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DirtHauler
12-16-2007, 03:09 PM
I have been scared out of my mind of motor graders ever since I saw what the front of a brand new truck looked like after one hit it. The truck had a computer problem that made it loose power while climbing a haul road on a construction site. The owner of trucking company came out and they worked into the night to try to fix it... That is when they got stupid and decided to tow it to the top of the hill with a motor grader that was on the jobsite. The owner got on the graded and they got it all hooked up with a 15 foot cable between the rippers and the front bumper tow pin. The owner started pulling on the truck while the driver did his best to steer. I guess the grader stalled and the story is that the grader had no brakes since the engine was not running. The grader took off backwards into the truck causing severe damage to truck. Kenworth and Cat covered the computer as warrentee work, but did were not humored when the owner tryed to get them to fix the rest for free too.

Please clear this up for me and while we are on the subject, what machines will "take off" down a hill if the engine stalls. Also can you lower the rippers/blade without the engine running? What about a big dozer or tracked loader, will they freewheel as well?

I love challenges and have passed up a few opertunities to take a shot at running a grader because of this fear of helplessness should the engine stall.

Ross
12-16-2007, 03:31 PM
CAT Graders (16H's anyway). The Park brake is engaged by Spring and released by air. The Blade could have been dropped unless the machine has load check valves on the blade lift circuit.

Hydrastatic drives wont free-wheel as a rule but large Cat dozers can free-wheel with engine running. The blade on a D9R for example can be lowered without engine power.

Ross

surfer-joe
12-16-2007, 05:52 PM
If it was a Cat grader, simply moving the park brake control into the "Park" position would have stopped it within a few feet. However, the service brakes on a Cat grader are air over hydraulic. If the engine dies, the service brakes will not work, also, the hydraulics on a Cat blade will not move up or down more than a couple of inches, which is only due to the hydraulic accumulator.

Beds will come down on Cat and most other haul trucks without engine power. Dozer blades and rippers will drop as will scraper bowls on most machines excepting the old electric LeTourneau's and Wabco's. Most loader buckets and booms will come down with dead engines. I'm not sure how these situations will change as we get into more and more electric or hydraulic controls.

On most hydrastatic equipment, brakes are spring loaded and apply as soon as the engine dies. Electric drives with air brakes are mostly the same tho I have run across a couple that didn't.

Where the owner of that "trucking company" got stupid is when he decided to try to fix the problem himself instead of calling the Cat house for help right away, particularly so as the truck was still under warranty judging from what you said.

Grader4me
12-16-2007, 06:30 PM
Dirthauler, what kind of grader was it? With the Champion graders (1996 - 1999) some of our operators have had a few scares. The brakes are electric over hydraulic and if the engine stalls the brakes are still supposed to work...supposed to...It's been my experience that they don't work very good once the engine stalls.

They are equipped with a handbrake and if set up properly will stop you. With the key on you can activate the float, which will bring the moldboard down. This is the only way to get the blade down if you stall the machine. When I was working on steep hills etc. I always had the hand throttle bumped up so that the engine would be harder to stall. I always had my service brake set up and working properly.

Don't let this stop you from learning to operate a Grader. Maybe if the owner had been more experienced this wouldn't have happened

DirtHauler
12-16-2007, 06:30 PM
If it was a Cat grader, simply moving the park brake control into the "Park" position would have stopped it within a few feet. However, the service brakes on a Cat grader are air over hydraulic. If the engine dies, the service brakes will not work, also, the hydraulics on a Cat blade will not move up or down more than a couple of inches, which is only due to the hydraulic accumulator.

Where the owner of that "trucking company" got stupid is when he decided to try to fix the problem himself instead of calling the Cat house for help right away, particularly so as the truck was still under warranty judging from what you said.


Yeah the "owner" was one of those guys who had more dollars then sense. His ego got in the way of just calling the dealer in the first place.


Makes sense to me now that it was just the service brakes that were affected by the engine stall. Parking brakes are offen not our first instinct when a machine starts to get out of hand. The first dump truck I ever drove was an old gas powered international cabover with hydrolic brakes. I had one of the front brake lines rupture between the frame and the brake assembly. I was on a very steep hill and sitting at a stop when it blew... the pedal hit the floor and we were off. I doubt the hand brake would have stopped me, but I did feel kinda dumb for not at least trying it afterwords. I opted for side swiping the concrete block wall on the uphill side of the road as a means of stopping before the next corner which I did not even wanna think about facing.

72V
12-17-2007, 01:23 AM
On the G series brakes I've been into, the air activates a chamber inside the chainbox/wheel bearing housing, pushing directly against the brake pack. The service brakes should hold as long as there's air in the tank. The blade won't budge a bit if the hydraulic pump is not turning.

