Special equipment
nCATS also operates two additional specialised rigs:
- high-velocity impact rig – was initially design for high-strain body armour work where unhardened balls are fired at targets and the shockwave measured, energy absorption is determined. This has more recently been developed for fundamental water droplet impact studies.
- tooth brushing rig – eight stationed rig for studying tooth brushing process, particularly the abrasive effect of toothpaste.
High-velocity impact rig
Location: Building 7 room 2023 - Bay 4
The impact rig was design at the University and manufactured by Safire and Associates. It is a pneumatically powered system supplied by the laboratory air lines. The air supply is connected to a valve and pressure gauge that regulate the pressure within an accumulator, which stores a defined volume of compressed air prior to release by a rapid‑acting valve electronically triggered via a foot pedal. The accumulator is connected to a smooth‑bored barrel, manufactured by a gunsmith to ensure a near gas‑tight seal with the projectile.
The barrel is mounted on dual gimbal assemblies, allowing precise adjustment of elevation and direction. Two light gates positioned near the muzzle record the projectile exit velocity. The projectile is typically a 9 millimetre (mm) diameter ball; unhardened balls are preferred, as hardened variants tend to shatter. The projectile is loaded at the rear of the barrel and fired into a test chamber designed to safely contain the impact energy.
The chamber is enclosed by two removable 10 mm thick Perspex panels, enabling visualisation of the impact event, including high‑speed imaging. Safety micro‑switches prevent firing unless the panels are correctly installed. The sample is mounted on a striker bar supported by vibration isolation mounts, with an accelerometer positioned at its end to record pressure waves generated during impact.
The rig has been adapted for doctoral research by replacing the striker bar with a plunger system to generate high‑velocity water slugs. By varying projectile energy and nozzle geometry, slug velocities exceeding 200 metre per second (m/s) have been achieved. Ultra‑high‑speed imaging, at up to five million frames per second, is used to analyse slug formation and surface impact behaviour.
TE85 Tooth brushing rig
Location: Building 7 room 2023 - Bay 3
The TE85 tooth‑brushing rig is designed and manufactured by Phoenix Tribology Ltd. It is configured as an eight‑station orbital system capable of producing circular orbital, elliptical orbital, and reciprocating motion. In this arrangement, fixed toothbrush samples are loaded against moving tooth specimens.
Toothbrushes are trimmed to facilitate attachment to the loading arms, which are equipped with adjustable counterweights to achieve neutral balancing. Spirit levels are provided on each arm to assist with accurate levelling. Tooth specimens, typically mounted in epoxy discs, are secured within radially sprung fixtures and housed in individual baths mounted on the motion plate. Load is applied directly to each toothbrush via dead weights acting on load rods supported by linear bearings.
The motion system comprises a platform mounted on an x–y slide assembly and driven by a double scotch yoke mechanism powered by an AC gear motor. Motion frequency is controlled by an inverter and can be adjusted between 0.2 and 2.0 Hertz (Hz). Displacements of up to 5 mm per axis enable reciprocating, elliptical, or circular orbital motion.
Eight computer‑controlled peristaltic pumps independently deliver toothpaste and saliva simulant to each station. Three‑axis force transducers may be fitted to selected stations to measure applied loads and frictional forces, with signals recorded via a high‑speed data acquisition system.
Specifications:
- load per brush: 150 to 500 grams
- motion X direction: 10 mm (fixed) (+/-5 mm)
- motion Y direction: 0 to 10 mm in 2 mm steps (+/-0, 1, 2, 3, 4, 5 mm)
- maximum frequency: 2 Hz (120 Revolutions Per Minute (rpm))
- automatically controlled parameters: frequency; test duration; fluid flow rate
- manually controlled parameters: load; Y amplitude
- measured parameters: frequency; load (optional); friction force (optional); number of cycles
- services - electricity: 220/240Volts (V), single phase, 50 Hz, 3 kilowatt (kW)
