Air Brakes--- how to use

[TRAILERKING]

Originally Posted by Wayne M

Also, teach the passenger how to move the driver out of the way, release cruise control, pull the yellow button and steer the MH, should an emergency be encountered and the driver becomes incapacitated while driving and slump over the wheel. Heaven forbid that any one should encounter that, but just be prepared.

Happy trails.

That is the best advice I seen on here yet. However learn yourself first then teach others.

[EricGT]

Originally Posted by Wayne M

I thought so also Les.

Another item is to turn off the exhaust brake when in stop N go traffic (slow speeds) and when driving in a city with low speed limits, (35 mph and below) and lots of red lights. A continuous light pressure on the brakes will cause them to glaze over. By turning the exhaust brake off you will be applying more force to slow down or stop and this will aid in keeping the brakes from glazing.

Here is a kicker for you: The "emergency brake" applied by pulling the "yellow" knob. Many think that if you pull that knob you will come to a screeching halt. That is not the case, as anyone who has attended the Freightliner class in Gaffney, SC can attest. If you are traveling down the highway at 60 mph and pull that knob you will be able to steer off to the side of the road to stop. It will NOT throw you against the windshield unless you are standing up and off balance. It will gradually and rapidly bring you MH to a stop. Depending on the condition of your brake system, some MH's will stop a little faster. If you have to pull that button don't expect to stop suddenly.

Also, teach the passenger how to move the driver out of the way, release cruise control, pull the yellow button and steer the MH, should an emergency be encountered and the driver becomes incapacitated while driving and slump over the wheel. Heaven forbid that any one should encounter that, but just be prepared.

Happy trails.

This imo perfectly helps illustrate my thread about how difficult it is to drive a class a diesel. The above sounds like a lot to go over for the novice driver. I can understand the pros of a DP, but this sounds like a pretty big con to me. Should an emergency ever happen to me, I would hate to be lying there trying to give a crash course to my driver on how to drive my DP so he/she can get me and our kids to the hospital. Worse yet...what if I was knocked unconscious even? Atving is not exactly the safest recreation out there.

I'm sure some will chastise me for this. But there is something to be said for just having a no frills motorhome I guess.

[Cooperhawk]

I did insist that my DW learn to drive the rig, and she did, however, whenever she drives I cannot stand the screaming as she meets other big rigs on two land roads or gets passed by one.

[flaggship1]

Originally Posted by EricGT

This imo perfectly helps illustrate my thread about how difficult it is to drive a class a diesel. The above sounds like a lot to go over for the novice driver. I can understand the pros of a DP, but this sounds like a pretty big con to me. Should an emergency ever happen to me, I would hate to be lying there trying to give a crash course to my driver on how to drive my DP so he/she can get me and our kids to the hospital. Worse yet...what if I was knocked unconscious even? Atving is not exactly the safest recreation out there.

I'm sure some will chastise me for this. But there is something to be said for just having a no frills motorhome I guess.

I'm not going to chastise you but will point out that those no frills Motorhomes have brakes too - and understanding them, their proper use with a Motorhome, and in various conditions would be equally complex - improper use in mountains will leave you you in dire straights - with nothing. Brakes are there to stop you - understanding how and why they work is roughly the same exercise air or not. I'll take air any day.

[GregOk80]

One of the most over looked things is to be sure to drain your air tanks completely and check for water. Most MH have air driers and might need a new filter installed. Most MHs have their lanyards to drain tanks in the right front just around the right front tire. I have a 2002 and have owned it for 2 years and all three lanyards were still stuck to the wheel well and had never been used. WOW!

[flaggship1]

Originally Posted by GregOk80

One of the most over looked things is to be sure to drain your air tanks completely and check for water. Most MH have air driers and might need a new filter installed. Most MHs have their lanyards to drain tanks in the right front just around the right front tire. I have a 2002 and have owned it for 2 years and all three lanyards were still stuck to the wheel well and had never been used. WOW!

How much came out of them?

[ru499]

Originally Posted by jetfromtn

The thing I had to learn is, the air holds the brakes open and when you apply the brake pedal it releases the air pressure and the spring closes the brake against the drum. Same thing happens when you apply the emergency brake, you release the air and the brakes close. It is completely opposite from what most of us are used to and there is a learning curve. Jim Thompson 2007 Coachmen Pathfinder 384 TS 2007 HHR

Sorry. Better read up on air brakes. When you push the pedal, the air pressure presses the shoes against the drum. The spring in the brake can releases the brake. The spring brakes work on the parking brake only.

