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Equipment Tests > Bullbars - customised
Bullbars - customised
Issue: December 2005
"A bullbar could mean the difference between a very long walk home and an anecdote about crazed wildlife on Australia's highways".
The words of one of our writers five years ago are still just as relevant today. But creating a custom-fitted bullbar is a big job. So how's it done? ARB's design department in Kilsyth, near Melbourne, showed us how. Manufacturing a bullbar requires careful consideration of a number of factors to ensure it properly serves its purpose.
Factors such as vehicle design, crush rate, airbag deployment, approach angle, accessory fitment, strength, weight and aesthetics are addressed in every bullbar before it enters production. All bullbar projects start with a marketing decision - is there a good market for it? Once marketing gives the green light and has procured a vehicle, the engineering team moves in. First thing to do is disassemble the front of the vehicle to see what the team has to work with. Modern 4WDs like the Discovery 3 are more complex than say Defenders or utes, as engine bays are becoming more crowded. At the same time, bumpers are becoming bigger, and things like washer bottles are being pushed out to reside within the bumper. That makes life difficult if the bumper is being replaced with a bar, so the engineers relocate, design around or replace. As ever, it's a trade-off between function, cost of production, aesthetics and robustness. All this design work is done on computer, using very precise 3D models of the vehicle created by a 'Faro arm'. This is an incredibly clever device - you tap its pointer on an object, then move it smoothly over the surface and it creates a 3D model, as it knows how far you've moved the pointer in x, y and z dimensions. It's a little like a GPS receiver's tracklog, but far more accurate, and takes a full day to properly map the front of an average 4WD. An engineer uses a Faro arm to create a precise 3D model of the Discovery 3.
The bar design also needs to accommodate a winch. Which winch depends on the vehicle, and in the case of the 2600kg Discovery 3, a 9500lb low-mount was selected as the winch to have. The bar also needs to feature two aerial mounts, and take two large spotlights. Once the bar itself is designed, the next step is designing the mount onto the vehicle. As ever, the newer vehicles are more difficult because many don't have two large chassis rails sticking out the front begging to have high-tensile bolts slotted in. The Disco 3 has a (high tech) separate chassis so bolting the bar on wasn't as hard as some of the now-common monocoque vehicles. However, it's not just a case of designing a robust mount and calling it good, because another problem - airbags, and the Discovery 3 has heaps of them. ARB goes to great lengths to make its bullbars airbag compliant, and the way it does that is based on one simple premise; don't change the crush characteristics of the vehicle. If they aren't changed, then all the safety features will work as designed. The difficulty of course is not changing those characteristics, and that needs testing. What ARB does is to recreate the equivalent part of the car where the bar will be mounted. In the case of the D3 that's just a Land Rover part (beam bumper front), which is replaced by an ARB impact absorber. So far we've dealt with force pushing the bar backwards, such as a large roo hitting it. But there's also the question of pulling force. Remember that the winch is on the bar, and that's trying to pull the bar off the vehicle. ARB designs the bracket so it's considerably stiffer and stronger when pulled as opposed to pushed, so the winch doesn't flex or stress the bracket. That's the red bracket in the above model of the impact absorber. So now the bar has been designed as a prototype. Now the bullbar has to be tested. The bar is fixed to the chassis, and so is the body but on flexible body mounts.
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That means the bar moves relative to the body, and some vehicles need a 25mm gap between bar and body. The Disco is particularly rigid and gets away with a 10mm gap. The winching capability needs to be tested too, with the most powerful winch the bar can take at maximum load (up a rocky hill, brakes on!), testing to see if anything breaks or deforms.
The final stage is tooling. Precision jigs need to be created, then it's time to get production going, the installation instructions written, the press releases out and Discovery 3 owners can enjoy the protection of a quality protective bullbar.
"A bullbar could mean the difference between a very long walk home and an anecdote about crazed wildlife on Australia's highways".
The words of one of our writers five years ago are still just as relevant today. But creating a custom-fitted bullbar is a big job. So how's it done? ARB's design department in Kilsyth, near Melbourne, showed us how. Manufacturing a bullbar requires careful consideration of a number of factors to ensure it properly serves its purpose.
Factors such as vehicle design, crush rate, airbag deployment, approach angle, accessory fitment, strength, weight and aesthetics are addressed in every bullbar before it enters production. All bullbar projects start with a marketing decision - is there a good market for it? Once marketing gives the green light and has procured a vehicle, the engineering team moves in. First thing to do is disassemble the front of the vehicle to see what the team has to work with. Modern 4WDs like the Discovery 3 are more complex than say Defenders or utes, as engine bays are becoming more crowded. At the same time, bumpers are becoming bigger, and things like washer bottles are being pushed out to reside within the bumper. That makes life difficult if the bumper is being replaced with a bar, so the engineers relocate, design around or replace. As ever, it's a trade-off between function, cost of production, aesthetics and robustness. All this design work is done on computer, using very precise 3D models of the vehicle created by a 'Faro arm'. This is an incredibly clever device - you tap its pointer on an object, then move it smoothly over the surface and it creates a 3D model, as it knows how far you've moved the pointer in x, y and z dimensions. It's a little like a GPS receiver's tracklog, but far more accurate, and takes a full day to properly map the front of an average 4WD. An engineer uses a Faro arm to create a precise 3D model of the Discovery 3.
The bar design also needs to accommodate a winch. Which winch depends on the vehicle, and in the case of the 2600kg Discovery 3, a 9500lb low-mount was selected as the winch to have. The bar also needs to feature two aerial mounts, and take two large spotlights. Once the bar itself is designed, the next step is designing the mount onto the vehicle. As ever, the newer vehicles are more difficult because many don't have two large chassis rails sticking out the front begging to have high-tensile bolts slotted in. The Disco 3 has a (high tech) separate chassis so bolting the bar on wasn't as hard as some of the now-common monocoque vehicles. However, it's not just a case of designing a robust mount and calling it good, because another problem - airbags, and the Discovery 3 has heaps of them. ARB goes to great lengths to make its bullbars airbag compliant, and the way it does that is based on one simple premise; don't change the crush characteristics of the vehicle. If they aren't changed, then all the safety features will work as designed. The difficulty of course is not changing those characteristics, and that needs testing. What ARB does is to recreate the equivalent part of the car where the bar will be mounted. In the case of the D3 that's just a Land Rover part (beam bumper front), which is replaced by an ARB impact absorber. So far we've dealt with force pushing the bar backwards, such as a large roo hitting it. But there's also the question of pulling force. Remember that the winch is on the bar, and that's trying to pull the bar off the vehicle. ARB designs the bracket so it's considerably stiffer and stronger when pulled as opposed to pushed, so the winch doesn't flex or stress the bracket. That's the red bracket in the above model of the impact absorber. So now the bar has been designed as a prototype. Now the bullbar has to be tested. The bar is fixed to the chassis, and so is the body but on flexible body mounts.
read on below advertisement
That means the bar moves relative to the body, and some vehicles need a 25mm gap between bar and body. The Disco is particularly rigid and gets away with a 10mm gap. The winching capability needs to be tested too, with the most powerful winch the bar can take at maximum load (up a rocky hill, brakes on!), testing to see if anything breaks or deforms.
The final stage is tooling. Precision jigs need to be created, then it's time to get production going, the installation instructions written, the press releases out and Discovery 3 owners can enjoy the protection of a quality protective bullbar.
