Jake Brakjes

http://www.youtube.com/watch?v=jiRoT-BTqqo&feature=related
KeithBrownTrainer@msn.com With Compliments FYI from Keith Brown
Jake brake From Wikipedia, the free encyclopedia
Jake Brake, or Jacobs Brake, describes a particular brand of engine brake manufactured and sold by Jacobs Vehicle Systems, Inc. While the term Jake Brake technically only describes Jake Brake brand engine brakes, it has become a genericized trademark and is often used to refer to engine brakes or compression release engine brakes in general, especially on large vehicles or heavy equipment.
An engine brake is a braking system used primarily on semi-trucks or other large vehicles that modifies engine valve operation to use engine compression to slow the vehicle. They are also known as compression release engine brakes.
See: http://en.wikipedia.org/wiki/File:Unit_injector.jpg

Contents
[hide]
1 Function
2 Legislation
3 See also
4 External links

A view of engine compression brake rocker arm (on the left)

See: http://en.wikipedia.org/wiki/File:Unit_injector.jpg
Function
When the accelerator is released on a truck, its forward momentum continues to turn the crankshaft and compress air inside the engine's cylinders. When the crankshaft passes the top-dead-center position, the compressed air in the cylinder acts as a spring and pushes the piston back down the cylinder, returning the energy to the crankshaft and pushing the truck forward. Little of the energy absorbed by compressing the air is lost, so the engine does not effectively aid in slowing the truck. Of equal importance, even with zero accelerator input, there will be some trace introduction of diesel fuel (make and model dependent) which will still undergo combustion. Any power created from this will hinder efforts to decelerate.
In a gasoline engine, some engine braking is provided during closed-throttle operation due to the work required to maintain intake manifold vacuum, the balance coming from internal friction of the engine itself. Diesel engines, however, are unthrottled and hence do not provide engine braking from throttling losses.
A compression release engine brake uses an extra lobe on the camshaft to open a second exhaust valve at the top of the compression stroke. The stem of this valve telescopes during normal operation so the valve remains closed, but is locked at full length by a solenoid when the engine brake is engaged so that the valve opens as directed by the cam. This releases the compressed air in the cylinder preventing it from returning its energy back to the piston and accordingly, the vehicle speed is reduced.
The driver controls consist of an on/off switch and, sometimes, a multi-position switch that controls the number of cylinders on which the brake is active. When the compression release engine brake is turned on, it will activate when the driver releases the accelerator. There are also switches on the clutch and accelerator pedals that will deactivate the compression brake when the clutch is disengaged or the accelerator is pressed.
Legislation
Compression release engine brakes may make a loud chattering or "machine gun" noise while being used, which has led many communities in the United States to ban them. There are signs on the side of some freeway offramps, or at municipal boundaries, that will say "Brake Retarders Prohibited", "Engine Brakes Restricted", even going as far to say "No Jake Braking", etc. These signs are referring to compression release engine brakes. This has led to special mufflers on trucks that also muffle the sound of the compression release engine brake. Also, some engines use a butterfly valve in the exhaust and/or stator travel beyond the normal operating range on the variable-geometry turbocharger to produce engine braking without the noise associated with a compression release engine brake.
[edit] See also
Engine braking
Exhaust brake
Retarder (mechanical engineering)
[edit] External links
Jacobs Vehicle Systems
Pacbrake Engine & Exhaust Brakes
Banks Power exhaust brake page

various Info

click , or copy and paste to your browser

Pre trip Check: : http://www.youtube.com/watch?v=jiRoT-BTqqo&feature=related

Uncouple _ re couple Semi Trailer (HC)

BURLEIGH DRIVER TRAINING SCHOOL 1
HC CLASS Qld test
Uncouple/recouple requirements — for class HC (heavy combination) licence test, you will be required to uncouple the trailer, drive forward approximately ten metres and reverse back on to the trailer to recouple. You are required to uncouple and recouple the trailer, with regard to all safe practices, in the correct sequence within 12 minutes. Extra time may be given for some configurations, eg flying saucer type coupling.
UNCOUPLE _-Correct sequence and procedure —
• Apply the park brake to the vehicle. /
• Alight from the cab facing the vehicle, .using Grab Rails and steps.
• Secure the wheel chocks (necessary esp.for vehicles that do not have a spring brake system).
• Lower trailer legs. (land, then 12 turns with ‘low speed. (usually see daylight)
• Disconnect, retract and secure:
•electric cable from the trailer • hydraulic lines from the trailer
• brake hoses from the trailer ‘(chains, where applicable).
• Release the turntable jaws/pin coupling. (pull handle)
• Where the vehicle has air bag suspension, operate the air dump valve (where applicable)
to prevent any damage to the vehicle.
Climb into cabin, secure seat belt and move forward 1 m , stop / wait 5 secs,
then move forward 10 metres.

