How fast is too fast?

[TheManicMonocle]

So, let's suppose you have a car, let's say a honda accord built in the last five years (for arguments sake), and you magically can make it go super fast somehow. The how isn't important, my question is, how fast can a car go before it starts to break apart?

[Gnoman]

The car falling apart isn't the biggest problem you'll face. Once you get up past 150 MPH or so, the car will start to fly, at which point you have no control and turn into a very short ranged ballistic projectile. That is why the cars in most autosports that aren't NASCAR have spoilers - they keep the car from lifting off.

[Dodom]

I didn't find data on exact speeds and car models involved, but quite a lot of engines meet their doom on the Autobahn due to overheating, so around those 240 km/h speeds, a car is already at risk of damage.

[Peelee]

The car falling apart isn't the biggest problem you'll face. Once you get up past 150 MPH or so, the car will start to fly, at which point you have no control and turn into a very short ranged ballistic projectile. That is why the cars in most autosports that aren't NASCAR have spoilers - they keep the car from lifting off.

I don't think an Accord will get airtime at 150. It's not the most aerodynamic design. Imean, a brick'll fly of you get it going fast enough, but the speed kinda depends on the shape, doesn't it?

[TheManicMonocle]

Either way, let's assume that your goal is to break apart the car, maybe so a scene in a book your writing makes sense..

[Miklus]

The tires on your Hando Accord is probably rated at 190kmh as the maximum sustained speed they can tolerate. I don't know at what speed they will fly apart, but there is a tire speed rating system in place for a reason. I would guess the tires would be the first thing to go, before the Honda takes off into the air like Gnoman suggested.

[Trekkin]

Either way, let's assume that your goal is to break apart the car, maybe so a scene in a book your writing makes sense..

Well, how broken do you want it? Caving in the windshield requires much lower speeds than turning it into a quark-gluon plasma, which would presumably total it.

[Excession]

So, let's suppose you have a car, let's say a honda accord built in the last five years (for arguments sake), and you magically can make it go super fast somehow. The how isn't important, my question is, how fast can a car go before it starts to break apart?

This is what happens when you try to set a speed record and something goes wrong. Tire exploded while trying to reach 220mph.

That was with a car designed for speed, modified for racing; I suspect the driver wouldn't survive in a stock Accord. As it was, an ambulance officer fainted at the scene, so I'm sure it wasn't pretty. Three months in hospital, years of rehab, and he never regained full use of the arm. From the article "parts were strewn along the route until we eventually got to the shell of the car...", does that match the degree of destruction you want?

[factotum]

Why does it specifically have to be speed that causes the car to break apart? A tyre blowout at even quite reasonable speeds can easily lead to a high-speed roll or an unscheduled trip into the nearest tree or street light. Just found this example of the sort of damage that can occur at relatively low (e.g. city driving) speeds:

http://koin.com/2017/02/05/car-cut-i...gresham-crash/

[Lord Torath]

What If: How fast can you hit a speed bump while driving and live? suggests that 200 mph is average lift-off speed, if you don't have spoilers giving you negative lift.

The bottom line is that at somewhere in the range of 150-300 mph, a typical sedan will lift off the ground, tumble, and crash ... before you even hit the speed bump.

If you kept the car from taking off, the force of the wind at those speeds would strip away the the hood, side panels, and windows. At higher speeds, the car itself would be disassembled, or even burn up like a spacecraft reentering the atmosphere.

I recently heard a story on NPR that a 300 mph wind can suck you right out of your seat belt. An airline lost one of the cockpit windows (side window on the pilot's side, IIRC), and the pilot was sucked half-way out the window. A member of his flight crew held onto his legs until they could pull him back in.

[halfeye]

What If: How fast can you hit a speed bump while driving and live? suggests that 200 mph is average lift-off speed, if you don't have spoilers giving you negative lift.

I once worked for a company that had diagonal speed bumps on their private roads. Those things were very effective, at high speed they'd probably roll a car right over.

I recently heard a story on NPR that a 300 mph wind can suck you right out of your seat belt. An airline lost one of the cockpit windows (side window on the pilot's side, IIRC), and the pilot was sucked half-way out the window. A member of his flight crew held onto his legs until they could pull him back in.

That's probably due to the pressure difference at altitude (the wind speed oughtn't to do quite that much), but even so you'd need to be close to the window.

[Lord Torath]

Yes, the 300 mph wind that sucked the pilot out of his seat belt was due to the high-pressure inside air flowing to the low-pressure outside air, not the airplane's forward motion. Once the cabin depressurized, the wind dropped, and they were able to keep him from falling.

