Wreck w/ ARB bend frame?

Log Out | Topics | Search Moderators | Register | Edit Profile

Thread Last Poster Posts Pages Last Post   Closed: New threads not accepted on this page

Author Message   Neal Glessner (Nealg) Posted on Sunday, April 28, 2002 - 11:03 pm:    I am thinking about getting a heavy duty front bumper. I was told that if you get a non-airbag verson that you are more likely to damage the frame if you get in a front end accident. It make sense since the bumber is bolted to the frame. How valid is this argument?   PerroneFord Posted on Sunday, April 28, 2002 - 11:24 pm:    The stock bumper is mounted to the frame. So is the mounting point the issue or something else? After reading here about guys bending ARB bumpers doing mild offroading in hilly, muddy areas, I wouldn't spend my money on one. -P   M. K. Watson (Lrover94) Posted on Monday, April 29, 2002 - 10:05 am:    neal fwiw, if you are in a crash that causes any metal to bend there is always a chance that the frame will be tweaked as well, regardless of the bumper. perrone is not entirely correct in his statement, the non-airbag version is not the bumper that most of the complaints are directed towards it is the airbag tested bumper. they have crush cans that allow the bumper to move inboard in the event of a low speed collsion. the non-airbag version does not have these crush cans. i have a non-airbag ARB bumper on my 94 and i can not complain about the bumper. it does what it is designed to do. now as far as frame damage....if you hit anything hard enuff its going to bend something, it makes no matter as to the make of the bumper. to blame the frame damage on one particular bumper is well silly. i have investigated a lot of traffic crashes in my time on the JOB and without a fear of being corrected i can say it was the operator that caused the frame damage not a bumper. the ARB is a good quality piece. if you got the cash buy it (i would go with the non-airbag version). mike w   PerroneFord Posted on Monday, April 29, 2002 - 11:27 am:    This is all I was saying. -P "if you got the cash buy it (i would go with the non-airbag version)."   JEspelien (Superj) Posted on Monday, April 29, 2002 - 11:30 am:    I hate to be blunt MK but the contention that bumper design has no effect on collision damage is what is silly. I suggest you go to SAE.org and do a search on motor vehicle collision performance. As for Neal's original question, It is possible that an aftermarket bumper may transmit forces to the frame rails that a factory bumper would have "absorbed" in deformation especially in offset collisions. As for the specific issue of ARB ABS compliant versus ARB Non-ABS compliant bumpers I have not seen the manufacturers crash test data on the ARBs so I�m shooting from the hip but here goes. The force needed to deform the crush cans has to be relatively small, given they are designed to be effective in low (sub 5 mph) collisions. Since collision forces increase at the square of collision speed the forces in a 30 mph are about 150 times those in a 2.5 mph crash. Consequently, the net effect of the crush cans in any road speed collision is going to be minimal at best. The real extra risk you run with noncompliant bumpers is unnecessary airbag deployment in a low speed collision, thereby turning a no/low cost parking lot accident into a multi-thousand dollar airbag replacement fest.   p m Posted on Monday, April 29, 2002 - 03:36 pm:    funny how ARB was never quite clear on this issue. JE, a "non-airbag compliant" ARB bumper won't yield as easily as the airbag version. As a consequence, the airbags may not deploy where they should have, with all the liability issues. the airbag-compliant ARB bumper is known to bend down while off-roading, causing collateral damage - see a photo from Kyle's window peter   Brad Bradford (Brad) Posted on Monday, April 29, 2002 - 03:44 pm:    I know people that have put old rail-road ties on for a bumper, and that thing would knock down anything and take all the abuse you could throw at it. But after all that he had bent the hell out of his frame. I front bumper should be sturdy, but it should also give before you do major damage to the frame.   p m Posted on Monday, April 29, 2002 - 04:06 pm:    Brad, doesn't it make you wonder - why couldn't they make the whole frame out of a couple of railroad ties... peter   Brad Bradford (Brad) Posted on Monday, April 29, 2002 - 05:18 pm:    Peter that is true, maybe I will make a hybrid LR with Railroad ties as a frame, after i am done how much do you thing it will weigh?   