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Author Topic: steep hills and no jake break??  (Read 7525 times)
RnMAdventures
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« Reply #15 on: October 26, 2011, 07:04:35 PM »

Someone on this board posted that you can go down lots of hills too slow but only one too fast.


Sounds like a proverb  Wink A very good one.
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Mike & Rosemarie
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« Reply #16 on: October 26, 2011, 07:09:11 PM »

Pretty sure Ned is talking about your Black Mountain! thats some hill in the summertime! We  have gone down it in 2nd with a 4 speed manual. When we got the jakes it was down in 3rd with manual trans and jake. Now that we have an auto and jakes, drop down to 3rd and we use the jake like the foot brake, when the speed builds hit the jakes. Some people jake all the way down. I dont know which is best but my thinking is if the jakes fail for some reason i can always air brake. By the way i always heard and was taught to hard brake on the downhill to slow but it dident seem right. Going to try the steady brake. I know this has been debated but its hard to argue with a pro drivers experience. Waiting for the Warriors opinion now!
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« Reply #17 on: October 26, 2011, 07:41:08 PM »

RnM, go to www.mountaindirectory.com for the info on passes and grades. They put out two books, one for the western states and one for the eastern states. Well worth having, anytime i go a new route i consult mine so i know what i can expect.  And by the way guys, sometimes, depending on where you are coming from, one side of a pass may be fairly flat as you are already at altitude, and the other side going down may be really steep and long, so the old "same gear down as you came up in" doesn't work! Found that out a time or two!!!
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
buswarrior
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« Reply #18 on: October 26, 2011, 08:06:20 PM »

Rant comes first:

Yup, talk is cheap, and this argument will be typed over and over.

There's more than one way to get down the mountain without burning the living #$@&^ out of the brake linings.

There are also lots of ways to set fire to your tires, the brakes get so hot, and the coach won't slow down, with you standing on the pedal, and calling on a God you have ignored for years, to come and pay attention to you...

And the "go down in the gear you went up" doesn't help a new guy who hasn't gone up the hill, and sure doesn't help a guy with a turbo and 1500 ft/lbs of torque who went up one gear down... though it is a fine old saying that describes the situation AFTER the hill has been run a few times in an older coach...

Now with that said...

The issue is that it takes a fair number of words to attempt to describe the goals, and how to reach them.

Your two goals are:

1) to keep the brakes as cool as you can, so they keep working, and

2) keep the speed of the coach under control.


Hot brakes are bad. The linings can be permanently damaged, and the brakes may not slow the coach properly, both during the intense heat, and then after the linings are burned. Many of us unwittingly purchase coaches with burned linings. Temperatures in excess of 800 degrees Farenheit are seen when this goes wrong.
(The linings are flaky and crumble in places if they have been burned. A good reason for a proper wheel end dismantle and inspection on some periodic basis.)

The coach will want to pick up speed downhill in ways that an automobile driver will never have experienced.

Since the driver usually has no way of knowing how hot the brakes are getting, "light steady brake application" has problems. What does it mean? How light? How heavy is too heavy? And who gets to pay the bills when the experiment goes wrong?

Also of particular note, light applications are notorious for only applying SOME of the brakes, not all of them, and not pressurizing/sharing properly, localized hot spots in certain wheel positions are a reality. The valving under the coach doesn't always respond as intended, especially relay valves, and a front wheel limiting valve is a killer in a 2 or 3 axle coach. And there are coaches out there with them fitted with the driver blissfully unaware...

The reason the so called "stab method" or "snub method" is advocated today, is that any newbie can easily tell how long they coast between brake applications, a newbie can tell if the coach is decelerating with some force, and a firm brake application is less likely to have the above mentioned, less than equal braking being applied.

The danger in all of this downhill talk, is that by the time you decide that you've done it wrong, it is too late, the smoke is pouring out of the wheel wells and not only will the coach not slow down, it is accelerating downhill, with your foot hard on the brake pedal.

Seek out the runaway ramp and hope the gravel is loosely packed.

So, the newbie wants a method in which he or she is able to use existing experience to make decisions.

How do you snub brake?

Reduce speed and gear down cresting the hill, as necessary. Choose a target speed, for a 6-7% grade, maybe 45 mph in 3rd gear in a 4 gear coach? You choose a speed that makes sense for the gears you have. You want high engine revs, to help keep it slow. It would not be wrong to be using 1st or 2nd gear/20 mph or even slower on the steep 12%+ back roads hills. Patience is a virtue, usually saves money and fer shure, saves lives.

