| Author |
Message |
tom mcswain (207.144.40.153)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 11, 2004 - 8:47 pm: | |
I HAVE A 1992 PREVOST THE DRIVE IS SELF ADJUSTING. THE PADE ARE IN GOOD SHAPE.THE PROBLEM IS ON A RAINY DAY I PUT THE PARK BRAKE ON AND THE BUS STARTED TO ROLL BACK. THIS HAS HAPPEN AGAIN ON A CLEAR DAY , MOST OF THE TIME IT WHOLES GOOD |
ralph7 (208.155.122.45)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 11, 2004 - 9:33 pm: | |
NEVER NEVER TRUST self adjustors They MUST be lubed and stroke checked IF they stick,skip, get stripped or are not used often problems! ON big trucks slack adjustors are ALWAYS checked for stroke length, if not in specs, adjustor is adjusted manually and tested for proper operation, if it fails it is replaced. My brakes are adjusted with less than 1/4in. side to side on each axle(LEFT 1in RIGHT 1 1/4)and 1 1/2 inch stroke max. on any wheel. |
John that newguy (199.232.240.173)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 11, 2004 - 10:01 pm: | |
It kind of reminds me of our old "wheel to the curb, lowest gear,
or use a chock" rule.
Imagine getting out of your bus to help passengers off and having
the bus roll away..... ugh. There goes the tip. |
Buswarrior (Buswarrior) (64.229.211.20)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 11, 2004 - 10:59 pm: | |
Hello Tom.
Where are you? Any one of a bunch of us will come over to give you a hand.
Please DO NOT DRIVE YOUR BUS until you have someone show you how to check your brake adjustment, and then fix what I expect you will find, your back brakes way out of adjustment.
If the backs are that bad, you have to worry whether you have adequate brakes anywhere under the coach. Just because it stops at the stop sign, that may be all it has.
Please be safe, and PAY SOMEONE if you have to to find out how to stay safe!
Cheaper than the aftermath of a civil suit...
happy coaching!
buswarrior |
doughtebonifiedbusnut (24.62.99.43)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 12, 2004 - 7:17 pm: | |
Hey Ralph,
I think what your saying is gthat you have 1/4 inch clearence between the shoe and the drum because you say that you have 1 1/4 to 1 1/2 of travel in the adjuster. I could not agree with what you are saying more except that you have way to much clearence and way to much travel. To correctly adjust the your brakes you should have no more than 1/4 inch of travel in your adjuster and if you jack the wheel you should take up the travel in the adjuster untill you can just begin to hear the shoe touch the drum. |
Buswarrior (Buswarrior) (64.229.210.229)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 12, 2004 - 10:03 pm: | |
ok, whoa, and hold on a minute....
Ralph is suggesting that he wants the brake chamber applied push rod stroke to be close to the same on both ends of an axle, within 1/4 inch. And that he likes to keep the stroke under an inch and a half.
I'll agree with that. You want close to symetry on either end of an axle so there isn't any balance problems: one side a little quicker or a little stronger, leading to the vehicle pulling under braking. An inch and a half is a healthy bit safer than the adjustment limit for most brake chambers, and Ralph is willing to do what it takes to stick to what makes him happy. He has my support.
dougthebonifiedbusnut, what are you trying to tell us? where is your 1/4 inch and under what conditions? A 1/4 inch of clearance between shoe and drum would be wildly out of adjustment, and a 1/4 inch of brake stroke is pretty much unattainable, that tight would leave the shoes dragging hard when released, even on a wheelend where the linings were cut mounted on the wheelend. It's pretty hard to get much less than an inch of applied stroke without dragging linings.
Help us out and elaborate please!
happy coaching!
buswarrior |
BrianMCI96A3 (65.40.119.51)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 13, 2004 - 10:36 am: | |
I personally have always disliked automatic slack adjusters.
As a mechanic it just seems slack adjusters never recieve much, if any, maintenance attention.
Yet, over the years I can count on less than one hand the number of Rockwell (by far the most popular and reliable adjuster) manual slack adjusters I have seen being replaced.
I couldn't begin to count the number of automatic adjusters I have seen needing replacement.
The last time I was aware of it the law requires the push rod and slack adjuster to form a 90 degree angle upon application with 90 psi of air pressure.
But an old timer taught me to adjust manual adjusters by turning the shoes down till they contact the drum and back the slack adjuster off a 1/4 turn.
Over the years I have found that procedure to give maximum stopping power along with an even braking application.
Make sure you eyeball the shoe to be certain it is contacting the drum though!
All in all that procedure can take less than half hour for an 18 wheeler... of course than depends on getting to the adjuster easily.
A bus may be more time consuming to adjust if every wheel needs to be jacked up to reach the adjuster, but the operation itself is an easy one.
Brian |
dougthebonifiedbusnut (24.62.99.43)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 15, 2004 - 12:35 pm: | |
Hey All,
So that you all know my credentials, I am a licensed A&P with 26 years in the heavy trucking industry. For the last 6 years I've been a full time technician for the Ma Army Nt'l guard working on two differant helicopter airframes.
I don't profess to be much of a writer but I will try to explain as best I can my experiance with brake systems and how to adjust brakes.
First lets define terms.
A. brake chamber,(I think this is what you mean)
1. There are two types of actuators
a.diaphram actuated
b.spring over air actuated
Both are adjusted the same way.If all the components in the brake system are in good working
order you can absolutely attain 1/4 of n inch of throw (or movement) in the actuator arm and not have the brakes hanging up. More often than not worn parts in the system is the most promenent reason for brakes hanging up and performoing poorly.
I would never use an auto slack adjustefr cause in all my years in the industry I never had a pair of auto's that did their job.(I have however been out of the indystry for 6 years but this could have changed.)
I have two methods that I have used for many years that work great. The first is used when you "cannot jack up the wheel".
Once again assuming all the components are in good working order
1)realese the spring brakes.
2)take up the adjuster until it will not take up any more.(will not move in the CORRECT direction any more.)
3)Back off the adjuster untill you have 1/4 of an inch of travel of the actuator arm NOT THE BRAKE SHOES. (that muvh travel in the shoes will put a big truck out of service.
The second condition is whenyou "can jack up the wheel"
1)realease the spring brakes.
2)while turning the wheel takeup on the adjuster until the shoes just begin to rub.BUT NO RESISTANCE IS FELT. At this point the brake is adjusted correctly.
One more important point.All air brake systems are desighned in such a way as to insure that the pressure (air) goes to the axle that is farthest to the rear first and than proportionately to the axle closest to the front. This is to insure that the front wheels are the last to apply at the least pressure.
Let me add just one more thing. On more than oe occasion different people have approprietly said that if anyone is not very familiar with the air brake system on their bus to have a proffesional do your brakes and have him instuct you on the proper procededures, the life you save could be mine. |
Buswarrior (Buswarrior) (64.229.208.113)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 18, 2004 - 10:47 pm: | |
Thank you douthebonifiedbusnut.
I like what I'm reading now. There will be some of our friends who will have a hard time getting their brake stroke down to a 1/4 inch due to the wear in parts you speak of. Since many (if not all of us, lol!) end up with old and worn out buses, I didn't want someone out there tightening up to a spec their equipment won't reach without dragging a brake.
happy coaching!
buswarrior |