Bumper Cars
Bumper Cars
(OP)
Just something I've been thinking about the past while and I can’t seam to find an answer any where.
Why aren't there big springs or shock absorbers in the front of cars to absorb the impact of a crash?
Why isn't there a shock absorber behind the front bumper to help alleviate some of the impact passed onto the passengers?
I've tried all over the net looking for a reason and I don't think I'm asking the right questions!
Is there anybody out there that has seen this and if so could they lead me in the right direction?
Thank you,
Regards,
Derry Manley





RE: Bumper Cars
You are asking the wrong question.
Try energy absorbing NOT SPRING.
Regards
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RE: Bumper Cars
RE: Bumper Cars
Thanks for the replies,
I do understand the difference between springs and energy absorbing, my question is why not add something like two pistons to the front bumper that absorb the impact energy and collapse at a certain pressure?
To me it seams logical, like putting rubber mountings on bull bars, if you actually plan on hitting things with the bull bars!
Thanks again for you comments, I'll keep searching!
P.S. ivymike, I like your thinking! :)
RE: Bumper Cars
*Without data, you're just another person with an opinion.*
Hydroformer
RE: Bumper Cars
It has been done, but such designs won't pass current crash tests as they cannot allow enough travel to absorb enough energy. The system needs to use the entire front structure of the car to do that and meet current requirements.
Regards
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RE: Bumper Cars
The shocks in the bumpers are there for the 5mph impacts. They're pretty much useless in a 35mph-40% offset frontal impact.
*Without data, you're just another person with an opinion.*
Hydroformer
RE: Bumper Cars
Hydroformer, you seam to know actual details about this kind of stuff, where would be a good source of actual spec's and requirements for the crumble zone of a car?
I'm trying to figure out if an idea I have is good enough for development!?!
Thanks again for all the comments and replies.
Derry
RE: Bumper Cars
Instruments measure the force of impact to each dummy's head, neck, chest, pelvis, legs and feet. Frontal star ratings indicate the chance of a serious head and chest injury to the driver and right front seat passenger.
NHTSA does a full frontal crash @ 35mph and side impact @ 38.5mph for gov. compliance. IIHS does a 40% frontal offset crash @ 40mph which is a far more brutal test. This closely mirrors a vehicle drifting over the center line and into a head on collision.
Lot's of stuff to absorb here so take your time
http://www.nhtsa.dot.gov/NCAP/info.htm#iq8
http://www.nhtsa.dot.gov/cars/testing/ncap/
Insurance Institute for Highway Safety (IIHS):
ht
European New Car Assessment Program (Euro NCAP):
http://www.euroncap.com
Australian New Car Assessment Program (ANCAP):
http://www.aaa.asn.au/ancap.htm
New Car Assessment Japan:
http://www.nasva.go.jp/english
My company is a member of http://www.mira.co.uk/
*Without data, you're just another person with an opinion.*
Hydroformer
RE: Bumper Cars
Thank you for all that, I was really expecting one link or look at Google!
This is fabulous information!
RE: Bumper Cars
I know that there is a whole range of tests at different speeds, but the highest speed I've come across is 64kph!
I understand that it is a regulatory requirement for them to be tested at this speed but is it that it would be too costly and difficult for higher speed impacts?
To me if two cars travelling at 60 kph hit in a 40% offset condition there would be a relative speed of around 120kph, depending on geometry and what not, with a deformable stationary barrier.
Hydroformer, you stated that the 40% off set models a car drifting across the center line, but wouldn't the on coming car also have a velocity component to play in the impact on the car.
Or is it that 60 kph hit each car?
Do I need to go back to my physics teacher and have him show me relativity again?
Dmanley
RE: Bumper Cars
Regards
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RE: Bumper Cars
"Hydroformer, you stated that the 40% off set models a car drifting across the center line, but wouldn't the on coming car also have a velocity component to play in the impact on the car."
