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Message |
HuskyPups (198.211.213.105)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 21, 2002 - 3:50 pm: | |
Hello All.
This may or may not be the place to post something like this and if so feel free to smack me around, but I thought I would share this story with everyone who posts to this board. The orignal is posted here: http://www.johnsoncitypress.com/ArticleDetail.asp?Category=LOCALNEWS&ID=8544
Brakes blamed for tour bus crash.
GATLINBURG — Investigators found malfunctioning rear brakes on a tour bus that crashed on a steep, winding road last month.
The driver and 11 passengers were injured in the Jan. 20 wreck along Ski Mountain Road. The bus was carrying 39 youth group members from First Baptist Church, Gaston, S.C.
Brakes on a rear axle “were so far out of adjustment the brake shoes were not making contact with the hub,” Master Tennessee Highway Patrol Trooper Arthur Galyon said.
But investigators couldn’t determine if properly functioning brakes would have prevented the accident, he said.
Driver Charles W. Hall had noticed a problem before the accident and stopped the Southern Connection bus halfway down the mountain to allow air pressure to build up, Galyon said. But when he resumed driving, the brakes still didn’t work and the bus crashed into a tree, the trooper said.
Investigators also believe brakes on the other two axles overheated and failed.
No charges have been filed.
After reading this article I have firmly decided make a serious investment in an air brake course when I get a bus.
FWIW
Dave |
RJ Long (24.127.8.58)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 21, 2002 - 8:45 pm: | |
Dave -
Why not be ahead of the game and take the air brake course BEFORE you purchase the bus.
That way you'll have an idea of what to look for during the buying process. . .
FWIW
RJ
PD4106-2784
Fresno CA |
Tom Caffrey (Pvcces) (12.146.33.18)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 21, 2002 - 11:49 pm: | |
Good idea, RJ.
The only drawback was that I knew when I was looking at our coach, I was going to have to convert it to spring brakes, so I was more reluctant on the purchase than I might have been otherwise.
Didn't hurt anything, because the seller took my first offer anyway.
Tom Caffrey PD4106-2576 |
Dan Bowes (24.64.223.203)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 22, 2002 - 2:20 pm: | |
Tom: When you take the Air Brake course you will find that the spring brakes are part of the Air Brake system. They act just like an emergency brakes when stopped and will assist in stopping the coach if you loose air pressure. Passing the air brake course is compulsory in British Columbia Can. and get the needed Air Brake endorsement on your drivers licence to legally drive. Really good knowledge to have!!
Regards; Stagecoach |
Tom Caffrey (Pvcces) (12.146.33.136)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 22, 2002 - 10:33 pm: | |
Hi Dan, I guess that I misled you. I have already taken the course and held a CDL since they were first required here. That's why I knew I would be converting to spring brakes right off.
Must be a few surprised people owning these buses when they have the pots bottom out from not knowing how to adjust the brakes.
As you said, really good knowledge to have!!
Tom Caffrey PD4106-2576 |
busasaurus (204.244.158.154)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 23, 2002 - 1:28 pm: | |
What about doing a brake adjustment? Getting under the bus to the slack adjusters looks next to impossible on some models.
The airbrake course says to check the slack every day and at the top of every big hill. Obviously the bus operator in this case didn't. Was he too lazy to crawl under, or was it impossible?
Maybe he had the automatic adjusters, but shouldn't they be checked periodically?
Bryan |
Scott Whitney (66.214.66.193)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 23, 2002 - 11:15 pm: | |
FWIW, I'd venture a guess that most people in the air brake classes are truckers. If you have ever looked closely at a big rig, you'll find that it is very easy to get to all the brake cans and adjusters on the tractor and the trailer both. Not so on a bus.
I've done it myself, putting on my grubbies, blocking up the bus and crawling full-on underneath the bus. For my rears, there is enought space to sit up and make the adjustments. For fronts, if I turn the wheels to both extremes I can get inside the wheel well and do the adjustment.
Not a fun project and I certainly would not do it at the top of every single hill. But then again, I don't drive thousands of miles every month either.
However, this is something everyone needs to know how to do or pay someone else to do it. I was going to have it done, but the shop I found who would do it, wanted $100 bucks. Decided to do it myself instead.
