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Featured image: Kyle Conner shows off just one of the tires on this enormous hybrid-electric dump truck (screenshot from video).

Clean Transport

What’s It Like To Drive One Of The Biggest Hybrids On The Planet?

Kyle at Out of Spec recently had an opportunity to drive what is probably the world’s second biggest hybrid vehicle. To take it for a short spin, he had to climb a set of stairs. It’s literally that big. It’s bigger than most two-story houses, even. Despite its massive size and weight, the vehicle’s two 1000-volt electric motors give it some unexpected get up and go!

The vehicle: a Hitachi EH4000 ACII mining truck. He was told it’s the second biggest mining truck in the world, and the vehicle could fit inside the back of the biggest one, so it’s quite a step up from #2 to #1. This is almost unimaginable, considering that even the second biggest truck can carry 244 tons (that’s almost half a million pounds, or almost a quarter million kilograms!).


Why Does A Tire Company Own This Beast?

The giant tires alone cost almost as much as a house in a smaller town, and they need to be good tires to even consider standing between the inertia of 244 tons and 2,500 horsepower. They weigh 12,000 pounds alone.

The opportunity to drive this came up at the Goodyear proving grounds in San Angelo, Texas. While there’s no mining going on at the proving grounds, the company owns the massive truck so it can test new Goodyear Off-The-Road tire designs out in the real world.

When you consider that the tires cost as much as a house for four people (and most trucks actually use six tires), a mining company has to make a HUGE investment in them. They certainly want the tires to last as long as possible, but between the weight they’re holding up and the amount of power such a vehicle has, they’re under quite a bit of stress. All of that energy means that sooner or later, someone is going to have to make one of the world’s biggest tire changes and spend as much as a fairly well equipped Model X doing it.

The Massive Hybrid Drivetrain

Between the rear wheels is something massive: a drive unit with two enormous electric motors. The vehicle does have friction brakes, but those are for emergency use only. Stomp on those, and they’ll be destroyed in one stop (and need an expensive replacement). Because the weight is just too much for a reasonable friction brake system, the vehicle uses regenerative braking for everything but emergencies (like a failure to regeneratively brake, or a panic stop).

Like most diesel trains, it’s not designed to be particularly eco-friendly. The series hybrid drivetrain doesn’t have a battery and draws its power directly from the generator on a massive diesel engine. The whole point isn’t really to save fuel as much as to be able to have full torque at zero RPM. This helps get the massive load moving in ways that a direct-drive diesel just wouldn’t be able to.

Because it lacks a battery, it has to expend the energy from electric braking through some giant resistors that blow heat away. Once again, that’s not an environmentally friendly solution, but it gets the job done without destroying friction brakes.

It might not be readily possible to make these vehicles a true hybrid, as the battery for one stop alone would have to be massive. For a long drive down into a mining pit, it’s just not that feasible to put all of that energy away. There are battery EV mining trucks, but their battery packs take up all of the space that this one needs for a massive diesel engine, and it’s not always possible to charge an electric truck at mining sites, which can be far removed from electrical infrastructure.

Driving The Mining Truck

While CleanTechnica has covered electric and hybrid mining trucks in the past, we’ve always looked at the vehicle’s capability, how clean it is, and other technical aspects. While those are certainly interesting, I’ve never come across information about what it would actually be like to drive one of these vehicles.

One of the first things he noticed was that it had very light steering, which has to take a massive amount of power and energy. All of that energy ends up in the tires, which is part of why they have to be so heavy and expensive.

Because the final drive is electric, the controls are surprisingly simple. Two pedals for accelerate and regen, a parking brake, and a shifter for forward, reverse, and neutral were all he used in the video (aside from the obvious steering wheel). No need for a manual transmission, clutch pedal, or the other complicated items you’ll find in things like semi-trucks. After all, it’s an electrified vehicle.

When he had a chance to go, it took off pretty well. Sure, it wasn’t a drifting machine, but given the massive weight of the vehicle, it surprised him how much it didn’t suck when it comes to acceleration. Braking did seem to take quite a bit of distance, but when you’re talking about one of the largest vehicles in the world, it’s no surprise that the vehicle would take some time to get stopped.

He asked the Goodyear guy how much it differed when loaded up with dirt or ore, and the obvious answer was that performance would suffer. Hauling 244 tons takes a lot of energy, so expect the vehicle to not take off as hard and not brake as quickly as it would unloaded.

While I’m sure you’d get in big trouble if you drove one of these on a public road (as it’s several lanes wide), the off-road private property legal situation is a little easier. Every mining company has their own training and safety rules, and even Goodyear requires some training to operate such a giant vehicle.

One thing’s for sure, it’s neat to see that the biggest vehicles on the planet are at least partially electrified. Even though most of them aren’t full EVs, the advantages of having electric final drive are just too hard to ignore. The power at zero RPM, the braking that doesn’t eat brake pads like most people eat food, and the mechanical simplicity (no transmission needed) are all advantages that just can’t be ignored (and aren’t).

Featured image: Kyle Conner shows off just one of the tires on this enormous hybrid-electric dump truck (screenshot from video).

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Written By

Jennifer Sensiba is a long time efficient vehicle enthusiast, writer, and photographer. She grew up around a transmission shop, and has been experimenting with vehicle efficiency since she was 16 and drove a Pontiac Fiero. She likes to explore the Southwest US with her partner, kids, and animals. Follow her on Twitter for her latest articles and other random things:


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