johnc Posted September 18, 2008 Share Posted September 18, 2008 From: http://www.howwedrive.com/2008/09/16/all-over-in-the-blink-of-an-eye-but-not-the-minds-eye/ “This is a reconstruction of a crash involving a stationary Ford Falcon XT sedan being struck in the driver’s door by another vehicle travelling at 50 km/h. One millisecond equals 1/1000th of a second. 0 milliseconds - An external object touches the driver’s door. 1 ms - The car’s door pressure sensor detects a pressure wave. 2 ms - An acceleration sensor in the C-pillar behind the rear door also detects a crash event. 2.5 ms - A sensor in the car’s centre detects crash vibrations. 5 ms - Car’s crash computer checks for insignificant crash events, such as a shopping trolley impact or incidental contact. It is still working out the severity of the crash. Door intrusion structure begins to absorb energy. 6.5 ms - Door pressure sensor registers peak pressures. 7 ms - Crash computer confirms a serious crash and calculates its actions. 8 ms - Computer sends a “fire†signal to side airbag. Meanwhile, B-pillar begins to crumple inwards and energy begins to transfer into cross-car load path beneath the occupant. 8.5 ms - Side airbag system fires. 15 ms - Roof begins to absorb part of the impact. Airbag bursts through seat foam and begins to fill. 17 ms - Cross-car load path and structure under rear seat reach maximum load. Airbag covers occupant’s chest and begins to push the shoulder away from impact zone. 20 ms - Door and B-pillar begin to push on front seat. Airbag begins to push occupant’s chest away from the impact. 27 ms - Impact velocity has halved from 50 km/h to 23.5 km/h. A “pusher block†in the seat moves occupant’s pelvis away from impact zone. Airbag starts controlled deflation. 30 ms - The Falcon has absorbed all crash energy. Airbag remains in place. For a brief moment, occupant experiences maximum force equal to 12 times the force of gravity. 45 ms - Occupant and airbag move together with deforming side structure. 50 ms - Crash computer unlocks car’s doors. Passenger safety cell begins to rebound, pushing doors away from occupant. 70 ms - Airbag continues to deflate. Occupant moves back towards middle of car. Engineers classify crash as “completeâ€. 150-300 ms - Occupant becomes aware of collision.†The reason why I post this here is to highlight a couple items that need to be thought of when reinforcing the S30 chassis for racing. 17 ms - Cross-car load path and structure under rear seat reach maximum load. This is the whole point of a roll cage/bar structure - to transfer load from one part of the chassis to another, spreading the load out and adding extending the amount if time before the force of the impact gets transmitted to the driver. 27 ms - Impact velocity has halved from 50 km/h to 23.5 km/h. A “pusher block†in the seat moves occupant’s pelvis away from impact zone. Airbag starts controlled deflation. Seat mounting is critical. The seat mounting system must be able to control and move the seat and driver inward during a side impact while handling a load of up to 4,000 lbs. Ideally the seat mount SHOULD deform the transmission tunnel on a hard side impact to move away from the hit. This deformation must be controlled and kept to a few inches at most. 30 ms - The Falcon has absorbed all crash energy. Airbag remains in place. For a brief moment, occupant experiences maximum force equal to 12 times the force of gravity. At this point all the energy has been absorbed into the chassis, but its still deforming from inertia. 45 ms - Occupant and airbag move together with deforming side structure. A key point, the driver, safely strapped into the seat and securely mounting into the chassis, is moving with the deforming side structure. Building the seat mounting so that it resists any movement will make the driver and seat part of the impact structure. Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted September 18, 2008 Share Posted September 18, 2008 Interesting read, thanks! Quote Link to comment Share on other sites More sharing options...
Xander Posted September 18, 2008 Share Posted September 18, 2008 150-300 ms - Occupant becomes aware of collision.†Why is it that we are always the last to get informed about something big happening Quote Link to comment Share on other sites More sharing options...
johnc Posted September 18, 2008 Author Share Posted September 18, 2008 Why is it that we are always the last to get informed about something big happening Probably because we're on the phone or texting when the car hits us in the driver's door... Quote Link to comment Share on other sites More sharing options...