MKTEF
12-17-2007, 11:15 AM
We have only EU marked equipment, and it can be different from yours.:)

Parkbrake is on all types of equipment made so that if u loose power, the brakes can still be applied.(one of the systems on the G976)

The normal brakes may also have an aqumulator with buildt up pressure, that gives u 12-20 complete brakes, pedal to the bottom.

This is according to a EU regulation. u must have 2 independent systems for stopping.

Our new Volvo G976 has a electric pump mounted with the brake pedal that gives u pressure if the engine stalls.(no aqumulator)
It starts pumping if u press the brakepedal.:)

We also have emergency stearing, some equipment have a system that are driven by the wheels movement through the gearbox.(ground driven)

The G976 has a electric pump located inside the engine compartement.
Starts if the pressure from the engine goes away.:o
The orbitrol works as a pump also, but needs more force, if u loose electrisity.(double systems)
Wich is what the Cat M dosen't have....

Ross
12-17-2007, 04:34 PM
We have only EU marked equipment, and it can be different from yours Yeah Alot of CAT gear here is different to the mainstream stuff in the states.


If it was a Cat grader, simply moving the park brake control into the "Park" position would have stopped it within a few feet. However, the service brakes on a Cat grader are air over hydraulic. If the engine dies, the service brakes will not work, also, the hydraulics on a Cat blade will not move up or down more than a couple of inches, which is only due to the hydraulic accumulator. The first statment is true but the brakes will work if there is air in the tanks, If no air is present then the Spring in the park brake chamber will be applied. The blade on the grader can be moved on certain models. Without load check valves and electronic float.


We also have emergency stearing, some equipment have a system that are driven by the wheels movement through the gearbox.(ground driven)
Most if not all CAT graders have Supplementary steering as standard here. Also a small Accumulator into the priority side of the combination valve. The ground dependant steering pumps are found on Volvo ADT's but I cannot think of any other machine that uses this method at the moment.


The G976 has a electric pump located inside the engine compartement.
Starts if the pressure from the engine goes away. Pre-lube starters Are mostly found on large engines(19ltr +) Great for doing services. (Nightmare to change)

The orbitrol works as a pump also, but needs more force, if u loose electrisity.(double systems)
Wich is what the Cat M dosen't have.... The orbital valve requires pressure to work and isnt really a pump. The orbit works like a Slip spool and simply varies the amount of Oil to the steering contol valve or Priority valve if we are still talking about graders.

Ross

Northart
12-18-2007, 05:17 AM
On the Cat 14H, loss of air , by rapid continuous, repeated, braking action, or air line leak will activate the parking brake , when air pressure drops below 90 psi !

If you have 140psi-90 psi you have brakes .

I'm puzzled by the story of the grader running backwards into a towed vehicle. Something is amiss in the story!

In 38 years of operating equipment, I never stalled a grader pulling or pushing vehicles.

I stalled out when I hit a rock,hard spot, stump,etc when under load, grading .

Just find the story weird !

DirtHauler
12-18-2007, 11:44 AM
On the Cat 14H, loss of air , by rapid continuous, repeated, braking action, or air line leak will activate the parking brake , when air pressure drops below 90 psi !

If you have 140psi-90 psi you have brakes .

I'm puzzled by the story of the grader running backwards into a towed vehicle. Something is amiss in the story!

In 38 years of operating equipment, I never stalled a grader pulling or pushing vehicles.

I stalled out when I hit a rock,hard spot, stump,etc when under load, grading .

Just find the story weird !

Well truck weighed 105,500lbs and was up hill at about 8% grade. That and the fact that it was an old grader that had not been warmed up and the person operating it was not an operater, simply a truck boss who knew how to make it move, not operate it properly.

Grader4me
12-18-2007, 12:49 PM
On the Cat 14H, loss of air , by rapid continuous, repeated, braking action, or air line leak will activate the parking brake , when air pressure drops below 90 psi !
Just find the story weird !

I find it weird that the park brake will spike at just below 90 psi. Usually the pressure will go down to 30 or 40 psi before the park brake will engage. Must be different then the old Cat that I operated.



Well truck weighed 105,500lbs and was up hill at about 8% grade. That and the fact that it was an old grader that had not been warmed up and the person operating it was not an operater, simply a truck boss who knew how to make it move, not operate it properly

I can see that happening.

Northart
12-18-2007, 11:04 PM
Hello Grader4me.

Maybe your air governor needs adjustment. To set the proper kick in , kick out psi.

Nothing more irritating than to have a minor slow leaking line, bleeding off air, all day, to activate the warning light and low air horn.

