Jacob Brake/ Telma Retarder Flashcards
(48 cards)
What year trucks have the Jake Engine Brake?
1995 2001 2002 2003 2006 2009 2016
How does the Jake Brake work?
Is accomplished by prematurely opening the exhaust valves near the top of the compression stroke releasing the compression pressure to exhaust
Results: engine retarding effort to the drive wheels
What components does the Jake Brake consist of?
- 3 position selector switch
- On/ Off Switch (activates or deactivates the system)
- Throttle sensor
When do you use the Jake Brake?
Descending grades
City Traffic
Approaching stop lights
Whenever vehicle retarding required
When do you NOT use the Jake Brake?
Wet Streets
During Aerial Operations
At Idle or Low Speed
How quickly does the Jake Brake activate or deactivate?
Less than 1/4 of a second
Engine should be fairly warm
Switch located on the dashboard
Throttle pedal released, Jake will activate
How many positions does the Jake Brake have and when can they be changed?
3 Positions:
Low/ Moderate/ Maximum
2 cylinders/4 cylinders/ 6 cylinders
Can be changed at any time ( causes no damage)
What is the Time Limit of the Jake Brake?
None; the engine cooling system will continually absorb and dissipate the heat
What year trucks have the Telma Retarder?
1995 & 1996
2000 & 2001
Where is the Telma located and how does it work?
Rear of Truck
Current flows through stator coils, magnetic field is created and passes through the rotors which creates a eddy current and oppose rotor rotation and slows the driveline in the drive wheels
When do you use the Telma?
Descending grades
City Traffic
Whenever vehicle retarding is required
What do the Telma controls consist of?
- ON/OFF switch
- Pressure manifold unit
- Low speed switch
- Five position handle (located steering column)
- Four lights- one for each stage
What does the low speed switch on the Telma used for?
Deactivates retarder when vehicle is below 2-3 mph
What are the four stages of the Telma and what PSI and effect do they have?
3 PSI - 25%
5 PSI - 50%
7 PSI - 75%
10 PSI- 100%
Starts with slight pressure on the pedal
When does the Telam deactivates?
Deactivates at 2-3 mph
ABS system activated
At low speeds
How much electrical draw does the Telma withdraw?
Each stages draws 50 - 60 amps
Total of 250 if all used
*if voltmeter drops below standard, turn off and consult Shops
Energy flows through coils called what?
Stator Coils
What portion of the apparatus is retarded to slow effort in the drive wheels?
Driveline is retarded
The pressure manifold unit is connected to the _____?
Brake Pedal
On a long downgrade, what position is advisable to maintain?
Position 2 ; obtains best endurance
Diesel engines have a substantially larger or lesser retarding effect than gas engines?
Substantially Less
The Jacob brake is a ___ engine attachment that, when energized, altars the engine exhaust valves operation, which converts the diesel engine into an air compressor.
Hydraulic
This is accomplished by prematurely opening the ___ valves near the top of the compression stroke releasing the compression pressure to exhaust
Exhaust
Uses the energy of the engines ___ stroke to provide vehicle retardation
Compression