***********************************************
RECOUPLE: sequence and procedure p2
• Ensure pin coupling/jaws are in the correct position for recoupling.
• Reverse prime mover/truck back towards the trailer. You are permitted to stop and observe the position
of the prime mover/truck in relation to the trailer coupling. Where applicable, activate valve to refill airbag suspension.
• After the prime mover/truck and trailer have coupled (GENTLY) you should check that all the mechanisms
have locked by:-
-attempting to carefully ease forward against the trailer brakes (i.e. tug test)
• apply the park brake, and if turbo has warmed down, turn off motor
Alight safely (backwards, using grab rails & steps see above)
-visually checking(touch) the coupling pin/handle to ensure locking pin/jaws have engaged
• Connect and check the condition of:
• brake hoses -hydraulic lines • electric cables {-chains if applicable (ensuring they are crossed).
• Wind up trailer support legs and secure handle (or lock in position or secure drawbar leg.)
-return to cabin and start engine and build up air pressure to operating level
-Turn engine off and walk around vehicle listening for air leaks and checking the condition of all tyres.
- Remove wheel chocks if applicable. And ask Examiner to assist with checking Blinkers and brake lights.
• Check trailer and footbrake stop lights, turn indicators, and sound the horn. This is done to ensure correct
functioning of the electrical system.
• An additional tug test should then be conducted on the trailer brake before moving or at low speed after
recouple, “when asked to do so by the examiner.” DO IT ANYWAY!!!

Clutch Brake

Clutch brake

The UD does not have a clutch brake..
Unlike any other type of transmission, non-synchronous transmissions often have a mechanism for slowing down, or stopping an idle gear. In heavy motor vehicles, this mechanism is called the clutch brake, and is used by depressing the clutch all the way to the floor. This is useful in HR or HC vehicles that have just started their diesel engines, and are releasing parking locks, and engaging the transmission from a stop. The clutch brake not only slows or stops the idle gear axis, but can also prevent shifting into gear until the clutch is lifted a few inches off the floor. In order to shift into gear, the clutch must be half way off the floor, otherwise the clutch brake will prevent the transmission from being shifted into or out of gear. Mechanics must often repair or replace the clutch brake in a non-synchronous transmission when an inexperienced operator wears it out, it becomes inoperable, or has lost its function.

Clutch Brake

What is a clutch brake on manual heavy duty truck transmissions?
In: Cars and Vehicles, Clutches and Flywheels, Mechanical Engineering [Edit categories]


A clutch brake is a circular disc with a friction surface that is splined to the input shaft of the transmission between the release bearing and transmission. Its purpose is to slow and/or stop the input shaft from turning to allow initial forward or reverse gear engagement in non-synchronized transmissions. It helps prevent premature wear of the internal transmission parts during those initial shifts.
To understand this in more detail, let's consider what is going on when a heavy truck transmission is shifted from neutral to first or reverse. When a truck is in neutral and the clutch pedal is not depressed, the master clutch is engaged. This causes power from the engine to drive the transmission input shaft, resulting in rotation of some shafts and gears in the transmission. However, the gears aren't engaged or meshed in a way that transmits power to the drive shaft. In other words, parts of the transmission are just idling but spinning.

When the clutch pedal is depressed, it moves the release or throw-out bearing toward the transmission and away from the flywheel. This unloads the springs in the master clutch, releasing the master clutch and decoupling the flywheel from the transmission output shaft.

Without the engine driving the transmission input shaft, the spinning shafts and gears in the transmission start to coast down. However, it would take a long time for these rotating masses to slow down, because they have a lot of mass and the only thing that is slowing them is gear and bearing drag.
If everything is properly adjusted, the master clutch is opened or released when the pedal is depressed about half way or so.
If there's no clutch-brake, and you then shift into first or reverse, the rotation of gears in the transmission won't all be the same on a non-synchronized transmission, and then the gears can clash or make a "thunk" as gears that are spinning are meshed with gears that are not spinning. Over time, this can wear or even damage the gears.
When a clutch-brake is installed, pushing the clutch pedal all the way to the floor pulls the release bearing even further away from the master clutch toward the transmission, which eventually squeezes the clutch-brake disc between the release bearing and the transmission case. Friction between these parts then slows and soon stops the transmission input shaft from rotating.
Now, gears can be moved into mesh in the transmission and there might be a bit of noise because the teeth aren't perfectly aligned, but they won't be rotating. If you time everything just right, you'll make the shift from neutral to first or reverse just as the gears are almost stopped, but not quite. A little rotation helps ease the meshing and can almost eliminate noise or "thunk" sounds.