[Chen]

Yes, the 300 mph wind that sucked the pilot out of his seat belt was due to the high-pressure inside air flowing to the low-pressure outside air, not the airplane's forward motion. Once the cabin depressurized, the wind dropped, and they were able to keep him from falling.

Yeah the 300 MPH wind would have been opposing his motion towards the window (it was the front window of the aircraft). Goes to show how much force you get out of that kind of pressure differential.

[Jay R]

On a purely practical level, "too fast" is determined by your reflexes, reaction time, and level of focus - as well as the reflexes, reaction time, and level of focus of the other drivers texting on their smartphones around you. The car flying apart is the least of your problems.

You are traveling at high speeds whilst sitting atop several gallons of explosive liquid.

[wumpus]

The tires on your Hando Accord is probably rated at 190kmh as the maximum sustained speed they can tolerate. I don't know at what speed they will fly apart, but there is a tire speed rating system in place for a reason. I would guess the tires would be the first thing to go, before the Honda takes off into the air like Gnoman suggested.

I typed in "honda accord tires" and followed the first choice (except for choosing a "2017 car" and "the sporty option (of accord)"). It came up with tires that were rated to 270km/h (168mph*). This was a straightforward google search and not looking for the "fastest rated tire".

I'd also assume that a standard Accord would go airborne far earlier than 270km/h. While you can point out that plenty of spoilers/wings are available for this car, to actually give the car enough downforce to drive at 270km/h is likely going to crush an unsupported trunk (the cars weighs 1600kg (3500lbs), expect to need to add a significant amount to that). Generally speaking, it takes a lot of work to get rid of the lift when designing high-speed sportscars (while Accord engineers try to maintain "honda" looks, pedestrian safety, and gas mileage).

https://www.youtube.com/user/EngineeringExplained : everything you wanted to know about the science and engineering behind how a car works. Explained as simple as possible, but no simpler (an interview mentioned how he tries to remain focused on reducing the length of his videos and making them as easy to understand as possible). Oddly enough, he insists that tires are the best way to improve car performance. Not so much so you can drive faster without them exploding (I'm sure you have to modify a *lot* of other bits to get an Accord anywhere near 270mph (or more accurately, the next step down in performance ratings), but more for braking and handling (he mentioned he changed the tires on his sports car and it went from "needs more braking room than an Escalade" (with cheap tires) to "outbraking a the super-lightweight-sportscar from fiat" (with the new-improved tires). They weren't cheap, but try to imagine any other way to take you from escalade status to the top of the sports cars.

* This was a US rating. I'm not sure how accurate it is because products failing at 168mph is one of the few cases in the US a product liability lawsuit won't go anywhere once the judge finds out you were doing 168mph...

[Frozen_Feet]

On a purely practical level, "too fast" is determined by your reflexes, reaction time, and level of focus - as well as the reflexes, reaction time, and level of focus of the other drivers texting on their smartphones around you. The car flying apart is the least of your problems.

You are traveling at high speeds whilst sitting atop several gallons of explosive liquid.

The explosive liquid won't be much lf a factor, really. It's surprisingly rare for a car in a crash to light up, let alone explode.

The biggest problem when speeding like the Devil's on your heels is that the road prolly won't continue in a straight line forever, so eventually, if you don't slow down, you will fly out of the next curve. 100 km/h is pushing your luck on a twisty gravel road - 60 km/h if it's frozen.

[factotum]

The biggest problem when speeding like the Devil's on your heels is that the road prolly won't continue in a straight line forever

I dunno, the OP is from the USA and there are a couple of roads over there that are dead straight for 100 miles plus--plenty enough to get up to car-destroying speeds.

[golentan]

I don't think an Accord will get airtime at 150. It's not the most aerodynamic design. Imean, a brick'll fly of you get it going fast enough, but the speed kinda depends on the shape, doesn't it?

Please forgive me, gods of physics, I am about to use imperial measurements.

Curvature of the earth is about 8 inches per mile. The time to fall 8 inches is about 0.2 seconds. So at a speed of about 5 miles per second (300 miles per minute, 18,000 mph) no matter what you're driving it will miss the ground unless it's trying to plough through it.

Temporarily, anyway. Escape velocity requires an additional 2 miles per second.

Do mind the landing...

[factotum]

So at a speed of about 5 miles per second (300 miles per minute, 18,000 mph) no matter what you're driving it will miss the ground unless it's trying to plough through it.

