pickup truck crash, would you want toolbox stored up against the cab, or at the back?

[CycloWizard]

The time period of the collision is also important, but it will be so short in this case that it probably wouldn't make any difference. If the colliding materials had significantly viscoelastic characteristics on the timescales in question, then it would become much more important.

 

[WoodButcher]

Seems like this has been made more complicated than needed. Isnt the issue simply that you dont want objects moving relative to the vehicle including yourself and that's one reason for wearing the seat belt?

Yes indeedy!
Loose load, at the back of the cab,
tied down, any place you want if you don't have a plastic bedliner.
bedliner? all bets are off.

common sense. period.

As to the seat belt thing I just threw that in to screw with all the heavy thinkers but it is true. I hope to get tossed clear if something happened in my van. There is more mass in tools and material inside my van than the body of the van itself and all that mass has sharpened edges made for destruction in one form or another.

An earlier poster mentioned a bowling ball in an old analogy, OK, I have a compact 20 ton hydraulic jack, probably weighs about 15- 20 pounds, not one smooth round edge on that thing, if I bothered having a cage in the truck it could cut through that sheet metal easily at 5 or 10 mph,,,
Forget about the heavy sharp objects, I carry laquer thinner to clean my blades and as a solvent for adhesives, flammable? yeah, along with propane tanks for heat in the winter and acetylene every now and then for plumbing.

Seat belt? thank you, no...

 

[canis]

I've been a carpenter since before I could drive and have been in and seen many wrecks cars, vans, and trucks with tools, equipment and materials of all sorts. Tied, loose, strapped, bolted and welded boxes and bits involved.
The one thing I can tell from over thirty years of observation you is that I'll pay the $37 dollar fine every time for the lack of seat belt and hope I get thrown clear of that mess. I try to tuck things down and away but if someone thinks he's "safe" by welding his toolbox to the tailgate and putting on the padlock will soon meet Murphy and his legalpad.
That said, IMO the best place to mount a box or carry tools on a truck is on someone elses truck. Failing that you put them where you use them most and are readily available and adjust as needed. Most of all drive defensively, use the tools you were given and pay attention. Shit happens, expect it.

Did you not wear a seat belt in the wrecks you have been involved in?

 

[mutz]

I will try to explain this once more.
<...>

yeah, you'r right, the time for it to hit, the "swinging" effect, i should've been more careful considering that,

take a bowling ball, and place it at the back of the truck, would it bend the cabin the same if you place it tight to it while breaking hard?

no, i guess not,
you'll have the momentum as jaha said (i couldn't understand his post though then..:hmm.

 

[CycloWizard]

Yes indeedy!
Loose load, at the back of the cab,
tied down, any place you want if you don't have a plastic bedliner.
bedliner? all bets are off.

common sense. period.

As to the seat belt thing I just threw that in to screw with all the heavy thinkers but it is true. I hope to get tossed clear if something happened in my van. There is more mass in tools and material inside my van than the body of the van itself and all that mass has sharpened edges made for destruction in one form or another.

An earlier poster mentioned a bowling ball in an old analogy, OK, I have a compact 20 ton hydraulic jack, probably weighs about 15- 20 pounds, not one smooth round edge on that thing, if I bothered having a cage in the truck it could cut through that sheet metal easily at 5 or 10 mph,,,
Forget about the heavy sharp objects, I carry laquer thinner to clean my blades and as a solvent for adhesives, flammable? yeah, along with propane tanks for heat in the winter and acetylene every now and then for plumbing.

Seat belt? thank you, no...

Or, you could simply store your tools properly. Launching yourself into oncoming traffic isn't going to be any safer than having some tools fly at you. Everything you are doing is really illegal and, if you somehow magically survived being ejected from your vehicle, you'd probably get locked up.

 

[mutz]

yeah, you'r right, the time for it to hit, the "swinging" effect, i should've been more careful considering that,

take a bowling ball, and place it at the back of the truck, would it bend the cabin the same if you place it tight to it while breaking hard?

no, i guess not,
you'll have the momentum as jaha said (i couldn't understand his post though then..).

i see what you say Pulsar, now you were talking about an 18 fit truck or so, (no matter the length though),

what you say, is that the box would remain it's "original" speed before the actual collision happens, so eventually, the box would go from, 60 (the truck breaks to 40), the box go on flying, then the truck gets to a complete stop while the box is in the air, so eventually, it hits the cabin at ~60mph, or, the original driving speed.

yet this is considering we are talking about few feet truck and not really a pickup as in a pickup scenario, the box would more possibly reach the cabin before getting to the actual collision (a matter of a split of a second).

at a 18 feet truck, the scene is totally different as mentioned.

