The Symphony turns 60!

In October 2021, A good read, Kenworth, International21 MinutesBy Dave McCoidNovember 28, 2021

It could be described as the sound of our people. If you claim to be a true truck buff, yet fail to spin around in anticipation the instant you hear ‘that sound’, you’re about as committed as Jacinda A is to the National Party conference. This year, our venerable old mate, the Jacobs Engine Brake, celebrates 60 years of slowing us all up.

There have been some milestone events in the modern truck’s evolution, things that have made a driver’s lot so much easier – diesel power, tilt cabs, radial, steel-belted, and tubeless tyres among them. In more modern times, central tyre inflation, LED lights, and the plethora of safety apparatus must surely feature high on the list. But none have resonated through history like the compression brake Clessie Cummins built.

It was released to the world in 1961, and in hindsight, this wonderful mechanism turned out to be so much more than a driving aid to early linehaul truckers. It played a significant sensory contribution to the DNA of a new, immensely capable and majestic generation of trucks – trucks that successfully enticed a legion of youth toward their cabs.


Although pretty well covered today, there’s still big tracts of not much in mid and southwest USA. In the late 50s early 60s there was certainly not much. No place for complexity.

Not hard to see why

The founding father of what is today Cummins Inc was Clessie Cummins, and his journey in the development of the compression engine brake has its roots well before 1961. In fact, you’ll have to go back another 30 years to 1931 when he, Ford Moyer and Dave Evans had a crack at the transcontinental truck speed record driving an Indiana truck, powered by a Cummins diesel engine, from the Big Apple to the City of Angels (New York to Los Angeles). With Clessie at the helm, the attempt almost came to an unhappy end, descending the long gravel sections of the Cajon Pass in California. It was that bum-puckering incident that got Cummins thinking about auxiliary brakes and retardation.

Through the late 1930s, 1940s, and 1950s, the demand for road transport rapidly increased in a United States economy generally driven by unfettered ambition, but also World War II and the population/economic boom that followed. That all meant the need for increased power and speed in the national truck fleet was a constant call.

One side of the problem – being the up bit – was easily solved by power and torque, and diesel engines had both in spades. However, controlling the ever larger, ever faster mass of the rigs on the other side – when they were aiming down the hill – was a far more difficult nut to crack.

The US Interstate highway network simply added to the problem of descending mammoth climbs. It’s not uncommon to be on the Jake for long periods of time on a long, lazy slope. Here a Pete on the westbound lanes of I70 had just rolled off a big pass near the Colorado/Utah border. You can see the road heading up the pass in the background.

The issue increased in importance immeasurably thanks to President Eisenhower and his Federal- Aid Highway Act of 1956.

If you’ve never experienced the US Interstate highway system, then the next paragraph or two will be difficult to conceive without analogy.

Imagine if someone in the Beehive woke up one morning and decided an efficient, highquality roading system was a key to economic prosperity and national security. Imagine also if they decided the first target for rebirth was the Napier-Taupo road section of SH5. What results from this lightbulb moment is a four-lane highway with a wide median, identical to the Waikato Expressway, running from Napier to Taupo. Dillons Hill, the Glengarrys, Titiokura, Turangakuma, and Tarawera now have at least 10 or 15 degrees shaved off their steepest bits. There are no corners as such, just sweeping gliding curves. Oh, and the Waipunga is now a scenic delight viewed from the viaduct meandering up the gully. If you have a truck that can do it, running 90kph (or in the case of most US states 112kph) from Bay View to Taupo at full load weight is there for the taking. Fill your boots.

Back, then, to the 1950s USA. Not only was the existing state-controlled road network crisscrossing the country becoming a busier proposition, with the stroke of a pen, Eisenhower spawned the 41,000km super-highway lattice that today crisscrosses the US. As we said – a road network where relief and topography took the back seat to economic requirements. Mountains were flattened, gullies filled, viaducts and tunnels installed for the real ugly bits.

Smoothing out the road was great for nurturing economic prosperity, but the huge, moderate, yet seemingly endless grades that resulted simply exacerbated the retardation issue. Not having trucks stuck in arrester lanes or arriving at the bottom of these new bitumen behemoths in an out-of-control fireball needed addressing.

Clessie Cummins hard at work figuring out how to slow down. Photo: Jacobs Vehicle Systems.

