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loadster
User Rank
Gold
CAFE and materials
loadster   2/26/2013 4:33:44 PM
NO RATINGS
Thanks so much for finally getting to the applicability of this article. Future Designs.

We will see more and more abuse and misapplication of lightweight materials in air and surface vehicles as we strive to shed mass and the cost of accelerating it. I have a 1996 Yukon and a VW Touareg and one weighs 1.5 as much as the other and the mileage is 1.5 times better on one. The payload, size and comfort are similar. As well as the horsepower. Much of the difference in mass contributes to the improved fuel efficiency and the rest is from better application of the fuel-joules and combustion by the powerplant. My yukon is 17 years old, and the only thing inoperative is that the CD player skips alot. I'd be very surprised if VW really meant for my T'reg to last much beyond that age. Its a solid design but the materials are just not more GMC steel and less plastic. An interesting application of plastic gears is the sundancer in my kitchen window that is a low voltage solar panel driving high torque gear set to turn a crystal prism that throws light spots in different directions. The gears are in a clear plastic housing that clearly shows their condition and allows UV attack every day. They used to be vibrant colored. Now they're faded and probably distorted from the heat. They still work but they're purely decorative. They don't belong in cars where window cranks should last at least as long as the engine.

Jack Rupert, PE
User Rank
Platinum
Re: An opportunity...
Jack Rupert, PE   2/26/2013 4:09:40 PM
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mr_bandit - That's a great idea.  The local shops (or at least the local NAPA supplier that they get their stuff from) could invest in a small printer.  No inventory required.  In fact, the OEM could license the part libary and they would need to be in the manufacturing business for the small stuff - pure profit.  This could also allow older cars to have the "right" components when the manufacturer no longer wants to see the actual hardware.

Pubudu
User Rank
Platinum
Re: 2006 Jeep Liberty has a similar problem
Pubudu   2/26/2013 5:42:02 AM
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I also have faced a same experience with my friends vehicle which is Jeep Liberty,

It's not only with the window regulator but with the door lock which is made out of plastic. The agent replaced the part without extra charging as yours. And they mention that it's a factory defect of the particular model of Jeep.



mr_bandit
User Rank
Gold
An opportunity...
mr_bandit   2/26/2013 1:19:38 AM
NO RATINGS
With 3D printers and scanners becoming common, a logical thing is to create the models for these parts, then print them on demand. Not sure what the softening point of PVC is (and another plastic is common, too), but better than losing an entire car. There are services that will print them in metal, too.

William K.
User Rank
Platinum
Failing plastic parts: They usually do!
William K.   2/25/2013 10:50:27 PM
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It was an interesting comment about how strong plastics could be, but those strong ones are not the cheap ones, ever. Adding to the fun is the tendancy to use only enough material to just barely do the job under ideal conditions. That assures that the assembly will fail before the warranty runs out, unless the product has one of those 10-day warranties. The other thing that leads to failure is a lack of adequate understanding about stress levels in plastic parts that yield "just a bit." When the part deflects then the original analysis is no longer valid, and troubles begin. And the final source of failure is the purchasing mentality that always wants to buy cheaper plastic, not regarding the quality of the cheaper stuff.

lbrac
User Rank
Iron
Saturn plastic regulator parts
lbrac   2/25/2013 8:34:27 PM
NO RATINGS
I had the same experience with my 1998 Saturn. First it was the window but after I purchased a new regulator assembly I decided to instead make a replacement part that would last. Shortly after the first window failed another failed. Then the sunroof failed. I found replacements for the plastic pieces made from machined aluminum online and installed a pair. They were over $100 but much less than replacing the entire sunroof and a replacement sunroof would have just failed agsain anyway.


Even when Saturn was separate from GM and made a relatively decent auto they apparently couldn't get away from using the same junk small parts. After GM became directly involved with Saturn they caused them to go bankrupt even before GM did.

BillK-AZ
User Rank
Iron
Re: Plastic in all the new cars
BillK-AZ   2/25/2013 6:12:26 PM
NO RATINGS
There is a similar problem with Buick Century vehicles of about 2004.

The drive mechanism is a cable with ball on each end that drives the window via a plastic slider that has two fingers that catch the balls on the end of the cable.  The assembly is in tension.

There are three cars in my hot Arizona neighborhood that have had the plastic break and then the loose cable jams up in the drive pulley.  In the three cases this happended on the side of the car that has the afternoon sun on it while parked in the driveway.

I fixed mine by carefully wrapping a steel wire in a sort of figure-8 that caught both ends of the cable and the wire now has the tension and not the plastic parts.

Ann R. Thryft
User Rank
Blogger
Re: Plastic in all the new cars
Ann R. Thryft   2/25/2013 5:59:38 PM
NO RATINGS
Thanks Ralphy Boy. You should have seen the look on my face when my clock/watch repair guy told me a) the gears were plastic and b) he couldn't fix it. I think I'd be even madder about it if I was forced to deal with them in a machine I used every day at work. I know darn well how amazingly strong plastic can be. But the material has to be fitted correctly to the design and the usage model.

Ralphy Boy
User Rank
Platinum
Re: Plastic in all the new cars
Ralphy Boy   2/25/2013 5:53:28 PM
NO RATINGS
 True that Ann...

The place I worked during the 80s & 90s bought a new lathe... It had plastic gearing in the headstock. The first time one of the gears failed every guy in the shop took his turn walking over to the opened machine and laughing or shaking their head... or both... mostly both.

It was a nice lathe for light work but we had to bar it from doing the bigger/tougher stuff. I'm sure the company thought the price was right and had never read about the plastic gears until they were buying repair parts.

I use plastic to make stuff all the time here. Right now I'm doing my first fixture made with PEEK. It's about 15 times as expensive as Delrin... which I normally use to make the same kind of fixtures. The main property that I need it to have is resistance to high temperatures.

It may see the plus side of 400F for a couple minutes at a time (I'm betting 480ish because the plastic will slow the normal radiant skin cooling that occurs). It will also see some nasty torques and G loads while at the minus side of zero or the plus side of 120F though not at max temp. Delrin is okay for the torques, G loads, and even the middling temperature stuff... But it will never survive the plus 400F. And since the PEEK is supposed to be 'a replacement for steel'... I think we're good. We'll find out by Friday.

So yup, picking the right plastic matters.

GTOlover
User Rank
Platinum
Re: Plastic in all the new cars
GTOlover   2/25/2013 12:26:01 PM
NO RATINGS
Yes, he was trying. I fixed it! I machined a part out of Al. Made sure the electric motor was fused and never had an issue since!

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