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theKbStockpiler Samba Member
Joined: July 07, 2012 Posts: 2316 Location: Rust Belt
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Posted: Sat Sep 20, 2014 7:41 pm Post subject: 914 bumper shocks: Are they rated at only 5mph? |
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Hi ,I'm panning on stiffening up my beetle and want a bumper shock that is stiff like the ones audi foxes had. 914 ones look like I could make them work but are they weak like beetle ones?
Thanks in advance! _________________ My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask. |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21520 Location: Oklahoma City
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Posted: Sun Sep 21, 2014 6:01 am Post subject: |
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They are all 5 mph. ...even the beetle ones. They simply work differently depending on what the bumper was made of and how the shock was designed to function. Many are a one time latching mechanism. Just designed to absorb or slow down force.....not designed to exert any back pressure. The beetle ones are like this......so in short they are really designed to be stiff. Ray |
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theKbStockpiler Samba Member
Joined: July 07, 2012 Posts: 2316 Location: Rust Belt
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Posted: Sun Sep 21, 2014 6:36 am Post subject: |
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They may be stated as (5mph) but the ones on a Audi fox where 10x stiffer than a beetle one. I got rear ended in a fox at about 30 mph and the bumper shocks actually accelerated the car when they decompressed. _________________ My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask. |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21520 Location: Oklahoma City
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Posted: Sun Sep 21, 2014 6:53 am Post subject: |
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theKbStockpiler wrote: |
They may be stated as (5mph) but the ones on a Audi fox where 10x stiffer than a beetle one. I got rear ended in a fox at about 30 mph and the bumper shocks actually accelerated the car when they decompressed. |
That may be....but none of that has anything to do with what the shocks are actually supposed to do.
They are designed to keep the main, body section from incurring more than "X" dollars of damage in a collision of 5 mph or less. The bumper and the shocks are designed to be expendable.
All of the shocks are designed for one single use only. In fact late shocks are not shocks at allm they have no fluid in many of the designs. They simply have an elastomer or spring filler and a latching mechanism inside that will not allow the shock to re-expand.....so they can only be used once.
Also....many of the oil filled ones. ..just like suspension shock absorbers....stiffen up and become solid as a rock over the years.....which is most probably what you experienced with the fox.
Since they typically do not make new ones for old cars, everything you find will be roughly 30-40 years old.....even NOS ones from my experience.....are solid and no longer function.
If your car is after 1973 and requires bumper shocks.....just find what fits and realize that in function it will be no different than a 1973 and earlier solid bumper mount in functionality. Ray |
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theKbStockpiler Samba Member
Joined: July 07, 2012 Posts: 2316 Location: Rust Belt
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Posted: Sun Sep 21, 2014 1:01 pm Post subject: |
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I want the bumper shocks to absorb energy. This decelerates the car and the shock stores the energy. I'm going to install a sub frame in a super beetle so the car could utilize` a stronger shock ,maybe from a heavier car. The mass behind a beetle at 5mph is 1/2 of a buick at 5mph. They cant all be the same except for the mounts. The type 1 bumper shocks are just a reusable bumper bracket that have a crush-zone. I have one good beetle shock to experiment with. 914 are light so maybe I should consider a 944 one. They are for sale once in a while. Domestic shocks usually have a design that goes inside the unibody frame so too much work would have to be done to modify them. I had 3 foxes , one of them a vw and I don't think the shocks freeze to the extent that beetle ones do. I got in two bad accidents with 2 and the radiator supports is what totaled both of them. The shocks did not stay compressed.
Hey , I remember back in the day when bumper shocks came out that some people felt that they were dangerous because if you go rear ended ,the shocks could accelerate you across an intersection or the like. I don't think that all of them are designed for 5mph. _________________ My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask. |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21520 Location: Oklahoma City
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Posted: Sun Sep 21, 2014 3:07 pm Post subject: |
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Yes....they were all designed for 5 mph. Whether some could protect to a higher or lower extent....who is to say.
