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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: RJ on August 02, 2006, 07:21:29 AM



Title: Intelligent Dumb Question:
Post by: RJ on August 02, 2006, 07:21:29 AM
OK, I posted this in another thread, but thought it might be better "out on it's own", so to speak.  So here it is:


Have any of you "popped" the emergency brake button at 50 mph on dry pavement to actually see what happens?


If so, please share your experience.


If not, why not?


Let the flames begin!!   ;)












PS:  There's actually a method to my madness here, be patient. . .


Title: Re: Intelligent Dumb Question:
Post by: TomC on August 02, 2006, 07:40:39 AM
Yes-it puts on the rear brakes in a way that you'd better be pulling over right now to stop.  I blew an air line on my big rig and had both buttons (tractor and trailer) pop at the same time.  Luckily I was in Wyoming on the interstate and quickly got onto the shoulder off the highway.

All of you should try popping your parking brake to see what it does.  But first try it at 20mph.  Then try it at 40mph-which I think is all you need to do to get the idea.

Any of you that still have the old driveline parking brake, PLEASE get rid of that and get maxi-brakes installed!!!  Those driveline brakes will have a hard time stopping you, let alone holding the bus still when stopped.  Besides, the maxi-brakes will hold the bus still, while the driveline brake will still allow the bus to rock several inches back and forth because of driveline slop clearances.  Good Luck, TomC


Title: Re: Intelligent Dumb Question:
Post by: belfert on August 02, 2006, 09:20:52 AM
I looked at a Scenic Cruiser with the owner once.  He said hit hit the emergency/DOT brake at 15 MPH once and it stopped him right NOW!  I think he said everything in the bus not fastened down went flying.

Brian Elfert


Title: Re: Intelligent Dumb Question:
Post by: DrivingMissLazy on August 02, 2006, 09:44:43 AM
I did a panic stop at 70 mph once when a truck decided to get off the freeway with no brake lights or turn signals. I did have a lot of blue smoke from my tires. However there was no indication of anything loose in the bus coming flying forward.

I believe most people have the mistaken impression that a 40,000 pound vehicle will de-accelerate very quickly. In my experience, that is not so. Definitely the bus slowed down quickly but not to the extent that things came flying forward thru the coach or to pitch someone out of a arm chair or off the couch.

I believe that stop was much more severe than would full application of brakes to only the drive axle.

Richard


Title: Re: Intelligent Dumb Question:
Post by: boogiethecat on August 02, 2006, 09:59:42 AM
Yes, I purposely popped the emergency brake valve while running my Crown at 25, then at 45 then at 70mph, because my feeling is that it's better
to find out what will happen under controlled circumstances when you know what's going on, than to find out (for the first time anyway)
when something goes wrong and you least expect it.  From that day on, you'll know what you're in for if you pop a line etc.

At all three speeds it's not strong enough to lock the wheels, but in all circumstances it is certainly what I would call "exceedingly trong" braking.  Much stronger
than I have ever done with the brake pedal.  But in at least my bus, its a nice heavy controlled deceleration.


Title: Re: Intelligent Dumb Question:
Post by: DrivingMissLazy on August 02, 2006, 12:24:33 PM
Have you ever had to try a full on emergency stop using the brake pedal?  And is not this control we are talking about actually only a parking brake, not an emergency stop brake?
Richard
Much stronger than I have ever done with the brake pedal.  But in at least my bus, its a nice heavy controlled deceleration.
[/size]


Title: Re: Intelligent Dumb Question:
Post by: Beatenbo on August 02, 2006, 03:00:02 PM
We have thread on dry pavement, maybe wet would be a thought..... I have over a million miles of bus driving in the last 40 years in about 13 buses, 10 of my own. In all these years I have less than six emergancy situations that called for full force braking. I thought one time last fall I might have to take the shoulder or median because of a sudden stop in construction. I agree with Richard this is called a parking brake. I sure wouldn't want to drive all over the country thinking it might be more braking than a foot application. I wouldn't put my brake blocks, drums, or any parts to that kid of abuse out of curiosity. If some sort of malfunction causes parking brake to activate I'll deal with it then. Never had a problem with parking brake in 40 years.


Title: Re: Intelligent Dumb Question:
Post by: Barn Owl on August 02, 2006, 10:14:30 PM
This could be a very expensive experiment. If you managed to lock your wheels for anything more than a very short distance you will get flat spots. Where I work we have had, and continue to have, some not-so-bright drivers lock up their trailer wheels. Then they complain about the thumping for mile after mile. But, itís no sweat off their back because they donít have to pay for it. In fact they have no idea how much a tire cost, much less a complete set plus labor.


Title: Re: Intelligent Dumb Question:
Post by: DrivingMissLazy on August 03, 2006, 05:32:46 AM
I think it is much easier to lock up the brakes on an empty trailer than it is to lock up the drive axle on a bus.

I recall seeing many posts in the past where the poster was complaining about not being able to lock up the wheels with the foot brake. And no I would not want to do it, but I had to one time in 150,000 miles of travel in the bus and I was glad I could. 
Richard


This could be a very expensive experiment. If you managed to lock your wheels for anything more than a very short distance you will get flat spots. Where I work we have had, and continue to have, some not-so-bright drivers lock up their trailer wheels. Then they complain about the thumping for mile after mile. But, itís no sweat off their back because they donít have to pay for it. In fact they have no idea how much a tire cost, much less a complete set plus labor.


Title: Re: Intelligent Dumb Question:
Post by: Happycampersrus on August 03, 2006, 06:25:31 AM
That ain't nuttin.

What till someone tries this STUPID trick and they "cam over" their brakes in the middle of the road.  ;) As Barn Owl says it could get expensive. Oh well, job security for us mechanics.

Call Me, I moonlight for $50 an hour.

Dale


Title: Re: Intelligent Dumb Question:
Post by: brojcol on August 03, 2006, 06:57:13 AM
Well, I did almost throw a guy through the front window of my 4107.  He was there looking at it to buy.  He sat in the passenger seat and I had no idea he didn't have on his seatbelt.  I came to a very sudden stop (using the foot pedal) and he nearly went flying through the front window.  Caught himself on the top of the bus.  Hurt his finger.  I was only doing about 10 mph.  Would've been bad if I was going faster...

Needless to say he didn't buy the bus (I think it was bigger than he expected as he had never owned a bus before).  I'm just lucky I didn't get sued...

I know these are big machines, but if the brakes are done right, they will stop when applied.  I cannot imagine needing to "lock them up" with the emergency brakes, but if that time ever comes, it will be because I am acting out of desperation, not to satisfy a curiosity! 

CURIOSITY WILL KILL YOUR CAT!!!

Jimmy


Title: Re: Intelligent Dumb Question:
Post by: Buffalo SpaceShip on August 03, 2006, 08:08:18 AM
Seeing how "pulling the poppet" at slow speeds is a requirement for most DOT pre-trip inspections, I'm surprised more busnuts haven't done it. .. at slow speeds anyways. At higher speeds, I can understand the trepidation. The most difficult part of the exercise would be finding a straight, zero-traffic stretch of road to try it on. I for one, would want to know what to experience in the event that I do need to pull the button in an emergency situation, so I'm going to do it. Gasp!

