The interaction of a high speed train pantographs with overhead lines is an important area within the rail industry. One particular trial required footage of the wave created by the contact force of the pantograph. Unusually regards high speed filming, the trial had to be done at night. Having previously worked on a similar day time trial, Slowmo Ltd was called on to provide the images.
The Photron SA-X2 mono high speed camera was the obvious choice for this application because of its industry leading light sensitivity. In order to illuminate the wires and pantograph, one of Slowmo’s powerful LED floodlights was used. As the floodlight is only rated at 200W (for 2KW tungsten equivalent) a small briefcase type generator was used for power. The camera was set low on a tripod, angled upwards towards the wires and a field of view of around 6m was set using a 50mm F1.4 lens.
With this night time set-up, amazingly a high speed train was able to be filmed at 2000 fps. Furthermore, the clarity within the image allowed one to easily assess the movement of the overhead wires as the pantograph passed underneath. Images over 3 consecutive nights were then recorded.
High speed images were required showing the terminal effects of different AP rounds on metal plates, fired from a distance of 550m, There was 15 firings in 7 series of trials, all of which were required to be recorded. Trial site regulations meant that no-one could be forward of the rifle.
The problems to overcome were firstly, how is the camera to be triggered and secondly, how can the recorded shot be downloaded quickly and the camera re-armed. Automatic download and re-arm has always been a built-in function with Photron cameras.
However, due to the time between firings only being around 15s, the stored memory needed to be trimmed first before saving (this is normally done manually on the laptop) otherwise the download time would be too great. A unique way of triggering the camera had to be developed and in order for the shot to be trimmed appropriately, this trigger had to be generated by the bullet hitting the plate (T=0s). Pre-determined mark in/mark out points could then be set allowing for a fast download and re-arm, ready for the next shot.
Phil Gotts from PGC Ltd hired Slowmo to provide high speed images for a series of firings testing the bullet impact properties of ceramic tiles as used in personal body armour.
Due to the brittle nature of the tiles and the high bullet velocities, an ultra-high frame rate was one of the prerequisites for the filming. In addition, simultaneous entry and exit points were required. This called for 2 x Photron SA-X2 mono high speed cameras.
Requirement was to capture the detonation and form of different shape charges over several trials. In all over 50 separate firings were recorded using 3 Photron high speed cameras. The location was the main arena at Radnor Ranges. One set of trials involved targeting the shape charge at a 105mm live shell. This shoot presented a number of issues, namely the velocity and brightness of the shape charge and the destructive nature of a potential shell detonation. For the shape charge, we used the Photron SAX high speed camera with the following settings – 50000fps, 1/1000000s shutter speed, 512 x 256 resolution, 50mm F1.4 lens stopped down to F18.
Slowmo Ltd was asked to provide a high speed camera provision for a series of trials taking place over a time period of around 18 months. The test location was the Flare Test Track at COTEC, Wiltshire. Images showing the flight trajectory and orientation of a projectile covering a distance of approximately 250m was required. Up to 5 Photron high speed cameras were placed accordingly, showing ejection point, primary and secondary flight phases and landing point. A Photron SA3 high speed camera was placed on the test track itself allowing unique views of the ejection point to be recorded. Each camera was triggered simultaneously allowing flight time to be calculated. An IRIG time code was also recorded allowing synchronisation with other electronic equipment.