However I would say that you are reading far more into the design parameters (size, mass etc.) as one could never know what YOU are going to be hit by regardless of the mass of YOUR vehicle.....add to that ...if you are on the brake and get nailed by a 4000 lb Buick....it makes no difference. It didnt work anywhere near what the spec said it should.
There was no way to plan or discern...in the testing....whether you were hitting something (and whether it was stationary or what its weight was)....or whether something was hitting you....and what its weight was.
I would say.....think about that. Whether 5 or 10 mph (and there was a 10mph spec at one point).....5 or 10 mph crash resistance against what weight and under what condition?
This is why the "shock absorber" theory for bumpers went by the wayside long ago. Modern bumpers are made with large plastic cellular inserts and flexible plastic outers. Not many have shocks at all any more.
The other reason why these never really prevented damage is because largely everything after about 1974-76 was crash cell/ crumple zone construction. If you make the bumper shocks stiff enough to actually prevent contact with the sheet metal.....the metal the bumper mounts are bolted to flexes the metal farther forward.
Through the years at least over on the STF there have been numerous discussions on the bumper shock issue. Its hard to see them other than simply a mounting bracket any more. Ray |
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bluebus86 Banned
Joined: September 02, 2010 Posts: 11075
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Posted: Wed Dec 03, 2014 5:59 pm Post subject: |
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some of them bumper "shocks" are dangerous. In fire fighting we learn not to stand in front or behind a car so equipped if it is on fire. if the bumper shock gets too hot in a fire, it can explode the bumper off the car, knee capping any near by person. I believe they eventually fixed this issue with a metal stop to prevent the shock from flying apart. But for some models of cars this is still a danger. I stay clear of the shock mounted bumpers when there is a car fire, approach from the side when fighting a car fire.
Of course all this 5 mph or 10 mph bumper stuff is nonsense when a jacked up SUV goes right over the low slung bumper. many vehicles are much higher up than our old 914's and Bugs. _________________ Help Prevent VW Engine Fires, see this link.....Engine safety wire information
Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022 |
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tisius Samba Member
Joined: July 11, 2011 Posts: 1570 Location: Rotterdam,NL (+Chicago,IL)
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Posted: Fri Dec 12, 2014 5:38 am Post subject: |
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Anyone wants to test their 914 bumpers???
I have a nice concrete wall behind my house
If you want to be sure that you have proper safety devices in your car, then buy a modern car; in that case you're definitely looking at the wrong car if it's a classic aircooled VW... if you get into an accident with an aircooled VW then you better start praying, because that's your only safety device
In short..... forget about it. _________________ drive it like you just robbed the bank
you don't have to be crazy to be into VW's, but it sure helps!!
.... if it ain't dutch, it ain't much! |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21520 Location: Oklahoma City
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Posted: Fri Dec 12, 2014 11:16 am Post subject: |
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tisius wrote: |
Anyone wants to test their 914 bumpers???
I have a nice concrete wall behind my house
If you want to be sure that you have proper safety devices in your car, then buy a modern car; in that case you're definitely looking at the wrong car if it's a classic aircooled VW... if you get into an accident with an aircooled VW then you better start praying, because that's your only safety device
In short..... forget about it. |
Well.... ...they are a little better than that.....I have totaled two type 4's and had several "I got hits" by other drivers over the years so I have a pretty good idea.
Not sure about a 914...just not much mass there. But the 411 and 412 were both crash cell cars. I have seen the actual result from that and its actually impressive.....but other than that...you are correct.
I just read an article when then thread started about how the manufacturers found the 5mph and pending (but dropped) 10mph requirement so ludicrous because of all the issues I posted here and more.....that its unenforceable.
They patently ignore it...and Canada was first to do so, then Europe. The 5mph bumper shocks literally are negated because if you get 5mph against a stationary object....depending on load and power.....your bumper will survive but the REQUIRED crash cell structure with generally flex negating the savings in repair cost. Ray |
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