Would rock sliders help in an accident?

[2flyfishin]

More steel, more mass still lost in the end
https://youtu.be/fPF4fBGNK0U

 

[1engineer]

You know...

I don't think you are a very good engineer. I would not trust your designs at all.

The point of my post was to specifically illustrate that the vehicles "crumple zones" are NOT equal once you add more high-strength steel to one car. In fact, the vehicle with the most steel tears through the other car as if it wasn't even there. No safety equipment came into play in my accident because my bumper simply destroyed 100% of the ford sedan. Our "crumple zones" were not equal. I have no crumple zone in the rear anymore, if you hit the rear of my truck at sufficient speed you will die and I will suffer no injuries. I dare you to do it... I can give you the information for a person who already tried that.

I actually WAS IN an accident where my speed was zero and the other cars speed was 50mph. I had more steel, therefore I did not sustain any injuries. YES, my 4runner was kicked in the air and flew forward about 30 feet, but it does not change the fact that no structural damage occurred precisely because the design of my rigid bumper transferred 100% of the damage and injury to the wimpier car. I really can't understand how you could argue with this. Additionally, I can't understand why you would even put forth the idea that the concrete IIHS data which states: "cars with more metal mass win in every accident" and claim that it is wrong somehow because you seem to believe that vehicles are somehow evenly matched in accidents. It is statistically unlikely that any two vehicles are ever evenly matched and will share exactly 50% of the damage and injury. The statistical likelyhood of that ever happening is so close to zero that it is disingenuous for you to even mention it as a possibility, being an engineer. Additionally, your supposition that installing sliders would make your car "flip" at any greater predictable likelyhood is supported by no evidence and I doubt someone who actually had the time to model this behavior using FEA would ever publish it as a factual occurence. Again that is extremely disingenuous as an engineer to say that your hypothetical situation which has never been modeled or proven amounts to a statistically likely possibility.

Furthermore-- you disregarding my maxima and minima solutions for why installing more metal can reduce the DeltaV is completely bonkers. How can any rational engineer put forth the idea that if you added your own "crumple zone" onto the side of a car by welding on sliders which did not previously exist, you would INCREASE the DeltaV??? What in the :fish: are you talking about? I would LOVE to see how you modeled that with FEA...

Lets take your example and my example and put them together. I have welded on sliders which stick out 100 feet from the side of my truck. You are going to t-bone me by running into the sliders that stick out 100 feet with another 4runner. Are you telling me that when you hit them, they do not crumple? They would not be absorbing the impact and lowering your velocity? And by the time you get to my truck door panel, your velocity has not changed at all? I can't believe you or any other rational person would suggest this.

Additionally, by extending the point where another vehicle hits the sliders PERPENDICULAR to the direction of a vehicle rollover, the torque required to "flip" the truck is INCREASED making it less statistically likely that the truck would flip over. If the sliders were hit from above or below (in your example a car would have to fall from the sky) then the torque required would DECREASE and make it more statistically likely that the truck would flip. Now how likely would it be for any vehicle to strike the top or bottom of the sliders and cause it to flip? I would hazard a guess that it is pretty unlikely. Most people would agree that a traveling vehicle would strike on the same plane as the target vehicle, causing the slider to deform (first absorbing some impact force) and thus able to transmit LESS force to the truck to flip it over.

It is not me who are violating the laws of physics, but you. Change in velocity is increased with less absorbing material in the same direction as the object is traveling, regardless of what that material is. Should the material be capable of semi-rigid deformation, the velocity energy is transferred to the deformation energy required to bend the material, resulting in the conservation of energy and the decrease in velocity of the original traveling body.

I would trust any car I designed to save my life over any car you designed...

Lol alright bro. You win. Your posts really make my head spin! If you ever design something be sure to post pics!

 

[wfo9]

I disagree and would like to know how you arrived at this conclusion. More steel is more steel, and the car with the most steel wins in all cases by transferring all of the injuries to the occupants of the car with the least steel.

LOL. In all cases,, eh.....

While we can sit here and guess all day long... the reality is... it's impossible to know for sure what will happen. Your best bet for safety is a 100% stock vehicle as it has been engineered and verified to meet certain standards.

I'm not saying adding sliders is necessarily dangerous...but they could be as they provide a ramp for certain height vehicles to ride up on and into the side impacted vehicles cabin.

Example scenario (guess): Someone runs a stoplight in a stock height 4runner with sliders. A lifted 4runner on 35s with steel bumper ends up T-boneing it. First the steel bumper is going to start penetrating the door structures, but the tires will hit the slider and push the bumper right into the windows and serve a 100lb bumper sandwich to the driver....