If you REALLY think that pulling the e-brake on your coach could lead to unnecessary damage, take a gander sometime at the mechanicals involved. On the DD3 cans, the aux. diaphrams are smaller than the service side's. And on spring brakes, their big springs can't come close to the force of an air diaphram. On dry pavement, it's physically impossible to lock up a drive axle carrying 7 or more tons with an e-brake application... esp. at 40mph. Good grief.

"Let the flames begin," indeed. Russ has been training coach drivers directly for a LONG time. And other busnut drivers (myself included) through these forums indirectly for quite awhile. I believe that this discussion is further training... and we should always be "in training". Here's to more continuing ed.!

Brian "still in training" Brown


Title: Re: Intelligent Dumb Question:
Post by: DrivingMissLazy on August 03, 2006, 08:45:57 AM
I did it on my Eagle which probably had spring brakes. I started of slow at 20 mph and did it several times till I got to 50 mph. Never skidded a tire as far as I could tell. A lot difference in just applying brakes to one axle as opposed to applying them to all axles.

Richard


Title: Re: Intelligent Dumb Question:
Post by: JackConrad on August 03, 2006, 10:59:33 AM
I may be wrong (wouldn't be the first time or the last) but, The knob is called a "parking" brake and is only an emerency brake in the event of catastrophic loss of air pressure, not for "emergency" stopping such as because someone pulled out in front of you. There is no way brakes applied only to the drive axle will stop you anywhere near as quickly as appliying brakes on all axles. And yes, I do check my "parking brake" as part of my pre-trip inspection, but only at a slow speed. Jack


Title: Re: Intelligent Dumb Question:
Post by: Buffalo SpaceShip on August 03, 2006, 01:42:33 PM
I may be wrong (wouldn't be the first time or the last) but, The knob is called a "parking" brake and is only an emerency brake in the event of catastrophic loss of air pressure, not for "emergency" stopping such as because someone pulled out in front of you. There is no way brakes applied only to the drive axle will stop you anywhere near as quickly as appliying brakes on all axles.
I agree, Mr. Conrad. In my post, by emergency, I meant an air-loss emergency, not a traffic-induced one.† Yours is a very critical distinction!

It be great if an airbrake industry person (Bendix, Meritor, etc.) would find our threads on DD3s and this one to provide some background and insight on these critical safety systems in our coaches.

Until then, I can offer up some more conjecture... I've read that the E-1 and newer E-3 treadles were designed to give only about 80psi to all brake chambers on a to-the-floor, "come to Jesus" stopping attempt. Anything more tended to lock-up the tags and fronts. According to Da Book on my old 4106, the old-style ICC systems (on 4106s, etc.) could divert MORE air to the rear chambers than the treadle valve alone. I suspect that even the smaller diaphrams of the DD3s would get all available air (up to 120psi), so it'd be an interesting experiment to compare stopping distance between the two (i.e. all chambers full service application vs. parking brake-only).

Speaking off... if the next bussin' event could be near a drag-strip, maybe we could put some of this science to the test. DD3's vs. springs, simulated air loss situations, treadle braking distance vs. parking brakes, etc. Why let the Bonneville boys have all the fun?!

bb



Title: Re: Intelligent Dumb Question:
Post by: Devin & Amy on August 04, 2006, 05:46:43 AM
Hi all,

Forgive my ignorance, but if I have a sudden air loss at highway speed, won't the E-brake pop?
 I had a situation similar to this except not at highway speed. I crowned a mountain at a campground close to Lebanon,TN when I "felt a pop in my foot". coming down the other side of the mountain I noticed that my pressure went below 70 p.s.i. w/o the accompanying rattle of my compressor kicking in. I took it slow to the campground knowing I was hurt and not wanting to fix the bus on a two lane highway. I entered into the campground at about 20 p.s.i. and almost got into a site, when the e-brake set at about 5 m.p.h. it hit pretty hard.
The compressor had internally combusted and had to be replaced. But if I would have lost an airline or anything else catastrophic in the system, do you have any time to think, or just react?
Again sorry for my ignorance, as I've been pretty lucky with a good sound bus.

Devin


Title: Re: Intelligent Dumb Question:
Post by: buswarrior on August 04, 2006, 07:54:14 AM
Russ,

You are one funny fellow!

Yes, I have aplied the parking brake at high speed.

And when this experiment is over, we need to go back and make some correction to some of these other posts.

Folks, don't be using this post as education, there are some myths being exposed.

happy coaching!
buswarrior


Title: Re: Intelligent Dumb Question:
Post by: gus on August 04, 2006, 01:35:27 PM
buswarrior,

If these are myths how about telling us exactly which ones are?

A general statement helps nobody, please be specific.


Title: Re: Intelligent Dumb Question:
Post by: RJ on August 04, 2006, 05:51:06 PM
Gusc (and others) -  Hang in there, I want this post to run thru Sunday evening, then I'll explain the method to my madness!

Promise!   ;)


Title: Re: Intelligent Dumb Question:
Post by: ol713 on August 04, 2006, 07:52:31 PM
OK, I posted this in another thread, but thought it might be better "out on it's own", so to speak.† So here it is:


Have any of you "popped" the emergency brake button at 50 mph on dry pavement to actually see what happens?


If so, please share your experience.


Yes;   I had a front tire blowout about a year and a half ago.   I remembered that in the drivers book
         for my MCI,  It said that I could do that in case of emergency.    When I had the blowout,
         I did apply the parking brake.  Everything went smooth.  The bus stayed on the road and
         everything was under control.  The only thing that was a bit unerving was the way the bus
         shook.  I mean everything . Even had a couple of seams split on the cabinets.  But all was
         OK.   Check page 9  (approx)  in the MCI drivers hand book.    Just keep good tires  on the
         front end and all will be OK.   Good luck.

If not, why not?


Let the flames begin!!† †;)












PS:† There's actually a method to my madness here, be patient. . .


Title: Re: Intelligent Dumb Question:
Post by: Barn Owl on August 04, 2006, 11:26:56 PM
Warning! This post will probably be come across as disjointed and seem to ramble on, but itís late and I am tired, so at this time I donít care. I might clean it up later if I feel like it.

Iím not going to pretend to know it all; I think there are a lot of members here that have been driving longer than I have been living. I have to supplement my lack of experience and knowledge by consulting others. I have only driven my bus, so Iím not sure what all buses are capable of. I do have a CDL and several years ago I did drive professionally (not buses).

Quote
it's physically impossible to lock up a drive axle carrying 7 or more tons with an e-brake application... esp. at 40mph. Good grief.

I know that spring parking brakes do not have the ability to lock up a fully loaded set of drive axles but they can if you donít have enough weight on them. I donít like to type so that is why I said if one ďmanagedĒ to lock them up and that saved me from having to delve into every possible scenario. Would an empty shell do it? I donít know, but I stand by what I said that if you did or could lock them, it can be expensive if you flat spot your tires.

I am fortunate to work with a very large company that has one of the fewest accidents rates per mile driven. Their training program is often emulated and copied. I have never seen anything on practicing this procedure. Our instructors do not teach this, and if there was a benefit to it, Iím sure they would.

I talked to several of our tractor mechanics about it and they also see no reason or benefit to doing it. Part of their preventive maintenance procedure is to test the parking brake. This is done by engaging the brake while the vehicle is stationary and attempting to move it. I had never heard about cam over so I asked: They said that in the ďold daysĒ there was a style that was prone to it if the brakes were not adjusted properly, but no one here (where I work) is old enough to have seen a set like that I† guess. They also said that the only time they have seen a cam over in modern brakes is when there has been some type of brake component failure. An example was given of a cracked or broken brake drum that would allow the shoes to hyper-extend up over the cam. By the way, the four mechanics I talked to said they would not pull the parking brake while moving in a bus if they owned one, even though it would probably not do any damage to the components.

