I have a friend who needs help getting a commercial liscense.....

[isawlogs]

Furby ,

 I dont think you will find Jake brake in the book  as they are a patent name of retarders from Jacobs vehicle system , just one brand of retarders . On newer trucks you can get magnetic retarters that are on the tranny .
So I  will stand corrected on the retarders .. if it is not the switch in the dash ... I'll blame it on translation ...

[beenthere]

From what I am hearing (reading), the practice of switching out the brakes to the front steering axle (while it may work the best) is now not condoned by the latest 'rocket scientists', and the answer (B) would be wrong to put down.  Possibly trying to hammer on those old logging road jocks who happen to know how to drive on ice and snow.  

[Furby]

No, it just says they are now automatic and can't be controlled by the driver.
Read post #28, that is from the manual, Wildflower posted a link to the PDF manual.

[DanG]

Well, I sure didn't mean to ruffle any feathers, either.  I just always felt that tests of that type were intended to determine if a person has sufficient knowledge of the equipment to operate it safely.  It could be that the bureaucrats that wrote the test don't know enough to ask the right questions.  It also could be that they are trying to eliminate the people that haven't done their homework.  I'm sure the information requested is documented somewhere, and the search for it will surely lead to the discovery of a lot of other useful knowledge.

There have been several serious accidents in this area, involving school busses.  Every one of them that I can remember have been the fault of the bus driver.  In one of them, about 3 years ago, a good man, father, Scout leader was killed when a school bus ran a stop sign in a heavy fog.  Visibility was estimated at less than 50 feet, but the bus came to rest 200 feet into a field.  The bus driver was charged with failure to yield and sent back to work.   The guy's kids don't have a Dad, anymore.

I'm aware that Tammy is a Supervisor in the School Bus service, and I'm sure, having met her and known her here, that she runs a tighter ship than they do here.  But that doesn't alter the fact that transporting children is a challenging and important job that demands serious scrutiny of those that are chosen to do it.  It is obvious to me that the screening process in my area is not nearly tight enough.

The air brake questions are part of the CDL test.  It is required of all drivers who operate vehicles with air brakes.  It makes sense to me that if someone doesn't know how they work, they shouldn't be operating them.

Charles, my response was certainly not a criticism of your trying to help a friend.  It was more an observation that perhaps the person in question should study the material more closely, so she could be a fully qualified driver, rather than someone who just did enough to get the job.

[J_T]

I think they just like trick questions  : Even if the person who desined and built the whole brake system and knew every screw in it were going 50mph down hill and a train on the tracks at the bottom and the brakes failed he ain't gunna git out and fix em :'( :'( Ever hit that pedel and no brakes seems you gain speed  ??? Not much time to react let alone repair : They may be checking reasoning ability with some them dumb questions ??? I wish her good luck  8) Ck I bet one out of five that give the test don't know they just know their abc's Could you call one them truck driving school's ??? Tell them if they don't know them simple things you an't siging up with them  ;D

[Rockn H]

Ck, I've been driving and working on my trucks for a while now and I would have to agree with Quartlow.
#1  If B is the parking valve on the dash, although at that point the parking brakes will be set and there will be a sudden stop.  When the buzzer goes off warning of low air pressure (60lbs) you need to be stopping. Again it would depend on where the leak is located.
The governor is mounted on the compressure just like the one in your shop and only shuts the comressure off at 120lbs and on at 90lbs.

A retarder serves the same purpose as a Jake Brake, only the Jake Brake is installed on the valves and opens the exhaust valve just before detonation.  The retarder is usually a flap installed in the exhaust pipe to create bake pressure.

[DouginUtah]

 
I'm not 100% sure, but I would be very surprised to find any school bus that has a Jake Brake. Correct me if you know I am wrong.

Just FYI, the big Kenworths, Freightliners, etc. don't have any brakes on the steering axle.

Here's a quiz for you. You know that using regular brakes converts the kinetic energy to heat energy. What happens to the energy that a Jake Brake absorbs?

-Doug

[Joe W]

In my opinion the anser to #1 is b the tractor protection valve.If you have a leak in the trailer,this will release and you won't lose all the air in the power unit.#2 is c if you'r service brakes are out of adjustment you'r spring or parking brake may not hold.#3 is c.That one is easy.#4 I think would be a,If I understand the correct meaning of retarder.Hey I remember driving an old 68 Mack that didn't have front brakes.Never came with them.D.O.T. didn't like to see that ,but there was nothing they could do about it.I've had a CDL A for about 15 years now and I remember some trick questions on the test too.Just my 2 cents,Good luck.