You have to take into account that with the 40% test the vehicle is slammed into a stationary (immovable) barrier. Hitting a brick wall is much different than hitting another car (granted) but you introduce way too many scenarios if you try to model different cars hitting different cars.
The testing is based on crashes that should have a reasonble expectation of being survivable. Start testing @ 120kph and the results will begin to look very similar (everyone's dead).
Long before the NHTSA crashes a car, several rounds of computer crash simulations and improvements have been made by the OEM. The OEM then crashes several vehicles from the pilot build to validate the FEA findings. All of this goes on before a single 'salable' vehicle is made.
Keep reading the links (and links within links), that should keep you swimmin' for a while.
*Without data, you're just another person with an opinion.*
Hydroformer
RE: Bumper Cars
While it would be nice to design cars so that they could be safely crashed at any speed, that is not cost effective. It makes more sense to concentrate on the crash speeds (and relative orientations) that actually cause the most injuries, rather than the alternative. I vaguely remember that in the two years after side airbags were introduced on one car that sold 30000 a year, none were set off. Is that $600 per car well spent? This is not a zero sum game.
Cheers
Greg Locock
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RE: Bumper Cars
If that $18,000,000 plus all that spent in a similar way on other models, was spent on extra emergency services at hospitals, or safer roads, I think more lives might be saved.
Regards
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RE: Bumper Cars
I'd like to see an overall road safety budget, that included expenditure on roads, emergency services, safety devices in cars and any other methods, rather than the current ad hoc approach.
Cheers
Greg Locock
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RE: Bumper Cars
-Jon
RE: Bumper Cars
Regards
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RE: Bumper Cars
Between these two events, the vehicle's structure needs to absorb as much of the energy as it can in order to lessen the secondary impact. (A tertiary impact is also considered as the occupant's internals contact the rib cage / skull).
Greg's on top of it with the design features incorporated into structural members to manage energy in a crash event. This goes well beyond frame rails and bumpers.
Modern FEA crashes record a multitude of sub-events (ie: radiator contacting a/c compressor @ C+27ms 16.2m/s). I've seen alternator bracketry changes because of a spike in the deceleration curve, or to change the resultant trajectory of an object in crash.
Structural design features are also incorporated to manage secondary crash elements such as strengthening or weakening the instrument panel, knee bolster, toe board, etc. Of course seat belts, airbags and padding also help with the second and third events.
A lot of these efforts don't result in additional cost or weight to components in the vehicle but DO contribute to the over-all engineering cost of the vehicle. I'd still rather buy a well engineered car and never take advantage of the crash management ability than to buy something mediocre and hope for the best.
*Without data, you're just another person with an opinion.*
Hydroformer
RE: Bumper Cars
extended hospital stays, certainly.
http://www.netcremation.com/
$495 barely buys a basic Maaco paint job
RE: Bumper Cars
It seems to me that the 60 kph test would be adequate to simulate such collision. While the relative speed is 120kph if each car has enough crumple zones to save its passengers in a test collision of 60kph with a stationary concrete wall then both cars would combine their crumple zones to save their passangers in this collision. In other words the change of momentum of each car should be the same as it would have been if that car hit a stationary unflexible barrier at 60kph. (of course here i am assuming the both cars are similar).
The problem is when you crash a "car" that does not have crumple zones, i.e. an SUV. Then the SUVs rigidity would not only hurt the SUV passengers it would hurt the car's passsengers as well.
That is why it seems completely ridiculous to me that the government requires cars to pass tough crash tests but has no such requirements of SUVs. The reasoning behind this that SUVs are classified as "trucks" and thus are "commercial vehicles" and therefore need not be as safe makes no sense whatsoever.
RE: Bumper Cars
And truck frames do, to a lesser extent, have crumple zones.
However, having as substantial crinkle-zone in a truck frame might not withstand the use of a snow plow, or towing a boat.
Smaller, unibody SUV's have more car-like structures because they aren't used like full-sizes.
David
RE: Bumper Cars
Bumper Impact Dampers
Best regards,
Matthew Ian Loew
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