Metal or plastic body?

[sawtooth]

I previously worked for a supplier for John Deere. Not sure now but in early 2000 they were pushing to change over as many components as possible to plastic in tractors and mowers. Main reason for this was to remove as much cost as possible from each product. I remember one piece in particular which was a structural piece for the hood of a 4000 series tractor. As metal it was very stiff but they went through 3 versions of a plastic one that when the hood was raised gave the feeling of a very cheap and wimpy hood support. I was very surprised they left it that way. They were even celebrating the fact it was converted to plastic material. Very junky in my opinion though. The material was a nylon 6 with 33% glass filler.

 

[MHarryE]

I have a different view than all the others. Plastics allow much more flexibility in the design so curves can be sculpted into the shape for clearance purposes. An example is our JD 7720 - sculptures sides provide tire clearance while increasing visibility. Cost - generally higher with plastic depending on the plastic type of which there are zillions. Seams don't show rust, paint doesn't peel, scratches don't turn into dripping red rust. Stiffeners can be molded into the plastic making the plastic lighter. Fading is a selection process - plastic doesn't mean fading unless the manufacturer opts to go for faded paint. That is a cost decision whether metal or plastic and customer feedback is the ruling factor. But if you are prone to doing something like dropping a tree over your tractor, it is going to be less expensive to pound out the crumpled sheet metal vs replacing the broken plastic.

 

[paulfun9]

I previously worked for a supplier for John Deere. Not sure now but in early 2000 they were pushing to change over as many components as possible to plastic in tractors and mowers. Main reason for this was to remove as much cost as possible from each product. I remember one piece in particular which was a structural piece for the hood of a 4000 series tractor. As metal it was very stiff but they went through 3 versions of a plastic one that when the hood was raised gave the feeling of a very cheap and wimpy hood support. I was very surprised they left it that way. They were even celebrating the fact it was converted to plastic material. Very junky in my opinion though. The material was a nylon 6 with 33% glass filler.

Now they can celebrate the fact that I spent my money on a Kioti rather than than an other JD.!

 

[Cherokee140]

I have a different view than all the others. Plastics allow much more flexibility in the design so curves can be sculpted into the shape for clearance purposes. An example is our JD 7720 - sculptures sides provide tire clearance while increasing visibility. Cost - generally higher with plastic depending on the plastic type of which there are zillions. Seams don't show rust, paint doesn't peel, scratches don't turn into dripping red rust. Stiffeners can be molded into the plastic making the plastic lighter. Fading is a selection process - plastic doesn't mean fading unless the manufacturer opts to go for faded paint. That is a cost decision whether metal or plastic and customer feedback is the ruling factor. But if you are prone to doing something like dropping a tree over your tractor, it is going to be less expensive to pound out the crumpled sheet metal vs replacing the broken plastic.

Shape has nothing to do with it, metal can be stamped into any shape you want...ever see a VW bug?

There is really only one reason to make it out of plastic, cost. It is cheaper for them to make it out of plastic....all the way around. From the equipment needed to make the part to the material the part is made from. Anyone that has every played with vacuum forming can tell you that.

I do agree that it will not rust, but it will get brittle and crack. I know that from experience with my JD lawn mower and its plastic hood....only 3 out of the 7 mounting tabs are left and it has duct tape now holding it on.

They are doing it to make the bottom line better for them all the while charging us even more for the part. Thanks but no thanks.

 

[gphil12873]

Well when they really started making out of plastic the price of steel was thru the roof. The price has came back down to tollerable levels...but the tractors hasnt....go figure.

 

[KennyG]

I probably ought to stay out of this but some of this discussion isn't making sense to me. Is anybody really sure that a plastic body part is cheaper than steel? Stamping out sheet metal parts is dirt cheap. The type of plastics used on body parts looks to me like a pretty sophisticated material. If plastic is so cheap why don't all our cars have full plastic bodies?

My tractor is only 4 years old, so I can't say for sure how it will stand up but I do know that if it had a metal hood it would have some dents at this time but because it's plastic it's in perfect condition. Maybe some plastic body parts do have problems, but I take care of a couple of Honda snowblowers that are probably 25 years old and the plastic body parts are in better shape than the metal parts. Motorcycles have been using a lot of plastic parts for over 30 years now and they seem to hold up fine if you don't crash.

Some people have talked about flimsy, but my plastic parts seem heavier and more rigid than a lot of metal parts.

 

[gphil12873]

well would you ride around at 75 mph in a plastic bodied car....or ride around in a 17 mph tractor? That isnt even a fair comparision. I just know steel was very expensive five or six years ago. Plastic has a place but not tractors I dont think.

