Aluminum really inferior for tractors???

[Henro]

The "Aluminum Axle Housings" thread got me wondering if Aluminum is REALLY inferior to cast iron for tractor parts subjected to stress/strain.

Is it?

Or is this another "rural legend?"

From the link listed below:

In Summary:

1. Aluminum, in the vast majority of applications, will exceed the corrosion resistance of cast iron and far outdistance steel.
2. Die cast 380 aluminum has a higher tensile strength than gray cast iron yet, in equal volumes, weighs about half.
3. Aluminum is an excellent conductor of heat. This fact makes it an excellent gearbox and motor frame material. Aluminum reduces oil temperature by conduction heat to the outside air much faster than cast iron or steel.

http://www.usmotors.com/Products/ProFacts/modernaluminum.htm

Rather than being disappointed, perhaps those of us that have tractors with aluminum axle housings should be feeling good about ourselves!

Except for the bolt-on mid pto housing, and I think a hydraulic pump, my Kubota B2910 appears to be all cast iron (including front axle).

I was about to feel good about this...now I don't know if it matters at all...

Does it really matter?

My guess is, if the aluminum is properly designed, it matters probably not at all. For equal volumes of material, the aluminum part may in fact be (gasp!) better!

So...what does the jury say?

 

[Bob_Skurka]

The "Aluminum Axle Housings" thread got me wondering if Aluminum is REALLY inferior to cast iron for tractor parts subjected to stress/strain.

Is it?

Pound for pound it can be stronger.

And as for iron, I'd be willing to bet that a lot of tractors are made with some mixture of recycled pot metal/iron mixture that is actually fairly weak and requires thicker castings than known alloys.

 

[Bob_Young]

If not a "rural legend", it certainly derives from the Ag experience, Henro.

I've seen Ag tractors in bad situations endure incredible abuse and yet shrug it off like nothing happened. All of these had one thing in common: a big heavy iron butt. Massive amounts of iron & steel were the foundation of the machine. Aluminum may have done as well, but that's not how they were made back then.

Still, iron, by itself doesn't necessarily equate to strength. There has to be enough of it as well as good design. CUTs, being for the most part, lightweight tractors don't use massive amounts of anything. So if the Ag experience/"rural legend" has any validity, CUTs may not be overly tough regardless of what they are made of.
Bob

 

[scott_vt]

Hi Henro,
Im not sure I would be overly alarmed about the use of aluminum in a tractor that I owned. Aluminum that is engineered properly can be extremely strong in many varied applications.

The problem with CUTS is getting the HP to the ground especially with ground engaging implements. Many CUTS are notoriously light for many chores that need to be done around the farmstead. With that said, it is important to have adequate weight to transfer that HP to the ground to accomplish any given task.

Case in point, why do so many CUT owners constantly talk about counterbalance weights or adding fluid to rear tires etc.

So my argument against aluminum is not so much a strength issue as a weight issue. Just my 2cents

 

[_RaT_]

The "Aluminum Axle Housings" thread got me wondering if Aluminum is REALLY inferior to cast iron for tractor parts subjected to stress/strain.

Is it?

Or is this another "rural legend?"

From the link listed below:

In Summary:

1. Aluminum, in the vast majority of applications, will exceed the corrosion resistance of cast iron and far outdistance steel.
2. Die cast 380 aluminum has a higher tensile strength than gray cast iron yet, in equal volumes, weighs about half.
3. Aluminum is an excellent conductor of heat. This fact makes it an excellent gearbox and motor frame material. Aluminum reduces oil temperature by conduction heat to the outside air much faster than cast iron or steel.

http://www.usmotors.com/Products/ProFacts/modernaluminum.htm

Rather than being disappointed, perhaps those of us that have tractors with aluminum axle housings should be feeling good about ourselves!

Except for the bolt-on mid pto housing, and I think a hydraulic pump, my Kubota B2910 appears to be all cast iron (including front axle).

I was about to feel good about this...now I don't know if it matters at all...

Does it really matter?

My guess is, if the aluminum is properly designed, it matters probably not at all. For equal volumes of material, the aluminum part may in fact be (gasp!) better!

So...what does the jury say?