I think the ground is going to be the least of your problems if you're attempting to achieve orbital velocity at ground level.

[wumpus]

The explosive liquid won't be much lf a factor, really. It's surprisingly rare for a car in a crash to light up, let alone explode.
The biggest problem when speeding like the Devil's on your heels is that the road prolly won't continue in a straight line forever, so eventually, if you don't slow down, you will fly out of the next curve. 100 km/h is pushing your luck on a twisty gravel road - 60 km/h if it's frozen.

Race car safety is rather concerned with fire. Don't expect to enter a race without being covered from head to toe in fire-protective gear (the difference between racecar helmets and motorcycle helmets is fire protection) and a fire extinguisher (presumably after putting in the roll cage, 4-5 point harness, helmet, HANS device you are likely to survive even a high speed crash (assuming you hit at a reasonable angle). You still have to worry about fire, and can expect a much harder time getting out of your car).

I dunno, the OP is from the USA and there are a couple of roads over there that are dead straight for 100 miles plus--plenty enough to get up to car-destroying speeds.

You mean like *everything* (ok, there are certainly plenty of cities. But lots of empty bits in between) between "the valley" of California and roughly Austin, Texas that isn't in a mountain? Not to mention plenty of other roads that don't have curves but do have traffic (I-95 [hits most major East Coast cities, probably the most driven in the country] is probably the chief example, but I-70 runs from Baltimore to Denver with few turns as well (I think after that it goes into mountains, so expect some turns).

On a lonely desert road, you can expect the basic physics issues. Tire failure, lift-off due to aero issues, heat issues (don't underestimate desert heat), armadillo and other wildlife (and tire bits) collisions [do *not* hit a cow]. Also don't run out of gas (easy to do at speed). Cars rarely go by and you really can't assume that anyone bothered to build a cell-phone antenna for the armadillos. You are likely to be a *long* way from a gas station (if you don't see signs saying "next gas station 300 miles" you aren't in the right place to try this sort of thing).

If you really care about this type of thing, look up "Bonneville Speed Week" and see what they do to avoid the various dangers. That event is pretty wide open (although expect to be required to make a bunch of safety-related modifications that will freak out your insurance agent). Similar events are held in places that can handle a U2 takeoff/landing.

[Bohandas]

I don't think an Accord will get airtime at 150. It's not the most aerodynamic design. Imean, a brick'll fly of you get it going fast enough, but the speed kinda depends on the shape, doesn't it?

Heck, IIRC even the Mythbusters' rocket car didn't lift off (the first one, not the one from the revisit that exploded, Though I suppose the second one one didn't either, not the whole thing at any rate, just parts of the top)

I dunno, the OP is from the USA and there are a couple of roads over there that are dead straight for 100 miles plus--plenty enough to get up to car-destroying speeds.

Indeed. Much of the country is uninhabited/uninhabitable wasteland, with roads just there to allow people to pass through, not to get to anywhere that's near the roads themselves. Presumably many of these roads would be straight and largely unoccupied

[Knaight]

Indeed. Much of the country is uninhabited/uninhabitable wasteland, with roads just there to allow people to pass through, not to get to anywhere that's near the roads themselves. Presumably many of these roads would be straight and largely unoccupied

The roads were also deliberately designed straight so that they could be used as runways in a pinch.

[Peelee]

I think the ground is going to be the least of your problems if you're attempting to achieve orbital velocity at ground level.

Well, in Kerbal Space Program....

The roads were also deliberately designed straight so that they could be used as runways in a pinch.

Nope. Myth.

Imean, it's not impossible there's a grain of truth to this, maybe some out in the desert in plains areas. But I doubt it.

[Larzzral]

I'm sure the OP loves how no one is focused on his theoretical dilemma where he states he doesn't care about all the other stuff, just at what speeds will the car fall apart.

Now as far what speed, over 300mph would definitely not tear you apart. In fact, with the way car panels are integrated into the frame, I'm thinking it would be rather extreme speeds. Now a car from the 80's or 90's where air resistance wasn't as great a design factor, speeds in the 200-300 may start taking parts off. And as soon as some flew off, more would fly off.

[wumpus]

I'm sure the OP loves how no one is focused on his theoretical dilemma where he states he doesn't care about all the other stuff, just at what speeds will the car fall apart.