Scott |
Tom Caffrey (Pvcces) (12.146.33.170)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 23, 2002 - 11:33 pm: | |
Bryan, I realize that the different coaches will be different in adjusting their brakes. However, if a person only looks under the coach without crawling under, the far side can is easy to see.
If another person inside the coach steps on the pedal, you can see how much the rods stroke, so their really is no good reason to be caught unprepared by a brake adjustment.
Yes, the automatic adjusters should be checked periodically. But all this is beside the point; when brakes are getting out of adjustment, you can feel it when you stop the coach.
The further out of adjustment the brakes get, the more pedal pressure it takes to slow the rig down. Also, if you attempt a hard stop with loose brakes, you just slow down.
There is no reason for a driver to let his brakes go that long unless he doesn't know how the brakes act or doesn't care if he can get his rig stopped quickly.
And yes, I do realize that people sometimes let others push them into doing things they shouldn't. To me, that just comes under the heading of not caring enough to take the heat.
Tom Caffrey PD4106-2576 |
John Ogle Jr. (152.163.206.196)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 24, 2002 - 9:42 am: | |
When I began studying the North Carolina CDL driver prep book I was amazed to find technical instruction (and requirements) and vehicle dynamics in a government publication. I have always been technically interested in machines and this book explained quite a few jack-knife saves I have seen (not my own). Any one considering a bus should look at their state license requirements. They probably have a separate bus section as does the NC book. |
George Myers (12.85.1.70)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 24, 2002 - 8:30 pm: | |
I looked in the CDL book here in Ohio and three books for Canada to find out just how many inches the slack adjuster should move when the brakes are freshly adjusted. Could not find any information. Does any other state book have this information, and what is the travel. In other words "What are the standards, in mechanical terms, that one should adjust their brakes to?" I'm looking for legal numbers here. I have too many opinions already, and they are all different.
George Myers |
Ray C (142.165.92.116)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 25, 2002 - 12:23 am: | |
George The Province of Sask. has an air brake manual that was put together along with help from
Bendix and the Province of B.C.. It states: Checking, pull the chamber push rod out to it's limit by pulling on the slack adjuster arm or by prying with a short bar. If push rod travel is 3/4 inch (19mm) or more, brakes MUST be adjusted.
Bendix had a complete air brake manual online that I downloaded a few months ago but I could not locate it on their site today. They still have quite a variety of individual component and troubleshooting manuals online however. |
GeorgeMyers (12.85.14.135)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 25, 2002 - 11:37 am: | |
Thanks Ray for the info.
"The Air Brake Handbook" from Bendix's web site is in a file that is more than 5 megabytes. It took 45 minutes to download, but having a copy printed out is well worth the time. It can be found at: http://bendix.com/downloads/air_brake_handbook. Note: there is no www. It prints out to 59 pages with illustrations. When you get to the index, download the handbook .pdf file. Adobe Acrobat reader required. It does not show on my copy of this message that I reviewed before posting, but there is an underscore between air(underscore)brake(underscore)handbook.
The 19 mm (3/4 inch) in the Sask book is the maximum stroke when the push rod is pulled out by hand. This, by hand, force is far less than the more than 1,000 pounds applied by full air pressure in the brake chamber. It is however, the stroke that should not be exceeded, not the stroke to adjust to. |
Don KS/TX (67.210.119.97)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 25, 2002 - 8:01 pm: | |
Old truckers tend to forget a lot of stuff, but I can recall always having to stop on the CA border and tighten up the brakes. My recollection is that all other states and fed standards was 3/4 inch, Calif was 1/2. We always bitched about it, because that was so tight that you often heated up the brakes and caused premature wear. Surely someone else younger than I recalls this? I would often stop on the way out and LOOSEN the brakes back up again. |
Dave Wheat (24.158.28.11)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 25, 2002 - 10:13 pm: | |
Gentlemen: Check out the following web site for quick and easy info on air brakes. Go to: www.e-z.net/~ts/ts/brakpg.htm |
Buswarrior (Buswarrior) (64.229.209.7)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 25, 2002 - 11:28 pm: | |
Hello all.
I'd like to offer some words of caution, since brakes are kind of important to being around to enjoy a cold one at the end of the day!