Back to the 6-7% example: Apply the brakes to scrub the speed down to 40mph, and let it coast. You should be off the brakes for many times longer than you were on them. As the speed creeps back up to the target of 45 mph, apply the brakes and snub the speed back down to 40 mph, and coast again.

If you have to get right back on the brake, then you are going too fast. If with each successive brake application, the braking effect seems to be weaker, you are going too fast. (or your brake adjustment is crap, and the heat is expanding the drums out beyond the linings reach...you want to get slowed down before you can't, but then you already know your brakes are properly adjusted... I hope)

So, slow down, cut your target speed by half a gear, so maybe use 39-40 mph as the target, and drop the 5 mph to 35 or so, or drop another gear and go lower, if the coach really wants to run down the slope.

Your principle is to choose a speed that you are mostly off the brakes, and occasionally snub.

Of course, into the right lane, four-way flashers on if your speed is going to be 15-20% slower than the crowd, and if it is single lane, those behind getting impatient really do want to see you launch off the cliff on the next bend. Resist the urge to meet or exceed their expectations... Just take your time.

This might also the time to wonder about some upgrades to the rear lighting for good daylight visibility of the signals?

happy coaching!
buswarrior



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« Reply #19 on: October 26, 2011, 08:10:30 PM »

Ed, as a new hired driver, we were trained on every piece of road there was around Banff, L. Louise, Jasper, Calgary and Edmonton (city tours, airport runs, etc). It took 3 weeks. So we pretty well knew what gear to use where. After a few months with more seniority, and more experience, we got turned loose on long distance charters. By then, we had more of a feel for a bus. Brewsters still trains this way. Not many companies do that anymore.

JC
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JC
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« Reply #20 on: October 26, 2011, 08:57:30 PM »

As an addendum to BW's excellent comments, I'd like to add the following:

Pay attention to the yellow caution signs put up by the highway dept for the truckers, if done so in the area you're traveling.

Staying within the guidelines of the signs gives you happy memories of the trip.

Oh, and add some $$ to the budget for Jakes, well worth the investment.

FWIW & HTH. . .

 Wink
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RJ Long
PD4106-2784 No More
Fresno CA
RnMAdventures
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« Reply #21 on: October 27, 2011, 01:49:41 AM »

Oh, and add some $$ to the budget for Jakes, well worth the investment.



RJ,

We have seriously considered getting a jake brake. Do you have any idea what it would cost to have Jake's put on my 4106?



RnM, go to www.mountaindirectory.com for the info on passes and grades. They put out two books, one for the western states and one for the eastern states. Well worth having, anytime i go a new route i consult mine so i know what i can expect.  And by the way guys, sometimes, depending on where you are coming from, one side of a pass may be fairly flat as you are already at altitude, and the other side going down may be really steep and long, so the old "same gear down as you came up in" doesn't work! Found that out a time or two!!!


Thanks Ed! I will have to get the books. Priceless info  Smiley
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Mike & Rosemarie
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« Reply #22 on: October 27, 2011, 01:50:22 AM »

  Pretty sure Ned is talking about your Black Mountain! thats some hill in the summertime!  (snip) 

     Yes, it's I-40 going downhill from about Exit 67 to Exit 72 (about 15 miles east of Asheville), exit 72 is to "Old Fort, NC".  It's kind of hard to go around - if you're heading from/to Asheville from/to Charlotte, you could take I-26 and "come in from the south" but that grade (between Tryon and Hendersonville, called the "Saluda Grade") is about as bad.  If memory serves, it's a little longer but not quite so steep.  I think that they're about the two worst grades in the southeastern US (but if there are any worse or as bad, I'd like to know about them).
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Bruce H; Wallace (near Wilmington) NC
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« Reply #23 on: October 27, 2011, 03:48:35 AM »

Hi I know this mountain very well.  big truck are limited to 35 mph.If you stick to that you will have no problems. gear down  only break lightly to keep speed down under 35, stay calm and you will be fine. If you are going thru I-40 toward Knoxville same  deal . good luck.   papatony
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« Reply #24 on: October 27, 2011, 04:23:15 AM »

  Thats really the key no matter what your driving, to use a low enough gear you dont need to brake, or only brake minimally to check your speed. If you have to stay on the brakes to maintain speed, your going to fast.