Changing the world forever … again

In 1955, while in the position of chairman, Cummins left the engine company he founded, and formed the Cummins Enterprises Company, working also for the Allison Engine Company in California. Observing what was happening in the industry and with 1931 still a vivid memory, Cummins was deep into midnight oil-burning on the issue of retardation. There had to be something that would allow the preservation of the truck’s foundation brake system, yet hold the rig back at a speed that satisfied productivity and safety.

The vastness of the US – remember Australia will actually fit inside the continental 48 – meant overly complex solutions wouldn’t work. The ability to remedy problems in the emptiness of the upper midwest and southwestern desert states simply wasn’t there. If stricken trucks found help, it would be a roadside garage with basic parts and mechanical capability at best. Additionally, and speaking to the subject of nothing has really changed’, rapidly increasing competition dictated that large amounts of payload were not available for donation to the solution. In other words, it had to be simple, light, and largely encompassed in what was already there. What he came up with in 1957 meant Clessie Cummins would once more change trucking forever.

His lightbulb moment utilised the perfectly timed motion already encompassed in Cummins and Detroit engines. These power units had a third cam on the main camshafts for activating the cylinder’s fuel injector. Cummins used this cam via a simple retrofit mechanism to open the exhaust valve. The basic principle was using the pistons to compress the cylinder’s atmosphere to 1/15th its original volume as per normal but, opening the exhaust valve near the top of the piston’s travel, rather than facilitating a combustive event via the addition of a volatile fuel. What resulted was compressive effort, the engine becoming an absorber of energy rather than the producer of it. Essentially, Cummins had turned the internal combustion engine into a big air compressor. It was now the bi-directional defier of gravity he sought.

Clessie Cummins’ original sketches for the compression engine brake, and the patent drawings. Photo: Jacobs Vehicle Systems.

Although the principle had been proved via mechanical transfer of the injector motion, it was soon discovered the actual solution was a fully hydraulic mechanism that used engine oil to transfer the motion of the injector rocker arm to the exhaust valve.

The first trial unit was fitted to a Cummins engine in a truck owned by the Sheldon Oil Company and run on Highway 50 down the Sierra Nevadas to one of the company’s plants at the base of the mountains on the eastern side.

Cummins initially offered the breakthrough device to his old company but ended up partnering with the Jacobs Manufacturing Company. In 1960 they opened a Clessie L Cummins Division (today named Jacobs Vehicle Systems) to manufacture the engine brake. The first production units left the factory in 1961 for fitment to an NH series Cummins engine, followed shortly after by units for Detroit 71 series motors.

The classic Jacobs Engine Brake encounter in 70s and 80s New Zealand. A W-model Kenworth long logs unit.

Fit for purpose

Intended as a US domestic product originally, in time, the Jacobs Engine Brake began to realise its potential worldwide. New Zealand was no exception.

The late 1960s and early 1970s saw traditional truck marques sourced from dearold mother England rendered largely obsolete against a wave of vastly more capable and fit for purpose machines coming out of the US and Europe. Trucks developed to cope with the Rockies, Pyrenees and the Alps, found a welcome home in New Zealand.

Obviously, with US trucks came this wonderful retardation device that played its part admirably in achieving trip times between key destinations once thought impossible. The battle to get the necessities of life across the mountainous terrain of both islands was finally being won by man and his wonderful machines.

Over the years, the Jacobs Engine Brake also found its way to the other side of the Atlantic. In those halcyon days of 1980s and 1990s Antipodean trucking, the new generation of Brits – ERF, Scammell, and Foden – sporting Cummins engines from the company’s European arm, probably produced the biggest cackle of them all.


International T and S Lines here in the Antipodes made the most of Clessie’s desire to stop them. The Napier-Taupo road awaited the Roadair T-Line, while the hills of the Tasman region were ready to be rattled by the HPH Trucking S-Line.

Pros and cons

If you had to ask the question, ‘Were there any negatives?’ to the whole Jacobs story, there are two potentials front of mind. One was a developmental lesson, and the other no real fault of the device itself beyond unfettered success. In fact, some would say the second topic is no issue at all… Rather, a bonus!

Early on, it became evident that the Jake Brake was hard on camshafts, an issue solved by the beefing up of motors as well as refining the engine brake itself.

