Millbrook: Testing times are here

Before any vehicle type can hit the road, it is subject to an exhaustive proving programme, and Millbrook in Bedfordshire is market leader for bus testing. Tim Deakin explains more about what happens with vehicles in this corner of the Home Counties.

Long lead times between a manufacturer announcing a new model and its first venture onto the road are not unusual, and happen for good reason. Exhaustive testing is necessary before going to market to ensure the vehicle both stands up to years of hard work and operates as efficiently as possible.

For most buses available to UK buyers, that means a trip to Millbrook. Purpose designed for vehicle testing, Millbrook Proving Ground was for many years owned by General Motors until changing hands around 12 months ago.

Millbrook’s 700-acre site offers over 70km of varied tracks to simulate almost any on-road scenario, and also has a huge amount of back-room equipment and expertise to allow vehicles of all kinds to be put through their paces – and even tested to destruction, if required.

All manner of operational parameters can be tested and measured, from fuel efficiency to whole-life durability, says Business Development Manager Simon Rowlands, and as technology has advanced so too have the methods used.

“Vehicles have become vastly more sophisticated, particularly with regard to exhaust aftertreatment and hybridisation,” he says. “That’s made it necessary for us to increase the number of measurements we make.”

Full scope of testing

“For example, we can measure emissions both pre- and post-aftertreatment. We also accurately measure fuel consumption using a variety of techniques. We have a long history of working with coach and bus manufacturers, and our own engineering teams continue to work closely with all the main players.”

Millbrook’s test facilities are extensive. Tracks vary from a high-speed bowl and mile straight to a city course and steep alpine routes. All are used by coach and bus manufacturers as they strive to make their vehicles as durable and efficient as possible.

“The mile straight is often used for brake testing, the high-speed bowl for mileage accumulation and the city course gives an excellent representation of the conditions a bus encounters in service, including lots of high-energy steering inputs,” says Simon.

Its facilities continue to be used for ongoing Low Carbon Bus (LCB) certification, with a dynamometer rather than track testing used to provide the necessary data.

This dynamometer’s measurements are generated by rollers under the drive axle and it gives full inertia simulation, allowing a load of between 450kg and 20 tonnes in 1kg increments to be set, all within a temperature controlled chamber.

“Our ongoing investment means we have plans for a new chassis dynamometer with increased capabilities,” Simon explains. “It will also be in a climatic chamber. It’s a big investment, but that’s the way testing is going.

“We have also recently invested in Portable Emissions Management equipment (PEMS), allowing measurements to be made on the tracks as well as the dynamometer.”

Millbrook really comes into its own when testing electric and hybrid vehicles. “The effect of hills on their range and performance is incredible, and it’s important to understand the gradient performance of electric and hybrid vehicles.

“It has become a much more significant part of manufacturers’ test procedures, and with PEMS this is a capability we have now,” he says.

Lightening the load

Millbrook can test all parts of a vehicle’s drivetrain, on either the track, a dynamometer or bench rigs, and in the climatic chamber an almost endless number of weather conditions to be simulated. Its temperature scale extends from -32 to 40oC.

“We can also run whole-life durability tests,” says Simon. “They look at both structure and powertrain, meaning most of it has to be done on the tracks. But we accelerate that testing. In a number of weeks, we can put the equivalent of 10 years’ hard work into the vehicle.”

Like gradient testing, structural testing has come to prominence recently. Operators demand that manufacturers remove weight from their buses, but still require long service lives.

To deliver that takes a strong understanding of a vehicle’s structure and what elements can be removed without affecting durability. The help of Millbrook’s engineers, and their experience in conducting structural tests, is invaluable when gaining this knowledge, and demand for such testing has increased as lightweight buses grow in popularity.

“When manufacturers design lighter-weight vehicles, they must understand how inputs affect them,” he continues. “We have a dedicated team which collects lots of data from the bus’ structure. They fit strain gauges and accelerometers, and harvest the data for use in simulation and validation.

“Then we’ll conduct a whole vehicle test. Using the variety of tracks we have, such as twist humps, Belgian pav and the city course, we put all manner of structural inputs into the bus.”

Component parts

Testing capabilities at Millbrook are extensive, and can replicate almost any conditions likely to be encountered, whether here or abroad. Vehicles are routinely shipped from all over the world for testing, a reflection on Millbrook’s expertise and facilities.

“Manufacturers use the experience and knowledge they gain from working with us to help develop future products,” says Simon, and some of that is gained only when a vehicle or individual component is stripped down after testing.

He adds that, particularly once a vehicle has completed Millbrook’s full-life durability testing, most knowledge is to be gained by reducing it to its component parts, bodywork included.

“We can take any vehicle down to its components, allowing us to examine how they have failed or deteriorated during the testing,” says Simon. “We also have the capability to section bodies into pieces to see what has happened internally.”

A busy future

Coach and bus design looks set to continue its rapid advancement, keeping Millbrook’s tracks and engineers busy. It can accommodate anything from short-term track rental to full vehicle homologation and achieving Whole Vehicle Type Approval.

Its engineers work in partnership with manufacturers’, and can provide a comprehensive redesign service. Millbrook can also plan and perform heavy work on existing vehicles, and certify them for use, where necessary. “We have a Vehicle Certification Office on site, which allows an efficient turnaround of approvals,” Simon says.

Millbrook, he adds, is “accommodating and flexible,” allowing manufacturers to stage strictly controlled testing to get the best out of their vehicles – which transfers to the operator when they enter squadron service.

Next time you take delivery of a coach or bus, it’s almost guaranteed that it will have benefited from Millbrook’s expertise at some point of its research and development process. Millbrook has played a direct part in many of the industry’s most significant developments, and will undoubtedly to continue to do so.

It also offers four venues catering for up to 1,250 delegates and is ideal for launches, conferences and exhibitions. Contact Luke Galliana on 01525 408388 or e-mail for more on tracks and events.