 

[D7E]

I have a different view than all the others. Plastics allow much more flexibility in the design so curves can be sculpted into the shape for clearance purposes. An example is our JD 7720 - sculptures sides provide tire clearance while increasing visibility. Cost - generally higher with plastic depending on the plastic type of which there are zillions. Seams don't show rust, paint doesn't peel, scratches don't turn into dripping red rust. Stiffeners can be molded into the plastic making the plastic lighter. Fading is a selection process - plastic doesn't mean fading unless the manufacturer opts to go for faded paint. That is a cost decision whether metal or plastic and customer feedback is the ruling factor. But if you are prone to doing something like dropping a tree over your tractor, it is going to be less expensive to pound out the crumpled sheet metal vs replacing the broken plastic.

I agree with nearly all of this but regardless of brand I find the paint comes off plastic worse than steel . The fenders on JD's , The hoods on NH 40 series and TM's can look like dairy cows and our cat backhoes have almost no yellow left just black plastic on the hoods . But then with tractors like the mf 2000 series that were very prone to the cabs rotting out and didn't have bolted fenders plastic is a lot better than cutting out and welding in panels !

 

[Baby Grand]

My personal preference is for metal, just because I have a good idea that that means steel of some suitable grade. If designed right, primed & painted properly, it will last and last. Dents & bullet holes can be fixed with relative ease and a new shot of primer & paint will protect it for many more years. The paint fades in the sun, but the steel is impervious to UV damage.

When you say "plastic", that could mean any of thousands of compounds - some very good and others, not so good. Almost all plastics degrade in sunlight, so it should really have a coat of paint to limit the damage. A carbon fiber hood would be nice - very strong and light weight up high, bringing the center of gravity down a tiny bit. But it would cost much, much more than steel. A polystyrene hood would probably last a few months before cracking and cost a little more to make than a disposable milk jug. The material the tractor company decides to use will be somewhere in between those two extremes, and will probably have some percentage of filler, like glass fibers, just to complicate the comparison. Fixing any plastic part requires a lot of skill and careful material matching/selection.

So, steel is simple and works. Plastic - not necessarily so, but maybe, sometimes.

 

[k0ua]

I thinks that some of problems with the plastics come in the attachment points. That seems to be the most problems with cracks forming at the tabs where hoods rotate around the bolt axles etc. If they could solve these problems then perhaps most people would look at plastics in a more positive light. I haven't had any problems yet with my JD, but it is still fairly new, with low hours and is garage stored.

 

[pmsmechanic]

Interesting discussion. I think that each has their advantages. As for cost of production who cares. That's not my problem. I want a tractor that is reliable and still has value after I'm finished with it. Is metal really easier and cheaper to fix vs. just going and buying a new hood? I like the fact that my 4410 hood and fenders have the color molded right in. I also like the fact that plastic absorbs more of the sound and makes for a quieter machine.

 

[paulfun9]

Interesting discussion. Is metal really easier and cheaper to fix vs. just going and buying a new hood?.

That question will depend on the end user.

For me fixing it is easy and everything needed is always at hand with the exception of paint.

What I find difficulty in understanding is how you consider one to be quiet compared to the other. with all my recent shopping for a new machine the difference wasn't obvious and I was looking hard for any and all differences between machines. To me the sound was just different but not any less maybe with a decibel meter one might actually be able to find the difference but I believe it to be so small that it wouldn't affect my buying decision one way or the other.

 

[Deere Dude]

Does anyone have thoughts on;

What is the plus or minus to metal versus plastic body's on tractors?

Best
Chris

I had John Deere garden tractors since 1966 about with steel fenders and fiberglass hoods and just sold the last one last summer. The only thing that broke was the nose on a fiberglass hood on a 110 GT.

I also had maybe 8 garden tractors with plastic hoods and fenders since they started coming out 30+ years ago. Not a problem.

I know have a X740 and a 3720 with plastic or whatever else it might be for the last 5 years and never had a glitch in hinges or paint or fading or cracking. Some scratches from tree branches, but that is it. I even rolled a rock about the size of a small football over the FEL and it bounced off the hood with not even a scratch. But I think I got lucky on that one. With a reputable company, I wouldn't worry about either. Both are time tested.
For the steel hooded folks, if I dropped a tree branch and crushed a hood, I sure wouldn't beat it back with a hammer and call it a day; I would replace it and they don't give those away either.