The clutch-brake is unusual because it always picks up grease from the release bearing. Modern clutch-brakes are designed to operate with grease, and they even require greasing or oiling before installation.

Clutch-brakes fail for two reasons. First, over time, the friction material will wear out. At some point, there will be metal-to-metal contact in the "sandwich" consisting of the bearing, clutch-brake plate, and the transmission cover. This might still slow the gears, but it can cause damage to the bearing or the transmission cover. It's also possible that the release bearing won't be able to move far enough toward the transmission to squeeze the disc, and the clutch-brake won't slow down the transmission shaft because there won't be friction in the "sandwich."

If you keep the pedal linkage properly adjusted and periodically grease the release bearing and clutch-brake disc, the disc can last for a long time.

However, the most common cause of clutch-brake failure is depressing the clutch pedal all the way to the floor when shifting during a range change--when the truck is moving. When you do this, you are forcing the little clutch-brake to try and stall the engine and stop the truck! Doing that only one time will often destroy the clutch-brake completely. This can also occur if the pedal linkage isn't properly adjusted and the release bearing squeezes the clutch-brake into the transmission case when making a range gear change.

Double Clutch explained

Double declutch explained

link to Wikipedia: Copy and paste to browser.
http://en.wikipedia.org/wiki/Manual_transmission#Unsynchronized_transmission

A double clutch (also called a double declutch) is a driving procedure used for vehicles with an unsynchronized manual transmission.
Before the introduction of synchronizers (1920s/30s) and helical cut gears, double declutching was technique required to prevent damage to an automobile's gear system. Due to the difficulty involved in learning the technique, and because of the advent of synchonized gearing systems it has largely fallen into disuse. However, drivers of large trucks still use double clutching, as those vehicles are usually equipped with the older, more efficient, and more durable unsynchronized gearboxes.
The purpose of the double clutch is to match the speed of the rotating parts of the gearbox for the gear you wish to select to the speed of the input shaft being driven by the engine. Once the speeds are matched, the gear will engage smoothly. If the speeds are not matched, the dog teeth on the collar will "crash" or grate as they attempt to fit into the holes on the desired gear. A modern synchromesh gearbox accomplishes this synchronization automatically.
When shifting up on a double-clutched vehicle, the clutch pedal is pressed lightly 2 or 3 cms, the throttle is released, and gearbox shifted into neutral. The clutch pedal is then released. As the engine idles with no load, the rpms will decrease until they are at a level suitable for shifting into the next gear. The driver then depresses the clutch again and shifts into the next gear. The whole maneuver can, with practice, take no more than a fraction of a second, and the result is a very smooth gear change
However, in order to downshift, engine revs must be increased usually 300 or 400 rpm)while the gearbox is in neutral and the clutch is engaged. This requires the driver to shift into neutral, release the clutch pedal, apply throttle to bring the revs up to a suitable speed, (eg 1000revs up to 1400 revs) depress the clutch again, keeping the revs up, and finally shift into gear. This operation can be very difficult to master, as it requires the driver to gauge the speed of the vehicle accurately and is often conducted as cars in front slow down, however this is overcome by
1. not changing down to stop in traffic.
2. planning ahead (system of Vehicle Control) when approaching a hazard, corner etc.
cheers
Keith

Double Clutch (condor story)

ease Porridge]
What's All This Double-Clutching Stuff, Anyhow?

Bob Pease
ED Online ID #6137
August 5, 1993

Copyright © 2006 Penton Media, Inc., All rights reserved.
Printing of this document is for personal use only.

