by "TheTurbochargedSquirrel" (thatsquirrel)
Published 11/30/2017 at 14:32
by "TheTurbochargedSquirrel" (thatsquirrel)
Published 11/30/2017 at 14:32
Tags: an unstoppable force meets an immovable object
; daydreaming with the squirrel
STARS: 0
I am daydreaming about adding a roll bar into my car to mount a harness to and for some extra protection when I start tracking the car. Simple enough concept however my car has side curtain airbags that will want to occupy the same space as the roll bar if they ever deploy. How would I go about getting these two to coexist with each other?
So for those who don’t know my intent with this car is to drive it as my daily, autocross, and track toy for the next several years until the time comes that I have a newer car as my daily and this car is going to be built for stage rally or road racing. As such my idea is to design and fabricate (with help from someone with cage building experience) my own main hoop, backstays, harness bar, and possibly main hoop diagonals such that they are a roll bar for now but I can add the missing bars later and have a FIA spec cage in the car (with my luck they will change the regs and foil my plan). The intention to build into a cage later means I would be trimming the interior panels back a bit and putting the main hoop closer to the shell of the car than an off the shelf roll bar.
This is what my car looks like with the headliner removed. You can see the side airbag along the top of the windows. I would like to maintain the front airbags while it is still my daily and an airbag fault would mean I would not be able to pass the state inspection so the side bags need to either stay in or be spoofed.
How would a side curtain airbag react to a roll bar like the one in the lead image? What if the bar was within, say, 1 inch of the undeployed bag? Just idle daydreaming for now, I probably won’t be acting on this project idea for a while.
"Spanfeller is a twat" (theaspiringengineer)
11/30/2017 at 14:40, STARS: 0
I have no experience, but I supose that...
Check where the headliner is meant to break when the airbags deploy and measure from there towards the inside of the cabin and stick the cage as close to the roof as you can so that it doesn’t mess with it, I suppose it probably has a thinner inner part (like with airplane tickets that are meant to be cut) and that might be a good place to start!
"e36Jeff now drives a ZHP" (e36jeff)
11/30/2017 at 14:41, STARS: 8
iirc, the side curtain are down-firing only, so if the rollbar is above and inboard of the top edge of the window they shouldn’t interfere with the airbags.
The real problem you will face is that should you be in an accident while on the road your squishy meat head will smack directly into the roll bar, which will cause significantly more damage compared to if you hadn’t installed roll bars. A cage, especially a cage that is in the vicinity of your head, is only safe if you are wearing a helmet designed to withstand impacts with roll bars(SA2010/2015 etc. M rated helmets are not designed to withstand rollbar impacts).
"Spanfeller is a twat" (theaspiringengineer)
11/30/2017 at 14:46, STARS: 0
he could also put the rollbar againts the unibody and change the airbag mounting point so that it is mounted on the roll bar.
But then the airbag would be too close, so I suppose that if he gets side-swipped he’s gonna end up looking like Harvey Dent.
Harvey Approves.
"nafsucof" (galinskiomatic)
11/30/2017 at 14:49, STARS: 0
Measure the resistance of the air bags and remove them and replace with resistors.
"TheTurbochargedSquirrel" (thatsquirrel)
11/30/2017 at 14:50, STARS: 0
The photos of the 2006 Cooper the IIHS tested show it popping out the bottom right above the pillar trim. I would assume my 2004 is the same but there are a number of differences between the 01-04 and the 05-06 facelift. The gas appears to deploy from the rear so I am wondering if I could pinch it a bit in the middle without introducing additional risk to front seat passengers.
If the main hoop is slightly to the rear of the b pillar like I am planning it might not even pinch that much and instead redirect the deployment towards the rear windows.
"crowmolly" (crowmolly)
11/30/2017 at 14:53, STARS: 0
The real problem you will face is that should you be in an accident while on the road
Also, he will have interfered with safety features of his car. Insurance companies don’t like that. Likewise with harnesses. They will have to be DOT approved and mounted in factory locations (or just leave your 3 points for street use).
"Spanfeller is a twat" (theaspiringengineer)
11/30/2017 at 14:55, STARS: 0
Guessing by the picture, the installation is going to be a pain in the ass, you’d need to make the rollbar sorta go inwards where the B pillar is, but if you’re a real human with legs, your head will probably hover around there. Plus there’s the helmet issue E36 mentioned.
Either you make it so inwards that its practically useless, or you make it wide enough that the airbags don’t fit and you’d need to remove them.
"TheTurbochargedSquirrel" (thatsquirrel)
11/30/2017 at 14:56, STARS: 0
I’m more just worried about how it would get pinched between the hoop and b-pillar.
Until it is a dedicated race car seeing minimal (if any) road use the main hoop will be the farthest forward point on the cage. The main hoop is behind the seat and outside of the reach of a head. When a full cage goes in all members that could be impacted by a head will be protected with appropriate SFI rated foam.