Had a frayed hose this summer that did that, finally let go. Man was I glad we got that fixed. :)

Grader4me
12-19-2007, 05:27 AM
Hello Grader4me.

Maybe your air governor needs adjustment. To set the proper kick in , kick out psi.

Nothing more irritating than to have a minor slow leaking line, bleeding off air, all day, to activate the warning light and low air horn.

Had a frayed hose this summer that did that, finally let go. Man was I glad we got that fixed. :)

Could be. I guess my point here is that at 90 psi I just can't see the park brake engaging. The governor would kick in around 90 psi and the low air warning buzzer should kick in at around 60 to 70 psi. Park brake shouldn't engage until it goes to 40 or 30 psi. If it engaged at 90 then a person would be making nose prints in the windshield many times a day. Am I wrong with this? I have been wrong before...many times....:)

Northart
12-19-2007, 04:58 PM
Hello Grader4me,

Are you running the G series grader ?

Its been a long time since I been on one now. That or my memory is really getting bad .

I do know, in the morning, when starting up, no brakes are released till you have 90 psi. And this covers all equipment, air brake systems. Trucks included.

Here in cold weather, when airlines start icing up, they lock up the brakes, when psi drops below 90. Dump trucks, belly dumps , loaders, graders , that come to mind immediately.

Properly operating air governors ,along with ice free,or water free,(dry) air and sound hoses,keep the air tanks filled, so you don't "put nose prints in the windshield". :)

Now, I'm not a mechanic, and I don't have a service book here, with the specifications. But that is the way my 14H grader behaved this summer.

The operating range for the brakes is 90psi-140psi.

The warning light would come on 1st, then the air horn. Then the brakes would get locked up.And I don't remember it going as low as you are saying. You were not going any where till you got 90 psi. Generally this would happen at the end of a run when turning around.

It was a hose that got rubbed, till it wore a hole big enough, to burst, of course in a line hard to get to under the engine.

Later, Northart

dumptrucker
12-19-2007, 07:38 PM
90 to 140 psi is the governor operating range. Turns compressor on at around 90 psi and turns off at 125-140psi.
Your low air warning buzzer comes on at around 60 to 70 psi, the parking brake or spring brakes should not come on until the air pressure reaches around 20 to 30 psi. If your brakes are coming on at 90 psi you have got a problem with your system.

Orchard Ex
12-19-2007, 09:38 PM
90 to 140 psi is the governor operating range. Turns compressor on at around 90 psi and turns off at 125-140psi.
Your low air warning buzzer comes on at around 60 to 70 psi, the parking brake or spring brakes should not come on until the air pressure reaches around 20 to 30 psi. If your brakes are coming on at 90 psi you have got a problem with your system.

I agree with dumptrucker (on trucks at least, I have no time in graders). The compressor doesn't even kick in until your down to 90 or maybe even less.

Grader4me
12-19-2007, 09:48 PM
Grader4me wrote

Could be. I guess my point here is that at 90 psi I just can't see the park brake engaging. The governor would kick in around 90 psi and the low air warning buzzer should kick in at around 60 to 70 psi. Park brake shouldn't engage until it goes to 40 or 30 psi. If it engaged at 90 then a person would be making nose prints in the windshield many times a day. Am I wrong with this? I have been wrong before...many times....


dumptrucker wrote

90 to 140 psi is the governor operating range. Turns compressor on at around 90 psi and turns off at 125-140psi.
Your low air warning buzzer comes on at around 60 to 70 psi, the parking brake or spring brakes should not come on until the air pressure reaches around 20 to 30 psi. If your brakes are coming on at 90 psi you have got a problem with your system

I would say that we are pretty close....:)

Northart
12-22-2007, 06:02 AM
Well, I'd like to see some Caterpillar Specs on this 1st,for the Cat 14H grader, before I advance the discussion further .

What the psi signals are for activation of the Warning Light, Air horn, and of the brakes !

What you guys are saying , sounds not unreasonable.

But what happened in the field, we are far apart . The machine ran fine till the air leak. Took several days to discover the problem, thought it was dirty air, drained tanks, to no avail.

Then the leak manifested itself, and was eventually found and corrected.

There was never any high road speed application of brakes, ala "nose prints". Usually during turn arounds in direction, they occured.

Till someone comes up with Cat Specs , to prove I was not reading the gauges correctly, or the machine air system is not adjusted properly , I got to let this rest.