[Furby]

Ck, I've been driving and working on my trucks for a while now and I would have to agree with Quartlow.
#1 If B is the parking valve on the dash, although at that point the parking brakes will be set and there will be a sudden stop. When the buzzer goes off warning of low air pressure (60lbs) you need to be stopping. Again it would depend on where the leak is located.
The governor is mounted on the compressure just like the one in your shop and only shuts the comressure off at 120lbs and on at 90lbs.

Not being picky, just trying to understand.........
The question is
1.  If the air system should develop a leak, what keeps the air in the tanks?


   a- the Governor .......  b-the tractor protector valve.........   C-the emergency relay valve  ........  d-the one way check valve

The compressor keeps the air in the tanks and is controlled by the Governor.
As long as the compressor stays running, it's keeping air in the tank.
Just like when you run a nail gun off your shop compressor, the leak is the gun, but while the compressor is running it's replacing as much air as it can.
There comes a time when the leak is faster then can be replaced, but isn't the compressor the only thing that keeps air in the tank?

[beenthere]

If these are typical questions for potential bus drivers needing this much analysis and reasoning to determine the answer, such as Furby is doing, then I'd say its a pretty tough test and designed beyond the needs of something a school bus driver needs to know. But its just my take on the matter.  :

I recall a Forestry Management test once, where the question was 'What is the most important thing to take to a fire' and the answer was "your lunch".  Gee, who could argue with that  :

[Jeff]

Thought it might be a good time to revisit a thread on "tests"

https://forestryforum.com/board/index.php?topic=11040.0

[Gary_C]

A retarder is a "Jake Brake" or engine brake. If you have long hills to go down it is better than the brakes to keep you from over revving the engine and losing control. If you do not have one your only other choice is to ride the brakes continually and they will overheat. With a retarder, you can just pump the brakes briefly to keep your speed under control and let the retarder do most of the work.

They absolutely should not be used when it is slippery as you will lose control very quickly. What happens is your drivers will stop and the other wheels will keep rolling with the load pushing you sideways or whatever way it wants. All you have to do is forget to turn it off when its slippery and when you back off the throttle your rear wheels will try to pass the front.

The answer is C.

[Murf]

When it comes to heavy trucks there are two types of "retarders", one is an an "engine retarder" the other a "brake retarder" and they get confused back and forth a lot.

An "engine retarder", often generically called a Jake Brake, after the name of the company Jacobs that invented it, which is sort of like a reverse turbo. Instead of using the exhaust to boost the air coming into the engine, it resitricts the air coming out. The theory being, if the engine gets slowed down, the wheels it ultimately connects to will also. It goes a long way to both saving brake wear, and also, on long slopes, prevents the brakes from over-heating caused by riding them to maintain speed and not run downhill faster and faster.

A "brake retarder" holds back part of the braking system compared to the rest. This is, as was metioned already, the little flip lever on the dashboard of older trucks. The idea was to limit or restrict the braking power to prevent steering axles from locking up under hard braking on slippery roads. Later tests showed they really just reduced the overall braking ability, and did very little to prevent lock-ups. Newer trucks don't have a manual selector, but some of them have an automatic limiter that works all the time, but delivers full front braking under severe braking.

[Quartlow]

Just FYI, the big Kenworths, Freightliners, etc. don't have any brakes on the steering axle.

Here's a quiz for you. You know that using regular brakes converts the kinetic energy to heat energy. What happens to the energy that a Jake Brake absorbs?

-Doug

I think you better go take a closer look at new trucks, front brakes are a required item since somewhere around 1975.

manually controlled Front axle limiters went to the wayside about the same time.

An "engine retarder", often generically called a Jake Brake, after the name of the company Jacobs that invented it, which is sort of like a reverse turbo. Instead of using the exhaust to boost the air coming into the engine, it resitricts the air coming out. The theory being, if the engine gets slowed down,

If you really want to get technichal. An engine brake, IE A Jacobs brake, or a cummins C_Brake. work by opening the exhuast valve at the top of the compression stroke. This results in all that compressed air going out the exhaust. In fact on a long down grades this released air will actually cause the turbo to MAKE boost pressure. The result is now instead of having an explosion of fuel and compressed air creating energy and forcing the piston down you have drag. as a result the vehichle slows since it has to overcome this drag. There isn't any theory about it it works.

Look at this way, if you push a piston to the top of a cylander and theres no explosion of fuel air mixture the pisto is going to stay there until you exer energy to bring it back down. As for the heat, it is dissapitated througout the drive line. withthe brakes your concentrating your engery in one place, with a jake the whole driveline takes up this energy

As for jake brakes causing a skid, it can and does happen. I've done it. Bobtailing in the rain and forgetting the jakes are on will give you some severe pucker power resulting in having to pry your but off of the seat when you do get stopped.

