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Author Topic: Governor  (Read 3477 times)
John316
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MCI 1995 DL3, DD S60, Allison B500.




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« Reply #15 on: October 13, 2008, 04:30:27 PM »

Makemineatwostroke we have a 95 MCI DL3.

Dr. Dave-Reloaded, good point I will wait till we're home to adjust the pressure. I shore would hate to blow a tank on the road. I think our pressure unloader is good since I just rebuilt the whole dryer.

Thanks for the input and advice, lots more will be needed Wink.

God bless,
John
« Last Edit: October 13, 2008, 06:09:10 PM by John316 » Logged

MCI 1995 DL3. DD S60 with a Allison B500.
blue_goose
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« Reply #16 on: October 14, 2008, 10:08:03 AM »

John, it seams you want to make sure that you have enough air to stop in heavy traffic.  Most of the time to make a stop you are only using about 30 to 40 lbs of pressure.  In a hard stop you won't see the gauge go above 100 lbs.  My bus has a duel gauge that gives tank pressure and applied pressure.  I have always been surprised at what a little pressure it takes to stop.  At low speed 10 to 20 lbs.
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Dallas
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« Reply #17 on: October 14, 2008, 10:30:15 AM »

whooooaaaaa, wait a minute...
If you are using 30-40 psi per application, it's wayyy past time to be doing some brake adjustments.

On all my trucks I either had an application gauge or installed one..

If the amount of air EVER went past 15 psi, I knew it was time to adjust. Even in a panic stop, my applications never approached 30 psi.

remember, the longer throw from the slack adjuster to the brake cam, the more air it's gonna take.

Have some one explaing the pinging method of brake adjustment, or it's also known as the "bang on the brake drum" method. Personally, I jack up the the wheel and adjust until the wheel just barely won't turn, then back off 1/8th turn, until it freewheels.
After a few times of this method, you'll know where to set your slack adjusters while on the road.

Good Luck!

Dallas
 

John, it seams you want to make sure that you have enough air to stop in heavy traffic.  Most of the time to make a stop you are only using about 30 to 40 lbs of pressure.  In a hard stop you won't see the gauge go above 100 lbs.  My bus has a duel gauge that gives tank pressure and applied pressure.  I have always been surprised at what a little pressure it takes to stop.  At low speed 10 to 20 lbs.
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Fredward
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« Reply #18 on: October 14, 2008, 11:22:12 AM »

The thing I always adjust when I get on the road with the bus is following distance.   Wink

(not being a wise guy here but it has to be said)

Fred

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Fred Thomson
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« Reply #19 on: October 14, 2008, 12:25:24 PM »

The pressure that I am talking about is the lbs that it takes to apply the brakes.  Not the amount of air used to stop.  I can stop at least 20 times in slow moving traffic before the compresser restarts.
I don't think you can make a max brake pressure stop at 30 lbs.  We must be talking about two different things.  If you have a gauge that shows how much pressure that you have put on the brakes, just push hard and witch it go past 100 lbs.  I am a CDL driver and do know how to adjest my brakes.  Sure would hate to make a panic stop with only 15 lbs. of pressure of course the system would have locked up at 60 lbs.
Jack
« Last Edit: October 14, 2008, 12:35:58 PM by blue_goose » Logged

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Sojourner
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« Reply #20 on: October 14, 2008, 12:31:53 PM »

whooooaaaaa, wait a minute...
If you are using 30-40 psi per application, it's wayyy past time to be doing some brake adjustments.

On all my trucks I either had an application gauge or installed one..

If the amount of air EVER went past 15 psi, I knew it was time to adjust. Even in a panic stop, my applications never approached 30 psi.

remember, the longer throw from the slack adjuster to the brake cam, the more air it's gonna take.

Have some one explaing the pinging method of brake adjustment, or it's also known as the "bang on the brake drum" method. Personally, I jack up the the wheel and adjust until the wheel just barely won't turn, then back off 1/8th turn, until it freewheels.
After a few times of this method, you'll know where to set your slack adjusters while on the road.

Good Luck!

Dallas
 

John, it seams you want to make sure that you have enough air to stop in heavy traffic.  Most of the time to make a stop you are only using about 30 to 40 lbs of pressure.  In a hard stop you won't see the gauge go above 100 lbs.  My bus has a duel gauge that gives tank pressure and applied pressure.  I have always been surprised at what a little pressure it takes to stop.  At low speed 10 to 20 lbs.

Very good safety post Dallas!

That the ways I and many of truck & trailer mechanic friends do.

Thanks for correcting it and you said it well. I was about to respond until yours came in.