now what i meant more, is take these salt flats they test car upon,
they have this rocket engined iron cart sat on train rails,
now this cart is going few hundreds Km per hour and is able to hit a full stop in a matter of a split of a second in order to test some accident scenarios.

now take a tennis ball, and let's say it's exploding coefficient is 300Kmph, so if the cart stops from 300Kmph speed to a full stop in a split of a second, the ball would explode.

now take two scenarios, at the first, the ball is tight to the cart "cabin" and at the second, the ball is placed at the rear of the cart bed, now at a full stop, instant stop, eventually the same would happen, the ball would either fly or squeeze at the cart cabin at 300Kmph and would break.

taking a deeper look at it, at the rear scenario, the ball would fly at the original speed, and then hit the cabin so would not be affected from any deceleration,
so would even hit it slightly faster.

Yup....your wrong . Jump off a 1 foot step ladder. Jump off a 10 story building next. Then decide.

no, you forget the speed element,
a box placed 1 meter from the cabin or a box placed few centimeters from it, would collide at the same force, relative to the driving speed and breaking time,
if on a test car, the collision is instant from a 100Kmph, the box would fly a meter at 100Kmph or 1 centimeter at 100Kmph and hit the cabin with the same impact,
no matter the distance, nor even if the box is tight to the front.

as an adder to what pulsar had said, at an 18 feet trailer, the box would even lose some of it's potential doe to friction or hitting the surface while rolling.

the distance seems like a myth,
don't fall for it .

 

[WoodButcher]

Did you not wear a seat belt in the wrecks you have been involved in?

No seat belt both accidents I was in, one as a passenger.
Your right CW in that my van is overloaded and could be ticketed but it comes to economics. I lose out on jobs now because others are cheaper, were I to get a bigger truck w/ all the cubby holes my prices would need to go up. Funny part is a bigger truck just means more crap, I downsized to a GMC Safari minivan in '02 to cut costs but still find that I needed to add springs, heavy shocks, load rated tires and replace brakepads and shoes every fall. Maintenence and common sense are key. I would bet that 80% of us in the trades run overloaded on a daily basis. Those that concern me are guys that buy passenger grade vehicles, load them with tools, put ladders on the luggage rack and go to work. Bring a picinic lunch to your local home center one weekend and watch people load their cars, now that's funny.

I've gone off topic, assuming the crash will dislodge the box, up close to the cab would be most desirable IMO. Located at the rear would mean 2 impacts, the crash itself and then the toolbox hitting an already damaged cabin and odds are it won't hit flat.

The fact that supernova87a posted this question makes me feel better that at least a few people think about things like this.

 

[sao123]

Yup....your wrong . Jump off a 1 foot step ladder. Jump off a 10 story building next. Then decide.

unless the thing you are crashing into has its own gravitational field... aka a planet... then jumping off the ladder isnt exactly a comparable scenerio.

 

[CycloWizard]

No seat belt both accidents I was in, one as a passenger.
Your right CW in that my van is overloaded and could be ticketed but it comes to economics. I lose out on jobs now because others are cheaper, were I to get a bigger truck w/ all the cubby holes my prices would need to go up. Funny part is a bigger truck just means more crap, I downsized to a GMC Safari minivan in '02 to cut costs but still find that I needed to add springs, heavy shocks, load rated tires and replace brakepads and shoes every fall. Maintenence and common sense are key. I would bet that 80% of us in the trades run overloaded on a daily basis. Those that concern me are guys that buy passenger grade vehicles, load them with tools, put ladders on the luggage rack and go to work. Bring a picinic lunch to your local home center one weekend and watch people load their cars, now that's funny.

Yeah, just don't run into me and kill me with all of the projectiles flying through your windshiled (you being one of the projectiles )...

 

[soydios]

It will of course hit with more force if its at the back.
Its not that the box is accelerating, its that the truck has decelerated so much that the difference in velocity at time of impact is going to be quite large.

/thread

 

[Swivelguy2]

edit: nevermind

 

[WHAMPOM]

Hi all, this is not highly technical, but more of a basic physics question.

Take a pickup truck, about to be involved in a head-on collision. A few friends and I are debating why the manufacturer recommends that you store heavy loads up against the cab rather than at the back of the bed. I agree that you should store them up against the cab, but not about the reason.

Friends say that obviously, if you store, for example, a heavy toolbox at the back of the bed, when it goes flying in the crash, it will have all this "momentum" that causes severe damage when it hits the cab (the body panel where the small of your back is located). I suppose they mean that this is worse than storing the toolbox hard up against the cab, because it has all that distance along the truck bed to "build up force" that is "worse".

I think this is a load of crap. When the truck stops, both a toolbox at the back of the bed and up against cab were going at the same velocity v, and have to be stopped by the cab body panel. It's not like somehow the toolbox at the back of the bed gains some extra "force" by flying through the air. In fact, if you take it to an extreme and imagine air instead as a thick fluid, if anything it would decrease the toolbox's velocity/momentum.