[etat]

Welll, i'm glad i'm not taking the test, and that my truck doesn't have air brakes.  I understand there's over 400 questions on ithe test.  I hope they're not all as confusing as this, I don't know, haven't seen it.

IF, it did i have airbrakes I figure i'd have to go out there and go over it from front to back to try to figure out how they worked, even though, it theory it 'seems' like it orghta be pretty simple.  Learn which brake or which lever you need to stop you, go with that, and if something goes wrong hang on! 

Uh, around here, there's LOTS of communities and small towns with signs that say..........'NO JAKE BREAKS ALLOWED'

I've 'heard' it's because they cause the engine to make too much noise.....BUT.........I don't know that either.  Just what I was told.

[crtreedude]

I once lived on a road that was going to a quarry - and most of the trucks were good, but a few of them would use their jake brakes.

Not a pleasant experience when you are driving near people's homes.

[Murf]

Quart, I wasn't trying to give a university-level disertation on the subject, I was trying to make it simple.

The Reader's Digest version .......... in crayon....... if you will.   :

[DouginUtah]

Just FYI, the big Kenworths, Freightliners, etc. don't have any brakes on the steering axle.

Well, I'm embarrassed.  I have to apologize for saying something that is not true.  :(  The bad part is I don't know where or when I came up with the misinformation.  I started driving long haul in 1973 so it is possible that is when I discovered no front brakes. I guess I am going to have to do some digging.

As for the quiz, the answer I was looking for was the energy is converted to heat in the engine coolant. It never occurred to me where the energy was going until I was eastbound coming down Donner at close to 80,000 so I dropped down one gear so I wouldn't have to heat up the brakes (I had smoked them a bit going westbound) and before I got down the over-temperature buzzer came on.

-Doug

[etat]

 If your motor gets hot  and you want to cool it off as quickly as possible roll your windows down and turn the heater and the blower on high.  This should help pull heat off of the motors engine coolant, thus helping cool the motor back down too.  If it's in the summertime you're very likely going to get hot doing it. 

[Tom]

good looking shirt, Charles.

[etat]

Tom, you are a very very wise person.   Just  so you know, that comment just made my day.  8) 8) 8)

[Quartlow]

As for the quiz, the answer I was looking for was the energy is converted to heat in the engine coolant.

See I forgot something  : nothing unusual for me. But your right some of the energy does get transfered to coolant

I started driving long haul in 1973 so it is possible that is when I discovered no front brakes. I guess I am going to have to do some digging.

easy enough mistake to make, my brother drove the same truck from 1963 to just a few years ago and it didn't have front brakes, DOT used to try and get him for it till he would point out the year and it didn't come with them

Uh, around here, there's LOTS of communities and small towns with signs that say..........'NO JAKE BREAKS ALLOWED'

if you see a sign the uses the exact wording of no JAKE BRAKES allowed contact Jacobs. The term jake brake is a registered trademark

Jacobs

The problem isn't so much jake brakes as it is unmuffled or poorly muffled jakes. With a properly muffled exhaust you hardly ever notice them.

The Reader's Digest version .......... in crayon....... if you will.

The wife took away my crayons,  :( :( something about coloring outside the lines

[Furby]

I know where there is a sign with that spelling, and it's right around the corner from the police station and fire barn.

[Rockn H]

If y'all look most of the No Jake Brake signs have in very small print "except for emergency only".  The thing that gets me is some towns out west ,for example, are located at the bottom of a 7 or 10 mile grade.  When you are fully loaded, you could start off the top at 20mph and without your jakes you would smoke your breaks and be out of control half way down. >:(

[mometal77]

I took the airbrake test in washington state.  Its like the same kind of tests you take at college like walking into three doors.  At first if you know nothing about them or never even seen an s cam ever it can be very hard.  Air breaks are very easy to work on i worked in a shop for a while didnt learn much over the guy highered a welder not a mechanic but i kept my eyes open ugh..  I dont get why they put questions like retarders in those airbrake questions.  I know they probably want you to know everything but it is only a class b license right and with airbrakes it is just an endorsement for a class b.   Usually with the buses go i found out the worst problem bus drivers have with school buses is putting on chains very physical and if you have never done it before can be a pain.  One friends wife got stuck down south and had the chain wrapped around the inner wheel.  Wasnt a picnic to say the least lots to learn.  I would find a local dealership tell her to take the book in and ask the questions and ask them to show the inner workings of  the air/breaking system.   
bob