Dragon's Teeth Development History

The Defence-Structures Dragon's Teeth Vehicle Security Barrier (VSB) is a freestanding road defence barrier system. Individual units (teeth) are linked at the front by a steel beam section and at the rear by flat steel plates (previously chain) to allow displacement during impact.

The Dragon's Teeth VSB was impact-tested in accordance with the BSI PAS 68:2007 Impact test specifications for vehicle security barriers in order to evaluate its performance versus a vehicle borne penetrative attack.

Test 1: the road barrier was set out as shown in Photo 1 with the frangible steel beam linking the front and chain linking the rear. The vehicle used was a 7.5t (N2) 2-axle rigid with an impact speed of 48km/h. The road barrier achieved a BSI PAS 68:2007 impact rating of V/7500/48/90 : 0/0.

The Dragon's Teeth Vehicle Security Barrier performed as expected with the road defence system stopping the load carrying platform of the HGV with zero penetration beyond the original rear face of the system and with no dispersion of major debris. The defence barrier was displaced in the direction of impact by 3m suffering minor damage to the teeth and frangible steel sections. See photos 2 & 3.

Test 1: Barrier before impact	Test 1: Overhead view after impact	Test 1: Side view after impact

Test 2: the road barrier was assembled using the same components as Test 1. The vehicle used was a 7.5t (N3) 2-axle rigid with an impact speed of 80km/h. The road barrier achieved a BSI PAS 68:2007 impact rating of V/7500/80/90 : 11.8/7.5.

The Dragons Teeth Vehicle Security barrier was assembled as in Test 1 using the original teeth but replacing the steel beam and chain links. The higher energy generated by the N3 class vehicle compared to the N2 vehicle (Test 1) resulted in the connecting chains breaking, causing the teeth to rotate and separate; allowing the vehicle to penetrate through the road defence barrier. The vehicle suffered significant damage and was immobilised. See photos 4, 5, 6. A re-design of the rear connection was required to prevent separation of the teeth and improve impact performance.

Test 2: View of Links after impact	Test 2: Side view after impact	Test 2: Front view after impact

Test 3: the setup was a repeat of Test 2 using the same vehicle class and impact speed. The rear links of the road barrier were re-designed to replace the chain link with an arrangement of steel plates to form a flat chain. The road barrier achieved a BSI PAS 68:2007 rating of V/7500/80/90 : 7.9/0.

During impact the rear connections performed well, absorbing the impact energy by deforming without breaking, thus holding the road defence system together. This gave a greater impact resistance by maintaining the overall mass of the road barrier. The impacting vehicle suffered severe damage and was immobilised. See photos 7, 8, 9.

Test 2: Rear view after impact	Test 2: From inside the barrier	Test 3: From outside the barrier

Test 4: to enable vehicle access through the Dragon's Teeth VSB a 4.5m aperture swing gate has also been developed. The gate, supported by 3 Dragon's Teeth either side, comprises a single boom and is manually operated with a simple latching mechanism. The vehicle used was a 7.5t (N2) 2-axle rigid with an impact speed of 80km/h, so that the gate could be performance rated at a similar level to the original Dragon's Teeth VSB. The gate achieved a BSI PAS 68:2007 rating of V/7500/80/90 : 6.2/10.3.

As before, previously impacted Dragon's Teeth could be used to assemble and support the swing gate. The impact resulted in the gate boom deforming significantly before unlatching. The impact caused severe damage to and immobilised the vehicle. See photos 10, 11, 12.

Test 4:	Test 4:	Test 4:

The Dragon's Teeth VSB has also been subjected to blast testing to further evaluate its performance.