p m Posted on Monday, April 29, 2002 - 05:26 pm:    who cares - define your own safety requirements. if your hybrid weighs just a few hundred pounds less than a garbage truck, you have a good chance of a long life without the airbags peter   Paul T. Schram (Paulschram) Posted on Monday, April 29, 2002 - 05:36 pm:    Please Peter, don't suggest such a manufacturing improvement! With Rover's problems with their frame vendor, they might just start hanging out around the local utility's scrap yard! As for air bag deployment, I have seen terrible crashes where they didn't deploy, minor crashes that totaled cars due to air bag deployment. In the case of five year old cars, the first question out of an insurance adjuster's mouth is "did the air bags deploy", if so, it is totaled-without even seeing the car! Of course, some of us have been in catastrophic crashes not wearing seat belts and survived where we most likely would not have, had we been wearing seat belts. Like everything else, it's a gamble. Me, I will someday make a bumper with little regard to air bag deployment. If they deploy, I will calmly cut off the remains and continue to drive my truck. IMO, YMMV, HTH, ETC... Paul   Ali Posted on Monday, April 29, 2002 - 06:45 pm:    The ARB (non air bag) bumper is quite stout. Mine has taken severe beatings on many occasions and still holds strong. I did get to see a DII with air bag ARB bumper this weekend in Moab. I thought it moved way too easily. This was very noticeable when the vehicle gently nudged a rock to see if he would clear it. Since this bumper hangs a bit low, this happened quite a bit to clearances. Each time, the bumper moved inboard and a litte upward.   JEspelien (Superj) Posted on Monday, April 29, 2002 - 06:46 pm:    PM the physics of that argument are all wrong. When the bumper or any other component yields or deforms it "absorbs" energy from the collision. This results in a smaller acceleration as measured by the SRS sensors. It is this acceleration that triggers the pyrotechnic charge to inflate the bags. Think in simple terms of conservation of energy: less energy in the equation expended bending stuff means more energy that MUST appear as an acceleration. There is no way the bumper not yielding could result in a smaller acceleration hence your argument can NOT be true.   p m Posted on Monday, April 29, 2002 - 07:39 pm:    Jay, don't teach me fucking physics again. Energy does not appear as an acceleration, i would beat my kid if i heard him saying so. This is a profoundly physics-illiterate statement, and I assume you posted it as a "version for the masses." Back to the subject, you're assuming that airbag sensors are accelerometers - do you know that for a fact? peter   Rob Davison (Pokerob) Posted on Monday, April 29, 2002 - 07:41 pm:    i think he means if your mass is big enough you'll never feel it. kind of like the earth bouncing if i were to jump. strap on arb's and 500lbs of other shit until you become a massive metal sphere rolling over idiots who don't get why non arb airbag bumpers are superior to stock bumper. rd   Jake Hartley (Jake) Posted on Monday, April 29, 2002 - 08:27 pm:    How hard is it for an INDIVIDUAL to take out an aging airbag? As they get older, don't they (as all explosives) destabilize? It would make sense to R&R or remove an old unstable bag before it blew up in your face...FWIW   JEspelien (Superj) Posted on Monday, April 29, 2002 - 08:34 pm:    There is no other form of approved SRS trigger. Never has been, never will be unless the statute is changed. I apologize for not responding with the exact terms and equations. I didn't think the elegant response in terms of conservation of momentum and impulse would get very far with most members. My posts shortcomings aside though your theory is still quite incorrect.   p m Posted on Monday, April 29, 2002 - 09:07 pm:    there is no theory, Jay. peter   p m Posted on Monday, April 29, 2002 - 09:15 pm:    OTOH - there is a theory, Jay. Imagine a vehicle A crashing into another vehicle B, that is, a movable object. In one case, the bumper is rigidly attached to the frame, and therefore will have the same value of deceleration as the vehicle A. In another case, the bumper is attached to the vehicle A via crush cans, assume for instance them being very easily crusheable. Here, the face of the bumper will be decelerating faster than the vehicle A (with a rate equal to the sum of deceleration of the vehicle A and the length of crush cans double prime). I can easily see how the airbags triggered by an bumper-mounted accelerometer will have more chance to activate on an airbag-compatible bumper (as compared to a rigidly mounted one). Your "layman-terms" explanation applies to the occupants of the vehicle, not the bumper. Elegant response is a correct response, whatever terms it takes to make it. peter   muskyman Posted on Monday, April 29, 2002 - 10:57 pm:    peter you are missing the purpose of the crush cans they are degigned to absorb slow impacts and pass on faster ones the cans can only crush at a specified rate whenthat rate is surpassed they transfer enough deceleration to trigger the bags. because of the elastic nature of steal the bumber can be "bumped" a bunch and still hold its relative position. the crush can shape is designed to spread out work hardening to prevent long term stiffening of the front end bumber mounts The design has worked in millions of production vehicles, the fact people are worried about it is kinda funny.   