As for the second topic? For others, particularly people outside the industry, the product’s Achilles heel was the altered engine note that came with its activation. A symphonic, rolling, timpanilike percussion of the airwaves.

Throughout the civilised world, it’s easy to ascertain where a Jacobs Engine Brake might be lurking. Signs on the outskirts of most towns petition the truckies to respect the quiet life locals aspire to live … especially at 3am.

Yet maybe the sad irony of this is, just like the modern truck itself, the Jacobs is a victim of its own incredible success. Signs like, ‘Please refrain from using engine brakes in town’ are probably not an indictment on the product, rather it’s users, who see the Jacobs as simply the way you slow a loaded truck, hill or no hill, sleeping town or not.

Interestingly, the federal government in the US required all vehicles manufactured after 1978 to meet specific noise requirements, and that was generally, not purely because of Clessie’s masterpiece. Modern aftertreatment systems have played a huge role in mellowing the Jake’s cry, and often times a fullbodied old-school Jacobs roar today is the result of tinkering from those who clearly vote for, rather than opposed on the question, ‘entertainment or irritant?’. In the event you do find your Jacobs a bit too loud and proud the company says there’s plenty of info on the website. Yeah, na.



When the new-era English arrived, they certainly woke the neighbourhood! (Top) A Fluidex ERF C-Series pauses at Sanson in the 1980s. (Middle) A Central Freightlines Scammell S26 runs south through the Waikato. (Bottom) Waitoa Haulage’s Foden S108 unloads at Moerewa freezing works, north of Whangarei (New Zealand Trucking magazine, June 1985).

60 years later

The global success of this simple mechanism in the six decades since barking its way onto roads of the US is difficult to convey. As an automotive invention that ticked every box demanded of it, the Jacobs Engine Brake had few peers in the second half of the 20th and early 21st centuries, and in March this year, the nine-millionth ‘Jake’ rolled off one of its assembly lines dotted around the world.

The two old faithfuls still afford the Jacobs Engine Brake its most common home. Cummins and Detroit Diesel trace their relationship with the product from the outset, and the Jacobs is still present across an array of both vendors’ offerings in various platform OEM products and bespoke installations.

Today, however, there are many ways to control the descent or inhibit a truck’s desire to proceed at pace. The Jacobs is often used in conjunction with other forms of retardation, and again, there’s nothing new there either. Ask many Kiwi loggers of the 1980s and early 1990s, and they’ll extol the Jacobs/ Caterpillar BrakeSaver combo passionately as the ultimate tug on the reins in trucks of their time. (See cover feature.)

Slowing up the future

That all begs the question, what of the future in a world attempting to draw the curtain closed on the reign of internal combustion as the dominant means of vehicle propulsion?

Engine retarding at Jacobs has evolved and become sophisticated over the years. Today, four main types of system, exhaust, bleeder, compression release, and the next generation High Power Density (HPD) brakes all contribute to the portfolio. In addition, Variable Valve Action (VVA) and Cylinder Deactivation Technology (CDA) aid in emissions control and fuel burn optimisation. Active Decompression Technology (ADT) affords smoother startups and shut down; and Fulcrum Bridge Technology makes lashless valvetrains compatible with engine braking and also aids in emissions and fuel burn.

“Our engineers are not just developing brake technologies, but also new and effective valve-control technologies to reduce fuel consumption and emissions for commercial vehicles with conventional and alternative powertrains. We continue to be a leader, not only in diesel platforms, but also other systems such as natural gas, hybrid, hydrogen combustion, and more as these solutions continue to be introduced in our industry,” says Steve Ernest, vice president of engineering and business development at Jacobs Vehicle Systems.

Most recently, Jacobs Vehicle Systems has partnered with Tula Technology, combining the expertise in both companies to further reduce CO2 and NOx in medium and heavy commercial vehicles.

There’s no sign of slowing down or stopping anytime soon.

Raise your glass

But for now, let’s celebrate 60 glorious years of slowing down with style. Whatever your tipple, the next time you fill your glass, raise it to Clessie Cummins and drink a toast to his other amazing contribution to our world.

BUT WAIT, THERE’S MORE!

The incredible people at Jacobs Vehicle Systems have donated a few prizes to give away to Jake-mad people! Keep your eyes on New Zealand Trucking social media for upcoming comps in the lead up to Chrissy.

And, if you want a hint, all we can say is, practise makes perfect.