  I grew up in Duluth, learned to drive there and took my driving test there. My Dad taught me never to ride my brakes. He drove back and forth from Minneapolis to San Franscisco between '43 and '53, more times than him and Mom could count, more than 25 trips that he was aware, and more than once on US 40 out of Denver through the rabbit ears. They saw trucks and buses and cars 1000 feet down over the sides of mountain grades, back then they didnt run right out and haul it out, pick up bodies, they didnt have the manpower or equipment. Most of it was burned, FUBAR.

  Back in Duluth, I cant count the Trucks that lost brakes coming down Thompson Hill on Cody Street and wrecked. Always same answer, its Minnesota, they didnt think Minnesota had any grades. Once they ran out of brakes and couldnt drop a gear they had a runaway truck. And there wernt any run offs, so they plowed through cars or houses or whatever was in their path. Putting 35 through into downtown sure stopped all that craziness.

  I was in 7th grade. One afternoon the whole building shook, we all thought it was an earthquake, stuff rattlin and books falling off shelves. A grain truck had lost his brakes coming down Cody. Having grown up in West Duluth, he knew (he lived, surprisingly, took 3 hours to cut him out) this one house was vacant. A big two story on a the NE corner. Built in the late 1800's out of big rough sawn oak, big oak timbers underneath (we used to sneak around in it). He rolled over the oncoming lane, up over the curb, and took the porches off every house for a block before crossing the street and aiming the rig into the corner of that house. Shoved the entire house 8 feet off the foundation.

  The worst one was a guy in a dump truck came down 24th street, couldnt stop, took out three or four giant oaks along the side of the street, jumped the curb, ran through a school gymnasium, then down into a creek. No one was ever really sure at which point he was dead.

  Use low gear, whatever gear holds you back without braking a bunch. Stay off the brakes. Im stickin with snubbing it.
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BRUISER
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« Reply #25 on: October 27, 2011, 06:38:30 AM »

all great info.. thank you all for what you have posted..

I see and understand always best to be in a low gear and I can decide if i want to shift into a higher gear but going back down into a lower gear will be very hard..

my original plan even before posting was to get into 2nd gear and just take my time going down and see how the bus reacts to this..

I guess the one thing I did not see answered unless I missed it.. is if I am in 2nd gear will the tranny only let the bus go so fast.. or will I still need to use the brakes a few times to slow it down, and if I was t onot use the brakes but let the tranny do all the work am I causing long term issues with tranny by doing this?

oh and one last question where is the best place to get jakes for a 8v71 in a MCI bus?

thanks again
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iMPAKS.com
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« Reply #26 on: October 27, 2011, 06:49:11 AM »

It's not the tranny you need to worry about, it's over speeding the engine.  Don't let it get any faster than the max speed you could make in a particular gear.
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« Reply #27 on: October 27, 2011, 06:58:31 AM »

It's not the tranny you need to worry about, it's over speeding the engine.  Don't let it get any faster than the max speed you could make in a particular gear.

thanks that is what I wanted to hear
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iMPAKS.com
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« Reply #28 on: October 27, 2011, 06:59:51 AM »

If you are in a low enough gear, it will slow you down enough that you will have to press the accelerator to not slow down too much. You might decide to upshift if you think there is nothing steeper yet ahead of you.

If you are in a gear that doesn't quite hold the vehicle back, you will gain more and more speed, necessitating the use of the brakes and/or Jakes to control it. You have to keep the engine revs at or below the max speed (usually 2100, 2200 rpm) so you don't damage the engine. The trans won't care about overspeed, it is the engine that will take the damage.

Of course, to be able to down shift, you have to be at around (depending on your bus) 1500 rpm, so that the lower gear will be able to engage and not over rev the engine.

JC

Len Silva beat me to it and explained it more clearly.
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JC
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Ed Hackenbruch
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« Reply #29 on: October 27, 2011, 07:14:53 AM »

Something else to keep in mind is that not all grades are the same.  What do i mean by this?  You can have a 6-7% grade that is straight or has 50 mph curves that goes for miles that you can cruise down in 3rd gear and never have to touch the brakes. You can have a 3-5% grade that has 15-20 mph curves and is only a mile or two long and go down it in first or second gear and be on your brakes for the whole way. The directory i mentioned will tell you about the curves and mph and i learned real quick to pay close attention to that, it tells me more about the road than just what the percentage of grade does.  Grin
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
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