Perhaps a visit to the old post by a guy with a JD4310 and broken lower links that kept breaking may help reaffirm why cast iron or steels are more desireable where it counts. Those on the JD 4310 and others in that group are aluminum housings. JD did a change on it beefing up the aluminum. Aluminum is stronger pound for pound, but that means a lot of aluminum and significant size increase. Have you priced aluminum? Cast iron also distorts less from heat making it ideal for heads, blocks, exhaust manifolds. Aluminum definitely has its place, I personally would prefer cast iron (high quality cast) at the high load points on my tractor. I much prefer a cast iron block and head over aluminum on my diesel tractor. I like my bike having aluminum.

 

[Bob_Skurka]

Aluminum definitely has its place

I agree with that, there are places where it is a real benefit and places were it may not be.

The problem with CUTS is getting the HP to the ground especially with ground engaging implements. Many CUTS are notoriously light for many chores that need to be done around the farmstead. With that said, it is important to have adequate weight to transfer that HP to the ground to accomplish any given task.

Scott, I'd like to respectufully suggest that weight/lack of weight is a matter of intended uses. Some of the CUTs, particularly the smaller Kubotas (B3030 and smaller) are designed to be light and powerful. But powerful in terms of PTO HP per pound/size. These are not designed with the intent of being HD machines that are going to excel in Box Blade work or plowing the farm field. These are, however, unsurpassed at operating PTO powered equipment without compacting the soil. They do require proper "ballast" to balance their loads, but the same is true for the heavier CUTs and while the lightweight tractors are lacking in traction compared to the heavier units, it seems like a reasonable trade-off for many owners since light weight compact tractors outsell heavy compact tractors by a pretty wide margin. I could also point out heavier tractors that have less lift capacity than lighter tractors and heavier tractors still require 'ballast boxes' for safe operation. Consequently I have to agree with you 100% that a heavier tractor has greater traction, but I'd also suggest that traction is often not the primary or overwhelming reason that people buy Compact Utility Tractors.

I've seen Ag tractors in bad situations endure incredible abuse and yet shrug it off like nothing happened. All of these had one thing in common: a big heavy iron butt.

I think we often look at 1950's to 1980's agricultural tractors and see that they are low horsepower and very heavy and we assume that a modern CUT that is designed like an aging design is a good thing. However modern agricultural tractors are now shedding weight and/or are improving technology to reduce ground pressure to prevent soil compaction.

 

[MossRoad]

If it was aluminum, you couldn't use your Chalkley cup!

 

[NTex6500]

I'm new to this forum and my opinion may not be very informed. I am a machinist by trade and have cut both forged aluminum and cast iron. If given a choice between the two and weight not being a factor I would much prefer the forged aluminum over the cast iron for strength and toughness. However, I Just bought a 65 HP compact tractor and one of the selling points for me was that it was the heaviest tractor in it's class and had huge honking cast iron pieces. I need the weight because I am going into the hay mowing, baling and brush clearing business. If I were looking for a glorified lawn mower I would have gone for the lightest well made cut within my budget that I could find and aluminum would have been the selling point.

 

[MessickFarmEqu]

They do require proper "ballast" to balance their loads, but the same is true for the heavier CUTs and while the lightweight tractors are lacking in traction compared to the heavier units,

I actually just came back from an M-Series Kubota training and they give exactly the same explination as what Bob does. Most Kubota tractors are designed to support a good 30% more raw weight than whats there. If you need a light tractor, you good to go - if you need a heavy one you can load up with weights and do that application as well. While Kubota gets pointed out because they tend to be at the low end of the scale, this also applies to most of your New Holland and Deere machines as well.

 

[Dargo]

If I were looking for a glorified lawn mower I would have gone for the lightest well made cut within my budget that I could find and aluminum would have been the selling point.

Actually, some of the ancient design 2wd tractors are just that; a glorified lawn mower. Without 4X4 as most all modern CUTS have, they lack any real pulling ability and all weight is for naught. A light weight 4X4 with (mostly standard) weights on the front will make the 50 and 60 year old designs obsolete and they will not only pull considerably more, but an FEL is almost useless on a 2wd tractor. That's why you almost never see a real workable FEL on an old 8N tractor. If they had a decent sized bucket and filled it, they would need another tractor to help pull them backwards.