Grader4me
12-22-2007, 06:42 AM
Hey Northart, I'm not out to try and prove you wrong. All that I was trying to get across is that in "normal conditions" with the brakes working like they are supposed to, I just couldn't see the park brake engaging at 90 psi. If there was something wrong with the brakes as you indicated then that is a different story. :)

John C.
12-22-2007, 03:21 PM
Trucks are not graders and graders are not trucks. You guy are talking apples and oranges.

The truckers are correct for their applications and pressures. Parking brakes are not supposed to be able to be released until they have a minimum of 60 PSI in the tanks. At the same time they will set the parking brake when air pressure goes below 60 PSI. You will see minor differences between trucks because of age and calibration of the gauges. The usual governed air pressure is 90 to 120 PSI.

Cat graders will not release the parking brake until it reaches 90 PSI. The usual governed range is 125 to 145 PSI. So why the difference?

Most truck use S cam brakes which make several mechanical advantages when applying the brakes. You have a big air can, a lever several inches long to apply that to and the wedge effect of the cam which make the brakes self energizing. It doesn't take as much air pressure to get a lot of braking force.

Late model Cat graders use air pressure directly against a piston pushing on pack brake disks. They don't have all the mechanical advantages of the S cam system. Since graders don't carry their own weight in material and don't travel more than about forty miles and hour, they don't need as much stopping power as a dump truck. Old graders as I recall used hydraulic oil to push on the pack brakes and the runaway issue was present then.

To the original question on a grader running away with a brake failure I would say a modern unit, a "G" series or higher, would have the fail safes that would allow the machine to be stopped. There is plenty of capacity in the air tanks to stop the machine. The parking brake is more than capable of stopping the machine and holding it in place when only the machine weight is considered. The last fail safe is the operator. All machines are inherently dangerous when the operator does not know what they are doing or they are operating the machine in an unsafe manor. Running a machine with an air leak would fall into both categories.

I'll have to check on the blade float issue on Cat graders. The "H" series operates it manually by pushing the control levers all the way forward and I don't know what would prevent it from dropping with a dead engine. The older machines used an electric switch so I would suppose the key would have to be on for it to work. I'll check when I get the chance in the future.

Northart
12-22-2007, 05:57 PM
Hi John C.

Good to see you, thanks for the reply.

So what activates the Warning Light and Air Horn ? A sensor, and is that adjustable or preset at the factory?


Must be electrical as there is a fuse in the console panel .

Northart
12-22-2007, 06:58 PM
Here's some published figures for Grader travel, and working speeds.:)

Orchard Ex
12-22-2007, 08:33 PM
Trucks are not graders and graders are not trucks. You guy are talking apples and oranges.


I have no experience in graders so I can't comment on that part. What I was commenting on was this part of Northart's post:


I do know, in the morning, when starting up, no brakes are released till you have 90 psi. And this covers all equipment, air brake systems. Trucks included.
Here in cold weather, when airlines start icing up, they lock up the brakes, when psi drops below 90. Dump trucks, belly dumps , loaders, graders , that come to mind immediately.


Are the trucks the apples or oranges?

72V
12-22-2007, 10:00 PM
This week, I did a test on the 143H, APN 3## I run, which cuts out at around 140 or 150 psi. Fanning the brake pedal with the parking brake off, the warning buzzer and flashing light came on at around 90 psi, and the grader still rolled freely at 20 psi. I couldn't get it any lower than 20 since the compressor built air as fast as I could lose it at that pressure.

John C.
12-22-2007, 11:12 PM
Hi Northart,
There is usually a pressure switch mounted on the service brake tank that activates the alarm. It is not adjustable.

Most of the horns on graders now days are electric.

How's the weather up north?

Northart
12-23-2007, 12:33 AM
Hello John C,


The mechanic and I didn't have much time to look for the warning light switch and air horn alarm switch. The switches that activate them.

We just were interested in getting the frayed hose replaced and back into business. In the middle of the dirt spread and planes flying overhead. :) LOL :drinkup

Now trying to reconstruct the repair 3 months and 500 miles away, wish I had the service manuals for the grader, now that I have all the time to read. LOL .

Anyway, the Cat 14H grader sure give good service. 3 hrs down time for the entire summer, over 1000 hrs . I had a Global Model, vs the USA model. Slight differences . Standard engine driven Fan and radiator, vs the hyd motor driven fan. A electric hydraulic prelube for the hyd pump. looked like a starter. Ran for 10 seconds, before engine. turned over. .

The weather sure has been on the goofy side here.

Rained most of November, then snowed, then rained, then got cold finally here in December. Was -20F most of this last week, now warmed up to +15F for the last several days.

Got about 12"- 16" snow here. Elsewhere they have nothing. Snowmachiners aren't happy . Rivers are still open.

Global warming is a real thing far as I'm concerned. The weather patterns just are not normal.