Metal Body

[Egon]

Are we all talking about the same type of plastic? There are different kinds.

 

[MMagis]

I figured I'd chime in since I work in the plastics industry, and I'm somewhat familiar with the processes and materials used in most plastic tractor parts. Egon is correct, comparing PVC, fiberglass, and ABS to the plastic used on most tractor parts I see at trade shows is an apples to oranges comparison. Most of what I've seen are HPDE (high density polyethylene). In most areas, HDPE really does perform better than metal. It's impact resistance is far greather than most sheet metal used on tractors. Anything that cracks HDPE would likely cause severe damage to sheet metal, and anything underneath it. It's almost impossible to dent. Replacement parts in the future will be much easier to come by, and maybe cheaper, but I can't promise that. UV exposure is almost a non issue. The color and the material itself is very stable.
Having said all that, I still prefer my tractor to be metal.

 

[Soundguy]

The fact that the material is still around in the future won't mean anything.. if the forms to make the part are not available.. plastic or metal.. etc.

What about heat tolerance? what temp does hdpe fail?

As for metal on tractors.. it ain't what it used to be.. some of the stuf nowadays looks like roofing tin metal it is so thin. I like my antique tractor hoods that are stout enough that you really want a neighbor to help you when you lift it off!!

Repair is another issue. I can weld/solder/braze on metal... I don't have any plastic repair skills. All the plastic repairs i've seen others do results in poor bonding of filler materials.. or ugly seems where a thermal fusion bond was made. I've seen some pretty passable repairs made to ruberized plastics using different types of silocone glues .. etc.. and then a top coat or not.

Soundguy

 

[MMagis]

Heat really won't cause it to fail, but it can cause warpage in some cases. At what temperature depends on a few things, including the thickness. Any of it should be safe to a couple hundred degrees. I would hope that those companies using it would have done thorough testing to be sure that heat will never be a problem, but I can only assume. HDPE can be repaired quite nicely, with an ultrasonic welder. But obviously, that's not something many of us have around the garage. Regarding the molds being around in the future to make new parts, I doubt that's a problem. From what I've seen, companies never throw ANY molds away.
Again, I don't really like it myself, but just trying to shed some light on why a lot of companies are switching to plastic. It might surprise some, but price is probably not the reason anyone is switching. Being a petroleum product, the price of virgin HDPE has skyrocketed.

 

[slowrev]

Switching to plastic for lighter shipping weight ? Since many tractors are imported.

I dunno, I like steel. How about a Delorean tractor with stainless sheetmetal ?
Plastic seems to have problems at the stress points where shinges and latches are attached.

 

[aesanders]

Here you go slowrev

Stainless tractor: http://www.samedeutz-fahr.com/lamborghini/

 

[john_bud]

Regarding the molds being around in the future to make new parts, I doubt that's a problem. From what I've seen, companies never throw ANY molds away.

MMagis,

Your comment reminds me of the story of why Chrysler didn't have any big block vehicles in the post "4 cyl only" era. They tossed out the molds needed to make engines larger than the 360 CID v8. I never knew for sure if that was a true story or not, but it is funny in a wierd sort of way.

jb

 

[Egon]

Can't confirm this but think it may have had to do with goverment regulated maximum piston diameter on engines for cars???

 

[biker128pedal]

I also work with plastics. HDPE is affected by UV light. The pigments used in it will fade. It will age. It can be painted but the surface preparation is more finiky then metal or other plastics. Polyproylene and Teflon are harder. This will get better in the future. For repair HDPE can be hot air welded. For small areas you can even use a soldering iron to melt a strip to use as filler rod.

The question about HDPE is are there any tractor hoods made of the stuff? Will it hold up to engine heat and hot oil should a leak happen. When I looked at the NH Bommers the sales guy told me the hoods were fiberglass filled. It looked like fiberglass filled ABS.

These can be repaired. From a realistic stand point you don't need a welder. Just the proper adhesive, a file and a sander.

As far as design the manufacturer needs to reinformce the hgoh streess areas like pivot point so they don't break. JD did not do a very good job on there LT155. I could not get a reliable repair to the bumber/pivot for my hood.

It is mater of design. Just like all things if you can wait a few years for the new design issues to be resolved you won't have to try to make a warraty claim for a poor design.

As fare as mold. After 15 to 20 years most will be sold. Hopefully someone will buy them to supply parts in the future.

Mike

 

[3RRL]

As far as design the manufacturer needs to reinformce the hgoh streess areas like pivot point so they don't break. JD did not do a very good job on there LT155. I could not get a reliable repair to the bumber/pivot for my hood...
As fare as mold. After 15 to 20 years most will be sold. Hopefully someone will buy them to supply parts in the future.

I was in the plastic industry too as a Custom Mold Making company. Started in 1968 and there have been a LOT of changes since then. You're right that some molds ar sold after their useful product life has expired. Like toy molds...they come up with new ones each year. But some molds where the product is around for many, many years, those molds are kept and repaired/maintained.
You're also right about the engineering design work. There's a world of difference between a product design engineer (who comes up with or designs the product or part) and the tooling engineers (who determine how best to make that product moldable and yet make it work for what it was designed). Gussets, fillets, wall thickness and raddii etc. are little things that help re-inforce the product without altering it's basic design funtion but make it mold better and last longer/perform better.