My explanation for the reason is as follows:

When you store something hard up against the cab back wall, in a crash it will probably more evenly distribute its mass against the body panel (because you've set it up that way), thus making the impact force of the toolbox spread over a larger area, and better using the body of the truck to protect you.

If the toolbox was at the back of the bed, it has a higher chance of changing angles while flying through the air, and presenting a sharp corner or edge on impact, and making the force much more concentrated into a point. Or in flying during a crash, it might go through the cab window aimed at your head instead of the body panel.

So I think that it is because of these more "practical" reasons than their notion of increased "force".

Am I wrong?

Thanks!

Think of it this way; place your hand on an anvil and lay an eight pound hammer on it. A little uncomfortable, but no broken bones. Lay your hand on anvil and drop the eight pound hammer on it. Notice any difference?

 

[DrPizza]

Think of it this way; place your hand on an anvil and lay an eight pound hammer on it. A little uncomfortable, but no broken bones. Lay your hand on anvil and drop the eight pound hammer on it. Notice any difference?

Close. A more accurate analogy would be drop a hammer and catch it, beginning 1 foot above an anvil. Versus put your hand against the anvil and catch the hammer dropped from the same height. Pulsar answered the thread in that the key to this situation is impulse. Spread the time that hammer stops out and the average instantaneous force is much lower than if you stop that hammer in much less time.

 

[mutz]

no,
a hammer dropped from 1 feet height is really not the same as a box flying at a cabin from the back of the trunk by a sudden deceleration.
the hammer is affected from gravity force and those is speeding till it hits the ground,
the box is not affected by any gravitational force those it just flies as the speed suddenly drops.

a more accurate analogy would be,
someone drops a TV at you at 30Kmph,
the TV hits you at 30Kmph,
does it matter whether he has thrown it from 10 meter or 50 meter?
the TV is going 30Kmph no matter how far it has been thrown from, that is a fact.

now it doesn't either matter whether you ran at 30Kmph and suddenly stopped when that TV is in your hands,
the same force will hit you, which is the weight of the object, times it's speed,
that is it.

the only apparent reason it is suggested that the box would sit near the cabin is due to the fact it can change position while flying through the air, hitting the cabin with one of it's corners and so apply much force at a smaller impact surface those possibly creating more damage,
the other possibility is the box can fly at a back window if present, those hitting the driver and casing again much more damage...

 

[canis]

no,
a hammer dropped from 1 feet height is really not the same as a box flying at a cabin from the back of the trunk by a sudden deceleration.
the hammer is affected from gravity force and those is speeding till it hits the ground,
the box is not affected by any gravitational force those it just flies as the speed suddenly drops.

a more accurate analogy would be,
someone drops a TV at you at 30Kmph,
the TV hits you at 30Kmph,
does it matter whether he has thrown it from 10 meter or 50 meter?
the TV is going 30Kmph no matter how far it has been thrown from, that is a fact.

now it doesn't either matter whether you ran at 30Kmph and suddenly stopped when that TV is in your hands,
the same force will hit you, which is the weight of the object, times it's speed,
that is it.

the only apparent reason it is suggested that the box would sit near the cabin is due to the fact it can change position while flying through the air, hitting the cabin with one of it's corners and so apply much force at a smaller impact surface those possibly creating more damage,
the other possibility is the box can fly at a back window if present, those hitting the driver and casing again much more damage...

What does the K in 30Kmph mean? Is English your first language?

 

[mutz]

no,
and it means Km ph.

no one can run 30mph .

 

[madeuce]

I've got a dent in the bed of my truck. I came to a sudden stop carrying equipment in the back. When I stopped it slid to the front and hit the bed next to the cab. The piece didn't shift. All it did was slide forward.

Had that equipment already been snug against the cab of my truck there would be no dent...

 

[DrPizza]

no,
a hammer dropped from 1 feet height is really not the same as a box flying at a cabin from the back of the trunk by a sudden deceleration.
the hammer is affected from gravity force and those is speeding till it hits the ground,
the box is not affected by any gravitational force those it just flies as the speed suddenly drops.

a more accurate analogy would be,
someone drops a TV at you at 30Kmph,
the TV hits you at 30Kmph,
does it matter whether he has thrown it from 10 meter or 50 meter?
the TV is going 30Kmph no matter how far it has been thrown from, that is a fact.

now it doesn't either matter whether you ran at 30Kmph and suddenly stopped when that TV is in your hands,
the same force will hit you, which is the weight of the object, times it's speed,
that is it.

the only apparent reason it is suggested that the box would sit near the cabin is due to the fact it can change position while flying through the air, hitting the cabin with one of it's corners and so apply much force at a smaller impact surface those possibly creating more damage,
the other possibility is the box can fly at a back window if present, those hitting the driver and casing again much more damage...