Also as luck would have it our state DMV uses our lot to test for the CDL license. I asked about the DOT pre-trip that was mentioned in an earlier posting about testing the parking brake at low speed. I was told that in the state of VA there is no such requirement, and the official had never heard of it (Does someone have a DOT web link that references this?). She said that she sees no real benefit to doing it.† The same driving methods and recovery methods are essentially the same for all vehicles. The example given is that if you can recover from a skid in a car you should be able to recover from a skid in a bus using the same techniques.

There are situations where one needs to be exposed to certain situations. When I was getting my pilots license part of the training was to expose the student to a stall/spin. This would allow one to recognize the dangerous situation and recover from it. I see the value of that. Pulling the parking brake at 50mph for kicks and giggles, Iím not getting. If it was proven to be beneficial then it would be a common practice.

Now Iím not against it, Iím to easy going to be.† If itís something someone wants to do, and they feel better after having the experience and knowledge of what happens after you do it, then thatís wonderful. My point is that if you donít, I do not feel that you would be placing yourself at some sort of disadvantage vs. those who have.

Quote
Hang in there, I want this post to run thru Sunday evening, then I'll explain the method to my madness!

Promise!† †

I'm waiting to see if I am falling into some type of trap.


Title: Re: Intelligent Dumb Question:
Post by: Happycampersrus on August 05, 2006, 04:52:25 AM
Hey, Barn Owl

The reason I posted the "cam over" is because alot of folks on this board have some really old buses such as the 4104's and Senic Cruiser's and some older than that. I am not going to get into a pissing contest with all the folks here, But I have took my little bottle jack and fixed cam over problems as recently as last year. My company that I work for has some old equipment and some newer stuff. I don't have the luxury of having all new stuff.

Now on to the next topic. I have yet to find any pretrip inspection that says to drive a vehicle down the road and pop the parking brake or emergency brake and that search also includes the states of Cal. & Fla. All I have read say just what Barn Owl describes.

Oh well guys do it your way, as I have missed something about this brake test. A little background on me is I have worked on farm and heavy equipment since the 70's. I graduated from Nashville Auto Diesel College in 1992, and have had class A's since 1993.


Dale


Title: Re: Intelligent Dumb Question:
Post by: JackConrad on August 05, 2006, 05:29:48 AM
   Perhaps I should explain my pretrip air brake test.  Not sure if it is exactly as DOT requires, but here is what I do. I build air pressure to 120, release parking braking, and put bus in gear letting bus creep to insure that parking brake is released. I then shut off engine, make a firm service brake application, let air pressure stabilize and hold for 1 minute to see if there is any pressure drop. Then continue pumping brake pedal until parking brake "pops", noting this pressure (on my bus this is usually  between 45-50 PSI). I then start engine and let air pressure build, noting how long it takes to build to 120 (mine takes a little longer because I have added an additional accessory tank). I then put bus in gear and try moving before releasing the parking brake. This procedure also alows me to see what pressure activates the low air alarm and at what pressure the alarm de-activates.
   Speaking of low air alarms, how many have both audible and visual low air alarms in working condition. I have been in several coaches lately that did not have working low air alarms SCARY!   Jack


Title: Re: Intelligent Dumb Question:
Post by: Beatenbo on August 05, 2006, 07:24:05 AM
Whew !


Title: Re: Intelligent Dumb Question:
Post by: Barn Owl on August 05, 2006, 07:52:31 AM
I was glad to learn about ďcam oversĒ because I am getting my education here on this board (Iím not sure if my 4106 is susceptible yet). I am lucky to have at work about 15 fleet mechanics to consult with (The best part is its free!), so when I hear something on this board that I want to know more about or I have a problem, the first thing I do is take my question to them. The old man who ran the airport where I learned to fly (He had thousands upon thousands of flight hours) drilled into all of his students that no matter how much you know, or think you know, you are always a student. This has served me well, and if I ever was a student, I am now more than ever. Thank you all for all for the time you take to share your knowledge and experiences with the rest of us. Have a great weekend everyone.

BTW: My low air alarm is INOP so I added that to my list. Thanks Jack


Title: Re: Intelligent Dumb Question:
Post by: Buffalo SpaceShip on August 05, 2006, 07:54:32 AM
Also as luck would have it our state DMV uses our lot to test for the CDL license. I asked about the DOT pre-trip that was mentioned in an earlier posting about testing the parking brake at low speed. I was told that in the state of VA there is no such requirement, and the official had never heard of it (Does someone have a DOT web link that references this?).


Right here is from California's: http://www.dmv.ca.gov/pubs/cdl_htm/sec10_a.htm
Under parking brake check: "Allow the vehicle to move forward slowly and apply the parking brake or set the brake and try to move the vehicle. The brake should not allow any movement."

Why the option? I suspect for some vehicles, it's easier on the clutch to test the park brakes when rolling. But either test accomplishes the same thing... to know that the parking brake will hold the vehicle on a grade when stopped.

Mr. Conrad's pretrip test is exactly what we should all be doing every time we start up our coaches to go somewhere. I, for one, will admit that I don't always do it.

While some might read this thread and think that Russ and Buswarrior are being coy and evasive... but I believe that their years of training coach drivers intends for discussions like this to make us all really think about (and for some of us, actually discover) how our braking systems work and respond in an emergency situation. And I'm pretty certain that Russ was not advocating that everyone go out, get their coach up to speed, and pull their parking brakes. But this discussion has opened up some very important dialogue about our coaches most important safety systems... and that's a very, very good thing, IMHO.

Brian


Title: Re: Intelligent Dumb Question:
Post by: Dallas on August 05, 2006, 08:14:45 AM
As an ex-truck driver of 27 years and around 3.2 million accident free miles, most as an owner operator, I will wait to make any comments on the advisability of "dynamiting" the brakes at speed, "cam-over", the ability of a loaded set of drivers with spring brakes to lock up the wheels, or the actual number of spring brakes on a semi-tractor until Russ hangs the final word on us in his experiment.

This has been an extremely infomative and useful thread so far, let's see how many can glean something from this.

Dallas


Title: Re: Intelligent Dumb Question:
Post by: rwc on August 05, 2006, 08:46:37 AM
While I have done lock up the brakes om motorcycles to see which way they want to slide so I would be prepared in an emergency I am not sure I would want to do this in a bus. I think that the pre-trip test as described above would be best.
   I get the impression that a "CAM OVER" is not a good thing but what exactly does this describe??
 Thanks for the enlightenment
    RWC


Title: Re: Intelligent Dumb Question:
Post by: Happycampersrus on August 05, 2006, 10:01:08 AM
What happens during a cam over is simple an often times caused by worn or improperly adjusted brakes.

The brake shoes are driven by the brake camshaft. It has a S shaped end on it. The cam is turned and the S contacts the rollers on the shoes, spreading them apart to apply the linings to the drum, thus applying the brake.

