As far as I'm aware, the AirBag sensors are accelerometers that are computer controlled to deploy if a certain deacceleration figure is experienced.
The airbag compliance, is more so to do with the actual timing effectiveness of the sensors. This is largely achieved in the crush can or deformation zones where the mounting points are although they are not directly related to the airbag system per se, they would affect the forces distributed through the chassis and to the sensor.
It would be in the larger manufacturers commercial interest to state that they are the only legal/approved way forward, alot of articles appear to be bent that way. However, it seems to me that a well designed crumple zone on the mounting points would allow for compliance. I think this is what smaller shop rely on.
An interesting article on the matter where Toyota rep basically says that outside of full scale crash testing you'd be guessing as noone apart from them has the detailed design data. This appears to be saying that no other manufacturer has it right... so go figure, everyone is competing for the business.
Bullbar safety up in the air (drive.com.au)
A wee thought experiment: If i covered my front bumper with cardboard, or a plastic cover, or paint protection(!) would this mean i have to crash test it?
At what stage does it become a bar?
How can i demonstrate legally that cardboard doesnt affect the airbag system?
Can i remake the exact design of my bumper in alloy is that legal if its the same design?
My thoughts are that if it distributes crash forces to the correct place, and that place (mounts) have a slide-style crush box to prevent low speed impact airbag activation, then this would be a demonstrated design characteristic for not adversely affecting airbag conditions.
Even in saying this, airbag deployment at speed (real crash/head on etc) would not be adversely affected with a full solid steel bar mounted directly to the chassis as the deaccell and airbag controller conditions would be met easily.
Small shops have this worked out I reckon and understand exactly what would be required to not interfere with critical airbag timing. Even if it did, HOW WOULD YOU KNOW (noone has access to the vehicle manufacturers actual design characteristics)? The only real way appears to be full scale crash test of a vehicle and ARB and TJM DO NOT do this for majority of vehicles outside of supplying factory delivered ANCAP ratings.
I personally would have no problem in strapping a full alloy bar on the front end as long as it didn't take me overweight if a supplier who would know much more about this stuff than i do, states that it has been built correctly.
______
EDIT: Re mounting, and why i think that the mounts are the thing that actually matter here
"The test is recorded using high-speed cameras and sensors fitted all over the test rig, and the results are checked to ensure the airbags only trigger when they’re supposed to and not earlier or as a result of an impact less than designed for.
The high-speed footage, when played back in slow motion, also allows the TJM testers to check deceleration rates. Measurements are also taken of the bar deformation and
how far it has moved within TJM’s patented mount system. This mount system is designed to absorb the energy of the impact, thus minimising how much of the force of impact gets transferred to the occupants within the vehicle, as well as how much load transfers into the chassis itself."
Engineering ADR-compliant gear (whichcar.com.au)
_____
Happy reading!
Reuben