Neal Glessner (Nealg) Posted on Tuesday, April 30, 2002 - 12:14 am:    And the answer is???????   ken Posted on Tuesday, April 30, 2002 - 12:53 am:    I think at certain speeds not sure what they are or mabey only in 4 wheel low the dealer told me that half of the air bag sensors turn off. that is why you don't see them going off on the trails don't know how true this is. DII   Norm Posted on Tuesday, April 30, 2002 - 01:33 am:    Since my '95 Disco has airbags, I'm probably going to opt for the airbag-compatible winch bumper. There must be a reason why ARB has spent so much money and effort to develop bull bars with crush cans, if only to comply with Aussie regulations. Secondly, if I get into a crash, I don't want to be crucified by an insurance adjuster or a plaintiffs' attorney because I put a non-airbag bumper on an airbag truck. There may be no physical effect at all, but that's just the type of thing these bastards would jump on and turn against me. In the courtroom, the laws of physics take a backseat to plaintiffs' attorney histrionics, especially when you consider the IQ of the average juror. (Believe me, I have seen it.) Having said that, I've seen the pictures on this site of twisted airbag-compatible bull bars which apparently can not withstand off-road rigors like the non-airbag version. My plan is to fabricate some bolt-on braces, easily installed for increased rigidity off-road but easily removed so they won't interfere with the airbag function on-road. Has anybody tried this on the ARB bull bar? Thanks, Norm   Ron Posted on Tuesday, April 30, 2002 - 04:41 am:    bla bla bla (not directed toward Norm ) Who cares! Work hardening, turning off at low speeds, brackets, its drivel. Bolt the biggest hunk of steel on there you can. Like the G-wagon commercial, it is much more desirable to go through what you hit than to stop. With the generally crappiness of the LR SRS system its a crap shoot anyway. Ron   christian Posted on Tuesday, April 30, 2002 - 07:15 am:    My bumper is the one depicted in Kyle's "Out the WIndow" My DII is the White Gold one parked next to Mongo's. The bumper failed at the crush can specifically at the "U" that is engineered into the drivers side can to allow for the left side of the winch to be placed within that "U". The impact it took to torque it down and to the left was on the first gate of a trials course. I was going approximately 5 mph. The increased length of having an ARB bumper installed without a lift did not help the situation. I rolled over the first little hump and before the next consecutive hump there is a valley. As the suspension came down with the bumper, the bumper hit at the shackle bracket mount on the lower left side of the bumper next to the roller fairlead location if I had a winch. As I bottomed out, I kept driving thinking I was simply hitting the bottom of the bumper or undercarriage. B Unfortunately, as I drove through the valley, the bumper was hung up enough to literally allow me to power over it somewhat and twist it downward. You can see by my included pics in Kyle's window that there is a bend toward the rear lower part of that "U" that is on the inside edge of the left or drivers side crush can. I did replace the crush cans and had each can welded inside with 1/4 inch steel all the way around the inside circumference of each can for rigidity. Hope the information helps... ***If anyone would like pics emailed to them, just drop me a line and tell me what you want***   RonLF Posted on Tuesday, April 30, 2002 - 07:52 am:    Has anyone had problems with the Disc Series 1 ARB air-bag bumpers? I have one on mine and I have not yet had a problem,I have hit things hard with it. Is this someting that is other a Series II problem?   Kingfish (Kingfish) Posted on Tuesday, April 30, 2002 - 08:03 am:    Muskyman, What are you talking about? "because of the elastic nature of steal the bumber can be "bumped" a bunch and still hold its relative position. " What have you been smoking? Steel does not have an elastic nature. I have a degree in materials science and they never told me about that unique feature. If you created some new type of steel (from iron and carbon, not plastic) you need to patent it. If not, stay away from the herb. The BS is so deep, I need a shovel.   