How JCB designed its way into the 400mph club 

In February 2025, JCB Chairman Lord Bamford challenged a team of experts to create another land speed record holder. Ryan Ballard, engineering director and Lee Harper, chief engineer of electrification and innovation, were tasked with getting the company back to the Salt Flats in Utah to clinch another accolade. This time, the brief was hydrogen combustion. In 2006, JCB’s Dieselmax achieved 350.092mph and in August 2026, Hydromax achieved 406.320mph. 

“This is a ground up new car," explains Harper. "Every facet of the car has been reworked and optimised which was absolutely necessary when we’re chasing the ultimate in performance. In truth, since Dieselmax, we’ve had 20 years of technological advancement. There are new tools, techniques and methods, all of which we took the opportunity to use to make this car the best it could possibly be.” 

Of course, aerodynamic performance formed a huge part of the development process, honed in CFD and wind tunnels which resulted in a 10% improvement over Dieselmax. “We’ve got a new reprofiled nose,” Harper says. “It’s a dual purpose structure which guides the air over the car but it’s also the ice tank which helps us to cool the front engine.

“By far the most important job of this nose is to coerce that air exactly where we need it to be. We maintain a stance of almost neutral buoyancy in the car. We don't want too much downforce, as downforce would cause drag. But of course, we don't want lift, because lift will cause instability beneath the car.” 

Completing the front end design is an underbody diffuser which evacuates salt so the wheels are running through clean air to reduce the drag from the salt surface. This nugget of wisdom came from Dieselmax’s chief aerodynamicist Ron Ayers who also worked on ThrustSSC which set the overall world land speed record at 763.035mph, the first and only land vehicle to break the sound barrier. Both streamliners and Hydromax were piloted by former RAF wing commander, Andy Green OBE. 

Green played a fundamental role in the design of Hydromax, bringing his experience from previous projects and tailoring the cabin to his liking. “Andy's our driver," says Ballard. "Every facet of the car has been has been designed around Andy, from a physicality point of view of putting him in the car and making sure he's sat in the right place, to the layout of the controls, the software, the display on the dashboard in front of him.”

As well as pushing the engines towards either end of the car for better stability at speed, other internal components such as the hydrogen tanks and tyres influenced the shell’s final form. “We’ve got an all new body profile which was necessitated by new tyres," says Harper. "Those tyres exhibit more centrifugal growth than we had last time, so we needed higher clearances — the whole body has been lifted up.” 

For the most part, the body looks smooth but engines need adequate airflow without creating unnecessary drag. On Dieselmax, air to the rear engine was fed through a snorkel. “What we noticed is that at the higher speeds, that snorkel actually places a very slight asymmetrical load on the car which is something we were keen to avoid for Hydromax,” Harper explains. 

The solution this time was four 'NACA' ducts, two at the front and two at the rear. Pointing to the small inlets just behind the cabin, Harper says, “These two ducts alone contributed around 4% of the aero improvement in this car. 

“We’ve pulled the canopy forward by 450mm and we’ve extended the tail by 560mm. That has given us space behind the driver to install the hydrogen tanks. We’ve tidied up the rear end and made it far tighter, that helps to reduce base drag on the car, the wind pulling on the back of the vehicle. 

“Beneath the fin, you’ll also see what we call a ventral strake, it’s an extension of the fin beneath the car in the rear diffuser area, which gives the effect of increasing the surface area of the fin but without increasing the drag drastically. It's quite a nice piece of development.” 

While JCB had a decent amount of in-house knowledge to pull on from Dieselmax’s development, the team also turned to aerodynamic specialists who worked on the Bloodhound LSR project. Given the extremely high speeds Hydromax targeted and achieved, some aspects of the design crossed over into aircraft technology including the friction brakes and testing facilities used for the tyres. 

Unlike JCB’s typical plant equipment projects, structurally, the makeup of the team was different to ensure vehicle development resulted in the safest design. “One of the very first things we did is take on a number of the original crew and team in an advisory board position, so they were independent and peer reviewing what we did," concludes Harper.

“We did this deliberately to challenge us and be independent and help make sure that we are safe. Ultimately, we didn’t want them ingrained in the team on a day-to-day basis. We wanted that independence to make sure what we were doing was absolutely the right thing to be doing, the optimal solution, that’s fundamentally safe.”