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Driving A Rock Crawling Off-Road EV At King Of The Hammers

King of the Hammers is one of the gnarliest races in motorsport. Held each February in the Mojave Desert, KOH attracts racers from all over the world hoping to conquer the infamous Hammer Trails. Drivers must traverse not only an open desert section full of sandy, silty whoops, but also rock trails with names like King’s Veto, Wrecking Ball, and Jackhammer, littered with car-sized boulders and vertical rock faces. This race ain’t for sissies.

The thunderous rigs that compete in this event usually ride on 40-inch tires with crazy amounts of articulation. They have massive horsepower and torque coming from their V8 engines, so loud I can feel the roar in my heart. This is no place for a racing EV, right?

Wrong. Ultra4 Racing, the sanctioning body of King of the Hammers, announced a spec EV class just last year, slated for the 2024 racing season – think of it like off-road Formula E. Ten teams were chosen to receive a battery, motor, and control unit and were free to build a car around these components. Unfortunately, the task proved to be a bit more complicated than anyone expected, but folks at KOH managed to get a demo car ready to show off at the 2023 races in anticipation of next year’s series.

Building The EV crawler

Ryan Kalb doesn’t have an official title, so I’ll just call him the Head Dude of EVs at King of the Hammers. When building the rig, Kalb looked around King of the Hammers HQ and saw an old Jeep-bodied race car with a blown 5.7-liter V8 engine, solid axles front and rear, and 40-inch BFGoodrich tires, as well as plenty of attitude. It’s perfect.

This demo rig is built using the same components the spec race cars will use. The 40-kilowatt-hour battery is supplied by Hypercraft, throwing electrons to a motor from Spicer Electrified. This 800-volt motor is good for around 700 horsepower and 1,000 pound-feet of torque, perfect for pushing those giant tires over rocks and boulders. Making them all work together is a control unit supplied by AEM Electronics.

I get my chance behind the wheel with Kalb riding right seat. He asks me to not roll it, pretty please, but I have plenty of experience driving EVs off-road. I competed in the Rebelle Rally in the Rivian R1T twice, drove a few stages in the NORRA Mexican 1000 in the Volkswagen ID.4, and even had the GMC Hummer EV out in the dirt. But this rock-crawling thing is a whole new ballgame.

Torqued Down

First off, it’s actually pretty loud. I expect the rattles and squeaks of a race car – I have my own off-road desert racer and it sounds like it’s going to shake itself apart. But with an open cockpit I’m surprised at how loud the motor is. Kalb and I have to yell to be heard over the din.

I run it first through some soft sand and it drives like I expect it to. In other words, acceleration is quick, there is a fair amount of regen, and steering – which is always scary in off-road race cars – is terrifying. There’s an insane amount of on-center play and its heft is almost too much since the rig’s power steering pump isn’t compatible with the EV powertrain. Good thing this is just a demo car.

What is completely new is the idea of a two-speed transfer case. After all, with about 1,000 lb-ft of twist under my right foot, why would I need low gearing? Kalb says it’s to keep the motor from spinning too slowly, thus creating too much heat. It also allows for more control in the rocks.

Speaking of, there is a little gathering of 3-foot-high rocks nearby, and Kalb tells me to head that way. This is nothing compared to what the drivers have to navigate during the race, but my training as a desert racer teaches me to look for the smoothest line possible. I’m not what you would call a rock donkey. Sure, I’ve done the Rubicon Trail in a stock Wrangler, but this little section would tear a factory-fresh Jeep apart.

The first little bit is easy, just rocks that are maybe 12 inches high. However, to move forward I have to put my front driver tire on top of a rock three times that size. Here’s where the control from the transfer case comes in. Instead of the motor delivering all the torque all at once, I have to coax it out. This is exactly what I want as I precisely place my wheels so the whole thing doesn’t go catty-whumpus on me. The front axle flexes and soon I have one wheel on top of the rock, the other wheel planted firmly on the ground.

As I slowly descend the rock face – no hill descent control here, folks – the passenger rear has to flex up and over a rock, using plenty of sidewall to keep traction. Kalb spots me back down a few more rocks to the soft sand and I issue a scream of victory. First EV rock crawling experience complete!

Charging In The Desert

At some point this baby needs to replenish its battery, not easy to do when your race is located 30 minutes from the nearest town – one that isn’t known for its selection of chargers, at that. Optima Batteries saves the day here with a portable, solar-powered Level 2 charger. Kalb says the demo rig has a 6.6-kilowatt onboard charger and can accept 240-volt power, but for right now, it’s not compatible with DC fast charging. However, Optima was able to charge a fleet of Rivians at over 200 kW while on the lakebed. Pretty cool stuff.

Kalb is not sure what the range of this demo rig is, but thinks it can run in the rocks for six hours. It will likely spend plenty of electrons in soft sand and high speeds, and the team will be doing more testing to get those numbers nailed down. Kalb also says he’s working on getting a better steering system in place, one with a pump that can work with an EV drivetrain.

When racers get their hands on the spec class package, they’ll be able to build any car around it. Teams can build a solid-axle rig or a buggy-like rock-crawler with independent front suspension – or even put the whole shebang into a side-by-side. While the gas-powered race cars usually race 240 miles or so, the EVs will have a shorter loop that will likely not require charging. However, they will still get a taste of both the open desert and the unyielding rocks.

Stay tuned, y’all. King of the Hammers 2024 should be quite… electrifying.

Photo Credit: Todd Van Fleet

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