With the impeding electrification we might eventually see walkers on skis-shaped feet, as a compromise between load distributed over a large area and a narrow tread not usable for growing. They'd also excel in the metric of total traction per peak surface load.
Key technology of electrification would be tethered drone swarms that feed from the cable they carry, because I'd assume that you'd want to separate batteries from your actors so that they are flexible you work from grid infrastructure just as well as from some battery truck tagging along on an access road (which brings us back to surface load, you wouldn't want the battery loading soil you still want to grow in).
As a John Deere Employee I have to be careful what I say.
I will say (because this is obvious from public information) that we are "looking" at electric tractors, but making them work is hard. 10 years ago we stuffed as many batteries as we could in a 100 horsepower tractor, and for 45 minutes it when head to head with a similar diesel tractor, then the batteries were dead. 100 horsepower just above a small tractor these days. Remember a Tesla might be able to produce 500 horsepower (I can't be bothered to look it up, but something very large like that seems reasonable), but to maintain speed on a freeway it only needs about 20 horsepower. A tractor is expected to produce the rated horsepower for 10 hours non stop.
Your idea of a feed cable is something we have looked at (you can find an announcement, though it might be in German). There are a lot of issues with making it work in the real world, though it might be where things go if diesel gets a lot more expensive.
It seems people (outside the agriculture industry) underestimate what todays tractors (and even more so harvesters, etc) can do and how much power that requires. Harvesters running 12-24 hours a day for days or weeks seem way out of reach of what the current battery technology can accomplish.
I'd bet on hydrogen engines (at least in the next 5-10 years) for larger machines.
On the other hand tractors are multipurpose tools and it highly depends on what it will be used for. If the tractor is only expected to run a few hours a day then batteries might actually work
Since the infrastructure already exists wherever there is serious agriculture, we should probably call that "liquid anhydrous ammonia engines". NH4 is a more practical carrier for hydrogen than its elemental form.
Basically when ya chart out gravimetric and volumetric density stuffing batteries doesnt seem to make sense. There may be some other options (feed cable, slower cycle, etc.)
Has anyone tried standing up a cable car-like system where overhead lines pull (and power) the tractor? You could use wind turbines as the poles that keep the wires up in the air (though I suppose you could also use subsurface cables but that would reduce the growing surface a bit; then again, there's always space between rows of crops).
In the horse age things like that were tried. It isn't practical to setup in a large scale, but if fuel prices continue to go up weird things might be more practical than fuel...
I would have thought electrification might work well on very specialist machinery - perhaps around horticulture, vinyards, greenhouses, etc.
But part of the appeal of a big powerful tractor is their huge versatility - you'd loose a lot of that if you needed additional infrastructure in place.
Not sure why you are responding to my comment either... but what you are saying makes no sense to me.
Obviously the pressurised air itself has mass, but I think its more to do with tyre deformation modifying the contact surface area. The air inside is just to distribute the load across the contact area.
I don't know. Googling, I was able to come up with some examples, but I've never seen them in real life despite growing up in a farming community.
My speculation: you only harvest in dry weather (so traction differences don't matter), and harvesting goes faster than say tilling, so maybe tires are preferred. You'll also see big fleets of combines going down the road to the next field; I think tracked vehicles are frowned upon on public roads.
Because treads are worse than tires for compaction overall. As a soils expert explained to me (phd in the subject), compaction is a function of weight, but the function is something like 0.2*(weight) (obviously it is more complex than that and depends on the exact soil type). Compaction happens only where the tires/treads touch the ground, and tracks touch a lot more ground when you turn so even though there is less damage across the field you lose all of that and more when you turn around. Not to mention tracks have to slide sideways to turn and that is bad for your topsoil.
> Not to mention tracks have to slide sideways to turn and that is bad for your topsoil.
It's unusual and perhaps not suited to large tracked vehicles, but there is an alternative to using differential track speed for turning: track warping. Basically the vehicle bends the tracks one way or the other to induce a turn. The turning radius sucks though.
>The whole point of tank treads is to maximize the ground surface area that the vehicle weighs on.
The treads don't spread weight much more than the wheels - look at tank treads in practice - they are somewhat loose between wheels. Most treads are somewhat loose, meaning the tension in them is not enough to be supporting tank weight. The exist to provide traction when they catch uneven surfaces, where wheels perhaps no longer make contact.
Their point is to allow the tank to catch on non-flat ground when things jut between the wheels. Treads allow grip on non-uniform surfaces.
But most of the time the weight of the tank is completely on (only a few of) the wheels.
explained a few comments above - the question isn't that of direct pressure (that could indeed be solved by using tracks), but sub-surface pressure. Probably how the overall structure is held together and distributes weight in depth under the overall vehicle surface.
In that sense, it would probably help making tractors more like ships...
Or like airships, floating above the crops and only touching it with the whatever devices are used... Fun aside, agricultural devices on rails are not uncommon, although definitely not for such large areas like a normal field (yet?).
Actually a dirigible fixture could probably reduce the weight on the wheels by an order of magnitude for (relatively) little cost. Assuming little maintenance for the dirigible fixture and reduced maintenance for the smaller drivetrain, this might actually make financial sense. But it would require a hanger for parking.
This article considers stresses further down, where the load has already had a chance to spread substantially over a large are.
Loosely speaking, at some depth it's the entire column of soil below that supports the weight of the machine, and piling on more weight will exceed the uncompressed strength from the column, and so it compresses to handle the load. The problem being that compacted soil is bad for plants ability to grow there.
Only where it the tires travel (and a bit to the side), which is why one heavy tractor are still better than many small light ones doing the same job: the heavy tractors does a bit more damage to a small area, but the light tractors do a bit less damage to a lot more area.
