Driving a 15-Ton, 160-Foot Wide Farm Sprayer Is Actually Easier Than You Think

Driving through the countryside, you might have seen some big machines loping around the fields. From tractors to combine harvesters, they come in all shapes and sizes. Field sprayers in particular are charged with dousing the land in chemicals, and I'm here to tell you what it's like to drive one.

It's been a few years since I last drove a sprayer, so there have been a few advancements since then, but the basic idea remains the same. The biggest sprayers are some of the largest farm machines around, particularly when it comes to width. They feature big wide boom arms covered in nozzles that spray chemicals on the ground. The wider the booms, the fewer passes you have to make through the field, and the fewer crops you crush under the wheel tracks. This saves time and increases yields, so bigger is always better when it comes to sprayers. 

In a past life, I worked for a company by the name of Hardi that specialized in building agricultural sprayers. In fact, Hardi is so focused on spraying that the company’s logo displays a diaphragm used in its classic sprayer pumps.

I worked in a variety of roles from marketing to engineering. This often put me out in the field, literally. Sometimes, that would be to shoot dynamic, exciting adverts for the product. Other times, it would be to test and develop new parts, or troubleshoot difficult engineering problems and improve our understanding of the machinery. This work gave me the opportunity to learn how to drive these giant machines. It’s an experience quite unlike driving a regular automobile. 

The primary sprayer I found myself driving was the Hardi Rubicon 9000, fitted with a 48.5-meter (159.1-foot) boom. As per the name, it’s a sprayer with a 9,000-liter (approximately 2,377-gallon) chemical tank. It’s outfitted with an 8.9-liter Cummins QSL9 turbodiesel engine and a 1,000-liter (264-gallon) fuel tank. It’ll burn through that in a single day’s spraying if you keep it going all day and all night.

The Rubicon 9000 is one of the largest self-propelled sprayers on the market. It wears giant 480/70-R54 tires, which stand six feet high and cost thousands of dollars each. Three people can fit in the cab if you really squeeze, but it’s intended for one driver and the occasional ride-along at most. The Rubicon is a front-mounted sprayer, with the spray boom right in front of the cab providing good visibility of what’s going on. Behind the cab is the giant 9,000-liter chemical tank, with the diesel engine sitting behind that at the rear. Underneath the sprayer, there’s a bunch of equipment and ports for filling up the tank with water and mixing in chemicals in powder form. 

Similar to most cars and trucks, to drive a sprayer like the Rubicon 9000, first you have to get on board. That involves climbing one of the ladders at the back of the sprayer and walking along the catwalk to the cabin. The catwalks are quite high up, around seven feet off the ground. You shouldn’t stand on the catwalk while the sprayer is moving, especially at speed—you could fall off! However, there is a brilliant handrail to hang onto that was designed by a very handsome red-headed engineer. 

Once you’re in the cab, you sit down on an air-ride seat like one you might find in a semi-truck. Pull the door shut, and the cabin is sealed, fed with filtered air from the HVAC system. It’s set up to ensure you’re breathing clean, pure air, rather than dust from the paddock or spray from the boom. In front of you, there’s a steering wheel on an arm that tilts out of of the way for easy entry and egress. There’s a pedal on the floor for braking, and a joystick covered in switches that falls to the right hand.

Much like a regular car, turning a key coaxes the engine into life, but that’s where the similarities end. That’s largely down to the nature of the Rubicon 9000’s hydraulic drive system. There’s no direct mechanical connection between the engine and the wheels. Instead, the engine turns a giant hydraulic pump. Hydraulic pressure is then sent to a hydraulic motor in each wheel, giving the sprayer four-wheel drive. 

The parking brake is released and the drive mode is selected via a dial. The modes are a simple tortoise/hare selection, determining the maximum possible speed. At full tilt, the Rubicon 9000 will do 56 kmh, or about 35 mph. 

Forward or backward drive is achieved with the joystick. Pushing the stick fully forward gives maximum acceleration. Pulling the stick back towards the neutral point will slow the sprayer. Pulling the stick backward from the neutral point will seamlessly engage reverse, and braking is achieved by once more returning the stick to the neutral position. It’s actually possible to drive solely with the joystick in this manner; there’s seldom any need to use the brake pedal. Regardless of whether braking by pedal or stick position, it’s all done by controlling hydraulic flow to the wheel motors. On a Rubicon 9000 sprayer, there are no brake discs or drums involved. 

Steering is straightforward: Turn the wheel left for left, and right for right. Again, there’s no direct mechanical connection to the wheels. Instead, the steering wheel merely sends commands to the computer, which then turns the front wheels via a hydraulic ram.  

Thankfully, it’s a machine that’s fairly easy to drive very slowly while you’re learning the ropes. Dial in the steering and ease onto the stick, and the machine will slowly creep forward. Being able to maneuver delicately is key when navigating the giant machine through tight gates or around sheds and other buildings. 

You also have the benefit of an all-glass cabin to see what you’re doing. Paired with a good set of mirrors, it’s not too hard to avoid running over dogs or livestock as you’re driving around. That’s particularly important when you’re a guest on someone else’s farm just trying to get your job done.

With that said, it is important to be very aware of what’s around you at all times. The sprayer cannot stop or steer quickly. This is exacerbated further when the 9,000-liter chemical tank is full to the brim, which adds around 20,000 pounds to the vehicle’s weight. As fun as it is to go blasting around from field to field at the full transport speed, it’s not recommended to do this on tight farm roads with poor sight lines. 