Let's remember how many come to this hobby (ok, insanity!) with little to no commercial driving background.
It's my occupation to instruct both commercial drivers and commercial driving instructors in airbrakes. So, I'm just another opinion! :-)
George, you won't find any "standard" except the legislated adjustment limit. The minimum stroke that a given brake will stroke without dragging depends on configuration, and mostly, how close to truly round the drum and linings are.
Tom, the trouble with waiting until you feel it, is that your brakes are already well gone by the time you feel it. If you had to panic stop, it won't stop too well, or at all, at that point.
Think of your brakes like you would a fresh water tank with no gauge, and a bunch of thirsty kids in the rig. By the end of the weekend, does drawing a glass of water out of the tap give you any indication of how much water is left?
During a braking event, depending on the severity of the brake use, your stroke may lengthen by more than a half inch from what it strokes cold. One of the tests that gets referred to suggests that we get about a tenth of an inch lengthening of stroke for every 100 degrees farenheit rise in drum temperature. Under mountain, or heavy highway stopping conditions, it would not be out of line to see the drums up to 600 degrees.
Referring back to George's note about the pressure on the brake components, a nice smooth stop, one that won't spill the spouse's tea, only takes a 10 to 12 pound application of air to the chambers. This is only 300 to 360 pounds of force out of a type 30 brake chamber, typical of the rears on most of our coaches.
Now, if your brakes have worn to the point that the chamber is stroking out near its maximum and can't do much more than press 400 pounds, you'll not "feel" that unless you call for more than that. Trouble is that you need that big 1000 pounds plus to drag the "love-wagon-on-wheels" down from speed, or keep it from running away on a big hill.
It's kind of a moot point if your bus is not stopping or slowing the way YOU NEED IT TO RIGHT NOW to state,"Geez, I think the brakes need adjusting, I can feel it now!"
Unfortunately, there are, as George has pointed out, many opinions, most of them based on invalid personal experience that has taken on mythical proportions, or something that a grizzled veteran told us when we were young. Most of these are not based on verifiable principles.
Let's remember that normally, our brakes go out of adjustment because we have worn away some brake lining, increasing the gap between the resting position of the released brake lining and the drum. The goal of re-adjusting the brakes is to keep that gap nice and small, so that the relatively limited stroke of a brake chamber will not be wasted drawing up that empty space.
The best way to check your brakes is by having someone make a full service brake application while you measure the change in stroke between released and applied. The legislated stroke limits are based on doing this little check with the tank pressure between 90 and 100 lbs. If it passes for you at a higher pressure, all the better!
Getting a good measurement using the applied stroke method assures you that you do not have worn cam shaft bushings, and other wear, or damage in the parts, that will rob you of applied pressure of the linings against the drum.
We all need to be aware of wear in the brake components, since the brakes are no different than any other part of our old buses. Fleets don't like to put money into a vehicle that they will be selling off at the end of the busy season. Do you blame them?
Some things for the newbies to ask themselves:
How many times has your particular bus been in the condition of a planned for rotation out of a fleet? Poor old thing may have been ignored more than once in its life!
When was the last time your bushings and pins were lubricated? (Don't do this unless a pro taught you, please!)
Can we afford NOT to have the wheel-ends looked at by a professional on a periodic basis?
I am fortunate to have access to scores of fleet mechanics from a couple of companies. If I didn't, I'd pay someone.
And be sure that they know you want a bill!
happy and SAFE coaching!
buswarrior |
Tom Caffrey (Pvcces) (12.146.33.213)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 26, 2002 - 12:04 am: | |
Dave, that's a heck of a page! I don't recall seeing anything as short and to the point on the subject of truck brakes.
Tom Caffrey PD4106-2576 |
Tom Caffrey (Pvcces) (12.146.33.213)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 26, 2002 - 12:17 am: | |
Hi buswarrior, I agree with most of what you say, but I have no trouble telling if the brakes aren't all the way adjusted up.
Is it because of the worsening angle between the pushrod and the s-cam lever that more pedal pressure is required?
Just curious.
Tom Caffrey PD4106-2576 |
Buswarrior (Buswarrior) (64.229.215.194)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 03, 2002 - 5:59 pm: | |
Hello Tom.
Sorry for the late reply, had a stomach bug that was going around.
