Plastic verses metal

[MChalkley]

I want to test the plastic scarifier teeth, if you don't mind...

Mark

 

[_RaT_]

Now Mark, everyone knows that scarifier teeth are made of rubber and not plastic, you must have been thinking of the attaching bolts, your silly. Rat...

 

[TomG]

Maybe test graphite ones. Could be exciting. Different version of a power hop.

 

[_RaT_]

I'm waiting for a touchless system, laser or polytritium crystal influx transfuser (like the one on Star Trek) type deal. No teeth to wear or break, Rat...

 

[W5FL]

They come on the plastic box blades. The only problem is you have to get plastic rocks first! /w3tcompact/icons/laugh.gif

 

[W5FL]

Most plastics is far from bullet proof and particularly not plexiglas. Lexan is the material used for "bullet proof" sign protection. It is certainly a very tough material and one that I have used for high stress insulators. It is one of the few plastic materials that has good UV properties.

Plastics ARE brittle. It is the plastisizers that keep them from being brittle. Unfortunately no one has come up with a way of keeping the plastisizers from being driven from the material in UV environments and the plastic again becomes brittle.

I strongly prefer metal, because you can repair it. Start a fire under that plastic hood and see how long it lasts!

Welding plastic is simply melting it together with a rod made of the same material for a filler. You had a weak material before you welded it and you have a weak material after you welded it. Works ok on low pressure containers, but not for structural elements. The main advantage of plastic in the agricultural world it that it doesn't rust and is light. The main disadvantage of it is that it is light and isn't usable in 50 years when everything else still is. /w3tcompact/icons/smile.gif

UV deterioration has not been solved for most inexpensive plastic materials. When you think it is, patent some cable ties that don't fall off in a couple of years! /w3tcompact/icons/smile.gif

 

[Anonymous Poster]

Many of the plastic parts like hoods and fenders are painted. The paint provides the UV protection for the plastic, just as it provides rust protection on steel. I wonder which would be worse off if they were both left unpainted.

There are two main classes of plastic. The thermoplastics and the thermosets. Thermoplastics such as Plexiglass (acrylic), Lexan (polycarbonate) or polyethelyne can be welded. A thermoplastic will soften and melt when heat is applied. Most often thermoset plastics are used for components like hoods and fenders. Examples of thermosets are epoxy and polyester resins (Bondo used to repair cars is a polyester resin with fillers added). They are usually combined with structural reinforcement like fiberglass or graphite fibers. They can not be welded. They do not soften or melt when heat is applied. They can be repaired with resin and fibers.

Not all materials are best at all things. For some applications plastic is better and for some applications metal is better. The best tractor would make each component out of the material that was best for the application and would contain both materials.

Bullet proof glass is actually a layer of glass, a layer of polycarbonate, and another layer of glass. The glass, in addition to providing scratch resistance, shatters on impact and dissipates the energy from the bullet over a larger area. Without the glass, some bullets would go right thru.

Andy

 

[W5FL]

That was good. Thanks. Register and participate more. /w3tcompact/icons/smile.gif I saw an old BUICK that was equipped with 1 inch thick bullet proof glass and had 1/2 in steel in all of the door panels. The biggest problem they had was getting tires to hold the car up! /w3tcompact/icons/smile.gif

 

[stvman]

I don't believe it's an either or thing both metal and plastics have their good points I have plastic fenders on my atv when in the woods quarters get pretty tight, you side swipe some trees,the steel wheels look like hell/w3tcompact/icons/mad.gif the plastic fenders look like new!!! Tell me would you like to replace the soft crash absorbing dash in your car with one made of diamond plate!!!/w3tcompact/icons/smile.gif/w3tcompact/icons/laugh.gif My neighbor has a (plastic) Saturn 270,000 miles of New England (salt infested) roads, looks like the day she bought it. All the steel is under the skin, and they crash test very well, ahhh technology it's a beautiful thing./w3tcompact/icons/smile.gif/w3tcompact/icons/wink.gif

 

[W5FL]

I really do understand composites and why they are superior in a lot of applications. Usually when I find something broke in my Honda or Cherokee, it was a pretty well designed part (Cherokee exepted), but it just didn't hold up as well as I would like for it to have done. No, I don't own a car, jeep, or truck with composite body panels, and probably won't as long as there is a choice. Almost every mechanical problem I can think of in them is due to the misapplication (cost savings) of composites in automobile design. Many of the problems appear to be UV related (yes, they were painted parts) or embrittlement issues.

