Jacob Brake/ Telma Retarder Flashcards
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
Provides maximum retarding power at ___ speed, therefore gear selection is important.
Rated
Maximum speed= rated speed
Gas engines have a what in the carburetor, which creates a vacuum and subsequent engine braking.
Butterfly Valve
Jacob brake continuous use times are?
Unlimited ( Cooling System)
Does the diesel engine have to be fairly warm before engaging the Jake Brake?
Fairly warmed but the engine preheater water temperature is sufficient
To turn on the Jake Brake, the switch is located where?
On the Dashboard
When the throttle pedal is what, the Jake Brake will activate
Released
Jacob Selector switch:
Low= Medium Medium= Moderate High= Maximum
During aerial operation, do not engage the jake brake during aerial operations. The practice causes undesirable retardation & what?
Engine Stalling
Possible engine damage
Installation of the Telma Retarder requires that the drive shaft is cut, balanced and attached to rotors that rest near the retarder with a very what clearance?
Narrow
The Telma Driveshaft is cut, balanced and is attached to what?
Two Rotors
The Telma Retarder: As current flows through the what, a magnetic field is created which passes through the Telma rotors
Stator Coils
The Telma Retarder: Electromagnets with alternate polarities are located in the ?
Stator Coils
With slight pressure on the brake pedal, it brings the Telma retarder what into operation?
Progressively
The Telma retarder draws large amounts of battery amperage, operators should pay greater attention to the apparatus what?
Charging System
If the voltmeter drops below set standards, turn off the Telma toggle switch and what?
Consult the Shops
It is advisable to combine the use of the Telma with that of the ___ to benefit from the braking effect of the engine.
Transmission
The Telma Retarder is attached to?
The Rear Axle
The Telma Retarder has a ___ position handle on the steering column?
5 position handle
The Telma Retarder has how many stage activation lights?
4
What is the Telma Model Driveline used on the 2000 and 2001 ALF?
Telma Model F2400 Driveline
2000-2003: What does it mean if the Telma light activates in the Cab Instrumentation Light Assy?
Telma is ON
The magnetic field creates what type of currents in the rotors? Which oppose rotor rotation and will slow the driveline
Eddy
The drive shaft is cut, balanced and attached to ___ that rest near the retarder with a very narrow clearance.
Two Rotors
Electromagnets with alternate polarities are located in the what?
The Stator
