Just how do you calculate how much power it will take to get a tractor to achieve speeds of over 100mph, and what challenges did the Ricardo team face integrating new technologies, and what was the inspiration for the JCB World’s Fastest Tractor?
We asked Ricardo Director of Application Engineering and Project Director, Matt Beasley and JCB Group Director of Engines, Alan Tolley for their insight.
Questions for Alan Tolley, Director of Engine Program, JCB
What inspired JCB to do this project?
"JCB produces fast tractors (the Fastrac), so we should have the fastest tractor! We worked with Guy Martin and NorthOne Television on a programme to create a replica of a WW1 tank, so we saw the opportunity to work together to produce another great Guy Martin TV programme and to develop the world’s fastest tractor. For JCB this is a project that excites and enthuses both our customers and our engineers. It is an opportunity to showcase our engineering expertise."
How did you approach the project?
"We had some debate about how fast we should aim for; but we knew we needed to have plenty of clear water between what had been done before. The Fastrac is a good starting point, as it is already a high speed tractor, with separate chassis and suspension. We also knew that we had to retain all the basic features and architecture of the production tractor so that the World’s Fastest Tractor (WFT) was instantly recognised as a JCB Fastrac and as a ‘real’ tractor.
"So within these boundaries we set about reducing weight, reducing drag and rolling resistance and increasing power. Also modifying the driveline for high speed tarmac running rather than lower speed field work.
"We used a lot of predictive analysis to determine the design and development path. We assembled a team of young engineers, many still apprentices or undergraduates, to design, develop and deliver the machine. We also enlisted the help of some of our key supplier – partners."
Why did you choose to partner with Ricardo?
"The tractor is powered by a JCB six cylinder engine. We knew we had to take the power from the 300hp used in our excavators and shovels up to 1000hp. So this was a similar task to the work we did on the 4 cylinder engine with Ricardo for the Dieselmax Land Speed Record (LSR) car.
"We knew Ricardo could be relied upon to deliver in the tight time frame, and we knew we could forge a unified high performance team with them, as we had on previous projects."
What was the biggest challenge on the project and how did you overcome it?
"There were several challenges that had us scratching our heads during development!
"On the tractor we had to control transient torque spikes upsetting the driveline, and spent some time developing the wet plate clutch hardware and software.
"Tyres – these high speeds are new territory for tractor tyres; we had some interesting rig test incidences during development
"With the engine, it was probably balancing the required running conditions at 1000hp with those for start up and light load running – though I’m sure Ricardo had some challenges on the base engine development on the dyno!"
Which of the technical innovations made for this tractor will find their way into the Fastracs and other JCB products of the future?
"Difficult to say, but engine up-powering/downsizing; clutch control software; high speed vehicle dynamics; we’ve learnt a bit about aerodynamics should we ever need it!"
Questions for Matt Beasley, Director of Application Engineering and Project Director, Ricardo
Ricardo is well-known for its expertise in both off-highway and high-performance niche products – particularly one-off specials like this. What capabilities do you bring for customers?
"This project is the latest example of the agility with which Ricardo can tackle high-pace, high-performance development programmes. From simulation, design, analysis, supplier liaison, procurement and engine build, through testing and rapid modification and optimisation, Ricardo delivered a 1000hp capable engine to JCB in just 9 months."
How did you calculate how much power would be needed to reach the record speed?
"After getting over the surprise of being asked to propel a 7.5 tonne tractor to over 100mph, we did our initial feasibility calculations with a spreadsheet which was developed during the course of the JCB Dieselmax Land Speed Record (LSR) car project in 2006. We knew from JCB’s initial estimate what weight we could expect for the finished tractor, and JCB did some early coastdown testing of a production Fastrac so we had some idea of the resistance to motion of a tractor. Later in the programme, when we had a better idea of the likely torque curve and the transmission ratios, we switched to using Ricardo’s IGNITE simulation tool, which is a tool we use a lot to optimise all kinds of vehicle powertrains. The final key factor is the length of the available track – you can have all the power in the world but if the gear ratios don’t allow you to accelerate to record speed in a short enough distance, the record isn’t going to be broken.
"To finalise the overall strategy, we modelled expected vehicle speeds with a matrix of different vehicle mass, aerodynamic drag coefficient, frontal area, track length and engine power. This enabled JCB to understand the trade-offs to achieve a target record speed – for example, with a shorter track, the mass becomes the dominant factor. This enabled JCB to improve vehicle performance by focusing on the most important aspects (and find a suitable track), and enabled Ricardo to define the right engine hardware to meet the required power and torque targets."
Tell us about the technologies you applied; why did you choose them?
"In the future the agricultural and construction sector will see increasing levels of electrification. However internal combustion (IC) engines will still play a significant role, because of their high power-density, energy-density and autonomy (range), together with their potential for use with low-carbon fuels.
"We chose technologies that reflect those which will be applied to future IC engines in this sector. Industry trends such as downsizing and hybridisation, together with customer demands for good transient response, machine productivity and fuel consumption, pushes more advanced technology into the engine’s air system, fuel system and structure. Several components were made using additive manufacturing (3D metal printing).
"We also had a “toolkit” of proven technologies from the Dieselmax LSR car, some of which, like water injection, ice charge cooling and a low compression ratio combustion system, we were able to use on the #JCBWFT."
What challenges did you face integrating these new technologies onto a tractor, and what solutions did you have to engineer? For example, can you tell us about the boost system? Why did you select a single-stage boost system rather than two-stage turbochargers as you used on the JCB Dieselmax LSR car, and what challenges did this create for you?
"Once the basic power requirements and technology choices had been made, the next challenge was to integrate and apply these technologies to this rather unusual machine.
"A Dieselmax LSR-style two-stage boosting system wasn’t chosen for the programme because package space was at a premium – we wanted to keep the hood styling of the #JCBWFT as much like the production Fastrac as possible. Hanging two stages of turbocharging off the engine would have created a huge packaging challenge which, whilst do-able, would have likely resulted in some aerodynamically-inefficient bulges in the bodywork.
"A second reason is that actually the peak torque of the 672 engine in the #JCBWFT starts to become limited by the transmission, axle capacity and traction – ultra high boost pressure is actually not needed in the lower gears. Hence, we chose an easier-to-package single stage turbocharger delivering a pressure ratio of ~5 and focussed our attention on improving the turbo lag of such a large turbocharger. The air pulse system and the electric supercharger – both similar to those used on some production cars and trucks – gives the turbocharger a “kick” of extra energy to spool it up quickly as the #JCBWFT accelerates through the gears."
Ricardo also helped develop the tractor’s aerodynamics – how did you approach this?
"Clearly a standard tractor is not designed to be particularly aerodynamic. Even at the high (by tractor standards) legal road speed of the production Fastrac, aerodynamic drag is a relatively small proportion of the overall resistance to motion. At speeds of over 100mph, it’s a very different story, so any measures to reduce both frontal area and drag coefficient (Cd) would be highly beneficial. JCB were able to reduce the frontal area relatively easily by lowering the tractor’s ride height and the profile of the cab.
"Quantifying the Cd is somewhat more difficult – tractors are not frequent visitors to high speed wind tunnels! At an early stage in the project Ricardo performed computational fluid dynamics (CFD) simulations of the external skin of the tractor to give some idea of where the focus of aerodynamic improvements should be. We used our virtual reality suite to enable Ricardo, JCB and Williams to collaborate remotely in a “virtual wind tunnel” and to allow us to see regions where significant drag would be generated."