"fourvalleys" (fourvalleys)
11/30/2017 at 15:02, STARS: 4
As others have mentioned, you’re making safety sacrifices by trying to make a dual-purpose car. Safety equipment for the street is very different from safety equipment for the track.
I’m a huge supporter of not using a daily-driver as a track car, period. If you need to rely on it the next day, don’t trust the people around you to not push you off course or to not drop oil.
Put the money into a dedicated track car. Safety gear isn’t cheap, but it’s worthwhile to run a HNR in any car with harnesses. The financial side of it is important, too. I had a pretty minor run-in with a tire wall in my DD and it still cost me over $4000 out-of-pocket... and that was WITH track insurance. If the car wasn’t driveable, it would have been even more expensive to tow it home and rent a car while it was repaired. In any case, I sure wish I had that $4000 when I bought a dedicated track car.
"TheTurbochargedSquirrel" (thatsquirrel)
11/30/2017 at 15:02, STARS: 1
The factory 3 points are going to remain in place for road use. The harness I have at the moment is actually expired (as of the start of the year, allowing me to get it for free) and will only be used for autocross etc. before being replaced at a later date.
"Rust and Dust - Oppositelock Forever" (rustanddust)
11/30/2017 at 15:30, STARS: 1
That’s gonna be tricky, and if any of our automotive engineers are in the SRS side of things, they can probably contribute a bit more than I can. All of my education in SRS is from collision repair (safety procedures for service and replacement, vehicle structure rigidity and airbag timing, etc).
With the location of the roll bar in the photo, I
think
you’d be OK. Side curtain bags are essentially rolled up like an ships sail. When they deploy, they pop the restraining bands and unravel downward, protecting occupants from banging heads into glass/pillars in a side impact/rollover/sudden inertia change. When they deploy, they pop the tops of the pillar interior trim loose (upper clips usually have a retaining strap to allow them to come loose but not fly around the vehicle), fold the edges of the headliner down, and essentially unroll downward and inflate. They’ll be outside of your “oh shit” handles, while the roll bar appears to be “inside” the “oh shit” handles.
I actually just got a 2017 Tundra in with deployed bags, and snapped a couple photos to show how/where they deploy. It’s a completely different vehicle, obviously, but the theory is still the same.
(Would’ve added a few more photos, but Windows 10 CE and my Nexus 5X seem to no longer play nice together)
"TheTurbochargedSquirrel" (thatsquirrel)
11/30/2017 at 15:35, STARS: 0
As far as track time goes until I have moved to a new daily driver this car might see a track maybe once a year, probably more like once every 2 or 3. My dad and I are talking about doing a track day next summer but beyond that it would just be an occasional occurrence. In a few years when I buy a new daily driver this car is going to be come the dedicated track toy.
Like I said, I am mostly just daydreaming right now. I’m working on how to install a bar for the harness I have and going all the way to fabricating a roll bar is a good way to achieve that. I’m going to be removing the rear seats and making my own delete kit over the winter because I never use them (you can’t even put someone in the seat behind me to begin with) and want to make a couch out of them. That also drops nearly 40 lbs and makes 2 large storage cubbies and a flat floor (the seats stick up a good 6 inches when dropped vs the floor behind them). Needless to say I have fallen down the rabbit hole a bit here.
"fourvalleys" (fourvalleys)
11/30/2017 at 15:46, STARS: 0
Needless to say I have fallen down the rabbit hole a bit here.
The problem with the rabbit hole is that you’re asking about safety. Street cars use a safety system designed to work together to protect you. Track cars and race cars use different equipment in a different system to keep you safe(r) on the track. Once you do one thing... you kind of have to commit to all of it if you’re actually interested in being as safe as possible.
It’s risky to run harnesses and a rollbar unless you’ve got the HNR to help reduce the risk of serious whiplash (or basilar fracture). The odds you’re wearing that on the street are low - a three-point belt and airbags will do so much more for you.
"TheTurbochargedSquirrel" (thatsquirrel)
11/30/2017 at 15:53, STARS: 0
I’m not using the harness on the street. The factory 3 point is going to remain in place for road use and probably never come out. The mounting for factory belts is far enough forward compared to where you want the main hoop for a relatively tall driver like myself that it is not obstructed by the hoop and can be used without issue. The front air bags and the silly little seat bags are staying until they have to go to meet racing regs (well past the point I would be streeting it).
"crowmolly" (crowmolly)
11/30/2017 at 16:02, STARS: 0
I got ya.
Just be aware that the bar pictured would fail with some sanctioning bodies. Bolt together is a no-no and the rear down bars are sketchy (to me at least).
And make sure you gusset the floor if you can’t mount to a frame rail.