FWIW

Sojourn for Christ, Gerald
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Ps 28 Blessed be the LORD, because he hath heard the voice of my supplications. The LORD is my strength and my shield; my heart trusted in him, and I am helped: therefore my heart greatly rejoiceth; and with my song will I praise him
Sojourner
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« Reply #21 on: October 14, 2008, 01:20:16 PM »

John316....if are worry that your pump may not pumping  fast enough or to spec, just follow the simple tests on page 9 (make sure the compressor's intake filter is clean): http://www.bendixvrc.com/itemDisplay.asp?documentID=2389

blue_goose....you already knew what your talking  about but others need to be more informed with a little detail via Dallas's post. Thank you for your supports.

Fredward...pointing out a rule of thumb about we "bus driver" should always leave plenty of lead spaces to be prepared of the unexpected.  Thank you for your supports.

It not of my business how anyone drive a big long rig on public road, however there has been a number of our pass bus nuts who have lost a limb or two or life as well totaled their coach.

So it very important that your brakes are properly maintain and adjusted at all time. You can have other coach problems but never under estimate the importance of maximumize the care of your air braking system for yours & other's safety. We always want you back safety.

Thank you John316 for your concern and other bus nuts are trying to help each other.

FWIW

Sojourn for Christ, Gerald
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Ps 28 Blessed be the LORD, because he hath heard the voice of my supplications. The LORD is my strength and my shield; my heart trusted in him, and I am helped: therefore my heart greatly rejoiceth; and with my song will I praise him
gus
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« Reply #22 on: October 14, 2008, 04:08:55 PM »

Beats me why you guys want to run these high pressures? Maybe my ole 4104 runs so low because it is so ancient (like me) but it is designed to run between 80-100 psi. As already posted, these high pressures just increase the leaks and the possibility of something failing.

I don't think you get a bit more braking above about 100 but I may be wrong. I'm ready to be enlightened about the advantages of high pressure?

Anyway, the only adjustment on the gov is for max-I think this has already been said.
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PD4107-152
PD4104-1274
Ash Flat, AR
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« Reply #23 on: October 14, 2008, 05:19:04 PM »

Hello gus.

You raise a very legitimate issue.

The rising pressures over time, from your 100 lbs 4104 to today's 130 lbs multi axles tractor trailers, have more to do with the government regulations and the demanded performance targets of the braking system, than with the fairly straight forward desire to stop.

Higher pressures are said to help with the application timing in the tractor trailers with multiple relay valves and more mileage on the airlines, albeit in a fractional manner. In a straight unit like a bus, there would not be a change of practical magnitude.

Higher pressure also packs more air into the storage tanks, giving the system a greater volume of air in reserve.

The first jump in pressures might have been in responce to the arrival of spring brakes, and the designers wanting a little more breathing room between the bottom of the operating range of the air system and the caging pressure for the springs. (Spring brake needs somewhere around 60 lbs of air to fully cage)

And , as always, how do we really know what pressure we have?

Who has calibrated their air gauge? It is not, and never was, a precision instrument. Off the top of my head, the error factor from the factory today is some horrible percentage that translates into over 10 lbs of air between the dual needles, if someone didn't bend them to align...

happy coaching!
buswarrior
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John316
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« Reply #24 on: October 15, 2008, 04:34:08 PM »

Thanks for all of the input.

In July we rebuilt the whole undercarriage of the bus, which includes the following: brakes, replaced S-cams, all springs, checked all brake shoes, rollers, etc.; we replaced all the bearings, and races; airbags; shocks; and the list goes on. I regularly check the slack adjusters, so I know that they are correct throw. Everything is greased per the MCI maintenance manual. I try very hard to maintain everything that I know of. The problem lies in I don't know everything about it yet, I am still learning. Wink
   
Blue_goose, we don't have duel gauges like you described. When making a brake application it doesn't take much to stop the bus (unless it is a panic stop). I have tested to see if we have any leaks by depressing the brake pedal, with the bus off, and seeing if there is any air loss, which there wasn't. Also driving down the road our compressor runs rarely.

Dallas we do a similar method of adjusting the slack adjuster. Thanks for the advice.

Fred, the biggest thing that we watch is distance. The roofing motto, about black roofing tar, applies here to distance, "Some is good, but more is better."

I really appreciate you all's advice. Braking is a big deal. I have seen to many accidents by not good enough, or not fast enough braking, or not keeping enough distance.

God bless.

John

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gus
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« Reply #25 on: October 15, 2008, 06:46:54 PM »

BW,

I can understand how higher pressures will store more air but a pressure reg could easily be installed to limit the overall system pressure past the tanks. As for long trailers, the trailer tanks and relays take care of the distance problem. When I see triple trailers it tells me that is not much of a problem.

I wouldn't trust my 54 year old system with much more than 100 psi, it leaks bad enough as it is!

However, about two years ago when my gov failed the gage went to 150 psi a bunch of times before I found out that the gov was bad. I don't know to this day how all the hoses and connections held up?

Which reminds me, I need to get that extra gov I need to carry in the future. Now that I have rerouted all the lines to connect to the new type gov it can probably be changed in 20 min and a new one is only about $20.
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PD4107-152
PD4104-1274
Ash Flat, AR
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