My analogy is just fine. And, since you don't realize that the force that it strikes the cab will be greater if it starts from the back of the truck, you're not even on the right track.

 

[mutz]

o.k, so i'm wrong, you'r right, fine,
now, would it be the same as a hammer drops from a certain height on your hand or rather you hold the hammer and it drops from the same height?

E:
an object placed on a stool 1 meter or tight to the cabin, would blast at it with the same force when a sudden (100-0 in a split of a second) happen.

there is not any acceleration implied with the distance/time equation,
the object would simply (being separated from the vehicle) keep the driving speed while the vehicle stops, i.e flying at 100kmph at the cabin or at the window.

the damage would be the same.
period.

that is the point, and you can argue about many aspects of this question even though it is relatively simple.

 

[mutz]

the main issue seems to be hard to explain, though pulsar did put it right to a certain extent,
the force that would be implied to the box in the two scenario's would be the same force, though the hit would not be the same,
no one has placed it inside a formula yet intuitively, it is obvious that the box at the rear would bend the cabin much harder then the box which is tight to it.

why?
maybe because the entire weight of the rear box would be flying through the air while part of the "tight box" weight is placed on the surface,
and,
we have the timing effect which the rear box would be flying while the truck stops implying more "momentum" then the tight box which would only cling, loosing it's momentum slowly.

other then that, i find it a bit hard to explain.

 

[PlasmaBomb]

What does the K in 30Kmph mean? Is English your first language?

Looks like he is using metric in the entire post... so that would be kilometers per hour (kmph or kph, note small k).

 

[Biftheunderstudy]

I would just like to point out that the key to this problem is not impulse. Impulse is defined as the change in momentum or the integral of the force over the time of the collision. If you take the second of the 2 definitions it is easy to come up with the wrong answer, that the toolbox has a shorter impact time and thus a higher impulse but the correct answer is to look at the change in momentum.

Take for instance a truck moving at 50mph, in the case where the tools are at the front the change in momentum is 50mph to 0mph (times the mass). In scenario 2, the tools at the back, they start at 50mph and end at 0mph thus having the same change in momentum and thus the same impulse.

This same type of question was given on a 1st year physics final exam that I invigilated this spring.

I think the correct answer is sort of buried in this thread across multiple posts being a cross between the deceleration of the truck and there being 2 impacts as well as the transfer of energy from the tools to the cab.

 

[canis]

I would just like to point out that the key to this problem is not impulse. Impulse is defined as the change in momentum or the integral of the force over the time of the collision. If you take the second of the 2 definitions it is easy to come up with the wrong answer, that the toolbox has a shorter impact time and thus a higher impulse but the correct answer is to look at the change in momentum.

Take for instance a truck moving at 50mph, in the case where the tools are at the front the change in momentum is 50mph to 0mph (times the mass). In scenario 2, the tools at the back, they start at 50mph and end at 0mph thus having the same change in momentum and thus the same impulse.

This same type of question was given on a 1st year physics final exam that I invigilated this spring.

I think the correct answer is sort of buried in this thread across multiple posts being a cross between the deceleration of the truck and there being 2 impacts as well as the transfer of energy from the tools to the cab.

?
Why do you think the other posters meant "the toolbox has a shorter impact time and thus a higher impulse"? Unequal forces can produce equal impulses.

 

[Biftheunderstudy]

Unequal forces can produce equal impulses.

That was my point, I was simply pointing it out since its a common mistake.

Like I said though, the correct answer has more to do with the acceleration of the toolchest and thus the force imparted to the cab. You need only make up some numbers (duration of collision for the chest and the truck as well as the initial speed) to reach this conclusion.

 

[twinrider1]

Hi all, this is not highly technical, but more of a basic physics question.

Take a pickup truck, about to be involved in a head-on collision. A few friends and I are debating why the manufacturer recommends that you store heavy loads up against the cab rather than at the back of the bed....

Accident physics aside, I disagree with the premise of the question. The mfg wants heavy loads up against the cab to maintain safe handling while driving. You want the weight between the suspension points/wheels. You don't want a big weight hanging off the back, behind the rear wheels. It adversely affects the CG. Makes you much more likely to lose the rear end in a turn.


Now, strictly regarding accident physics, I wonder if would actually be safer to have a large movable weight in the rear of the bed rather than it being coupled to the front of the bed. I believe the total energy of the impact would be the same either way. If the weight is fixed, the occupant absorbs the energy in one event. But how about if the weight is at the rear and can move. It's going to take energy to move that weight. And it's going to take time. Better to have two smaller events than one severe event. Spreading that energy over time is safer.