 

[pmsmechanic]

For me fixing is easy too but if I spend three or more hours straightening out and painting a hood when I could have been billing my time out fixing for others then it's cost me money to fix my own hood. My experience with metal is that it amplifies sound and vibration vs absorbing it like plastic does. I won't go out on a limb and say one is quieter on a different tractor than another as every tractor is built differently. A metal hood lined with foam is quieter than one without and it's pretty hard to control all the variables when you aren't building the tractor. There's just a few of the idea's that I'm tossing out to generate some discussion.

 

[drizler]

FWIW I see there are some new products out there to repair plastic cracks. Check out youtube and you will see a couple that are quite interesting. V it out and rough it up then apply the glue to the powder and it seems to melt and leaves behind something that looks like a weld. How well it holds up I don't know but it sure looks good.
I have fixed a plastic hood on a snowmobile using regular automotive 2 part epoxy products by Fusor and it seemed to work in spite of the bouncing flexing of the very thin plastic hood. The stuff sands and paints well too. One thing I have noticed from plastic parts on cars is the way they hold paint. For some reason they just hang on to paint far better than metal. The big feature here in the rust belt is that they don't rust out which is major. As long as they are painted they also don't seem affected by UV from being parked in the sun at least as I have seen on cars.
My big issue is ease in cracking if stuck in sub zero weather. It's not a big issue for many but I live in cold country and do things in the cold. I just don't like things that stick out unsupported that can be bumped into like fenders. Hoods probably fare better due to their rounded shape but are more vulnerable to being slapped by branches . All of this would be a moot point if you could replace plastic parts for a reasonable price but manufacturers seem to see this as a place to gouge customers with high prices. Fiberglass is unaffected by heat cold and sun but they takes more time and effort to produce so manufacturers prefer plastic.
Here is another thing to consider in the repair realm. Ding a steel fender or what not you can fix it next winter or never if you choose. Get a crack in plastic and you better stop drill the end of the crack at the very least or it will just keep growing in many cases. You pretty much have to address it soon or more damage will likely follow. Myself for something like a tractor I will take metal. It just makes more sense for the use of the machine to me on a long term basis.

 

[jc21]

I'm on the fence on this ... the plastic hood on our seven year old JD X320 looks almost like new when cleaned up. The Xenoy plastic alloy (PET+polycarbonate I think) has proven to be tough stuff surviving kids walking on the hood, 40lb sacks draped over it etc, etc. The one piece metal stamping for the rest of tractor still looks good too except for a nickel size spot next to the footrest where the paint is gone- I think some trapped road salt from snowblowing the end of the driveway is the culprit.

There are advantages and disadvantages to both metal and plastic but in the end if it's engineered and manufactured properly, I don't really have a preference- if it works, it works. Now if JD could make a seat that wouldn't disintegrate (two so far, going aftermarket this time), I'd be a happy man.

 

[paulfun9]

Cost of replacement vs fixing. I find that in most cases when the travel time and fuel cost is added to the part that needs replaced fixing it here is almost always the less expensive route..

 

[Cherokee140]

FWIW I see there are some new products out there to repair plastic cracks. Check out youtube and you will see a couple that are quite interesting. V it out and rough it up then apply the glue to the powder and it seems to melt and leaves behind something that looks like a weld. How well it holds up I don't know but it sure looks good.

There are also little metal "Z's" that you can melt into the back of the plastic and that will do a real good job of holding it together. They work real well. Then you prep the surface just like you would fix a bumper on a plastic car bumper. Paint with the same kind of paint...it has to be able to move. A tad of filler, (no great bondo please) and you are good to go.

I wanted to add...I think you can get them at Eastwood.

 

[MHarryE]

Twenty years ago we paid $18k for tooling to form the metal snouts on our new born head and the next year $250k for a plastic mold for the next gen. Yes, vacuum mold would have been cheap but you don't vacuum form a plastic that will take the beating of corn cobs being smashed against them. We tried literally hundreds of compounds optimizing the plastic - minimize corn damage compared to steel, minimize corn loss by cushioning the cobs so they don't bounce out of the corn head like with steel, lighter weight so the combine could lift adding 4 more rows.

And since my last post on this thread I got caught in a fast developing hail storm with what I later found reported as up to 4 1/2 inch hailstones. Hood, half of the roof, and trunk lid all dented. Plastic and glass no damage. The hood on my car is stiffer than the steel hood on my Kubota tractor. I suspect that my steel hooded Kubota would have been dented in that storm while my plastic hooded Kubota would not have seen any damage. That's just a guess - I would not want to go through a storm like that again.

 

[sawtooth]

Ok so your great grandpa is 100 years old now and still has a tractor he bought new when he was 25. Would you rather have a collector made of heavy metal that can be restored or old brittle plastic? Nough said. LOL!