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Plastic

Started by denise 20352, July 25, 2006, 08:32:58 AM

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denise 20352


  I want to know...who was the doofus who decided that it was OK to make moving parts and structural parts out of plastic?

  We have a setup with a swamp box and a cental HVAC unit on our roof, and there is a flapper that closes so that AC and heat doesnt try to go back out the swamp cooler.  This part consists of an aluminum frame and aluminum louvres, connected to the frame with plastic hinges, which, naturally, broke.

  Plastic is fine for a stationary appliance cabinet, and it has some uses in the medical industry, but it has no legitimate use in machinery or automobiles.  Yes, I include electrical connector blocks, because you can make them out of phenolics.  Imagine how much easier it would be to restore your car if there were no plastic parts in it!  Theyre all broken, theyre all hard to find, and they cant be repaired.  There are some synthetic composite materials that can be used in some applications now, but plastic does not cut it!  Even nylon because frangible after a few years.

  I still remember when I was 7 years or so old in grade school, we were shown a propaganda film about how wonderful plastic was, and how it could replace metal parts like gears.  At 7, I knew that it was horse hockey...so why doesnt a full-grown mechanical engineer get it?

-denise

Bruce Reynolds # 18992

Gday Densie,

It is a thing called, Planned Obsolescence.

You have to remember that the car makers only want the cars to work, within reason, until the Warranty Period runs out.

Plus, once the initial purchaser sells it, they arent going to care either if it collapses in a heap.

Plus, it is easier to make a plastic part with multiple facets and curves than one out of steel, and any steel in a car adds to extra weight.

Bruce,
The Tassie Devil(le),
60 CDV

Rhino 21150

Engineers understand plastics, bean counters dont. Plastics resist water and organics very well. They dont resist abrasion. I LIKE plastic pipes in houses. I DONT like plastic faucets. They move.
If everyone took care of their cars the way we do even the Japanese would be in financial straights.

Bill Gauch

I realize that you are just venting and any contrary opinion will spoil that, but I will provide one anyway. :) Plastics, in general, kick ass. Right now I am sitting on a cushioned plastic chair, typing on plastic keys, looking at my almost entirely plastic LCD monitor. If my desk werent 30+ years old, Im sure it would be plastic too. Now, specifically, I wouldnt be supprised if the plastic hinges didnt break for purely mechanical reasons. I would probably guess it wasnt all too UV stable and, in addition, couldnt take the temp. swings. There arent many plastics I would bet my life on if they were left outside. Even ones with UV stabilizers still break down. They just do it more slowly. Personally, I find the price and weight savings of plastic parts too significant to pass up. Think about how much a modern SUV would weigh if all that plastic was steel. And speaking of steel, one thing that has always bugged me to the highest level is the fact that license plate bolts are raw steel. Since they stopped giving out new plates every year/5 years/etc., you never take them out. When you finally have to, due to selling your car, an accident, etc., you end up spending an hour with a drill and a can of WD-40. Personally, I think its all a conspiracy created by the drill, WD-40 and car manufactures so they can sell one extra drill bit every 10 years.

David #19063

Yes, plastic is fantastic is certain applications, in fact superior.  However, in others...well, not so good.

I wonder how much the plastic fuel rail recall on all the 90s Northstars and Shortstars cost someone?

Replaced it with stainles steel fuel rails!

Our 96 Concours fuel rail was leaking when ours was replace...thank good no "fire in the hole" when my wife and son were in the car!

David #19063

Note to self...

Do not attempt to type after 2nd glass of red wine!

LOL!

John Tozer #7946

Good forgives you David.

denise 20352

> Right now I am sitting on a cushioned plastic chair, typing on plastic keys, looking at my almost entirely plastic LCD monitor. If my desk werent 30+ years old, Im sure it would be plastic too.

   I have a laptop with a plastic case.  The battery is in a plastic holder, which is not good, because my last laptop had three extra batteries, and the tabs were broken on every one of them so that they wouldnt stay in.  The keys are plastic, and if I have to pop the caps off to clean under them, there is a good chance that one or more will break.  The space bar is the most likely, because they have springs that go into plastic slots, which, of course, break...because that is what plastic does.  Monitors, go into a computer room and see how many of them have holes burned in the plastic tops because they cant stand heat.

   My vacuum cleaner has a beater bar made of rubber and metal, with metal bearings, which is great, except that they put the bearings into plastic holders, which broke.  All of the engineering and machining that it takes to produce a ball bearing was totally circumvented by the use of a cheap piece of plastic.

   My favorite chair, a recliner, is made of wood and metal with a soft suede cover, no plastic parts, which is why it will last ten years or more.  If the hinges, bushings, or any part of the mechanism were made of plastic, it would be broken within a year or two.

