Ground pressure of tracks

[T Hectares]

At a CTF workshop yesterday ( maybe someone from on here was there ? ) Dick Godwin of Harper showed some soil pressure figures from a pressure pad buried in the soil and then driven over,comparing a 12 ton MF tractor to a 16 ton Challenger,the data showed a lower pressure from the Challenger but it showed the track idler's exerted a higher pressure than the front and rear drive rollers,
I didn't think about it at the time, but i wondered which of a twin track or quadtrac system was better at reducing ground pressure, or whether a small 700 Challenger/ 8rt Deere was much lighter on its feet than a heavier 600 Quadtrac.
Would more idlers on the quad result in more higher pressure spikes, and would the double tracking effect lead to a firmer footprint.
I know there are advantages / disadvantages to both systems, and i have operated both, but i was looking at this purely from a ground pressure point of view.

 

[sumo]

on a similar note I've often wondered when watching any tractor (crawlers included) when pulling very hard, virtually all the weight (drawbar weight of implement included) is on the rear wheels, even a quadtrack is lighter on the front.
This will seriously mess up any ground pressure calculations, sadly only making them any use if the tractor is trundling around?

 

[FarmyStu]

on a similar note I've often wondered when watching any tractor (crawlers included) when pulling very hard, virtually all the weight (drawbar weight of implement included) is on the rear wheels, even a quadtrack is lighter on the front.
This will seriously mess up any ground pressure calculations, sadly only making them any use if the tractor is trundling around?

You should take this in to account when you do your calculations. But many don't. However, with a mounted implement the rear tyres will be under most load at the headlands with the implement out of the ground. This figure can be calculated on a weighbridge.

 

[nick...]

on a similar note I've often wondered when watching any tractor (crawlers included) when pulling very hard, virtually all the weight (drawbar weight of implement included) is on the rear wheels, even a quadtrack is lighter on the front.
This will seriously mess up any ground pressure calculations, sadly only making them any use if the tractor is trundling around?

You are spot on there.when watching any crawler working they are light at the front of the tracks which puts a huge amount of weight under the rear.probably worse with linkage mounted equipment.
Nick...

 

[Darren]

There was a comparison test done in France. I did upload it on here somewhere. Tracked combine vs wheeled. The tracks were more harmful through peak loadings. A tracklayer may be better when stood or levelled up with a dozer blade but any twin track is virtually the same as a two wheel drive tractor when pulling from 3 pt hitch. Nearly all the weight is on the drive wheel. The older flat track challengers when pulling from drawbar. Which is what a crawler is designed to do really. They're drawbar was pulling from up front, near the front idler thus keeping a better weight distribution. That's what I've found in 20 odd yrs of driving them anyway

 

[warksfarmer]

To get a pressure pad in the soil means digging it up, therefore loosening it so it will never go back down as you would find soil in the middle of a field.

 

[Robt]

Warksfarmer... isnt that irrelevent as you are testing the ground pressure. surely the same pad and the same soil disturbance would happen if the are testing tracks or wheels etc. It would affect result

 

[warksfarmer]

Warksfarmer... isnt that irrelevent as you are testing the ground pressure. surely the same pad and the same soil disturbance would happen if the are testing tracks or wheels etc. It would affect result

True but surely we all want to know what it does in our fields and the only way is to bury a pad for 12 months?

 

[T Hectares]

Isn't loose soil representative of a secondary pass, like on ploughing ?
But it's jumping to conclusions saying it was loose soil on top, the soil may have been reconsolidated by simply treading it back in on top, I don't know either way, but am fairly sure either loose or consolidated it would give the right comparison.
I remember in the dark and distant past there was a tyre v track comparison in profi maybe 12-14 years ago ( that makes me sound really old ) where the only point I can remember, was that when a crawler had a 3 point linkage implement raised, it had a higher ground pressure through the rear drive wheel, than the equivalent tyre, but back in work it was better ( I think, it was a long time ago !! )
It was twin track v Quadtrac I was intrigued about, as when a machine is in work and loads transfer, it's not as straightforward as weight divided by contact area.

 

[willvf]

True but surely we all want to know what it does in our fields and the only way is to bury a pad for 12 months?

agree if you want to know real impact on soil but in practice this won't be fixed for any given soil as water content, structure, cultivation all have an effect. I guess the significance of the pad buried is getting a comparison of the relative effect of different tyres, track, load distribution etc. As long as it is buried in the same conditions for each tyre or track then the results still tell you something in relative terms but obviously not in absolute terms.

 

[Robt]

yes true, but the study was comparing tracks and wheel over a pad... Only have to look at late winter drilled wheat to see wheel tracks all season....
Track ( if weighted correctly) all the way

 

[Pingu]

yes true, but the study was comparing tracks and wheel over a pad... Only have to look at late winter drilled wheat to see wheel tracks all season....
Track ( if weighted correctly) all the way

I'm a big believer of tracks but in late drilled wheat this year can see everywhere quadtrack turned but not where a dualed 936 turned due to no smearing of the soil which is compaction. Tracks in the wet I'm not 100% sure on, only if can stay straight...

 

[Halftrack]

Spent a LOT of time years ago driving wheels and tracks over research soil pressure test rigs ( Lee, they were pushed into the soil on the end of a pole from trench dug alongside test strip) (Shaun, the rear axle loading increased massively when towing under load over the sensors, even when weighted correctly)

We used to run everything except the sprayer on tracks at one time............ only use tracks now when soil conditions are too extreme for tyres.

 

[Brisel]

I'm a big believer of tracks but in late drilled wheat this year can see everywhere quadtrack turned but not where a dualed 936 turned due to no smearing of the soil which is compaction. Tracks in the wet I'm not 100% sure on, only if can stay straight...

Crawlers are frequently still out in the field when wheeled tractors have left the field long ago. Were the 936 & the Quad in the same field at the same time?

 

[Pingu]

Crawlers are frequently still out in the field when wheeled tractors have left the field long ago. Were the 936 & the Quad in the same field at the same time?

Same weeks at end November on very similar fields and both running at similar pressures well going by case's quoted 6psi for a quad. Weight is still weight no matter time of year and tracks smear when turning. Yes they will keep going but should you! In my experience I admit a well ballasted wheeled tractor will never be far behind tracks especially xerions etc. Will add wheats grown out of it but it's gotta knock it somewhat

 

[Knockie]

Not much smearing with the Quad, I spread fert with the Quad onto growing crop loaded up with 5tonnes of liquid, Bateman on 710's running 3/4 full leaves more of a mark.
I've taken off 2 1/2 tonnes of weight off the front and replaced with tank.
I'm sure the Quad is weighted 60/40 front to rear and when under heavy draught it is running at near 50/50.
Cheers.
SD.