A cam over is when the S cam is driven to far on the rollers. Sometimes the slack adjuster has to be removed to put the cam back in place. Worn rollers, Worn linings, and Worn drums or drums that have been turned to much can cause this situation. Todays brake shoes have larger rollers to help prevent this and larger rollers are available to replace yours upon doing a brake job. CHANGE THE ROLLERS EVERYTIME you do a brake job even if they look good, replace them.

If you keep good brake maintenance you probably won't ever encounter this problem.

Dale


Title: Re: Intelligent Dumb Question:
Post by: gus on August 05, 2006, 03:47:35 PM
I would never test spring brakes under way, at barely rolling speed it is bad enough. Of course in a real emergency I might try anything, but not just for a test.

The older GMCs, of which I have one, had an ICC brake button for emergency application of the rear brakes only. These are air brakes, not spring, and all the books say not to use this for a parking brake-for obvious reasons. I have never read anything in the operating manuals about testing these while at speed.

Locked up rear wheels can take you off the road unless the brakes and the road surface are perfect, not likely in the real world.


Title: Re: Intelligent Dumb Question:
Post by: Buffalo SpaceShip on August 06, 2006, 10:58:20 AM
 ::)Video Alert! ::)

Well, Russ, I not only pulled my parking brake at speed... I have the video to show it!


I was only able to get up to 40mph, but itíll give everyone an idea of what it might be like faster. I then ran the same test at around 40mph for a full service brake application.

I have DD3s on my coach (air-assisted aux. diaphragms that take care of parking AND emergency stopping), and itís a 2-axle, 35í model, tipping the scales at a little over 25,000 pounds.

Rather than me ramble on about my observations, I had my kiddos shoot video of the entire exercise. I edited them together briefly into a file showing both applications (on one you can even hear stuff falling to the floor), and then I show them side by side with a time counter.

I would LOVE to see someone shoot video of spring brakes being popped on at speedÖ and see if I need to eat some crow about some speculations I made about springs vs. DD3s in a previous thread.

The exercise and the results were eye-opening, to say the very least. I want to thank Russ Long for suggesting it in this post!

I welcome any and all observations and points based on what you see (or donít see) here.

Without further fanfare: http://www.thefamilybus.net/videos/parkingbrake.wmv

Cheers,
Brian Brown

EDITED for DUM SPELIN ERORS on 8/8/06


Title: Re: Intelligent Dumb Question:
Post by: RJ on August 08, 2006, 04:48:50 PM
Bump   :D


Watch this space for comments on Wednesday morning!


Title: Re: Intelligent Dumb Question:
Post by: buswarrior on August 08, 2006, 05:10:41 PM
Brian Brown is my hero!!!!

If you haven't seen his video, click the link and get onto it!

Cecil B Demill got nothin' on you!

happy coaching!
buswarrior


Title: Re: Intelligent Dumb Question:
Post by: buswarrior on August 08, 2006, 05:23:25 PM
And, hats off to you having your kids intimate with the machine!

That's how the next generation gets smarter, fill them up with all the present stuff early, so they can move on from where we leave off!

What a GREAT DAD!!!!

You guessing that spring brakes will do the job in the middle spaces between your two shoots?

I gotta get my teenagers to learn that video stuff!

happy coaching!
buswarrior



Title: Re: Intelligent Dumb Question:
Post by: Buffalo SpaceShip on August 08, 2006, 05:31:24 PM
Brian Brown is my hero!!!!  What a GREAT DAD!!!!

Aw, shucks, Buswarrior! Now I'm blushin'.

I think the real heroes come from the likes of yourself and Russ, using your decades of bus driving and training experience to help some of us newbies learn the ins and outs of our 12+ ton machines... and be safer, more knowledgeable drivers and owners.

But thanks all the same, sir.

You guessing that spring brakes will do the job in the middle spaces between your two shoots?

Well, I did stick my neck out on a previous thread, saying how the DD3s must be superior to spring brake cans because of their complexity. After doing the test, though, I'm not so sure. If they're any worse, it'll take a looooong time to stop a spring brake coach. I have to defer to you experts... and take my licks if I'm wrong.

Sooo... If anybody has a spring brake coach, 30 minutes, and one of those handy digital cameras that shoot videos like mine, I'd be happy to edit the video for a side-by-side-by-side comparison.

This is all so very educational, gentlemen,
bb


Title: Re: Intelligent Dumb Question:
Post by: Happycampersrus on August 08, 2006, 05:43:09 PM
I used the water truck at work for this experiment. It's a 1979 ford ex oil truck with spring brakes. I checked and adjusted the brakes before my run. Well gotta admit that I was really surprized at the out come. LOL.

That is all I'm gonna say untill RJ post.

Dale


Title: Re: Intelligent Dumb Question:
Post by: buswarrior on August 08, 2006, 06:14:24 PM
Brian, I think I can snap a video with my Sony camera without the help of the kids. Amazing the help the camera manual can be when Dad gets desperate to learn!

Too dark here, or I'd go now.

I'll whip off a couple different in-service transit bus models tomorrow and e-mail them to you in the evening.

happy coaching!
buswarrior


Title: Re: Intelligent Dumb Question:
Post by: Buffalo SpaceShip on August 08, 2006, 06:35:06 PM
I'll whip off a couple different in-service transit bus models tomorrow and e-mail them to you in the evening.
buswarrior, you'll likely find the files too large to email (anything over a few megs is too big). If so, drop me an email on my profile account and I'll give you a way to transfer the files directly to one of my domains.

Thanks!
Brian


Title: Re: Intelligent Dumb Question:
Post by: RJ on August 08, 2006, 11:40:47 PM
Oops. . . trade association meeting tonight ran much longer than expected, so no comments until Thursday AM.   :(

Sorry to keep you all in suspense, but I promise I'll "get-'er done!" 


Title: Re: Intelligent Dumb Question:
Post by: TomC on August 09, 2006, 03:25:10 AM
Brian- thank you for that test! It is about correct at what I've also found.  Your brakes did exactly what they are designed to do, since floating down with the parking brake wouldn't be very good performance, but the service brakes sure did work!  This test is just one of many you should do to be familiar with any type of driving situation.  I can remember as a teenager goofing around in the rain in a parking lot doing doghnuts, eventually getting it to be very controlled.  To this day that training makes emergency maneuvers controlled to the point I've never had an out of control crash.  Along those lines (not to say you should even try to do a doughnut with the bus [doesn't have enough power anyway]), practice behind the wheel at driving forward, backwards, turning, will make the inevitable tight backing into that RV space alot more relaxed on everyone!  Good Luck, TomC


Title: Re: Intelligent Dumb Question:
Post by: Len Silva on August 09, 2006, 06:20:05 AM
Brian- thank you for that test! It is about correct at what I've also found.† Your brakes did exactly what they are designed to do, since floating down with the parking brake wouldn't be very good performance, but the service brakes sure did work!† This test is just one of many you should do to be familiar with any type of driving situation.† I can remember as a teenager goofing around in the rain in a parking lot doing doghnuts, eventually getting it to be very controlled.† To this day that training makes emergency maneuvers controlled to the point I've never had an out of control crash. † Along those lines (not to say you should even try to do a doughnut with the bus [doesn't have enough power anyway]), practice behind the wheel at driving forward, backwards, turning, will make the inevitable tight backing into that RV space alot more relaxed on everyone!† Good Luck, TomC

Have you had any controlled crashes? I thought that only happened when landing an airplane. :D
Len


Title: Re: Intelligent Dumb Question:
Post by: Brian Diehl on August 09, 2006, 06:22:44 AM
Question... I don't know how this works on a GMC ... †But on my 96A3 the parking brake is regulated by a pressure regulator. †My 96A3 service manual calls for 85psi out of the regulator. †85psi is a lot of pressure to be applied to the brake actuator and while I haven't tried to use the park brake on pavement, at 20 mph on dirt it locks up my drive axle. †Have you checked your pressure regulator to make sure it is giving the correct amount of air to your park brake diaphrams? †

I'm going to be out this weekend with my bus and I will give the park brake a try at 40mph. †Well, I'll try it at 20mph first, then try it at 40. †I'll have my jeep behind me, so it should be a good test. †I'll let you guys know what I find out.