Once you’ve gotten the sprayer from the farm shed to the field, it’s time to unfurl the spray booms. You might think this is as simple as pushing the “unfold” button, but you’d be very wrong. When I drove one back in 2018 at least, it was an all-manual process. 

First, you hold a switch to raise the booms out of their transport cradles. Once they’re up, holding another switch unfolds the first stage of the boom. The entire boom frame is then lowered slightly, and the switch can be pressed to unfold the second stage. Finally, the third stage of the boom can be unfurled with a final switch.

To protect the 48.5-meter (approximately 160-foot) boom from damage, the outer ends of the boom feature special breakaway sections. These are mounted with a special sprung hinge. If the outer section of the boom hits a fence post, tree, or other obstacles, the breakaway folds out of the way, protecting the rest of the boom structure from damage. Often, if the hit is hard enough, the breakaway will be damaged. However, they’re relatively cheap and easy to replace. Without this, hitting the tips of the boom would risk bending or warping the entire structure. 

With the boom unfurled, spraying can begin. The sprayer is typically driven at a constant speed of around 10 to 20 mph when spraying to prevent the droplets from being excessively buffeted by the slipstream when traveling faster. Special ultrasonic sensors monitor the boom height above the ground to maintain the right height for proper chemical application and to prevent the boom from hitting the ground. To help, the boom has its own fancy suspension system that helps keep it level above the ground during spraying. 

Many farmers elect to program in GPS routes for the sprayer to follow, allowing the machine to largely drive itself in the field. It’s by no means fully autonomous; it’s more like cruise control for following a simple pre-programmed path in a field. This works because there is very little traffic in crop fields for farmers to worry about. Keeping an eye out the window for obstacles while the sprayer does its thing is normally good enough to keep the machine on track. Some drivers will actually watch films or read books while sitting in the cab during spraying. 

Assisted GPS technologies like RTK are used to provide accuracy down to the inch level. This allows the sprayer to trace the same exact path time after time, minimizing the amount of crop damaged by the wheel tracks. Many companies are working to fully automate sprayers, allowing them to operate around the farm with no human in the cab. However, that’s realistically still a few years away from the mainstream, at least. 

Overall, in my experience, the Rubicon 9000 was a capable and well-regarded sprayer. At the time of its launch, it had the biggest tank capacity of any self-propelled sprayer, along with the widest booms in the market. This offered farmers big gains in productivity. In particular, being able to spray more land without having to leave the field to fill up with more chemical could shave hours off a day of spraying. 

The sprayer was available with a wide variety of GPS and steering systems, and configuring these could be difficult. Similarly, getting various different spray booms set up to “ride” just right took some work from experienced technicians. Often, there'd be a day or two of field testing a new machine on a customer's farm to get the auto-steering and boom controls working properly. The sprayer would also get a once-over ensuring there were no leaks in the hydraulic or spraying systems.

Reports from farmers were typically positive once their machines had been set up properly and handed over. Between the Rubicon's independent suspension and boom control systems, it was credited with having a smoother ride than many competitors in the segment. Combined with the comfortable air-ride seat in the cab, it made a great platform for long spraying days.

Due to the price tag and scale of the machine, Rubicons were typically bought by "broadacre" customers on huge farms, growing crops like lentils or wheat. These farms have fields measured in the hundreds or thousands of acres. It could sometimes take five to 10 minutes to drive from the nearest road to a filling station in the center of the crop.

My work primarily concerned the mechanical side of things. I never spent much time in the driver’s seat, running spray operations on crops. Instead, I focused on shakedown runs and stress testing components. More often than not, I was busy on the walkie-talkie or manhandling the data-logging laptop during testing. I was lucky enough to work with more experienced pilots who had the ability and confidence to push the machine hard.

It’s quite something to drop a 15-ton machine over a hill at 50 kmh (31 mph), especially with the gigantic, heavy boom fully deployed. There’s an immense amount of mass moving around, all kept in check by gigantic hydraulic rams, dampers, and springs. As a bonus, because the cab is right up front, you almost feel like you’re going to plow into the ground.

Of course, you’d never drive like that outside of a testing situation. In normal spraying conditions, the machine rides impressively smoothly. Each wheel has a completely independent suspension, with huge airbags for each paired with giant shock absorbers. Having a smooth ride for both the machine and the boom is a prime selling point for sprayers. The smoother the boom rides, the lower you can run the boom without it hitting the ground. This means less spray is blown away by the wind, which saves money on chemicals and gives better results for the crops. 

With a price tag typically in excess of $650,000 AUD new (approximately $450,000 USD), Rubicon customers would often be met on their farm by one or more staff for setting up their machine and teaching them how to operate it effectively. The company also ran an Australian parts warehouse that aimed to keep machines up and running with a minimum of fuss. Roving techs would often head out to a farm to help out with troubleshooting and repairs if needed. 

Since I last drove a sprayer, the technology has continued to move at a rapid pace. Today’s sprayers feature advanced nozzle control systems that can target individual weeds, spotted by advanced drones surveying from overhead. Automatic steering systems continue to improve, and full autonomy will probably reach farms before we see it on our roads. Farmers are always willing to pick up new technology if it saves them money or makes their work easier. 

While it’s routine for many farmers, there’s something special about driving such a gigantic machine. Leaning on the stick and feeling the leviathan start to move underneath you is a powerful feeling. The sheer power of the hydraulics lets a mere flick of your hand command many tons of metal and machine. 

If someone offers you the chance to drive their giant machine, I’d advise you to take them up on the offer. Just be sure to treat it with the respect it deserves. You can get into a lot of trouble when you put 15 tons of farm equipment in the wrong place!

Got a tip? Let the author know: lewin@thedrive.com