braking on big mountains...

The only problem I see with the new method is you are building more Kinetic energy ever time the truck is allowed to accelerate. Where as a steady application your Kinetic energy is constant. Of course there is another way to descend a grade without the use of brakes.

 

Oh......Yeah.....The right way, Proper speed and use of the jakes and the brakes (the way I generally do it) My jakes were acting up last year and I had to go back to the old "use the brakes" method for a while till we figured out what the problem was and fixed it...

On certain grades when you are running really heavy you need all the tools in your arsenal to get it down without tearing something up and at that point you need to know what works and what doesn't...

Lucky for us the steeringwheelholder types never run over 80,000 and so are never really put to the test as to whether they can use the brakes properly or not.

 

Well where I come from we run 53 ton trucks off of 8-13 mile 6% grades and that's the on road drivers. I learned early in driving how to fix jake brake issues. Cause it sucked to run a truck off big hills without jakes. It can be done but I won't suggest stabbing your brakes on the way done. If there is one thing I have learned is you never know what's around the next corner coming off a hill.

 

I've done it maybe 4-6 times in 15 or so years. I've never had a truck with a jake until recently and it seems only useful for making a little bit of noise hardly any perceptible slowing except if I'm empty. I never ran across the Rockies.

 

The CDL schools teach many bad ideas, badly. They get away with it because of the "shortage" of drivers, and the anti-analysis nature of this industry. This industry runs on rumors, resentment, and wives-tales. Data is not allowed without a permit.

Almost every new-hire driver, no matter how much experience, drops trailers too-high, never too low, and never consider kingpin to tandem distance on a trailer unless they question going over the axle weight limits. "That's how my first company trained me" seems to be a religious mantra. If you don't know why you are doing something, and the alternatives, and why those alternatives are wrong and the other way is right, you are just painting by numbers.

CDL schools do not adopt new information from the industry back into the classroom. They just keep teaching what they taught years ago in the same old way.

 

Try a gear baby it will do ya wonders ,ive been runnin filly all week and if your worried bout a hill try 18 bundles of wet mulch that will show u the correct meathod.

Sit dn.and hold on!!!!!! And get r done. Allways

 

Better pick your VOCABULARY wisely or YOU won't last here.

 

like that'd be a bad thing.

 

Your brakes convert the energy of motion (kinetic energy) to heat energy, that is their job.

the formula for kinetic energy = (mass X velocity X velocity) / 2
convert pounds to kilograms
convert mph to km/s

Assume 80,000 lbs truck and trailer, target downhill speed is 40 mph and increases to 45 mph. All have been converted to appropriate metric units for calculation only.

Kinetic energy = (36287.4kg X0.0179km/s x 0.0179 km/s)/2 =
Kinetic Energy @ 40 mph = (36287.4 X 0.00032041)/2 = 5.813421250867999 joules

Kinetic energy = (36287.4kg X0.0201 km/s x 0.0201 km/s)/2 =
Kinetic Energy @ 40 mph = (36287.4 X 0.00040401)/2 =
7.330234136148 joules

When speed increases 12.5% (from 40 mph to 45 mph) the energy the brakes must dissipate increases 26%.

Conclusion: it's vital to keep speed increase out of the brakes if overheating is a concern. Keep the speed slow enough and keep just enough brake pressure to prevent speeding up during the descent. If you claim some other method is better than the Light & Steady Method please show us the numbers to back up that claim. If you go slow enough you can use either method. If you can do it without smoking the brakes, keep doing whatever method you prefer. Just don't pretend speeding up and slowing down is less stress on brakes than keeping the speed steady, it's not.

If your brakes begin to overheat and you suspect you may need to stop, stop at the first safe place to stop. If in doubt, stop.

 

http://www.e-z.net/~ts/ts/downhill.htm

The above link explains why snub braking is the preferred method. Here is the relevant piece of the article;

•Steady, low pressure application of the brakes may not cause all the brakes on the vehicle to apply and may result in some brakes -those with the lower activation pressures- doing more work than others. Specifically, in many cases the tractor brakes will do too much of the work while the trailer brakes loaf and you might then get fade at the tractor axles.. Other brake problems can be aggravated by the low and steady braking technique. What you want is all the brakes working some of the time, not some of the brakes working all the time. The application pressure must be high enough to ensure that all brake chambers apply and that all linings make solid contact with the drums - about 20 psi or higher.



http://www.johncglennon.com/papers.cfm?PaperID=36

Downhill Braking

John C. Glennon, Jr., BSAT


[ Reprinted from the Trucker's World Magazine, Volume 5, Issue 6, June 2001]


When the Commercial Drivers License (CDL) manual was first published, it recommended that a driver use a light and steady application of the brakes when descending steep grades. This recommendation was based on an old theory that heavy brake applications would generate more heat than light applications. This method (controlled braking) was commonly taught to drivers and, even after changes were made to the CDL manual because this theory was proven wrong, the method is still taught and practiced today.

Snub braking is now the recommended method of downhill braking. This method works by: first, choosing the correct gear for the hill; second, allowing the truck to speed up to the maximum safe speed as it descends the hill; third, applying the brakes hard to slow the truck down 5 mph; and then repeating this process to the bottom of the hill. To understand why this method is recommended takes some understanding of the basics about how brakes work. Slowing a truck with it.s brakes, creates friction between the brake shoes and brake drum to convert the kinetic (forward movement) energy of the truck into heat energy dissipated by the brakes. The amount of heat energy produced is dependent upon the weight of the truck and the amount of slowing desired. Assuming these two factors remain constant, the manner in which the brakes are applied, hard for a short time or lightly for a long time, will not change the amount of heat energy and heat produced by the brakes. This heat energy will be distributed among all the brakes that are working. Again, assuming all other factors constant, the more brakes the system has working the cooler each brake will be.

This explains why the old theory of light and steady braking is incorrect. However, to understand why snub braking is the recommended practice, you must also understand the basics of pneumatic balance. Trucks have relay valves to control the application and release of the air brakes. A standard truck-trailer usually has one relay valve for the tractor drive axles and one for the trailer axles. The relay valves are controlled by air pressure from the foot valve (brake pedal). This control pressure opens the relay valve allowing the desired amount of air pressure from the air tanks to pass through the valve and supply pressure to the brakes. Pneumatic balance is created by having equal air pressure at all wheel ends. Pneumatic imbalance is a result of these valves that open at different pressures. For example, a tractor may be setup with a relay valve that opens at 15psi (15psi crack pressure relay valve) and the trailer being towed may have a relay valve with a 3psi crack pressure. A vehicle setup this way would only apply the trailer brakes during controlled brake application, which typically has an application pressure of less than 10psi. However, a .snub. brake application of 20 to 30psi will open all valves and apply all brakes. This type of imbalance can also be a result of contaminants and alcohol in the air system that can cause these valves to hang-up and have higher than normal crack pressures.


Now can we finally put this discussion, debate to rest???

Dont argue with me go argue with University of Michigan Transportation Research Institute.