That is a pretty crazy guess about what could happen, but the point is... you can't predict what will happen on a modified vehicle.. It's going to totally depend on the circumstances.

I think the concussion of... could help, could hurt is 100% accurate. Which basically means.... we don''t know. It's such a complicated subject with so many variables... not really worth much discussion beyond leave it stock if you are concerned. Or just stay at home if you want any 100% guarantees about car accidents.

 

[duffdog]

Lol alright bro. You win. Your posts really make my head spin! If you ever design something be sure to post pics!

I am an electronic engineer who specializes in videoconferencing. Would you be interested in a schematic? I have tons of those:lol:

 

[sactown]

I was the passenger in a GMC crew cab dually with a big steel bumper that rear ended a parked civic. Truck had a cracked light and the civic lost abut 2 feet. I'll take lots of steel when I can get it.

 

[rayofsi]

while i did not buy rock sliders for protecting the 4runner in a collision. I do believe in many instances it will provide some level of protection over a 4runner without sliders.

 

[engineeer]

You know...

I don't think you are a very good engineer. I would not trust your designs at all.

It is not me who are violating the laws of physics, but you. Change in velocity is increased with less absorbing material in the same direction as the object is traveling, regardless of what that material is. Should the material be capable of semi-rigid deformation, the velocity energy is transferred to the deformation energy required to bend the material, resulting in the conservation of energy and the decrease in velocity of the original traveling body.

I would trust any car I designed to save my life over any car you designed...

This is the politest way I can put this: you know just enough to get you into trouble.

What you said is kind of like me saying, "If you're designing defibrillators you should make them the highest voltage and current possible to have the best chance of resuscitating someone because more voltage and more current = more power = best chance of getting the heart beating again because the heart needs power."

 

[A.Wilson013]

I'm an engineer.

No, I'm an engineer!

I'm a better engineer.

No, I'm a better engineer!

We get it, you're engineers.

+10 internets to the clown who tried to register the name, "engineer" but saw it was taken and thought, "man, I really MUST have everyone know I'm an engineer... add an e."

 

[1engineer]

I am an electronic engineer who specializes in videoconferencing. Would you be interested in a schematic? I have tons of those:lol:

I make big heavy things move. Only been doing it for 25 years though. I've done enough schematics to last me a lifetime and not of the electronic kind. The high pressure hydraulic kind.

 

[4Reak Show]

The coefficient of friction relative to angular momentum circumvents various routes. Therefore, multiple scenario driven argumentation derivatives may extinguish masculine criterium upon investigative irregularities.

Forevermore, universal law abiding representative opinions will correspond relative to individual statistical analysis and imaginative creations which ultimately result in a singular situational activity of epic and unrelenting proportions.

Upon intense ejaculatory events resulting from, BUT NOT INCLUSIVE UNTO, said situational anomalies, one may conclude an overwhelming accurate observation:

You need a jerk sock



Case closed everyone!

 

[Jhalko]

Well this thread got entertaining pretty quick. layball:

 

[scottiac]

Slightly different scenario, but my no-longer-with-me 3rd gen had a big steel bumper and we got rear-ended at about +30mph. The cabin did not deform at all, but we took one mother of an impact because all of the hit transferred through the steel bumper to the steel frame, and rocked the crap out of us.

Plus side, all of the "stuff" in the cabin was unharmed, minus side, my wife got pretty hurt in the impact. We'll call that net "bad".

While I am an engineer it's an anecdotal example. Modern cars are designed to collapse in places to mitigate transferred energy, and by armoring up, we change that design. Sometimes for good, sometimes, not so much.

On the other hand, the ford focus that hit us got pretty badly crunched, but not nearly as badly as when he bounced off us into the side of a semi... Yikes!

I'll be adding armor (skids and sliders at least) to my new 4runner, but I'm under no conception that it will make me more or less safe in an impact accident.

 

[e60ral]

I am an electronic engineer who specializes in videoconferencing. Would you be interested in a schematic? I have tons of those:lol:

i know your posts aren't technically engineering services, but i think you should refer to the intentions of the fundamental canon items 1&2

 

[wfo9]

Slightly different scenario, but my no-longer-with-me 3rd gen had a big steel bumper and we got rear-ended at about +30mph. The cabin did not deform at all, but we took one mother of an impact because all of the hit transferred through the steel bumper to the steel frame, and rocked the crap out of us.