   Plastic desks and chairs, we had them in kindergarten.   They couldnt stand up to the weight of five-year-olds, and most of them were cracked.

-denise

Denise


  Then there are appliances...particularly the appliances that are sold as a particular department store brand...

  Tony bought the refrigerator that we have because he had young kids at the time, and a gallon of milk would fit in the shelf in the door.  Guess what fits in the shelf in the door now?  Nothing!  The door liner is made of plastic, which warps when exposed to temperature changes, so the shelves fell out, one at a time.  The milk jug should be made out of plastic, because it only has to last two weeks.  You expect the door to last a little longer than that.

  We got a washing machine from the same department store appliance company, whose agigator didnt, after a few months, and found that a plastic coupling that held the mechanism together had snapped.  When we went to get a new one, the guy at the appliance store said, "These are always breaking".

  And years ago, I had a vacuum cleaner, made by the same company, that had little plastic wheels on the back, which broke and snapped off after a few months.  A friend of mine spent $250 on a vacuum cleaner because she wanted one that would last years without problems, and after less than a month, the little plastic impeller broke.

  There are places where even a moron should know that you cant use plastic.

-denise

Bill Gauch

Well, from the sounds of it, you may want to investigate your purchasing decisions. It seems like you buy based on some criteria other than quality. That, or you put high levels of beyond-design stress on your plastics. To bring this back to cars, I would much rather have a plastic dash than a metal one. I would much rather have a lot of things made of plastic on my new cars for the weight savings alone. As I said, could you imagine the weight of a modern SUV if everything was made of metal. Of course, all this discussion assumes that something was designed/engineered for function instead of price. Most modern consumer-grade products, however, are designed purely for low price. You can buy for quality, though... In addition, we could turn this into a different-but-the-same argument about any broad category of materials. VW Jetta door handle mechanisms are made of pot metal. After about 5-10 years of opening a door, the mechanism breaks and the handle doesnt work. There is my license plate bolt argument. Modern cars with 100K tune-up intervals frequently have their spark plugs galled, heat or pressure welded in place causing expensive repairs. Aluminum corrodes ultra quick. Most stainless is brittle. Dissimmilar metals  result in electrolisis. Dont like metal? Fabric fades and tears. Vinyl gets too hot in the sun. Leather requires regular cleaning and conditioning. Maybe wood? Typically available soft woods rot easily. Exotic rot-resistant woods are slow growing and usually wild harvested bringing up ecological issues. In addition, your wood needs to be quarter-sawn if you have any hope to reduce shrink/swell effects. Hmm... What else? Stone is always an option. The biggest problem with that is that your feet get ground up into hamburger when you push them through the floor to try and stop.  That, and they dont provide enough of a counterbalance to a side of dinosaur ribs. Damned stone cars...

Denise 20352


> Well, from the sounds of it, you may want to investigate your purchasing decisions.

   I didnt buy the washing machine or the fridge, and, as I mentioned, the Kenm^H^H^H^H department store brand vacuum cleaner was years ago.  I have since set a family policy against buying any applicances from that department store.  Still, you missed part of the message:

> A friend of mine spent $250 on a vacuum cleaner because she wanted one that would last years without problems, and after less than a month, the little plastic impeller broke.

   The most important part of the machine, the part that spins around and slings stuff into the bag, was plastic, so of course, it broke.  For $250, you should expect better.  A hard steel impeller, properly treated against corrosion, would have lasted ten years, which is acceptable for a small appliance.  How do I know?  Because so many of the big steel Kirbys from the 60s are still pumping dirt.  Theyre heavy and awkward, but they still work.  Why not make the case out of plastic, so that the machine is lighter, and the moving parts out of durable metals?  Because they want the sh** to break after two years so that youll buy a new one. The problem is, theyre breaking after two months, because theyve gotten carried away with using plastic.

>  It seems like you buy based on some criteria other than quality. That, or you put high levels of beyond-design stress on your plastics.

   Sometimes a vent turns into a debate, which is actually a good thing, but getting personal anbd turning it into an  argument is not.

> What else? Stone is always an option.

  And sometimes it just gets downright silly, which is a resonable way to close a discussion.

-denise

Rhino 21150

My closet has a zillion poles for clothes: wood. The pole holders: 2 X 4s. Many shelves: wood (real). Brass hardware everywhere. Except the pole holders, which WERE plastic. They broke last weekend, all of them. Now they are brass. Plastic is ill suited to tension. On the other hand my bird feeder is mounted on a piece of 4" PVC pipe. The squirrels STILL havent figured out how to get up it. Two years! Some sort of record I think. Of course if they do get to the halfway point they will discover silicone oil.
My La Salle memorabilia is hung on the wall with METAL fasteners.