Car Tech: What are the pros and cons of plastic cars?
- 6/6/07 1:57 PM
Plastic Vs Steel
by DaveMcLain - 6/21/07 6:25 AM In reply to: What are the pros and cons of plastic cars? by wcunning
I think you'll find that plastic parts can be good for some areas of an automobile and not good at all to really terrible for others. For instance, when it's exposed to engine compartment heat plastic tends to get brittle and fail over time. Ford experimented with plastic intake manifolds on the 4.6 several years ago and most of them have now been replaced by aluminum versions.
Also, steel, castiron and aluminum are ALL easily recycled materials that are used in car construction. Not far from our shop is a scrap yard where every day 5 tractor trailer loads of old cars, farm equipment, washing machines etc get hauled to "the grinder" in the city where they are pulverized and made ready to be melted down and made into brand new steel once again. While that might seem to be low tech it's really a sensible use of materials and resources, steel is a good thing.
plastic bodies
by wcoffey81 - 6/21/07 6:28 AM In reply to: What are the pros and cons of plastic cars? by wcunning
plastic auto panels have been around for quite a few years. GM has been the leader but there are plenty of others. i am currently driving one of my brother's P-Body Fieros. there are still plenty of the U-vans (lumina, transport, sillouete), saturn's and of course the well known corvette running around on america's highways. the plastic panels are not lighter but they are easier to form into complex shapes and it saves the automakers money because dies for the p-panels seldom wear out. the other benefits are no rust and few dents. one bad thing is they tend to grow and shrink acording to the outside temperature, far more than steel, and that make panel alignment an issue. yes they use some nasty chemicals to keep the panels flexible but the steps taken to keep the steel from corroding are every bit as bad and hang around just as long.
in the late 90's i was one of the most highly trained body repair technicians in this part of the country and i spent a lot of time learning plastic panel repair. this thread brings back a lot of facts and figures i will never use again so THANKS to whoever started it.
several areas of caution keep coming up in my head. one is "lightweight" or lighter than steel. unless you get into some of the exotic materials like carbon fiber the "plastic" panels generally mean more weight in the end. the other is in recycling, a steel fender can be melted and remade into another fender. a plastic fender will be reused in something else because of contaminates, like paint. they become products we knew as blended.
The only way
by Coloboma - 6/21/07 6:41 AM In reply to: plastic bodies by wcoffey81Well, like it or not, there is going to be more plastic in our future. When gasoline prices hit $10 a gallon, the best way to improve mileage is to reduce weight. I think cars will go to welded tubular frames with plastic panels. In an accident, the plastic will break away, but the driver will be safe in the steel cage. This sturdy frame will allow "5 mph bumpers" to come back, yet deform in a controlled way to reduce G forces in a serious accident. We are spoiled on living room luxury in our vehicles. This will come to an end, because it is incompatible with safety and fuel efficiency. Yes, we can get 50mpg, but the laws of physics won't allow 50mpg in a 3500 pound vehicle. They must be lightened up, and the only way to do that is welded tubular frames, plastic panels, smaller engines, and lower levels of comfort and luxury.
mixed bag
by wbowblis - 6/21/07 6:36 AM In reply to: What are the pros and cons of plastic cars? by wcunning
Composites (plastics) have many advantages over steel, including the ability for some of them to be deformed and recover completely. Of course they don't rust. For bumpers and similar applications, you can use an unreinforced plastic that will absorb an impact with little or no damage. In high strength applications however, you need to use reinforced plastics, with fiberglass or carbon fiber, for example. These are far stronger than steel on an equal weight basis and in the rollover example I read, would easily support an SUV on it's roof. The downside is that if you exceed their ability to be deformed, they fail totally. Steel deforms easily, and in a major crash will become mangled, BUT it retains strength. Many years ago, I totaled an all steel VW beetle (the original one, not the new one). I was shaken, but unhurt and the car had to be more than a foot shorter than before the accident, but I still drove it home. There's little chance that a plastic car would be intact enough to do that although in a modern vehicle, I would have still been unhurt.
Another concept I've read here several times is that "my vehicle was undamaged" being translated to "safe". Some of these has to be luck... you were hit in such a way that you were uninjured, but tests done decades ago proved that the best scenario in an accident is for the vehicle to absorb the energy rather than the occupants. If the vehicle does not deform, that increases the accelerations that the occupants have to endure and increases the chances of injury or death. My brother had a Chrysler that had so much space in front of the radiator that you could stand in it. That car could crumple more than 2 feet before hitting anything solid. That space had only one reason to exist: absorb energy in an accident. Bumper to bumper rigidity is not safe. A vehicle that does not deform has not absorbed energy, but transferred it to things that can absorb it, like the occupants. Energy that is not absorbed has to go someplace. A rigid vehicle would rebound from hitting a rigid obstacle, increasing the acceleration the occupants must endure. One that crumples, will stop.
It's simple physics that a lighter vehicle will take the brunt of the impact in an accident, but I choose to not haul around 5000 pounds because I could hit something. Aside from the fuel cost, that weight makes the vehicle far less maneuverable and less able to avoid an accident. One isn't better than the other, it's a personal preference.
Go back and read...
by jty12388 - 6/21/07 6:44 AM In reply to: What are the pros and cons of plastic cars? by wcunning
I am not going to say anything that has not been said in previous posts, but it seems people would rather blab than go back and read.