Title: Re: Intelligent Dumb Question:
Post by: Buffalo SpaceShip on August 09, 2006, 07:55:28 AM
Have you checked your pressure regulator to make sure it is giving the correct amount of air to your park brake diaphrams? †

Brian D., from the air system schematic, I don't remember there being a regulator in that side of the system (I could be wrong, since I don't have the book in front of me).

The park brake air could also be throttled back by the ports on the inversion valve. Plus, the aux. diaphram on the DD3 cans is quite a bit smaller than the service side.

Believe me, I was shocked at how little force is applied compared to a service brake application. My fronts can't supply anywhere near the braking force of the rears, so even with them removed from the equation on a park brake actuation, it shouldn't be that different.

Ideally, my next video should show the pushrod extension of both park brakes and service brake applications, since its obviously much less on the park brake one. It's very probable that less pushrod extension on a park brake application is by design to avoid flat spotting the drums over time when busses are sitting. But I'm just speculating again. Hmm...

Any other thoughts/ ideas out there?
Brian B.


Title: Re: Intelligent Dumb Question:
Post by: kyle4501 on August 09, 2006, 08:31:07 AM
The spring brakes on my dump truck are on only one of the 2 rear axles. You must have 50 psi air to start releasing them (60 psi for the yellow pop valve to stay disengaged).

So My guess is that the spring brake applies the same force as if the service brakes were applied to ONE axle at 50 psi.

In the case of my truck, that makes for a gradual stop allowing time to het her off the road if you are in light traffic. If in heavy traffic, it allows you to get a lood look at what you are about to run over† :o - assuming they didn't respond properly to the air horn.† ;D

I do know that if the spring brakes are on, you will not move the truck even with ultra low gearing!


Title: Re: Intelligent Dumb Question:
Post by: JackConrad on August 09, 2006, 09:57:11 AM
How many pounds of air pressure do you think you are applying to the brake cans in a normal braking application. I will wait until tomorrow to tell you how much pressure I use on my MC-8.  Jack


Title: Re: Intelligent Dumb Question:
Post by: gus on August 09, 2006, 08:43:35 PM
Don't get pressure and force mixed up. 50 psi on a 1 square inch piston is 50 lbs of force. 

The same 50 psi on 10 square inches is 500 lbs of force, same air pressure.

So, there is more to braking force than psi of air.

If, as someone said in the string, the spring brake cans are smaller than the service brake cans then the 50 psi required to release the rear brakes does not mean that the springs apply the same force as the service brakes at 50 psi.

My god, I'm beginning to sound like the professor!!


Title: Re: Intelligent Dumb Question:
Post by: JackConrad on August 10, 2006, 04:12:04 AM
In an average, "I am going to start applying a little brake to start slowing down" application, I use about 10-15 PSI of air pressure, a firm application uses about 25 PSI and a PANIC stop uses about 85 PSI. (these pressure are with an E-1 service brake application valve) Multiply that pressure times the can size (which is total square inches) and you have the brake application force. On our MC-8, the front brakes are 24, the drive axle is 30 and the tag axle is 12. So a specific amount of air pressue applies a different amount of braking force on different axles.  A 50 PSI application to a 30 brake can applies 1500 PSI to the S cam. I have seen 30/24 spring brake cans as well as 30/30 cans. I do not think you can get a can that has a parking chamber larger than the service chamber.  The return spring forces also vary based on the size of the brake can. On our bus this ranges from 39 to 12-1/4, with a stonger return spring on the larger cans.  Jack


Title: Re: Intelligent Dumb Question:
Post by: RJ on August 10, 2006, 10:07:26 PM
OK, everybody. . .

For your reading pleasure, choking over your morning coffee, or fuel for your flames, here's my take on this whole thing:

http://r4106.blogspot.com/2006/08/intelligent-dumb-question-answered_10.html

Enjoy!   ;)

(URL to blog edited 8-10-2006 @ 2231)


Title: Re: Intelligent Dumb Question:
Post by: JackConrad on August 11, 2006, 04:03:23 AM
Russ,
   Thanks for a great article. This shoulkd be required reading for avery busnut.  Jack


Title: Re: Intelligent Dumb Question:
Post by: belfert on August 11, 2006, 05:59:48 AM
The busnut I had talked about with Sceniccruiser on the first page of the thread actually had a seperate emergency brake I think called an ICC brake.  That brake was the one that stopped him right now at 15 MPH.

Brian Elfert


Title: Re: Intelligent Dumb Question:
Post by: DrivingMissLazy on August 11, 2006, 06:21:02 AM
Excellent writeup Russ, as always. You are a credit to the Bus Nuts community and to the busing industry as a whole.

I agree with you regarding the bus portion of the article. I am not experienced in the trucking industry so I can not comment on that portion.
 
I agree because your statements exactly match the tests I performed on my Eagle several years ago and with results as I posted earlier in this thread:
Quote
I did it on my Eagle which probably had spring brakes. I started off slow at 20 mph and did it several times till I got to 50 mph. Never skidded a tire as far as I could tell. A lot difference in just applying brakes to one axle as opposed to applying them to all axles. [/b] Richard


Thanks again for all your excellent posts.
Richard



OK, everybody. . .

For your reading pleasure, choking over your morning coffee, or fuel for your flames, here's my take on this whole thing:

[url]http://http://r4106.blogspot.com/2006/08/intelligent-dumb-question-answered_10.html[/url]

Enjoy!† †;)

(URL to blog edited 8-10-2006 @ 2231)


Title: Re: Intelligent Dumb Question:
Post by: Chris 85 RTS on August 11, 2006, 10:26:02 AM
While I have read and understand and agree with your article, I was wondering if the parking brake setup like that on my RTS could be an exception.  It is single drum mounted on the pinion of the differential.  It provides great holding power when stopped, I can not move the bus even under full throttle, but it seems to me that putting the parking brake in that location could be a weak spot in the driveline.  I'd hate to think that the pinion could be snapped by the sudden application of the parking brake at speed.  Now, I suppose that the designers were smart enough to recognize this and designed the system so that this would not happen, but I am not sure I am ready to test this theory as it would be very costly to replace the differential should something bad happen.  I've done the try to accelerate test with the parking brake so I know it works.  Seems like the discussion here was mainly about emergency braking systems that apply braking using the normal service brakes in a different manner of application.  Any comment about this slight varient? 


Title: Re: Intelligent Dumb Question:
Post by: FloridaCliff on August 11, 2006, 12:19:47 PM
Russ,

Excellent article.

I had mine trip at low speed and it was an almost instant stop.

It gave me the impression that it would always stop that way, but your information and Brians test

have shown me my expectation from the earlier emergency stop was wrong.