Plus side, all of the "stuff" in the cabin was unharmed, minus side, my wife got pretty hurt in the impact. We'll call that net "bad".

While I am an engineer it's an anecdotal example. Modern cars are designed to collapse in places to mitigate transferred energy, and by armoring up, we change that design. Sometimes for good, sometimes, not so much.

On the other hand, the ford focus that hit us got pretty badly crunched, but not nearly as badly as when he bounced off us into the side of a semi... Yikes!

I'll be adding armor (skids and sliders at least) to my new 4runner, but I'm under no conception that it will make me more or less safe in an impact accident.

Sounds about like what I would expect... and my general attitude is the same. However, I do think adding aftermarket bumpers is much more risky than most would think.

It always surprises me up that people think they are somehow safer with these big steel bumpers out on the road.... There are low speed scenarios where they may help mitigate damage.. but I would guess in most scenarios they will multiply the transfer of force to the occupants significantly. On the front especially, it is very much like removing a shock absorber, since the stock crush can has to be eliminated. Any impact will go directly to the frame and much more will make it to the occupants. The frame and bumper will still absorb energy... but you have eliminated some of the engineered crumple zone.

Very similar situation in the rear.. since you are more or less linking the rear frame rails with additional structure. If you happen to get hit by a tin can... or run into a small animal that is low to the ground and < 20% of your mass... you are in luck. Otherwise... the bumper armored up rig is probably at a big disadvantage in terms of protecting the occupants from injury.

Side impacts are much different though, since cabin intrusion is the bigger concern. But so many variables to consider, that it seems impossible to come to any type of conclusion beyond "it depends".

 

[Victor_inox]

full coverage insurance is cheaper and much more efficient for keeping vehicle in top shape.
Don`t know about you but I have one body and like it uninjured.
Idea or rigid steel sliders/bumpers transferring all that kinetic energy without absorbing any is bad for most important part- occupants.

 

[engineeer]

I'm an engineer.

No, I'm an engineer!

I'm a better engineer.

No, I'm a better engineer!

We get it, you're engineers.

+10 internets to the clown who tried to register the name, "engineer" but saw it was taken and thought, "man, I really MUST have everyone know I'm an engineer... add an e."

Yeah what a bunch of jerks these engineers are answering the OPs question and qualifying their response by pointing out the fact that they are engineers. It would be like some blowhard on WebMD answering people's questions about health issues and pointing out that he's a doctor...what kind of absolute jerk would do something like that?

Also, just because I look like this doesn't give you the right to call me a clown.

 

[Dorobuta]

I don't know where to begin with this post. It's like you are mixing and matching physics and outcomes, which is illegal to break the law of physics in all 50 states and pretty much in the whole universe.

First [MENTION=78273]Jeremy556[/MENTION] arrived at the conclusion he did because he is correct and understands physics, and he followed the laws. You are wrong because you didn't.

Mass COULD win in specific cases, although mass is not just "more steel" added to the sides of a vehicle. Also, you used the word "all" and nothing is ever "all." For example, If we were in identical vehicles with identical mass going opposite directions and had a head on collision at the exact same speed, the only difference is I was wearing my seatbelt and had functional airbags and you weren't and didn't, who would walk away and who would be carried away? I win and we had the exact same mass. Not really relevant to the discussion

Now, let's say I was in a Toyota Corolla and you were in a solid steel vehicle with 100% rigidity that weighed 2X what the Corolla weighs. Again, you don't have a seatbelt or airbags. Who will walk away from a 30 mph crash? Me. You would, again, be carried away because you do not have enough strength to support your body mass at 30 mph. You also have no energy absorption (no crumple zones) in that steel vehicle. Sure, you had more mass but so what... that's all you had. Ignoring the seat belt issue. he does have the benefits of your crumple zones. The crumple zone will absorb some portion of the energy. This portion will not be transferred to the other vehicle. how much depends on the crumple zone and a host of factors.

