model will join a collection of similar models owned by the architect Norman Foster. Lord Foster commissioned the project, based on a long-term partnership between his practice and Amalgam.
A project like this is complex for a variety of reasons. Most importantly, the integrity of the aircraft has to be maintained, so moving it for scanning purposes isn’t an option. Mobile 3D scanning instruments are the best option for large machines that need to be kept in controlled environments.
As part of the Battle of Britain Memorial Flight (BBMF), the Spitfire is at an operational RAF base, and scanning procedures cannot interfere with its day-to-day operations. The topography of the Spitfire also requires different types of scanning systems in order to produce the information needed to produce an exact scale model. So, who would be up for the job?.
Enter Physical Digital
Physical Digital’s scanning expertise embraces a wide range of projects, including Formula 1 and automotive, heavy engineering, marine craft and aeronautical designs; the company was recently involved on a project to digitise Ralph Lauren’s classic car collection. With so much past experience, managing director, Tim Rapley knew that his team would need several scanning options in order to collect every piece of relevant data from the Spitfire. Forward planning is essential on a project like this, he asserts. It helps us to achieve the right result and reduces the amount of time we spend onsite.
Data from the scanning will be used both for the creation of the model, and also archived with the BBMF for use in refurbishment or repair work on the aircraft. For the Spitfire project, Physical Digital used GOM systems TRITOP, ATOS and Touch Probe to ensure that the data captured was as comprehensive as possible.
TRITOP photogrammetry technology uses coded and non-coded markers to create a framework for the subject to high levels of accuracy. For the Spitfire, 5mm diameter markers were used across the airframe. Moveable parts, like the cockpit, rudder, ailerons and elevators were captured in their extreme positions so that the model could show the deflection angles of these control surfaces.
The resulting file builds a framework, based on creating 3D co-ordinates from 2D images. This file is then imported into the ATOS software where it is used as a reference frame for the 3D scanning process. For this project, Physical Digital used two scanning systems to help reduce the project time scale: an ATOS IIe and an ATOS III Triple Scan - the latest system available from GOM UK. The combination captures both components and positions and compiles the data into a single project. 3D scanning produces a mesh file that in this case will be used both to create a physical model, and a digital archive for the BBMF.
For a shape as complex as the Spitfire, there are areas where conventional TRITOP and ATOS scanning will not produce the best results, so an optically tracked Touch Probe is used instead. This interacts with the ATOS sensor so that difficult-to-scan areas can be captured and recorded accurately. CAD models from the scan data are created in Geomagic, enabling new components and tools to be reverse engineered, re-designed, optimised and manufactured with precision.
Modelling
Once the data has been captured and processed, the model makers begin work on a project which will take several thousand man-hours to complete. An entire master set of components needs to be modelled using a range of skills, including digital machining, traditional engineering and manual craftsmanship. Once the components are complete, they are painted and finished in exactly the same way as the original aircraft would be, resulting in accurate colour, finish and even polish detail. When the components are finished, it takes another 300 man-hours to assemble the model, which is finally presented with its own replica log book.
Tim Rapley summarises: “Whilst we work in a diverse range of engineering sectors, this has been a fantastic project to be involved with. Amalgam produces incredible models and it gives us a huge amount of pride to work with them and to be entrusted with one of the most famous examples of British military engineering history. This has truly been a team project, and our thanks go to the BBMF, Amalgam and GOM UK who gave us tremendous support throughout.”