We have created an extended arm prototype version of the current central mount bar. Our original central mount bar only and always allowed for only one width setting for mounting the Rock Flap arms. The new extended central mount bar allows for a second setting for mounting the Rock Flap arms, which provides for an additional 100mm wider coverage of the Rock Flaps.
Over the last couple of weeks, we have travelled one of these prototypes about 1500km up and down through Namibia, so we are comfortable that it works under specific conditions; with wider prototype testing, we now want to ensure that it is workable under most conditions.
Allow us to explain: the BOSKAR Original © Rock Flaps work very well; however, we originally designed them to fit perfectly behind the tow vehicle for a very specific reason – wind resistance. The issue does not exist at typical 4×4 or off-roading speeds, but at highway speeds.
We have found that if we extend the central mount bar by anywhere from 100mm to 150mm, the flaps cover a wider wheel basis of a wider vehicle or a wider towed caravan or trailer. Hoverer, the wider coverage comes at a terrible cost: because the outer edges of flaps are now hanging in the full force of the wind that flows around a vehicle travelling at speed. The flaps tend to ‘wind-flap’ quite a bit should the vehicle travel as speeds above 90km/h. If the vehicle travels faster, say at standard 120km/h highway speeds, and there is an additional wind load of a normal 15 to 30 km/h head-wind from either directly in front of the vehicle, or coming anyway in a 1° to 60° left or right from the direct front the vehicle, the resultant wind-load of as much as 160km/h, can either directly bend the central mount bar, or induce vibration which results in heat-induced metal fatigue. This specifically happens around the compression edge of the central mount bar.
In all of the above the actual Rock Flap portion remains functional, but the central mount bar can become compromised. It must be understood that the central mount bar must be able to bend for normal 4×4 or off-roading use to ensure the flap arms don’t bend or buckle destructively. This ensures only one, cheap component needs replacement in the worst-case scenario, and not the more expense flaps.
We have now created the prototype (after several tens of attempts) with an extension, with both the original hole set and with an additional hole set. The original hole set allows the flaps to be set safely behind the vehicle for travelling at speed, and the wider set allows for the flaps to be extended that little bit to protect a wider wheel basis of a wider vehicle or a wider towed caravan or trailer. Testing thus far resulted in a workable configuration under the conditions we experienced.