I think I read it 3 times already, but stop acting like these are plastics that your kids toys are made of. Take a hammer to that GLX Resin window and see how far you get. These are high quality materials that aren’t going to shatter easily.
Second, crumple zones are simple physics. The more energy your car absorbs the less there is for your body to absorb, the longer it takes your car to stop (or speed up if you are being hit) the less acceleration your body has to take. Yes at low mileage collisions it would be nice if your bumper was not ruined, but when is the last time anyone died from backing into a light pole. And I am sure you have a story about an old 3 ton car that someone walked away from after a horrible crash, but there are incalculable variables in a car accident so you really have to look at the big picture.
Third, if making these plastics will be more expensive than steel, why are they doing it. I think we have a consensus that their major goal is to make money. I have no idea what the cost of doing this is, but if it actually costs more than they must have some strong evidence that it will make their cars better in some other way, perhaps safety?
1/4 inch panels
by King Biscuit - 6/21/07 6:50 AM In reply to: What are the pros and cons of plastic cars? by wcunning
Give us a break, no car ever had 1/4 inch panels.
Pros and Cons of Plastic Cars?
by timmullins - 6/21/07 7:04 AM In reply to: What are the pros and cons of plastic cars? by wcunning
Why plastic? The material uses more oil to make in that quantity than is required to change the oil in a car. And it's very old technology. Flammable, brittle when cold, or when it gets a little old. Need I say more? What it is is cheap, that's why the auto makers love it. But there are far better materials available today. Try epoxy resins for example. So strong that it's possible to make an airplane from them and not even use a frame. Ceramics are getting really advanced as well. If you do the research, you will find engines have been made out of ceramics. Why plastic? Cheap is the name of the game here, make no mistake about it.
ceramics
by wcoffey81 - 6/21/07 12:16 PM In reply to: Pros and Cons of Plastic Cars? by timmullinsi remember Ford had a ceramic blocked engine on dislay several years ago. i don't remember if it was steel sleeved or if it was all ceramic. but you run into the old problems of cost, repairability and real-world usage
Plastic body
by Neal Gaskin - 6/21/07 7:07 AM In reply to: What are the pros and cons of plastic cars? by wcunning
Plastic body? YES! Did you see the Formula 1 wreck where the car went into the wall at almost 90 degrees at 170MPH? The driver in the composite (plastic carbon fiber) capsule WALKED out of the hospital a few hours later!!
Great mileage; Increased performance from smaller engines; Better braking, less tire wear due to light weight; No corrosion; easy to repair; can be made from petroleum, soy, peanuts or many other sources, can be recycled; styling is far easier and virtuall unlimited (common platform and variable bodies or even multiple bodies.
Plastic bodies - can't wait!! Waited on someone to build a Prius type of car - it was well worth the wait!!
F-1
by wcoffey81 - 6/21/07 12:12 PM In reply to: Plastic body by Neal Gaskinthe cockpit of those formula one cars are about $100,000 each and i don't think the carbon fiber is recycleable. so you just made a $150,000 prius....still interested??? OH, and the insurance is going to be $750 a month because it can't be repaired!!! i still think i would take a new "old style" VW beetle to use for going to work and back and getting groceries. $8000, 30+mpg and it can be fixed anywhere. yes, if i run into something it will probably bend the bumper, kink the frame rail and destroy the fender. it's the stupid penality "I" yes that's "I" should pay for running into something
plastic cars
by jemal38 - 6/21/07 7:21 AM In reply to: What are the pros and cons of plastic cars? by wcunning
with plastic, they wont rust which is good in the winters but for safety I rather have that steel box. Just the other day I seen a grand-am which is constructed of plastic run right in to another car in a parking lot no both cars are totaled. Bring the steel box back, it might hit you over the head at the pump but I'll be safe if i get hit.
Who cares?
by bruceberman - 6/21/07 7:26 AM In reply to: What are the pros and cons of plastic cars? by wcunning
I don't care what they make them out of . . . . as long as they are safe
and reliable.
What about Kevlar? Isn't it a man-made plastic??
by rmonroe041 - 6/21/07 7:35 AM In reply to: What are the pros and cons of plastic cars? by wcunning
I am sure that if the right people get together to construct a "car shell" composed of plastic, I'm sure they can come up with a strong (plastic) material capable of withstanding high impacts, or high heat, and/or even throw in one of our most amazing products, Kevlar, and make said vehicle bulletproof!
If memory serves me right, I believe the government (or the powers that be) make the helmets for U.S. soldiers out of a bullet-proof plastic.
Unfortunately, in my years of living in this country, I know for sure that once the public chooses to swallow this concept whole, and plastic vehicles become the norm, "said autobody plastic manufacturers" will change their recipes and begin to make lower quality plastic bodies, to screw the consumers, and stuff their pockets with the profits!
(As in the previous posting regarding the '82 Riviera..., "a small legal civilian tank." They just don't make 'em like they used to!)
kevlar
by wcoffey81 - 6/21/07 12:01 PM In reply to: What about Kevlar? Isn't it a man-made plastic?? by rmonroe041kevlar is just the fibers used to reinforce whatever resin you mix it with. i do beleive the helmets are bullet resistant not bullet proof and some of that come from it's shape. if you made an SMC type product with kevlar fibers it would be very strong and i think it's how some of the light weight armor plating is made. their new vests have a type of ceramic plate the make them a bullet resistant vest. four problems come to mind but you are on the right track!! (1)cost, (2)cost, (3) repairability, and (4) cost
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