Very informative.

Cliff


Title: Re: Intelligent Dumb Question:
Post by: pvcces on August 11, 2006, 07:44:42 PM
Russ, excellent article. I especially liked your explanation of the kinetic energy involved.

Thanks.

Tom Caffrey
Suncatcher
Ketchikan, Alaska


Title: Re: Intelligent Dumb Question:
Post by: Happycampersrus on August 12, 2006, 06:03:52 AM
Chris 85RTS,

I don't believe you would want to try this "experiment". The maintenance manual C-8123 for the RTS section 5C-1 says "The control valve is not spring-loaded and will not "pop-up" to automatically apply the brakes in the event of low system pressure" So that got me curious then I called 505-347-7500 and spoke to Bob Benton at Millennuim Transit Service (They build the RTS) and he does not recommend trying this on a bus with the pinion mounted PARKING brake. He did say that you can and should use it in an emergency situation, but no test have been conducted to see what the effects would be from repeated use in this way (every 3 days). :-\

Dale




Title: Re: Intelligent Dumb Question:
Post by: MC7S50 on August 12, 2006, 07:30:15 AM
Hey Russ

Thanks for the informative lesson about the well-designed safety features of our braking systems.  I can tell you were a professional trainer!  I certainly learned some valuable info. 

Safety is always a big concern of mine because I see evidence that proper maintenance is not always carried out on bus conversions.  Also, understanding of how the systems work is not always what it should be. 

My congrats on furthering our understanding while having a good time doing it!

John


Title: Re: Intelligent Dumb Question:
Post by: Buffalo SpaceShip on August 12, 2006, 10:31:01 AM
A most excellent, informative article, Russ, as always. Your dedication to safety and thoughtful posts are always appreciated. I've learned sooo much from you over the years, sir.

Buswarrior sent me some stills of his transit garage AND a video of pulling the spring brakes on one of their Fishbowl transits. I edited a new version of the video, and now must fully retract anything I've said about spring brakes taking longer to stop a coach than DD3s!

New video (same link)  is here: http://www.thefamilybus.net/videos/parkingbrake.wmv

Cheers,
Brian


Title: Re: Intelligent Dumb Question:
Post by: buswarrior on August 13, 2006, 04:52:17 PM
Wow, Brian's editing skills are GREAT!!!

What a great video, and not because I helped!

happy coaching!
buswarrior


Title: Re: Intelligent Dumb Question:
Post by: buswarrior on August 13, 2006, 05:25:42 PM
Hello all.

One of the little things I caught up in this long thread, and would like to help with is the concepts around what the brake chamber pushrod is doing when we brake.

First, the brake chamber's job is to squeeze the brake linings against the inside of the drum when we apply air pressure with the brake pedal, or spring pressure when we put on the parking brake control, or regulated air pressure if we apply the parking brake control with DD3.

So, no matter which parking brake system, or whether we choose service or parking, the brake chamber push rod extends the linkage (slack adjuster, camshaft, S cam, rollers, shoes to linings) and rubs the linings against the inside of the drum.

MYTH BUSTER:

The distance that the pushrod extends does NOT change according to the pressure applied. Once the linings are against the drum, that's it for pushrod travel. What changes is the amount of squeeze, once they are against the drums. The rods do not push out any further once the linings are in contact with the drum. (unless you want to measure the very small deflection as the brake spider flexes under the extremes of full air pressure, but I don't think that matters for our discussion here)

Now, as the drum heats up during a stopping event, it grows slightly, and as it grows, the push rod will extend to compensate for the linings moving outward to stay in contact .

This is why we need to keep our brakes well adjusted. They "grow" longer under heat.

For a given application pressure, the amount of squeeze will also slightly weaken, as the volume available to it slightly increases with the slight extension of the rod. Pressure drops slightly. This is normal, and you don't really knowe about it when you are sitting upstairs. This is one of the smaller parts of what is referred to as brake fade.

The reason for regulated push rod travel limits is the serious situation you would be in if the drums heated up enough that the push rod ran out of travel, due to plate the diaphragm pushes on, hitting the inside of the chamber.  It is commonly considered that pushrod stroke can lengthen over half an inch between cold and the heat of a hard stop from highway speeds.

Descending a mountain using the brakes wrong, will extend them further, and ruin the brake linings, another whole thread!

Great thread and explanation, Russ!

happy coaching!
buswarrior


Title: Re: Intelligent Dumb Question:
Post by: pvcces on August 13, 2006, 07:31:31 PM
Thanks, Brian.

I really liked the work you did on this thread.

Buswarrior, what do you think of the newer extra long travel chambers? I don't think that we can use them because of insufficient room.

Tom Caffrey
Suncatcher
Ketchikan, Alaska


Title: Re: Intelligent Dumb Question:
Post by: gumpy on August 14, 2006, 10:04:52 AM
Well, I certainly learned something because of this thread and the work Brian and Buswarrior did.  I, like many, thought my bus would come to a screeching halt if the button were popped at 40 mph. I, like many, had tried it at low speeds (i.e. < 10 mph), and it had stopped rather abruptly, so without really thinking about it, I assumed it would stop that way from 40 mph or higher. After viewing Brian's video, I got real curious, and brave, and so on the way to dump my tanks after my recent trip, I found myself on a section of road where there were no other cars and bravely popped the valve up while at 40 mph. Guess what. My MC9 reacted somewhere in between Brian's and Buswarrior's video clips. Very soft, yet steady braking to a stop. Nothing abrupt about it. Didn't break the fridge free from it's mount and throw it through the windshield or anything like that.

I didn't compare it to a full brake application, as I know how that one works from experience driving in MN.

I'm really glad this thread came up. This is something I'll do at least once a year.

Thanks for the great information. It's opened up my mind more to think about the actual workings behind this and now it's more clear in my mind what's happening and why. I don't think the parking/emergency brake would stop the coach on a steep downhill, but it might keep you from losing control till you got to the bottom should you suffer a catastrophic brake failure of the service brakes.

craig


Title: Re: Intelligent Dumb Question:
Post by: buswarrior on August 15, 2006, 07:14:04 PM
Hello Tom.

Long Stroke Brake Chambers are a great thing!

If you can get them to fit in your application. The bodies are bigger, in that they have greater depth in the same axis as the pushrod travel. In order to make them longer stroke, the body of the chamber has to be deeper so the plate that the diaphragm acts on has more depth to move through before hitting the end of the chamber.

These long stroke chambers exhibit a flatter power curve over their length of stroke, a fancy way of saying they don't weaken as much as they get out to the end of their stroke. Graphed, the long stroke is superior to a standard stroke as it gets out to maximum stroke. They are safe and legal out to 2 and a half inches for a 30-30, which gives a busnut a little more time to not worry about going underneath to re-adjust.

Even if you can't fit long strokes in the rears, you should be able to fit them on the steers and tags, when the time comes for replacements, longer stroke means more room for mistakes, misadventure and neglect, not that any of us would ignore our brakes....

Many? Most? Some? truck fleets are spec'ing long stroke chambers exclusively, and have been for quite some time.

Long Stroke chambers work especially well with automatic slack adjusters. More room for the adjuster to do its job while staying a legal stroke length.

