DEAR
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SIR
WHO'S JAKE?
• I was lucky enough to drive a friend's truck last week and the vehicle was fitted with what I understand was called a Jake Brake. This was a most impressive additional braking system and I wonder if anyone at Commercial Motor could tell me how it works and if I could have one fitted. I currently run a Volvo F12.
A Reddin Aberdeen Scotland • The Jacobs Manufacturing Company is the American company which makes the engine brake commonly called "the Jake Brake". This device works on the principle of turning a Power producing diesel engine into a power-ab.sorbing retarding mechanism and it is certainly more effective than a conventional exhaust brake.
Probably the single biggest disadvantage of the Jake Brake is its cost. Norde Rolarding Systems of Worksop, the division of Hendrickson Norde which is the UK agent for Jacobs brakes, says a *cal current fitted price is about £1,500. The Jake Brake will only fit certain American engines, namely Cummins (10 and 14 litre), Caterpillar, Detroit Diesel Allison, and Mack, and is not suitable for a Volvo 12 litre, or any other European engine.
The brake itself fits on the cylinder heads of these engines, the standard exhaust valve rocker being extensively modified so that the hydraulically operated Jake Brake can hold open the exhaust valves and thus use the engine's compression to retard the vehicle, when the driver switches in the brake. The control system can be arranged so that the driver can select the degree of engine he requires, using two, four, six or (on Detroit engines only) eight cylinders.