For the less experienced folks reading along with us, we should probably define what is meant by being able to "feel" the brakes. Without careful clarification, a newbie will unwittingly put themselves off the side of a mountain, waiting to "feel" something!
In my earlier post, by "feel" I meant a noticable deterioration of the braking effort of the bus. In other words, when you put the brakes on to slow or stop, they don't. This usually involves a bad responce from the driver,(insert bad words of your choice here) or in the least, raises some concern because it didn't slow down quite right.
Waiting until the brakes are far enough out of adjustment, such that it affects your stopping distance is the "feel" I was referring to. This is obviously a very dangerous way to signal a maintenance interval!
Tom, have I got it by saying you are refering to a much more subtle nuance in the "sharpness" of the brake application to slow or stop?
In our journey, another variable must be considered, and that is vehicle familiarity. Because we drive the same bus all the time, and have many miles, and brake adjustments behind us, we may acquire a sence of when it might be time to crawl underneath to do a little wrenching. Or we may not? Depends on who we are?
If we wanted to be sure, we'd get an engineer or two off the Board to do some testing with us to see if we can feel when they have backed off the brakes. I am aware of some testing done with professional drivers that found that they were not able to reliably identify brake adjustment problems by "feel" until it had reached a dangerous condition. Now, vehicle unfamiliarity rears its head here. The truckers weren't in their own rigs. But something to consider: How will I know when I know my bus well enough to know the brakes are still safe?
As for angle of slack adjuster to pushrod stroke, some "simple" high school physics has been raised to mythical proportions in the transportation industry. Yes, 90 degrees is strongest, but just how much different are the angles that we might see under the bus? Not enough to be of significance. Certainly one should aim for 90 degrees applied when installing a new brake chamber and trimming off any excess pushrod length, but with a properly installed chamber, the angle has little effect on braking.
As the brakes wear, it takes more air volume to fill the brake chamber so that the pushrod will reach out to close the increased gap between lining and drum. The return spring in the chamber also has to be compressed a little more, taking just a little more pressure away from the linings. Of course, if the brake chamber "bottoms out" becuase the brake is completely out of adjustment, more air pressure will have to be applied to boost up the strength of the other brakes to make up for the one that is now doing nothing.
Perhaps we should focus on the really important point that a driver should KNOW FOR SURE that the stroke of each and every pushrod under their bus is within the legal stroke limits for that size of brake chamber. Until one reaches a level of familiarity with one's bus and the driving conditions that will wear out the brakes, it doesn't hurt to periodically run the bus up on a set of ramps or boards and crawl/garage creeper under and measure them.
How often do we check the oil? Why would we check it more than the brakes?
As long as we block the bus, we can do one end at a time, if the thought of carrying that many boards bothers us. We already have a healthy supply onboard now for leveling with, using on soft ground to stay unstuck, ballast for the patio awning, or whatever, don't we?
With practice and an excellent working relationship with the co-pilot, in an open parking lot, we can set up, measure/adjust one end, drive around, remount the boards, measure/adjust the other end, drive off and pack up in as long as it takes us to do the motions.
Just enough time for the ice in your beverage to be taking effect!
If we are attempting to establish a verifiable ability to manage this safety critical maintenance function through prediction, be sure to measure first, to see what we had to start with, and measure after we use the wrench to be sure: 1) we did it right; and 2) that something hasn't broken or worn in there. As noted in the earlier post, a tight adjustment measurement confirms all manner of wellness in the brake components.
If we found any of the first measurements to be beyond the legal limit, we have been driving for a while now with some of the braking capacity missing! Good thing we didn't have to panic stop in that time!
Hope this helps some more!
happy and SAFE coaching!
buswarrior |
Tom Caffrey (Pvcces) (12.146.33.55)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 05, 2002 - 11:32 pm: | |
Hi Buswarrior.
You have raised many good points in your post and I will be giving much thought to them.
I already had it in mind to install an application pressure guage and I probably will, yet.
I would imagine that any difference in braking effort that can be felt would show up on the guage as lower application pressure.
The points you make bring to mind to cases where parents sometimes let total strangers babysit their kids that they wouldn't even consider letting drive their car. Not smart!
Thanks.
Tom Caffrey PD4106-2576 |
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