On new equipment, I would not order anything else!

happy coaching!
buswarrior


Title: Re: Intelligent Dumb Question:
Post by: Barn Owl on August 15, 2006, 10:10:56 PM
Do I qualify for a PhD. after reading this post? With this type of an education I feel like Iíve earned one. Great job everyone! This was one I thoroughly enjoyed.


Title: Re: Intelligent Dumb Question:
Post by: TomC on August 16, 2006, 03:30:02 AM
To all that contributed, this has been very interesting.  And as mentioned, there is a big difference between buses and trucks when comparing the two since axle weights between the two are different.  Here are some facts on brake area between the two:
My transit has 14" x 6" front and 14" X 10" in back.  That works out to be 4,926 sq in of brake area.  Parking brakes 3,079 sq in.  Based on a 36,000lb rated GVW that works out to be 7.3 pound per sq in on the service brakes and 11.69 pound per sq in on the parking brakes.
A typical 5 axle truck will have 15" x 4" front and 16.5" x 7" on all other brakes for a brake area of 13,388 sq in.  Parking brakes 11,974 sq in.  That works out to be (based on a fully loaded 80,000lb rig) 5.98 pound per sq in on the service brakes and 6.68 pound per sq in on the parking brake.
To put that into an easy comparison, for a truck to duplicate the transit performance, the truck should weigh 97,659lb.
On the other hand for the transit to duplicate the trucks performance, the bus should weigh 29,490lb.
But once again, we're talking momentum, and the ability to stop from highway speeds.  Because of the higher weight continuously on the buses axles, they will stop shorter.  The only time a truck will stop best, is when loaded-otherwise wheel lockup can occur.

And to clear up a point in my thread a few back, I said I had never been in a crash where I lost control of the vehicle, compared to someone else hitting you when they are out of control.  Good Luck, TomC


Title: Physics lesson re: Russ's post
Post by: Clarke Echols on August 16, 2006, 10:13:41 AM
I'll pick a few nits, but Russ's treatise is well worth the read.

Momentum and kinetic energy are related, but not the same.  Momentum is mass times velocity.
Kinetic energy is mass times velocity squared, which is the same as momentum times velocity.

Momentum is measured in foot-pounds-mass whereas kinetic energy is measured in foot-pounds-force.
Mass is a measure of resistance to acceleration (from Newton's first law: bodies in motion tend to
stay in motion, bodies at rest tend to stay at rest unless acted upon by an external force).

To get mass into force, you multiply pounds mass times the acceleration of gravity (32 ft/sec/sec).
1 pound of force is the amount of force required to accelerate one pound of mass so that
for each second its velocity changes by 32 ft/sec.; hence, 32 ft/sec/sec or 32 feet per
second squared.

A bus that weighs 32,000 pounds, traveling at 50 ft/sec (a little over 40 mph), the momentum
is 1,600,000 foot-pounds (mass).  The kinetic energy is 80,000,000 foot-pounds (force).

The amount of work required to stop a bus is equal to the kinetic energy which must be
converted to heat through friction (including air resistance which can be significant at higher
speeds).  Thus 80 million foot-pounds of work must be done.  That is equivalent to the
amount of work required to lift the bus 80,000,000 divided by 32,000 feet into the air,
which is 2500 feet (almost a half-mile).

On the other hand, the  amount of work to stop the same bus at 10 ft/sec (about 6.5 mph)
is only 3,200,000 foot-pounds, equal to lifting the bus 100 feet.  Thus a 5-to-1 increase in
speed increases the energy required to stop (kinetic energy in the bus that must be
dissipated) by 25 times.  Kick the speed up to 70 mph, and the energy to stop goes up
100-to-1.

That's why they say "speed kills".  It's the kinetic energy that must be converted into something
else that can wreak huge damage in an accident where the vehicle comes to a dead stop in five
feet or less instead of 500 feet or more.  That allows you to bend a lot of metal.

A 35,000-pound bus at 60 mph hits a 3000 pound car, head-on, coming the other way at the
same time.  The bus slows down about 5 mph.  The driver of the car has what I call "an abrupt
experience".

A jack-knife occurs when the centerline of a tractor and the centerline of the trailer are not
parallel or coincident with each other.  If a trucker tries an abrupt stop on ice, for example, and
turns the steering ever so slightly, the two halves are no longer going in *exactly* the same
direction.  The slight angle causes the force from the kinetic energy in the trailer to have
a lateral component (velocity is a vector, having both magnitude (amount) and direction) along
with the longitudinal component that is still parallel to the axis of the tractor.  This longitudinal
force tries to push the fifth-wheel sideways.  If the available friction between the driver tires
on the tractor and the pavement is less than the lateral force, the tires slide sideways (or
creep by scouring thanks to the pliability of the tire tread), increasing the angle until it eventually
takes over and most of the trailer force is pushing the drivers sideways.  That's bad -- very bad.

Clarke


Title: Re: Intelligent Dumb Question:
Post by: DrivingMissLazy on August 16, 2006, 12:16:42 PM
Hmmmmmmm! Would you mind saying that again please Clarke? I think I misssed something. LOL
Richard


Title: Re: Intelligent Dumb Question:
Post by: NCbob on August 16, 2006, 04:34:35 PM
I'm going to jump into the skillet, so to speak, with this question and a comment.......

My MC5A has plenty of brake shoe area, more than enough drum area but for whatever reason (probably passenger comfort..totally disregarding driver panic and blood pressure...) MCI had a treadle valve design all their own..in fact the Service Manual suggests the methods for rebuilding that valve or suggests that you send it back to MCI for a rebuild.

I find that it's not aggressive enough for my emotional comfort. Yes, I can live with the DD-3 actuators, that was discussed at great length in another thread.  What options do we MCI owners have for a treadle valve replacement which might be more agressive?
And...what is the downside of changing it out to a Bendix truck type?

I'm sure I'm going to hear all the typical flack about re-designing the bus and the associated liabilities an owner would assume in doing so but what I'm really looking for here is some factual data...the difference in braking distances to the "Maximum point of Retardation" not necessarilly the ability to 'lock 'em up and put flat spots in the tires' at a given weight and speed comparison.

While I doubt that anyone has done these tests under a 'lab comparison' situation....I surely would appreciate some input.

Bob



Title: Re: Intelligent Dumb Question:
Post by: buswarrior on August 17, 2006, 03:16:57 PM
Hello Bob.

Two things which you can do, and feel good about spending the money, and call it preventive maintenance, if nothing else...

Send the treadle valve in for re-build, and change out the relay valve down the back. Check to see if MCI recommends any upgrades to what your coach has currently.

Or, if you feel adventurous, plumb a good air gauge into the lines downstream from both of them and be sure they are delivering the proper pressures. A fellow I know went to Europe for his airbrake technician training and uses these techniques to find all manner of bad valves, sometimes right out of the manufacturer's boxes!!! The Europeans are way ahead of us on diagnosing brake problems. They plug gauges in all over to confirm proper pneumatic functioning, cut the new shoes for a brake re-line right on the vehicle to ensure they are truly round, centre the wheel-ends on install, put the vehicle on a dynometer to test the brake torque... Very few places in North America know, or bother, with these methods. Brake re-lines last longer if they are cut on the vehicle, ensuring they are round, in orientation to the axle.

