Safety Engineering Opportunity?

[GerryO]

All other contributing factors and bad decisions aside, how can cars with electric windows and doors locks be made safer in terms of making underwater escapes more successful?

http://www.tracypress.com/pages/full_st ... id=9582145

Don't know the general condition of the car as a result of the accident, if seat belts were worn, the official causes of deaths (drowning or other injuries?) and if airbags deployed. All very tragic, and it would seem that a small number of sensors and new safety features might help prevent similar deaths.

http://lfsv2.securesites.net/issues/art ... icles.html

Several people I work with are friends of the girl, straight A student/only child, who should have started attending classes at UC Davis this week, and another mother lost both a son and a daughter in the same accident.

[AZhitman]

Interesting... Seems to me it wouldn't be hard to engineer some sort of internal switch (maybe inside the doors) that actuates the windows to go down IF the switch is submerged.

[C-Kwik]

All other contributing factors and bad decisions aside, how can cars with electric windows and doors locks be made safer in terms of making underwater escapes more successful?

My understanding is that the window switches are required to work underwater for a certain period of time. Maybe even the door lock switches as well. I'm not sure I'd want windows to open automatically either. A sealed up car buys some time to gather yourself. A violent impact can leave you dazed and disoriented. Automatically unlocking doors can certainly have some value though.

[Hijacker]

I'm confused. Did Greg bump a 2 year old thread?

The issue with the windows and doors isn't whether they work when submerged. It's a matter of the pressure being exerted from the water outside the vehicle. Enough force is applied on the window and door to make it impossible to actuate the window motor or open the door until the pressure has equalized on both sides of the door. Mythbusters devoted an episode to submerged escapes, and they found that the only real way to get out was to let the car fill up, open the door, and then swim up. There are devices on the market that are designed to shatter a window if the car becomes submerged, so that's an option as well.

One last thing. even if the switch can operate submerged for X length of time, it does no good if the fuses pop from shorting when the system gets submerged. You'd have to waterproof a closed circuit for it to work.

[C-Kwik]

I'm confused. Did Greg bump a 2 year old thread?

Didn't even notice the date. Greg is probably trying to pad his post count.

Actually, I'd guess he was going through unanswered posts or something.

The issue with the windows and doors isn't whether they work when submerged. It's a matter of the pressure being exerted from the water outside the vehicle. Enough force is applied on the window and door to make it impossible to actuate the window motor or open the door until the pressure has equalized on both sides of the door. Mythbusters devoted an episode to submerged escapes, and they found that the only real way to get out was to let the car fill up, open the door, and then swim up. There are devices on the market that are designed to shatter a window if the car becomes submerged, so that's an option as well.

Was the water pressure enough to keep the window from opening? It plausible in my mind, but ultimately depends on the pressure differential and the surface area of the window.

One last thing. even if the switch can operate submerged for X length of time, it does no good if the fuses pop from shorting when the system gets submerged. You'd have to waterproof a closed circuit for it to work.

Depends. Water is non-conductive in pure state. As solutes are dissolved in it (especially ionic solutes), it becomes more conductive. I suspect most bodies of water are fairly low in conductivity (excluding seawater). There are a few scenarios I can think of. If the fuse itself is submerged, the voltage potential across the fuse won't be very high so little to no current would travel through the fuse. If the battery is submerged, the voltage potential across the water will not include the fuse. Lastly, if the component in the circuit is submerged, the high resistivity of the water would just act as a parallel resistor. And unless the component is on, the current will be limited to that dictated by the resistivity of the water. As an initial assessment, I don't see any particular reason fuses would blow (the resistivity of fresh water appears to be in the kilo to mega ohm order of magnitude; saltwater can be problematic). I suspect there would be a negligible problem with the potential for voltage drop due to excess current as well as I can't think of a scenario where the water would be in series as part of any circuit.

[Dattebayo]

One of these saved my aunt's friend one time last year in Florida when she fell asleep at the wheel and drove off a bridge.

[Hijacker]

http://mythbustersresults.com/episode72

Found the episode with results.

Depends. Water is non-conductive in pure state. As solutes are dissolved in it (especially ionic solutes), it becomes more conductive. I suspect most bodies of water are fairly low in conductivity (excluding seawater). There are a few scenarios I can think of. If the fuse itself is submerged, the voltage potential across the fuse won't be very high so little to no current would travel through the fuse. If the battery is submerged, the voltage potential across the water will not include the fuse. Lastly, if the component in the circuit is submerged, the high resistivity of the water would just act as a parallel resistor. And unless the component is on, the current will be limited to that dictated by the resistivity of the water. As an initial assessment, I don't see any particular reason fuses would blow (the resistivity of fresh water appears to be in the kilo to mega ohm order of magnitude; saltwater can be problematic). I suspect there would be a negligible problem with the potential for voltage drop due to excess current as well as I can't think of a scenario where the water would be in series as part of any circuit.

In a perfect world. Unfortunately, 99.9% of the worlds water isn't de-ionized and is full of minerals and other good conductors. My biggest concern is the battery arcing and shorting out. Most automotive batteries aren't built like marine batteries and can't survive arcing out from submersion. Of course, I'm not gonna toss any of my vehicles in the river behind my house to see how long I can use the electricals before they short out to test it. Mythbusters say I can use my windows for a few minutes after submersion, then so be it.

[C-Kwik]

In a perfect world. Unfortunately, 99.9% of the worlds water isn't de-ionized and is full of minerals and other good conductors. My biggest concern is the battery arcing and shorting out. Most automotive batteries aren't built like marine batteries and can't survive arcing out from submersion. Of course, I'm not gonna toss any of my vehicles in the river behind my house to see how long I can use the electricals before they short out to test it. Mythbusters say I can use my windows for a few minutes after submersion, then so be it.

Sea water is the biggest concern. It appears to have a resistance of about 0.2 ohms. At 12 volts, that's a current of 60 amps. The other figures I posted were figures for naturally occurring water. Depends on the mix, but the lowest of the range was almost in the kilo-ohm range. This would put you in the milli-amp range as far as current is concerned.

http://water.epa.gov/type/rsl/monitoring/vms59.cfm

Even industrial wastewater would only draw 0.12A. Though, I'd be more concerned about other things than drowning. Either way, there isn't nearly as much opportunity to drive off into the ocean. And salt heavy bodies of water inland are pretty rare. Just not something I'd be concerned about statistically.

[AZhitman]

I'm confused. Did Greg bump a 2 year old thread?.

*SOMEONE* needs to pop into the Mod forum on occasion...

[Hijacker]

I check the mod forum every day :P