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Discussion Starter · #1 ·
I was trying to think of ways to create a bumper that absorbs energy and is easy and cheap to replace. What about a bumper made of, say, 6" PVC pipe? You could use a straight steel pipe as a backing to bolt to the vehicle frame, then overlay it with foam, then cut out a section of the PVC and overlay it on the steel tube.

You could gain ground clearance over a stock bumper, and when you drag it over a rock or something, it will deform but won't dent. If it breaks, take a trip to Home Depot and spend a few bucks for a new bumper. You can't use it for recovery, but that is what hooks are for.

And if you get in an accident, it will absorb some energy, unlike a rigid steel bumper. Easier on your vehicle and the one that you crash into/ crashes into you.

What do you guys think?? Is it feasible?
 

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Got my eye on you.....
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Lawsuit waitin to happen after an accident.
 

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PVC will crush and explode under the impact you'd see in a crash. There would be shrapnel of plastic flying everywhere, probably going fast enough to break windows and/or become lodged in someone's flesh, put eyes out, etc.

actually steel is going to absorb energy A LOT better than PVC pipe would. The forces involved in an accident are tremendous... Force = Mass * Acceleration. Use 1/8th wall or 1/16th wall bumpers, they are much thinner than the frame and will bend under force. Thats why the stock bumper is so thin... Fill it with expanding foam insulation if you like. Its all about Elastic Modulus and Young's Modulus.

try steel bumpers with rubber stock absorbers on them, like delivery trucks have:
http://www.mcmaster.com/ctlg/DisplC...h=1280&ToolsetID=ToolMultiPageNav&ToolsetAct=
 

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GROUND POUNDER
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You could also line the front of the bumper with thick rubber. That would help for the slow speed "fender benders". You might want to browse around on Mcmaster Carr's site.. they have all sorts of plastic/rubber stuff.

Basically, if it's "cheap" and "effective", the manufacturers would've been doing it already.
 

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Discussion Starter · #5 ·
The rubber pads are a good idea. Low profile bumper + thick rubber = win?

The steel bumpers though.. I've seen pictures posted after accidents, and people are proud of the bumper not taking damage. Then one guy posted a month later saying his frame cracked. It was after a Mustang hit him at 50mph but it looked like his XJ had no damage.

Which bumpers are thin enough to deform and absorb energy?
 

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Which bumpers are thin enough to deform and absorb energy?
this is what the stock bumpers are designed to do. notice the fronts have rubber bumpers, and the rears have a "crush zone" on a TJ. On XJ's they have "impact quality foam" front and rear with a plastic sleeve, just like almost every other vehicle made since the mid 80s.
 

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Discussion Starter · #8 ·
this is what the stock bumpers are designed to do. notice the fronts have rubber bumpers, and the rears have a "crush zone" on a TJ. On XJ's they have "impact quality foam" front and rear with a plastic sleeve, just like almost every other vehicle made since the mid 80s.
I meant aftermarket steel bumpers.

How much energy can the stockers actually absorb though? They aren't required by federal regulation to absorb anything, because the XJ is classed as a light truck right?
 

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I meant aftermarket steel bumpers.

How much energy can the stockers actually absorb though? They aren't required by federal regulation to absorb anything, because the XJ is classed as a light truck right?
no. all bumpers on vehicles in the US are required to survive a 5mph impact into a concrete wall with no damage (aside from a scratched finish).

pretty much the entire point to aftermarket bumpers is beefing up the front or rear end for off-roading, they don't care about crash testing. however, some are crash tested to work with airbags, and the ARB front bumpers are only ones that are that I know of. think about it - hitting a tree, rock or resting on your bumper in a breakover angle situation would destroy a stock setup, or any setup ment to collapse, but beefy bumpers are designed to armor the vehicle from damage.
 

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Discussion Starter · #10 ·
no. all bumpers on vehicles in the US are required to survive a 5mph impact into a concrete wall with no damage (aside from a scratched finish).

pretty much the entire point to aftermarket bumpers is beefing up the front or rear end for off-roading, they don't care about crash testing. however, some are crash tested to work with airbags, and the ARB front bumpers are only ones that are that I know of. think about it - hitting a tree, rock or resting on your bumper in a breakover angle situation would destroy a stock setup, or any setup ment to collapse, but beefy bumpers are designed to armor the vehicle from damage.
No, all vehicles aren't required to have 5mph bumpers. The regulation only applied to passenger cars, and they were required to hit an immovable object at 2.5mph. They consider that equivalent to hitting a parked moveable car at 5mph. NOW the regulation is 2.5mph, not 5mph. So that means hitting an immovable object at 1.25mph

http://www.nhtsa.dot.gov/Cars/Problems/studies/Bumper/Index.html

49 CFR Part 581, "The bumper standard," prescribes performance requirements for passenger cars in low-speed front and rear collisions. It applies to front and rear bumpers on passenger cars to prevent the damage to the car body and safety related equipment at barrier impact speeds of 2½ mph across the full width and 1½ mph on the corners.
No. The Federal bumper standard does not apply to vehicles other than passenger cars (i.e., sport utility vehicles (SUVs), minivans, or pickups trucks). The agency has chosen not to regulate bumper performance or elevation for these vehicle classes because of the potential compromise to the vehicle utility in operating on loading ramps and off road situations.
The agency concluded that reducing the impact speed from 5 mph to 2½ front and rear impact speed best satisfied the statutory criteria that the bumper standard "seek to obtain maximum feasible reduction in costs to the public and to the consumer." The agency also concluded that reducing the impact speed to 2½ mph and eliminating the Phase II damage criteria would not have an adverse effect on safety as measured by the number of crashes, deaths or injuries that occur annually.
Ironically, I think PVC can easily meet the weak 1.25mph standard... Auto industry lobbyists "for the lose" :(
 

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GROUND POUNDER
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I'll take a stout bumper over a "crushable" bumper anyday of the week... I hit rocks alot more than I hit other vehicles.

At slow speeds, a crushable bumper on a Jeep might help some. A head-on into something at 60mph in a Jeep and I don't think it really matters what type of bumper you have.

My biggest fear (while driving my Jeep) is getting "T-Boned" in the side.. :eek:
 

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winkosmosis said:
They aren't required by federal regulation to absorb anything, because the XJ is classed as a light truck right?
you clearly know the answer already so why ask?

My biggest fear (while driving my Jeep) is getting "T-Boned" in the side.. :eek:
ditto. thats where the cage and rockers come in handy:2thumbsup:
 

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Discussion Starter · #14 ·
you clearly know the answer already so why ask?

ditto. thats where the cage and rockers come in handy:2thumbsup:
I don't know the answer. My license plate doesn't say Texas Truck on it. The feds could easily classify it as a car.
 

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Heres my solution. Remove the whole front bumper and watch where you are going. PVC eh thats a big mess to clean up.
 

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Can't help but agree with the naysayers. A PVC bumper is only a good idea to hide behind a real bumper for holding fishing poles and such. Make one out of 2 x 5 x 3/16 " inch steel tubing and be done with it....:cheers:
 

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Leave The Pvc Alone!

If you're not convinced: Take a piece of pvc pipe and seal it. Leave it out in the sun for a month or two. Then, go out and hit it with a sledge without eye protection. I rather you wear an eye patch than whoever is unlucky enough to be in your way...

Good gawd some people don't want to hear (I avoided the language filter and got a warning) other then "hey great idea".
 

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I agree PVC is a bad Idea, have you thought of papermache, no flying schrapnel. J/K
If your worried about getting in a car accident maybe you should look at another type of vehicle with higher safety ratings.
 
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