"TheTurbochargedSquirrel" (thatsquirrel)
11/30/2017 at 16:13, STARS: 0
The only thing legal about that bar design is that it is made of tubular steel. The down bars are not even in the same time zone as the top of the hoop, I have no idea where they are going to in the back, bolt on harness bar, nowhere near the shell of the car. It was just a good example photo. Whatever I do will be built to FIA standards.
"ITA97, now with more Jag @ opposite-lock.com" (ita97)
11/30/2017 at 16:14, STARS: 2
While I don’t have an answer for the side air bag question, I can offer some general advice.
The idea of building the back half of a cage in a street car and building it out into a full cage later on isn’t bad, but you’re going to want to carefully target the sanctioning body and class you want to play in down the road. Sanctioning bodies have very, very specific rules for roll cages. The number, degree and placement of bends in each tube will be regulated, as are methods and amounts of attachment points. I’ve known more than one person locally who bought a car with an existing cage that was built for drifting and/or track days who later learned that they would have to cut out what was there and start over again from scratch to get an SCCA or NASA logbook issued to go racing for real.
In general, roll cages in rally cars and road racing cars are very different animals designed to do different things. Rally cages tend have most or all sections “X-ed” out, way more attachment points (even in places like A and B pillars), tons of extra gusseting and are usually made with larger tubing. Some of these differences would be illegal in many road racing classes. In a rally car, taking a side (or even shiny side down) impact into a tree at interstate speeds is a design consideration. In road racing, cage rules are developed for primarily for impacts into fairly broad things like walls and other cars.
My take on a quick read of FIA 253-8 is that while it might be possible to build a cage that could legally do both, you would probably end with less cage than you want for rally (and certainly with not nearly as many attachment points, which probably has performance consequences as much as safety ones in rally), and way too much cage for road racing. I suspect one would end up with a road racing car that is considerably overweight and relegated out of competitiveness on track, and a car with not nearly enough rigidity on a rally stage.
"TheTurbochargedSquirrel" (thatsquirrel)
11/30/2017 at 16:20, STARS: 1
I will certainly be looking at the different regulations for different types of racing. It’s honestly far more likely that it will end up as a stage rally car than a road racing car but we will see what the future holds.
"ITA97, now with more Jag @ opposite-lock.com" (ita97)
11/30/2017 at 16:28, STARS: 0
Rally would be a lot of fun. I’ve never seen a car that was built to do both rally and road racing. The hardware on rally cars is seriously cool stuff, but I also end up looking at it and thinking things like “those badass wheels are impressive in their ability to survive bumps, jumps, rocks and off-course excursions, but are at least 5lbs/wheel too heavy to ever consider running on my racecar.”
"TheTurbochargedSquirrel" (thatsquirrel)
11/30/2017 at 18:01, STARS: 0
A car to do both rally and road racing would have to have 2 different sets of suspension. A car set up for rally would a ton of fun on a track but would be rather slow.
On the topic of rally wheels being heavy most people don’t even bother to try to balance their gravel tires because it takes so much weight to offset the weight of the tire and the fact that they are going to be unbalanced by mud anyway.
"ITA97, now with more Jag @ opposite-lock.com" (ita97)
11/30/2017 at 19:39, STARS: 0
It sounds like you need two minis, and a daily driver. :)
"pip bip - choose Corrour" (hhgttg69)
12/01/2017 at 06:08, STARS: 0
remove the airbags.
"Cash Rewards" (cashrewards)
12/01/2017 at 09:33, STARS: 0
I don’t think any safety stuff was changed with the facelift. If I remember correctly, it was a slight hp bump, revised gearing, new tail lights, and optional diff
"TheTurbochargedSquirrel" (thatsquirrel)
12/01/2017 at 09:45, STARS: 1
Changes in the facelift as far as I am aware include new head and tail lights, new front and rear bumpers, revised gearing in the S, new gearbox for the Cooper, new dashboard, numerous other little interior changes. I know at least the driver and passenger front airbag was changed in the revision to match the new steering wheel and dash panels so it is possible the rest of the system was updated too.
"cluelessk" (cluelessk)
12/06/2017 at 15:40, STARS: 0
I would never daily a car with a full cage with regular restraints and seats. I wouldn’t want to remove somewhat modern safety equipment for a street car. The vehicles crash zones work along with the air bags and seat belts to soften hits. Full cage changes all of that.
Watch crash test videos to see how much you move in an accident. Depending on the hit, your head will hit the A-pillar bar.
"TheTurbochargedSquirrel" (thatsquirrel)
12/06/2017 at 15:53, STARS: 1
No full cage while it is a daily. The idea now is to build a rear half cage roll bar that can be built forward into a full cage down the line when the car becomes a full time race car. At that point the car will be a full on race car with all associated racing equipment.