But for tractors, all of the cracked steering wheels, knobs, switches, etc. that failed were also probably due to misapplication (cost savings) of composites. The steering wheels don't usually fall apart, because they knew they would crack and put a metal reinforcement inside them. No, I will take my tractor fenders, hoods, etc. out of metal until composites give the same serviceability. I liked the John Deere metal floorboard better than the Kubota Rubber Mat (which I saw a couple that were cracked), but after having my feet on the rubber mat all day, I now like it MUCH better. /w3tcompact/icons/smile.gif

Tractors need to be heavy for most agricultural applications. The main reason for composites is ease of manufacturing, low cost, and light weight. Seldom is the composite superior to the metal part unless light weight is of high importance as it is in airborne vehicles.

Kubota has a really nice little metal M110 Tractor Model (for $42.00). It looks really well made and I would have bought one except the wheel rims were made out of composite and really looked cheap, although I am sure it was very strong. /w3tcompact/icons/smile.gif Guess perceptions are hard to overcome.

 

[W5FL]

My son has a couple of ATV's also. The fenders do their job well and their job is to keep mud and sand from hitting the driver. That seems to be a good application of composites and they also seem to hold up well. The scratches would have been much worse on metal. /w3tcompact/icons/smile.gif

 

[Bird]

Wen, have you seen any of the composite body impact wrenches Ingersoll Rand is making? They look like plastic toys, but are rated as the most powerful 1/2" and 3/8" impacts made. And they're becoming very popular with the big truck mechanics because they can use a lightweight easy to handle half inch impact instead of getting the big heavy 3/4" one a lot of times.

Bird

 

[W5FL]

Composite case? Sounds like a good application to me. That way when they are thrown in the corner, they just bounce. Thats what I need - a 1/2 inch impact wrench that is lightweight (advantage) and has the power of a 3/4 inch (check those wheel lug bolts). Are they expensive or is it one of those that if you have to ask the price, then you can't afford one? /w3tcompact/icons/smile.gif

 

[Bird]

Wen, Northern Tool has the half inch model (IR2131) in their new catalog for $184.99 ($10 more if you want the long nosed model - 2" longer anvil), and the 3/8" model (IR2112) for $179.99. Sears is also selling them, but I don't know their prices. Apparently they really are the most powerful for their size, and the only ones I've worked on were the result of very obvious severe abuse, and oddly enough, the parts are relatively inexpensive and they're easy to repair.

Bird

 

[stvman]

Wen: I guess if I lived in Texas (have you ever seen a salt truck?/w3tcompact/icons/laugh.gif/w3tcompact/icons/wink.gif) I would be more inclined towards metal but I have seen a lot of nasty looking tractors,cars,trucks etc...that are monuments to rust, that prove the composites might save money but in many applications will out last and out perform a metal counterpart. As far as the hood of a tractor or a car there are composites that are not flammable and when heated would serve to smother a fire not accelorate it. If you ever saw the panels that cover the space shuttle/w3tcompact/icons/cool.gif if they were steel we would only be returning charred remains from space/w3tcompact/icons/shocked.gif. It's not always cost savings ie...carbonfiber,airbags,bulletproof vests /w3tcompact/icons/cool.gif I just think sometimes it's very easy for people to think plastic=milk jug /w3tcompact/icons/smile.gif/w3tcompact/icons/smile.gif

 

[al f]

I actually did have a friend in college who spent a summer internship doing field trials on a baler for New Holland. Pretty cool. /w3tcompact/icons/cool.gif

Al

 

[al f]

I guess what it comes down to is the enormous breadth of materials (thermoplastics and thermosets) that are covered by the word "Plastic".

Al

 

[al f]

Actually plasticizers make plastics more flexible, not higher inpact /w3tcompact/icons/shocked.gif. The plasticizer in the flexble PVC that covers your dash does volatilize and cause deterioration. There are materials right now that work better than the PVC and plasticizer for these applications. GM even announced this year they were going to eliminate PVC in auto interiors and replace it with these new materials (TPV's). That is until they found out the costs: this material is about 5 times as expensive as the PVC they use now. They immediately withdrew that comment and are not going to change. It's not the plastics that aren't ready, its the bean counters /w3tcompact/icons/laugh.gif. No offense to all of you accountants /w3tcompact/icons/wink.gif

Al

 

[W5FL]

Nope, never saw a salt truck. They sand the streets here. A lot of people come here to buy used cars and take them back East.

I do know a lot about materials, though, and most plastics in consumer products are selected primarily for cost.

The bean counters always win in the US (watch your latest IPO shaping up).

That is not completely true in Japan.

Toyota Camry is a domestic vehicle.

Several Fords are imports. /w3tcompact/icons/smile.gif

 

[Anonymous Poster]

Here you go kicking the bean counters again./w3tcompact/icons/laugh.gif Bean counters provide information some other person, probably an engineer promoted beyond his abilities makes the final decsion./w3tcompact/icons/laugh.gif My wife is an engineer for satellite navigation (GPS) so I refer to her as a rocket scientist./w3tcompact/icons/laugh.gif I have a plastic tractor and like it so far. I suspect Kubota will follow suit in a year or so.