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Author Topic: Intelligent Dumb Question:  (Read 16379 times)
RJ
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« 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!!   Wink












PS:  There's actually a method to my madness here, be patient. . .
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RJ Long
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TomC
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« Reply #1 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
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
belfert
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« Reply #2 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
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DrivingMissLazy
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« Reply #3 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
« Last Edit: August 02, 2006, 09:46:21 AM by DrivingMissLazy » Logged

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« Reply #4 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.
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1962 Crown
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« Reply #5 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]
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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming:  WOO HOO, what a ride
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« Reply #6 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.
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Barn Owl
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« Reply #7 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.
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« Reply #8 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.
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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming:  WOO HOO, what a ride
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« Reply #9 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.  Wink As Barn Owl says it could get expensive. Oh well, job security for us mechanics.

Call Me, I moonlight for $50 an hour.

Dale
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brojcol
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« Reply #10 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
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« Reply #11 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
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Brian Brown
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« Reply #12 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
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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming:  WOO HOO, what a ride
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« Reply #13 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
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« Reply #14 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

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Brian Brown
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