Now as far what speed, over 300mph would definitely not tear you apart. In fact, with the way car panels are integrated into the frame, I'm thinking it would be rather extreme speeds. Now a car from the 80's or 90's where air resistance wasn't as great a design factor, speeds in the 200-300 may start taking parts off. And as soon as some flew off, more would fly off.

That's because "fall apart" isn't going to happen. The car will either become airborne and lose control and crash, blow out a tire lose control and crash, or overheat (possibly suddenly causing engine braking loss of control and crashing). Anything that interferes with keeping the direction the car is moving and tires aligned will cause the situation to get worse and worse until a crash, and this requires wildly less force than to rip parts off of a car.

Oddly enough, cars have been tested in wind tunnels since the 1980s and got reasonably good in the 1990s. The catch is that most people don't like the looks of a truly aerodynamic car, so they only make it "look aerodynamic" and try to avoid a really bad configuration ( this wiki has a list of drag coefficient). I don't really expect any parts to come off (rearview mirrors being an exception, and presumably they can handle a headwind going downhill), for a great test google the Top Gear episode of a turbo porsche racing a VW beetle (the beetle was simply dropped an equal distance). I don't think anything came off the beetle [before crashing] even at terminal velocity.

PS: what it takes to go 300mph: https://www.youtube.com/watch?v=F76-npz0CeI [again, engineering explained]

[Grey_Wolf_c]

The catch is that most people don't like the looks of a truly aerodynamic car, so they only make it "look aerodynamic" and try to avoid a really bad configuration

[citation needed]

I've checked the wiki page you linked to, and from what I can see, cars are getting more aerodynamic, and the concept car that seats more than one person look pretty average-looking to me. Yes, you can get a lot more aerodynamic, but not if you want a vehicle that can fit a family and groceries. In fact, I wouldn't call it a car at all - it is better described as an enclosed motorbike.

So, what truly aerodynamic looks are rejected, rather than functional issues (like extra internal space)? The only one I know of is the "golf ball surface" concept that mythbusters tested.

GW

[Lord Torath]

Indeed. Much of the country is uninhabited/uninhabitable wasteland, with roads just there to allow people to pass through, not to get to anywhere that's near the roads themselves. Presumably many of these roads would be straight and largely unoccupied

Maybe in the western desert states (Nevada, Arizona, New Mexico, West Texas, Southern Utah). Most of the country has people spread all over the landscape, in either cities, farms, or ranches.

There are also very few straight highways. If there are no natural obstacles (hills, canyons, mountains, buttes, plateaus, etc), the highway planners typically throw in a zig and a zag every few miles, just to help keep drivers awake^{[citation needed]}.

[halfeye]

[citation needed]

I've checked the wiki page you linked to, and from what I can see, cars are getting more aerodynamic, and the concept car that seats more than one person look pretty average-looking to me. Yes, you can get a lot more aerodynamic, but not if you want a vehicle that can fit a family and groceries. In fact, I wouldn't call it a car at all - it is better described as an enclosed motorbike.

So, what truly aerodynamic looks are rejected, rather than functional issues (like extra internal space)? The only one I know of is the "golf ball surface" concept that mythbusters tested.

GW

It's a strange thing, but the coupe is aerodynamically more efficient than a long tail.

[wumpus]

It's a strange thing, but the coupe is aerodynamically more efficient than a long tail.

That doesn't seem to match the data of crazed DIYers who build long-tailed cars. A kammback (think prius) is pretty close, but the long tail typically works a bit better at absolute drag reduction. The kammback is often best overall, due to lack of materials, weight, crosswind susceptibility, overall goofiness...

[MarkVIIIMarc]

Road quality becomes a real thing over ~110mph Corvette or Accord.

But assuming quality road we then worry about drive ability. having other cars out there even at non-rush hour makes speeds over ~110 quite dangerous

Straightness? The suburban Interstates here I'd venture my semi-sports cars can handle every turn on at just above 100mph. I see a pattern. Old stretches like I-70 through St Louis proper I am don't think so. Coming over the river it does something ill conceived diving off to the right after you go over the new bridge. Then up around Broadway there is that "soft left" which last time I ran it at ridiculous speed I straightened a bit by using a few lanes. Something newer like I-270 is much better.

Saying your tires are up for it, you run into drivetrain issues. My ancient MarkVIII has enough of an O/D to make speeds around 100 bearable. My Mustang is geared too low. My Aurora interestingly enough has no governor but falls in between on final drive ratio.

So my verdict is for real everyday 30minute commutes anything above 100mph and your car will soon come apart because of mechanical failure or hitting something.