Now let's go to the sliders and what Jeremy told you. Let's say another 4Runner with no sliders hits you broadside in your 4Runner with sliders and skids and one thousand pounds of gear inside. You definitely have more mass and you have that slider so you should be golden right? Wrong. What is going to happen is this:

The 4Runner hits you at 40 mph right in the slider. You are sitting still, so all your extra mass means nothing in the F=MA world because you have no "A." Your slider then transmits all of the force not absorbed by the crumple zone of the moving vehicle from the impact into the frame rail. What's going to happen to your vehicle? It's going to bend first, both frame and slider, then it's going to move sideways and up (because of friction of the opposite side tires on the road) at right at 40 mph. Your body won't be moving right at that moment, because there is slack in your seatbelt, so you stay in one position while the door glass rushes sideways towards your head at 40 mph. The side airbags pop and save your life but, because of your sliders transmitting pretty much all the energy into one frame rail, you are not only going sideways, you are possibly going to go up and over onto your side and possibly your top and possibly flip completely. That kinetic energy not absorbed by the crumple zone of the oncoming vehicle has to be dissipated somehow, and if you didn't have those sliders, the door and inner crash beams would have absorbed the energy and probably/possibly left you rocked but still on your wheels. But because you thought sliders were a good idea in a side impact, you are going to go for a hard ride. The guy that hit you in the other 4Runner after recovering from the force of the airbags deploying / exploding gets out to see if you are OK as you are hanging upside down, because 4Runner drivers are cool like that. His energy got absorbed while your energy got transmitted for awhile.

Bottom line, if you have more mass then the other vehicle, and you both are using all your safety gear, and you hit head on, and the crumple zones on both vehicles are comparable, THEN the vehicle with the more mass will inflict more damage to the other vehicle. That is a lot of conditions though and rarely does it work out that way. happens more often than not in areas with a lot of older heavier vehicles on the road. (outside the rust belt)

Bottom line, more mass does not always win and sliders will prevent door dings in a parking lot.

See above in blue While I basically agree, it isn't as cut and dry as you make it out to be, and the whole seatbelt thing really was irrelevant to the rest of the discussion. no matter which vehicle you were in, in any of the scenarios, not wearing a seatbelt would have ended badly.

I was in a stationary vehicle that was rear-ended by another vehicle of about the same size. He impacted my trailer hitch. the trailer hitch receiver was bolted to my frame. no crumple zone. all the the energy was transferred to my vehicle. except for the part absorbed by his crumple zone. Other than removing some chrome from my trailer hitch and a small scuff on my rear bumper, I suffered zero damage. His truck was totaled. all, but a very small portion of the energy was absorbed by his crumple zone. Anecdotal to be sure, but I got the benefit of his crumple zone. You cannot ignore that in the discussion. YMMV

 

[4Reak Show]

Calm down you nancies. These engineers get so mad about people not agreeing!

Realize this: I'm an 11 year Master Certifed Auto Technician and do you have any idea how many times regular joes like Apple employees, firemen, grocery store clerks, teachers, and yes even engineers have combatted me on issues I see with my own eyes on a daily basis?

It's constant. The internet gives everyone a voice and platform. And an ego. And toughness to say stuff.

Let's do it right: petition these auto manufacturers to do crash testing on trucks with sliders and end all the arguements.

Anyone in??

 

[Victor_inox]

Opinions like a$$h0les-everyone has one, but the truth is -not everyone`s opinion deserve considerations and it`s OK not to have an opinion for just about everything.

I`m OK with linguistically challenged engeneeers, eng1neers or whatever spell was available at the time. :lol:

 

[SkyHighJK]

Long time lingerer to this forum, and first time poster .... thought this would be a fun opportunity to chime in! (FTR, I don't own a 4Runner but am certainly hoping to get one very soon!! TRD-O/R)

Back when I was a 16 year old 11th grade punk driving a used Volvo 960 (in-line 6, rear wheel drive!) I got front-driver-quarter-panel clipped by a city bus. I was pulling out of a fast food drive-thru in Los Angeles onto a busy street and, being an inexperienced dumb-dumb I failed to properly check the road before I edged out into the street. As soon as I do WHAM I get smacked by an MTA bus carrying a full load of people. My car bounced a couple times, maybe 4 or 6 feet to the side. Scared the crap out of me.

Front bumper flew off the car and the quarter panel / headlight array needed to be replaced, but other than that there really wasn't much damage at all (somehow). Gotta say --- those mid 90's Volvos really were built pretty well! Not sure if having sliders or a big steel bumper would have helped much in that case ....... But damn it woulda looked cool! :lol:

I think it goes without saying that the Bus, in this instance, won the fight. Looked like there may have been a scratch on its front-loader bike rack.

That was a tough phone call to the parents..... "Hey, uh, mom? Everything is TOTALLY OK but I, uh, sorta just got into an accident with a bus. ...No, like a city bus. Yes, it was my fault. Yes, I can still drive the car, I'll just stash the bumper in the trunk of the car!!"

Anyway, thanks T4R.org for letting me lurk around here for quite a while. I've learned a ton and hope to contribute more in the future once I finally get my new baby!

-SkyHighJK