Thread: Airbags, bull bars and kangaroos

If hitting a roo triggers your airbags then either the roo is filled with reinforced concrete and bolted to the road, or the bar was grossly badly built and put a huge jolt through the body. The sensor looks at the deceleration rate of the vehicle and determines whether it is sufficient to require the bags to deploy (ie. are you being hurled from your seats). That's slowing a 2.5t car noticeably and very suddenly. Much, much more abruptly than the worst jolt you can create by spikiing the brakes (try that as a reference point). Even a big (~75kg) squishy roo just can't generate any meaningful slowing of a huge lump of car. I have done much testing for a couple of OEMs on exactly this. Just not going to happen...

Originally Posted by DiscoClax

If hitting a roo triggers your airbags then either the roo is filled with reinforced concrete and bolted to the road, or the bar was grossly badly built and put a huge jolt through the body. The sensor looks at the deceleration rate of the vehicle and determines whether it is sufficient to require the bags to deploy (ie. are you being hurled from your seats). That's slowing a 2.5t car noticeably and very suddenly. Much, much more abruptly than the worst jolt you can create by spikiing the brakes (try that as a reference point). Even a big (~75kg) squishy roo just can't generate any meaningful slowing of a huge lump of car. I have done much testing for a couple of OEMs on exactly this. Just not going to happen...

Just the sort of info I wanted, I honestly didn't think it would otherwise it would be a flaw. I just never thought of it before and it just raised a few questions.
Other than the big old F truck i had the other cars/utes were much lighter than the disco.
Glad to hear I'm not going to get blown in the face if a sensor gets smashed up.

Cheers Jim

Have a look at this,a large 'roo will definitely set off airbags.Bar or no bar.
These are D3/4,but i wouldn't have thought a D1 would be any different.In fact being lighter,a D1 would decelerate faster i would have thought,than a D3/4.
I have seen a pic of the same thing happening to an LC200.


Hit large Roo...

Wow. That should not have happened. Seriously. Something is not right there. The amount of deformation on that bullbar is negligible. Looks like it had just rotated about the collapsible mounts a bit and not translated rearward at all really. The first ~2" of bumper/bar compression manages the crash pulse through the critical phase. If you get through that you are pretty much into a "must fire" event as you are starting to load up your chassis rails and get some significant deceleration happening. Then it comes down to timing of the deployment so the airbags catch you and don't smack you in the face or deflate before you get there. But in the first two inches you generally shouldn't see a deployment, even into a rigid wall... If the driver and passenger in that vehicle didn't have some mild facial abrasions from contacting the bags, it shouldn't have fired (ie. they didn't actually do anything).

I didn't think D1s had decelerometers like D3s etc. I thought they just had simple switches in their crush cans at the front of the chassis rails so that when the crush cans deformed it activated the switch and set the airbags off.

Not sure about the D1 but the soft dash RRC's have the SRS sensors bolted to the sides of the battery trays, left and right. I suspect the D1 ones would be the same. One roo would decelerate a sensor quite adequately without a roo bar fitted if it hit the vehicle in the right place.

I have hit roos in various brands of cars fitted with roo bars and air bags and At No time did the air bags deploy.
I once hit a bid red buck at 130 which destroyed the alloy roo bar on a ford transit without the air bags deploying, However when i was involved in a head on crash as a passenger in the very same ford transit the bags deployed perfectly.
In my experiance it takes a hell of a lot of inertia to deoy the airbags and even a full sized boomer wont impart enough inertia to deploy the bags on a large heavey vehicle.
maybe if you hit a decent roo in one of thise piddly little buzz boxes that pervade the cities and even the bush the bags may go off But not in a D1.

My missus hit a roo in my D1 before the (NON SRS BULLBAR) was installed. 60-80kph
Did a bit of damage, broken plastics, however it did NOT set off the airbags.

I thought they might have been faulty but after reading this thread im not so sure now.