A Question About Garage Door Speed

So, as part of a haunted house story, I have an idea where a garage door would come down so quickly that it would slice through a pickup truck's roof, and pulverize someone's skull. My question is: Is that possible? And more broadly, how quickly can a garage door come down if say, something breaks?

 

well, i suppose that depends on the size and the type of garage door. Our garage door was light enough that my dad could kinda lift it, as the track it had helped a little, but the moment he let go it fell fast with a big thud so if it breaks i imagine it could grievously injure someone, though idk about pulverize.

 

Fair enough. Happy to know your dad wasn't hurt by it in this case.

 

Well, I wanted to know how implausible it was because I wanted to write an investigator noting the implausibility about it in disbelief. If garage doors could do this all the time, well, it wouldn't come off as implausible then, and the investigator's perspective wouldn't make sense.

 

I'll vote for impossible.

The house I live in has the original garage, with a wood door that's 8 feet wide and 8 feet high and VERY heavy. It's on an electric opener, but (like all overhead garage doors in the U.S.) counterbalanced by two heavy coil springs. This door didn't have an electric opener for the first 35 or so years of its life -- my brother and I installed it for our mother after our father died and Mom's health and strength began to degrade.

There is also a detached 2-car garage with doors that are 8 feet wide and 7 feet high. These are also wood construction, albeit significantly lighter in weight than the first door. These also have electric openers, and they are also counter-balanced by coil springs. On all the doors, we have experienced coil spring failures over the years. With one spring broken, the 8-foot high door is heavy, but can be opened by an adult without the electric opener. The 7-foor high doors are of lower quality; if a spring breaks on one of those, the door gets crooked in the track and can't be closed at all.

When we replaced the springs on one of the 7-foot doors, we bought the wrong springs. With that one, it now opens itself to a height of about two feet unless latched, or restrained by the door opener.

Consider also that for an overhead door with an electric opener to fail and fall, TWO things have to fail: First, the electric opener has to fail in such a way that the mechanism totally loses control of the door; in addition, at least one of the counter-balance springs has to break.

In the unlikely event that such a double failure should occur, even my heavy door could not slice through a vehicle roof and kill an occupant. That door is heavy enough to put a severe dent in a vehicle's roof but not heavy enough to kill an occupant of a vehicle.

 

If it's a regular residential garage door, I doubt it, unless it's been rigged Jigsaw style. My understanding is that modern car roofs are supposed to withstand about 1.5 times their weight but that's for rollover crashes, not an evil clown house garage door with tempered steel blades that could slice through along a set plane.

You might want to ask a physics forum, as I think the weight of the door, the angle of the tracks and number of wheels on the tracks will be factors.

The tracks on my garage door look like they are made of aluminum, and sometimes when it gets really cold, the garage door becomes stuck or gets off track, presumably due to the tracks contracting in size (I think). I can usually fix it with a hammer though, using the nail remover portion to push it back on track. My only point is that when a garage door falls due to some failure, unless it's rigged, there may be some friction to slow it down, reducing the force on the car below.

But industrial garage doors may be different, and possibly have more vertical tracks (i.e. straight up and down instead of curved like mine).

 

Okay, the last part matters a lot here, and was why I started this thread. In hindsight I should've guessed this from the wood construction, but still, this is good to learn.

 

That original, wood garage door dates to 1950. Modern garage doors are MUCH lighter in weight, typically with an aluminum or vinyl skin over a layer of foam insulation.

A potentially more dangerous failure (which might or might not fit your story) is the coil springs themselves. When the door is up they are mostly relaxed, and they are dully extended when the overhead door is closed. They store a considerable amount of energy. When they fail, they can launch pieces with enough energy to seriously injure someone. Today they are required to have a safety cable running through them to capture the segments when (not if) the springs break. That was not required when my house was built in the 1950s -- I don't know when it became mandatory.

 

More realistic would be for the garage door to break, someone to check the spring (which is dangerous on its own, even without the ghost, but a lot of people do it anyway) and they get killed that way.

 

I'd vote for plausible with a later explanation. I mean, it's a haunted house, so maybe the original owner was a psychopath mechanical engineer who made devastating inventions. I mean, NO one expects that from a garage door. So...it makes it interesting. (That said, you'll have to be diligent in creating a scenario where it makes sense. You can make your own rules as long as you stick to them. Maybe have other household gadgets go nuts.)

I should add...in real life, I've never heard of that kind of thing happening...

 

As you have described it, it doesn't sound very plausible. It would however be very easy to use the poltergeist to trigger this to happen. It runs on magic. Also couldn't you use the other objects in the garage to kill someone? A flying circular saw would be just as deadly as the garage door. A lit match into the gas tank of the car would be equally deadly too. Obviously the poltergeist is responsible.

 

For a haunted house story? Plausible...I mean look a the entire Final Destination franchise...it is built entirely on people dying based on extremely implausible ways. I'm with @Homer Potvin that if someone is reading a story about a haunted house they are already suspending their disbelief so a ghost-induced garage door accident is hardly far-fetched.

 

I think the reason for the OP's original question was that an investigator would be reading the report, and whether his reaction that the accident seems so implausible to be either supernatural or foul play is a legitimate reaction his character would make.

 

But isn't that the whole point? How many books/films have been made with the trope that someone experiences some supernatural occurrence followed by an investigation that shows no evidence that it could have occurred at all...

 

A pickup's cab is also too high to allow for much acceleration of the door prior contact.

I like the convertible idea.

 

I remembered a news story about a lady whose garage door was missing a safety feature and it fatally pulled her up into the mechanism as it opened.

https://www.dailymail.co.uk/news/article-3741798/Woman-dies-getting-caught-automatic-garage-doors.html

Perhaps this is an area where the truth is more horrific than the fiction. I'd suggest to research how automated doors really have killed people, and to re-arrange the scene around a plausible (.: relatable) accident. I have a security gate at the front of my house and the installers were at pains to explain all the safety features they have to add by law - e.g. computer logic to help it guess if it's squashing someone - but my perception is that anything that happened would be slow and horrible.

I take the point raised by others that there is some suspension-of-disbelief in horror anyway - and some creative license. But that's a precious resource, and usually horror should leverage the mundane as far as possible before wheeling the ghoulie out onto the stage and showing that we're all mortal, we die in ridiculous or even comical accidents - and if that wasn't bad enough, there's a malevolent, supernatural logic to it all. (Which the ghost or monster embodies at the end of the story so that it can be purged from the reader and their community).

For any accident the door and the truck might have to be established - with the unusual features (or lack of them) the scene requires to be plausible. The doors on a barn or an aircraft hangar might give you a nasty clonk - but to crush someone's skull through the top of a truck that's designed to keep people alive in a 70+ mph impact with another ton+ also-steel vehicle - it's virtually inconceivable with anything they have ever put on houses. In London some mansions have underground car parking with security gates - but those specifications have tended to grow in line with the safety features.

What if the accident was framed differently? The character gets out of the car, but (as an anti-ghost tactic) they've left a whacking-great acro-prop balanced next to the mechanism - and it topples on their head while they're locking the car.

 

Yeah, this.

I've moved away from this idea primarily because a garage door with the strength to slice through a truck's roof is going to be very obvious, as it would need be made of steel, or some other material that doesn't make sense for a garage door. Otherwise, it doesn't matter how quickly the door drops, because it doesn't have the weight or strength to get through the roof of a pickup truck, or similar vehicle.