Also, the MCI's, with that rod arrangment back to the bulkhead mounted treadle valve, also leaves us open for the ravages of time bending or otherwise weakening the mounts that all that linkage is attached to. If there isn't proper travel, we won't get full braking. And the mounts can flex when you stand on it. Get an assistant and watch it carefully.

happy coaching!
buswarrior



Title: Re: Intelligent Dumb Question:
Post by: NCbob on August 17, 2006, 04:37:37 PM
Some great suggestions, BW...I believe I'll have time for the treadle rebuild (or perhaps I'll get lucky and get an exchange from MCI).

I'm in the process of replacing the rear actuators and if time permits...the fronts as well before we leave for FL for the winter.  I might even be able to set up a dial indicator on the brake treadle linkage and check for mounting, etc.  Again, thanks for the places to look.

I'll report back on any problems I find.

Bob


Title: Re: Intelligent Dumb Question:
Post by: Stan on August 17, 2006, 05:28:37 PM
NCBob: You can get a lot more agressive brakes if you change to a softer brake lining.  The trade-off is shorter brake lining life.


Title: Re: Intelligent Dumb Question:
Post by: JackConrad on August 18, 2006, 04:50:25 AM
   When we purchased our MC-8, the brakes were "adequate". Slack adjusters were checked for proper adjustment. Brakes were still "adequate".  We drove the bus like that for several years.  When I installed the Australian Cypress flooring in the driver's area, I had to remove the brake/throttle assembly from the floor. This required disconnecting the rod from the brake pedal to the service application valve (E1) that is mounted on the bulkhead below the driver's area. After installing the new floor and re-installing the brake/throttle assembly, the rod was now the wrong length due to the increased floor thickness. I re-adjusted the rod allowing only about 1/16" of play in the brake pedal. The first drive after this, I almost put my wife through the windshield! It seems that this rod had been out of adjustment, with too much free play, not allowing a full application to the brake service application valve.
   I also installed a brake application pressure air gauge in the new dash. A normal light application to start slowing down is about 10-15 PSI. A normal full stop application is about 25-30 PSI. A hard (maximun) application is about 85 PSI.  Jack


Title: Re: Intelligent Dumb Question:
Post by: NCbob on August 18, 2006, 05:17:08 AM
Very interesting, Jack....and a good place to start my search.  My guess is that we take too much for granted with these systems.

I sure wish I could find the time to attend the Bendix Air Brake school in ATL that Jim Shepherd recommends so highly..but right now we're running in full throttle trying to finish everything we can in order to fulfill the already loaded schedule.

Thank you and the others for taking the time to post your reflections.

Bob


Title: Re: Intelligent Dumb Question:
Post by: Eric on April 01, 2012, 09:54:24 AM
I'm Bumping this because after several years of being on this board i just found this article... I think with all the new people that have joined this is a MUST READ for everyone... and perhaps a refresher for others.. as more and more of us go for older buses as i'm looking into now, this is something anyone looking at a bus needs to understand!


Title: Re: Intelligent Dumb Question:
Post by: buswarrior on April 01, 2012, 10:19:01 AM
A word of caution from later posts.

The video is resident elsewhere, perhaps someone else remembers where?

After the video shoot, from the large difference in results, Brian's brakes were found to be contaminated by way of leaking wheel end seals, thus, its stopping distance was far longer than it should be.

The evidence, as recorded in the video, could be re-packaged to serve as a warning as to what happens to your ability to stop if the wheel end seals are leaking into the brake drums.

He tore down the wheel ends shortly after this thread, discovered this, and fixed it all up.

No matter spring or DD3 systems, when everything is up to snuff, they all stop much the same, with a transit coach having some advantage due to the larger swept area of the brakes installed for the constant stop and go.

So, take your coach out, ensure all is secure, which you should be doing every time it moves anyway, and give it a whirl!

happy coaching!
buswarrior



Title: Re: Intelligent Dumb Question:
Post by: RJ on June 11, 2014, 04:21:12 PM
All -

Brian's great video has been found.  It's now on YouTube, here's the link:

Bus Parking Brake vs. Service Brake application (http://www.youtube.com/watch?v=EOx7J2_qetU&feature=youtu.be#)

FWIW & HTH. . .

 ;)


Title: Something You Do BEFORE Buying The Coach!
Post by: HB of CJ on June 11, 2014, 08:38:56 PM
BEFORE I bought my 1974 Crown Supercoach 40' 3 axle 10 wheeler ex-schoolie, I conducted two emergency brake tests.  The first was popping the maxi at in indicated 65 mph.  The old girl just hunkered down and stopped very quickly indeed with no detectable brake fade or wheel lock up.

The second test was also done immediately afterward also at around 65 mph.  Maxed out in 9th gear.  I stood on the brakes very very very hard.  Crowns have huge brakes and they work just fine, let me tell you.  The seller was sitting behind me on the right side and he just smiled.  No problem.

The old Crown stopped faster than many front end heavy empty half ton pickup trucks.  Yep.  Superb binders indeed.  Absolutely no drift and no detectable wheel lock ups or tire smoke either.  As expected with a Crown.  About as big of brakes that will physically fit.  Some help here .... 8-10"x16.5" front?  12"x16.5" rear?  Not sure.  Too long ago.

People, with all respect, these are NOT destructive tests.  They are just a working function test of the primary safety system of the Bus Conversion....the brakes.  I did this test again AFTER I purchased the Crown BEFORE I drove it home from Apple Valley CA to Cave Junction OR.  Again, no problem.

Later my mechanic did a complete brake inspection.  He said I had huge brakes.  New front drums.  New brake shoes all around.  Two new cans and lots of new hoses and stuff.  New shocks. Are these tests  abusive?  Maybe.  Destructive?  No way.  Routine?  Yes.  Like a bleed down brake test.  Important?  You decide.  HB of CJ (old coot)


Title: Re: Intelligent Dumb Question:
Post by: Bryan on June 18, 2014, 10:28:39 AM
Yes-it puts on the rear brakes in a way that you'd better be pulling over right now to stop.  I blew an air line on my big rig and had both buttons (tractor and trailer) pop at the same time.  Luckily I was in Wyoming on the interstate and quickly got onto the shoulder off the highway.

All of you should try popping your parking brake to see what it does.  But first try it at 20mph.  Then try it at 40mph-which I think is all you need to do to get the idea.

Any of you that still have the old driveline parking brake, PLEASE get rid of that and get maxi-brakes installed!!!  Those driveline brakes will have a hard time stopping you, let alone holding the bus still when stopped.  Besides, the maxi-brakes will hold the bus still, while the driveline brake will still allow the bus to rock several inches back and forth because of driveline slop clearances.  Good Luck, TomC

Could you tell me a little bit more about maxi brakes? And how do I know what I have? Thanks!


Title: Re: Intelligent Dumb Question:
Post by: RJ on June 18, 2014, 03:02:18 PM
Bryan -

Look at the brake cans on the rear axle. 

If you have three air lines going to the cans, you have DD3 brakes.

If you have two air lines, you've got spring brakes.

Maxi brakes is a generic term for these brakes, similar to how Kleenex is now a generic term.

There is a ton of information about brakes on Bendix's website, well worth snooping around for awhile under the service & support tab.  Even have tutorials about your air compressor!  www.bendix.com (http://www.bendix.com)

FWIW & HTH. . .

 ;)


Title: Re: Intelligent Dumb Question:
Post by: Len Silva on June 20, 2014, 06:09:05 AM
It was fun looking back to the beginning of this thread from 2006.  So many members who are no longer around or just inactive.  I miss you guys.