COmputoman Posted September 18, 2008 Share Posted September 18, 2008 The time line for a z collision is probably a lot shorter. 1Ms Car touches z 4Ms z starts to crumple 15 Ms Z turns into tin can being stepped on 300 Ms Driver wishes he had welded a roll cage Quote Link to comment Share on other sites More sharing options...
katman Posted September 18, 2008 Share Posted September 18, 2008 Probably because we're on the phone or texting when the car hits us in the driver's door... LOL!! Quote Link to comment Share on other sites More sharing options...
DavyZ Posted September 19, 2008 Share Posted September 19, 2008 ...Ideally the seat mount SHOULD deform the transmission tunnel on a hard side impact to move away from the hit. This deformation must be controlled and kept to a few inches at most. Interesting thought. The mount should deform, but the seat certainly should not! My brother and I owned a Datsun 510 in high school. He was T-boned by a Ford LTD and the Recaro steel seat structure is what kept the door from really messing him up, or so a few said at the time. I can't remember if the mounts broke or not, but the seat was moved to the center of the car--that much was true! Thanks for the read. Makes one think about the Z... Davy Quote Link to comment Share on other sites More sharing options...
DemonZ Posted September 19, 2008 Share Posted September 19, 2008 Fully stopped in 405 gridlock, I got rear ended in the Honduh Accordian over the weekend. I broke the seat back and the seat scootcher-upper track thing, and I'm not a big guy. Poor brother in law sitting in back gets his knees crammed by my seat breaking. I don't know if it was designed to fail that way or not, because I seemed to have gotten bruised the least. My passenger did not break her seat, and her knees got banged into the dash. I must be slow because it was like 3000MS after the initial impact that I was like WTF just happened??!! (driver did not brake at all, no screeching tires, no nothing). 1ms after I realized I'd been rear-ended, surprise! a SECOND car bashes us again. The cabin stayed intact, though the roof buckled. I'm glad the car held up so good. Quote Link to comment Share on other sites More sharing options...
slownrusty Posted September 19, 2008 Share Posted September 19, 2008 Interesting read John! Yasin Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted September 20, 2008 Share Posted September 20, 2008 Thanks for the post John! Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 21, 2008 Share Posted September 21, 2008 I broke the seat back and the seat scootcher-upper track thing, and I'm not a big guy. Poor brother in law sitting in back gets his knees crammed by my seat breaking. I don't know if it was designed to fail that way or not, because I seemed to have gotten bruised the least. My passenger did not break her seat, and her knees got banged into the dash. Mercedes is known for their engineering of the seatback latches not to fail in a rear-end colllision. Something about Frau Knockwurst getting a high speed rearender and being ejected out into the unlimited lane where she lands through the window of Baron Von Shikelgruper's 969 at 320+ kph... Can't have people flying out the wrong ends of the car, they could hit and damage another vehicle! Impetus behind SCCA and most sanctioning bodies requirement for a seat-back brace. Luckily you only broke the seatback---you could have been in bro in laws lap...or worse, on the windshield (or through it) of the vehicle that impacted you from behind. As I recall there was quite the tabloid TV Show about rearward ejections some time ago. Collapsing the seatback totally compromises the entire seat belt system. You just slip out fron underneath it and bounce aroudn. Want some photos of a frontal offset crash test of a 1970 240Z at "35mph" against a Toyota Tacoma? http://www.cardomain.com/ride/2969745/9 I'd put up a teaser photo, but apparently the site is down for maintenance right now, and I can't access the 'small' format photo. Driver had fractured left hand, fractured left clavicle (got pinned three days later) bumps on knees, and abrasions on his right hand where it apparently slipped off the steering wheel and broke out the center pod of gauges in the 240's dashboard... Quote Link to comment Share on other sites More sharing options...
DavyZ Posted September 22, 2008 Share Posted September 22, 2008 Almost looks like DEATH. Davy Quote Link to comment Share on other sites More sharing options...
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