Jake puts the brake on Volvo
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EXCLUSIVE MI Jake Brakes are now available for 12-litre Volvo engines — and they're sailing through their UK field trials.
Until this year the American compression engine brakes were fitted only on the 10 and 14-litre Cummins and Caterpillar lumps that power ERFs, Seddon Atkinsons and Fodens.
But since March test units supplied by Jacobs have been doing their stuff in a brace of F12s operated by Tay Valley Transport of Aberfeldy, Perthshire and Richard Cartlege Haulage of Middlewich, Cheshire.
Off-road dumpers
TVT hauls baryte rock for the oil industry out of Foss quarry, north of Aberfeldy, and trunks it on to Aberdeen. As well as the 6x2 F12-360 tractor it uses Jake Brakes on four of its seven Cummins-powered off-road dumpers.
"They're fit and forget," says TVT boss Andy Wilson. "We tried Voith and Telma retarders on our dumpers but had problems with heat build-up and distortion and dirt ingress. The Jake Brakes are great things."
The only problem TVT has had on the F12 is a loose wire: "We pushed it back on and away it went."
TVT's dump trucks at Foss face a tough 5km run down to the road transfer point over gradients of 25% (1-in-4), and the Jake Brakes dramatically reduce brake wear. "On the other dumpers the disc brake pad life is virtually non-existent," says Wilson. "We were changing them every six months, but with the Jake dumpers it can be up to four years."
The Jake-equipped dumpers can also make the downhill run up to 10 minutes quicker thanks to the extra retardation which keeps the service brakes fresh. So far the retarder is available for TD120, TD121 and TD122 engines. "If we could get it for our FL1Os we'd fit them as well," says Wilson. The payback period is "very, very quick," he adds. "We're talking about months rather than years.: Since March his Jake-equipped F 1 2 has covered 36,000km without any problems.
Middlewichbased Richard Cartlege is equally pleased with the Jake Brake on his Jreg F12-400. He previously ran a Jake on a Foden, and specialises in Continental bulk tank work with two Volvos, a Scania and an ERF. "It's great," be says. "I think it should be compulsory on all 38-tonners, or something similar to it." However, he stresses that to get the best from a Jake Brake "drivers have got to get used to keeping both feet flat on the floor".
The brakes on Cartlege's tankers have an easier life than those on Wilson's dumpers, but the Jake still earns its keep in extended lining life. "Our other Volvo is an F16 which is just over three years old," says Cartlege, "That's got a very good exhaust brake and it's still on the original linings. I'd expect the F12 to go three to four years on its original linings." By comparison, his two-year old Scania has already had new linings fitted.
To see how the Volvo/Jake combination performed we rode along with TVT driver Tom Findlay over the twisting downhill country roads between Foss and Aberfeldy. The 3+2 rig was fully freighted at 38 tonnes.
The Jake Brake works by turning the engine into a compressor, popping the exhaust valve just before the piston reaches top dead centre to stop the normal ignition phase. The forward motion of the truck then forces the piston back down ready for the next compression stroke. The Jake Brake has three settings: high, low and off. On TVT's F12-360 it is activated when the driver lifts off the throttle and deactivated whenever the clutch is used.
When pulling away downhill Findlay used the Jake Brake to good effect to control the acceleration.
When descending the narrow Scottish roads it was also invaluable for holding the artic at a steady speed, particularly when used with the Volvo exhaust brake. According to Findlay: "It means that I can have the vehicle in a higher gear and know that the service brakes are always fresh."
Proprietary fitments
Ironically Volvo does not approve retrofitting Jake Brakes to its 12-litre engines and warns operators that it could invalidate engine warranties. However, it stresses that this is "... not a criticism of the Jake Brake, It simply means that if proprietary fitments have not been tested by Volvo trucks, the company will not approve them."
Jacob's technical product support manager Mike Spencer says that the two UK field trial F12s will be carefully monitored for another nine months. Meanwhile the F12 Jake Brake, designated the Model 122, will continue to be offered to other interested operators on a pre-production retrofit basis.