Rob Davison (Pokerob) Posted on Tuesday, April 30, 2002 - 10:12 am:    norm, dont buy an ARB if you get an airbag compatible one if you plan on going offroad, you will end up hit a small bump and wrecking your fenders and grill. it's just that simple. rd   M. K. Watson (Lrover94) Posted on Tuesday, April 30, 2002 - 10:44 am:    "Secondly, if I get into a crash, I don't want to be crucified by an insurance adjuster or a plaintiffs' attorney because I put a non-airbag bumper on an airbag truck. There may be no physical effect at all, but that's just the type of thing these bastards would jump on and turn against me. In the courtroom, the laws of physics take a backseat to plaintiffs' attorney histrionics, especially when you consider the IQ of the average juror. (Believe me, I have seen it.) Having said that, I've seen the pictures on this site of twisted airbag-compatible bull bars which apparently can not withstand off-road rigors like the non-airbag version. My plan is to fabricate some bolt-on braces, easily installed for increased rigidity off-road but easily removed so they won't interfere with the airbag function on-road." norm i agree with your statement as it comes to those who PRACTICE the law ( i hope my wife doesnt read this and if she does honey i love lawyers) but not to start an arguement is not your second statement a violation that any good ligator would love to find. "What have you been smoking? Steel does not have an elastic nature. I have a degree in materials science and they never told me about that unique feature. If you created some new type of steel (from iron and carbon, not plastic) you need to patent it. If not, stay away from the herb." kingfish, not to start an arguement with you but i do have a question. if steel has cant bend and then return to its natural postion then how does a spring work?... i beleive the term musky was looking for was MEMORY. if i am wrong please feel free to flame me and then correct me. hehehe mike w   JEspelien (Superj) Posted on Tuesday, April 30, 2002 - 11:33 am:    PMS The primary SRS triggering sensor is never mounted on the bumper. Some SRS designs have a null accelerometer mounted on or near the bumper supports to null or prevent triggering in certain types of low speed collisions. I mentioned momentum-impulse as the elegant and correct way to model collisions involving plastic deformation because it avoids having to measure or estimate any deformation distances. For an accurate calculation using work-energy we must be able to determine the distance over which the forces involved act. Even using high-speed photography it is almost impossible to accurately determine one collision distance. For an accurate calculation using momentum-impulse all we need to measure is the elapsed time for the collision. Since computers excel at measuring time the precision using momentum-impulse will be many orders of magnitude greater than if we use work-energy and estimate the distances.   Kingfish (Kingfish) Posted on Tuesday, April 30, 2002 - 11:47 am:    Mr. Watson, no offense taken buddy. Memory is the same as "elastic". Once deformed, it will resume its previouse shape unless it deforms too far. Then it doesnt. Take a spring and squeeze it sideways slightly with pliers. It will remain deformed and will not "look" like it did before. An elastic material would spring back. The design of a spring is what makes a spring. That's a trick question. The previous post was directed to bumpers, not springs. Take a ballpeen hammer and hammer your bumper with it. You will see that your bumper has taken on a new shape.   Leslie N. Bright (Leslie) Posted on Tuesday, April 30, 2002 - 12:32 pm:    Elastic versus plastic deformation behavior. Elastic strain rebounds when the deforming stress is removed. Plastic strain remains when the deforming stress is removed. Ask a structural geologist to explain the difference between strain and stress sometime..... but make sure you take some time with you.... -L   my96disco (Trevorh) Posted on Tuesday, April 30, 2002 - 12:45 pm:    While we are somewhat on the topic of airbags, I was wondering what happens when these vehicles start to reach the magic 9-10 year mark. I have heard that the air bags need to be replaced. Can anyone shed some light on this? Thanks Trevor   RonLF Posted on Tuesday, April 30, 2002 - 12:51 pm:    The "10 yrs" air bag deals is just a way for the "Car Companies" to cover themselves if an old car's air bag doesn't work when it's 10 yrs old. It's look a warrenty on your air bag.   Norm Posted on Tuesday, April 30, 2002 - 11:09 pm:    "norm i agree with your statement as it comes to those who PRACTICE the law ( i hope my wife doesnt read this and if she does honey i love lawyers) but not to start an arguement is not your second statement a violation that any good ligator would love to find." That's why I use a pseudonym -- knowing full and well that anything I say can and will be held against me in a court of law. ---Norm   minirover Posted on Thursday, May 02, 2002 - 08:24 am:    I just wonder why Kyle hasn't posted on this topic,since he knows everything.   Kennith Posted on Tuesday, May 07, 2002 - 12:43 am:    Heres the deal, If you off road regularly and harshly, get the normal ARB, or my personal preferance the Trek Outfitters offering. If your truck spends most of it's time in parking lots, and your driving record is not devoid of wreckcidents, buy the air bag compatible version. All physics aside, an off road impact is the same as a parking lot impact (aside from the fact that rocks don't give like cars do), which is the same as the impact that those crush cans are designed to absorb. All this jargon dosn't matter at all, the question you need to ask yourself is how much time do you spend on rocky trails?