Tyres tracks and weight

[mountfarm]

If you’ve got a 230hp tractor on wheels (600 front 650 rears) that weighs 9t (with a front weight for traction) against a 12t 230hp crawler, the crawler due to the larger footprint would pull better. But what’s causing less ground compaction in normal working conditions so not the current mud bath we’ve all got in our fields. Is it weight or amount of tread on the soil?

 

[Kiwi Pete]

Weight/mass !

Tyre size affects ruts/ wheelings appearance, but it's the weight of the machine that causes compaction at depth

Something the weight of a pickup will compact down to about 17 inches on uncompacted, damp soil, but the more compacted it is the less depth it will affect (due to the bulk density increase of the soil)

To really increase the footprint, you'd make the machine wider and longer to support the increased mass, which is why compaction is a bigger problem today than when a Super Major was considered "big"

that's the simple answer

In real terms, soil structure makes a massive difference, as does the other forces at play as you work - a slipping tyre will compact more per tonne than a simple rolling tyre, because of the almost 'shearing' action it puts on soil aggregates.
Forward speed is also a factor, lots of things are, but basically mass is mass.

 

[Farmer Fin]

Is it not a factor of what exerts the maximum pressure at a given point. Directly below the rear axle in a standard tractor. I’m assuming the same could be said for tracted tractor?

Total mass comes into play but not as much as maximum pressure. Hence wide tyres.

 

[Matt L]

If you’ve got a 230hp tractor on wheels (600 front 650 rears) that weighs 9t (with a front weight for traction) against a 12t 230hp crawler, the crawler due to the larger footprint would pull better. But what’s causing less ground compaction in normal working conditions so not the current mud bath we’ve all got in our fields. Is it weight or amount of tread on the soil?

Also if the implement is set up badly on the crawler and set up well on the wheeled tractor there can be peak loading of the drive wheel on the crawler as it pitches increasing compaction.
Headlands with mounted drills show it as a crawler will pitch up onto the back when the linkage is raised, this puts massive loading onto the soil right under the rear axle.

 

[deleted user 837354]

Cripes yes, the wrong combination of implement with tracked tractor can cause mayhem. There was someone on the forums who was vehemently against using crawlers with anything on the linkage for this exact reason but I forget who it was. The second the linkage is raised the weight is shifted to the rear driving members and ouch. Crawlers may also weigh a lot for their size.

 

[homefarm]

It has been discussed on here many times before.

Lots of differing opinions not sure there is a proven answer in the field with so many variables.

I look at it from the opposite side.

To compact something we use a vibrating roller, heavy slow multiple passes but most of all vibrating.

I do not think contact area makes that much difference in this application compared to the other factors.

So my conclusions are fast is better than slow, light is better than heavy, avoid multiple passes over the same point.
The conditions in the field are never normal but dry is better than wet.

Vibration is almost never mentioned but has the most effect when trying to compact. I think combines compact more because of the shaking action of the sieves. Potato harvesters and balers also vibrate perhaps power harrows?

There is then the question of which type of compaction is most damaging deep or surface.
When does rollling to consolidate become compaction. We have lots of that this year, unrolled wheat is much happier.

 

[GeorgeK]

From Challenger:
A Challenger MT700C’s 635mm (25in) wide tracks offer a total contact area of 3.10m², compared to 1.2m² provided by 710/70 R42 and 600/70R30 Tyres
So in theory the crawler would have to be 2.5 times heavier than the tractor to exert the same pressure on the soil, but as said above, the real world isn't this simple

 

[nick...]

Nearly every picture you see of a crawler pulling the rear end of the tracks are allways a bit more in the ground than the front of the tracks
Nick...

 

[Andrew]

If you have a 9t weight and a 12t weight, the 12t will be worse for the ground. Increasing the footprint will reduce the depth of damage, but a larger area will be compacted.

If you want traction, you do need a certain amount of ground pressure. Rubber tracks tread lightly, so light that in some conditions they don’t force the track cleats into the soil, then they just spin.

 

[Brisel]

If you have a 9t weight and a 12t weight, the 12t will be worse for the ground. Increasing the footprint will reduce the depth of damage, but a larger area will be compacted.

If you want traction, you do need a certain amount of ground pressure. Rubber tracks tread lightly, so light that in some conditions they don’t force the track cleats into the soil, then they just spin.

This. Wheel slip creates shallow lateral compaction that really destroys the soil in wheelings. Deep compaction is caused by weight, regardless of how that is spread. Deep compaction cannot be repaired by a mole or subsoiler as it is beyond the depth of them. Tyres tend to cause more shallow compaction which can be fixed.

As above, torque can upset the spread of weight by tracks as the weight transfers onto the rear drive wheels. It seems illogical that adding the right ballast to a crawler can actually reduce the compaction.

 

[Sharpy]

Is there any advantage to the quadtrack style tracks?

 

[Lewis821]

Is there any advantage to the quadtrack style tracks?

Yes on the headlands, twin track crawlers by their nature churn up headlands and will spin on a heavy dew where a quadtrac/rx will go in most conditions.
It will be these reasons that within a couple of years there will not be a JD twin trac machine only the 8/9rx