PRELUDE: Recently [in 1992], a pair of California Condors were released into the wilds of the San Gorgonio wilderness area of Southern California. This was a significant event, because there had been Condors flying around those mountains from the year 60,000,000 B.C. to 1986 A.D. But in 1986, the naturalists convinced the California Fish and Game Dept. that to prevent the Condors from going extinct, they had to capture all of them and put them into protective custody until the breeding stock had reached a viable level.
For six years, these naturalists tried various approaches to bring the number of Condors to a healthy status, and they did finally succeed. One of the important tricks they used was whenever Mama Condor would lay two eggs, one of these naturalists would sneak in through a trapdoor, remove an egg, and put it in an incubator. The Mama would look down and decide to lay another egg, since the number of eggs didn't look like a very large number. (Apparently Condors aren't as smart as crows, which can count up to 5 or 6 fairly consistently.) Anyhow, by this procedure, the Condor families were tricked into raising two clutches of eggs—one that the family would raise, and another that would be hatched and raised by the naturalists, behind the scenes. This trick was called, "Double-clutching."
Now, if you have driven old cars, or trucks, or sports or racing cars, you will be amused at this play on words. That's because double-clutching is also a procedure to save wear and tear on your gearbox, and on your clutch, at the expense of a little extra work for your left leg. What exactly is double-clutching (or, as the British call it, "double de-clutching"), and why is it significant?
Let's say you're accelerating in second gear. When you're ready to shift into third, properly:
First, you take your foot off the gas and press in the clutch 2-3 cms. You shift into neutral, AND let the clutch out. You wait perhaps 0.3 to 1.0 seconds for the engine to slow down from its high revs, depending on how fast you were revving when you started to shift and how much inertia the engine has to slow down. THEN you press in the clutch 2-3 cms and shift into third, and let the clutch out quickly, feeding the gas appropriately. If you have judged it right, when you let the clutch out, there isn't any JERK. And when you shove the lever into third, the gears and engine are at a synchronized speed, so there's minimum wear on the synchronizers, which are the tiny clutches that bring the clutch plate and the gears into smooth synchrony. There's also usually less wear on the clutch plates.
What's the big deal? The main point is that when you try to shift into third gear, the engine has slowed itself and the clutch plate down to the right speed—just about the same speed as the gearbox—so it saves wear on the synchronizers and the clutch. It can also save shock and strain on the whole drive-train, because the speeds are just about synchronized when you let out the clutch.
Changing Down eg 6th to 5th.
First, you keep your foot on the gas and press in the clutch 2-3 cms. You shift into neutral, AND let the clutch out. You add 400 Rpm and keep your foot on the gas (eg 1000 revs = 1400 revs) , depending on how fast you were revving when you started to shift and how much inertia the engine has . THEN you press in the clutch 2-3 cms and shift into 5th, and let the clutch out quickly, keeping the gas appropriately. If you have judged it right, when you let the clutch out, there isn't any JERK.
Well, big deal, you say. Cars haven't needed double-clutching since the synchromesh transmission was popularized 70 years ago. Why bother? Why fool around with anachronistic motions? Isn't it just buying trouble? Even Tom and Ray Magliozzi* claim that double-clutching is silly and stupid and wasteful of energy. Ah, but I can give you reasons why it is beneficial.
First, in most cars, the actual gears are always in constant mesh, and the synchronizers only decide which pair of gears to connect to their shaft.
But many trucks and some racing cars are still set up with a non-synchromesh gearbox. With trucks, because they have so many gears, it's noticeably more efficient not to have all of the gears in mesh all of the time. So with the "crash-box," you HAVE TO double-clutch, or you will not be able to shift. The same holds true for racing cars—to gain the last couple percent of efficiency, only one set of gears is in mesh at any time, and you have to actually synchronize their speeds or you can't get it in gear. Despite the obvious drawbacks of having to double-clutch, the gearbox is stronger and more efficient than a comparable synchromesh one, and has less tendency to overheat.
Other reasons for double-clutching:
One very important reason is that, if your clutch linkage ever fails, you can still shift and get home by double-clutching, getting the engine and gears' speeds synchronized and then just EASING the shifter into the right gear. In younger days of driving VWs, I have lost my clutch about 3 times, and each time, with careful planning, I've been able to drive home safely. One time I pulled into the Customs House and discovered my clutch was out. I eased along carefully and managed to get all the way home, 50Km where it was convenient to put the car in the shop to have the clutch repaired—much more convenient than in the middle of a vacation, or the middle of nowhere.
Another reason is that on some old cars, first gear isn't synchromesh, so if you need to shift into first without coming to a full stop, you have to double-clutch. Also, a lot of cars these days are made with weak, chintzy synchros, so they soon wear out, and to drive them gracefully, you need to double-clutch.
Note, when down-shifting, you have to shift into neutral and then bring thr revs up (400rpm)y before you shift into the lower gear. It requires practice and a good feel, a good touch, to do it right, especially considering the embarrassing noises you make if you miss your shift into a low gear on a crash-box. For example, you should aim to have the revs just a little high, so if you miss, the engine will soon slow down, and then gears will be at the right speed to mesh and the cogs will slip in....

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