[ken500]

gents

I normally do not post much , but this subject has gotten my full attention . First let me start by saying that I am not trying to step on any one here BUT the amount of miss guide information about air brakes is absolutely scary !
I agree with those people from Canada , everyone who drives any thing with air brakes should have a air brake endorsement . period .
secondly I will not attempt to educate any one here , but I will give those interested my background.
15 years local school dist. school bus mechanic (air brake certified )
14 years local Budweiser dist . responsible for 26 tractor / trailer combos
all with air brakes .
So please do your self and others before you drive your coach again , go down to your local dmv and get the proper information and take the test .

[adonh]

From how stuff works.com

Air-brake Components in Trucks and Buses

Foundation brakes are the most common air-brake systems found in trucks and buses and work the same way as in rail cars. Using the triple-valve principle, air builds up inside the brake pipes or air lines, releasing the brakes. Virtually all of the roadgoing vehicles equipped with air brakes have a graduated release system where a partial increase in pressure dictates a proportional release in brakes.
The following components are exclusive to a foundation air-brake system in a truck or a bus:

• Air compressor: Pumps the air into storage tanks to be used in the brake system
• Air compressor governor: Controls the cut-in and cut-out point of the air compressor to maintain a set amount of air in the tank or tanks
• Air reservoir tanks: Hold compressed or pressurized air to be used by the braking system
• Drain valves: Release valves in the air tanks used to drain the air when the vehicle isn't in use
• Foot valve (brake pedal): When depressed, air is released from the reservoir tanks
• Brake chambers: Cylindrical container that houses a slack adjuster that moves a diaphragm or cam mechanism
• Push rod: A steel rod similar to a piston that connects the brake chamber to the slack adjuster. When depressed, the brakes are released. If extended, the brakes are applied.
• Slack adjusters: An arm connects the push rod to the brake s-cam to adjust the distance between the brake shoes
• Brake S-cam: An s-shaped cam that pushes brake shoes apart and against the brake drum
• Brake shoe: Steel mechanism with a lining that causes friction against the brake drum
• Return spring: A stiff spring connected to each of the brake shoes that returns the shoes to the open position when not spread by the s-cam or diaphragm.

At idle (foot off the brake and vehicle's air system charged), air pressure overcomes the diaphragm or the s-cam is in the closed position, resulting in a released brake system. As soon as you depress the brake pedal, the air pressure decreases, turning the s-cam and spreading the brake shoes against the drum. The compressor refills the reservoir tanks and when you allow the pedal to retract, the air pressure increases back to the original state.
Emergency air brakes complement standard air-brake systems and can be activated by pulling a button on the dash (near the one with the light that we saw in the introduction). Before you can drive a vehicle with air brakes, you must push in the emergency brake button to fill the system with air. As long as the emergency system is pressurized, the emergency brake will remain free. If the system has a leak, the pressure can decrease enough to engage the emergency brake. In addition, heavy trucks are often equipped with an exhaust brake that aids the braking process, but this relies on the engine, not the air-brake system.

[cbeierl]

Originally Posted by adonh

From how stuff works.com

Air-brake Components in Trucks and Buses

Foundation brakes are the most common air-brake systems found in trucks and buses and work the same way as in rail cars. Using the triple-valve principle, air builds up inside the brake pipes or air lines, releasing the brakes. Virtually all of the roadgoing vehicles equipped with air brakes have a graduated release system where a partial increase in pressure dictates a proportional release in brakes.
The following components are exclusive to a foundation air-brake system in a truck or a bus:

• Air compressor: Pumps the air into storage tanks to be used in the brake system
• Air compressor governor: Controls the cut-in and cut-out point of the air compressor to maintain a set amount of air in the tank or tanks
• Air reservoir tanks: Hold compressed or pressurized air to be used by the braking system
• Drain valves: Release valves in the air tanks used to drain the air when the vehicle isn't in use
• Foot valve (brake pedal): When depressed, air is released from the reservoir tanks
• Brake chambers: Cylindrical container that houses a slack adjuster that moves a diaphragm or cam mechanism
• Push rod: A steel rod similar to a piston that connects the brake chamber to the slack adjuster. When depressed, the brakes are released. If extended, the brakes are applied.
• Slack adjusters: An arm connects the push rod to the brake s-cam to adjust the distance between the brake shoes
• Brake S-cam: An s-shaped cam that pushes brake shoes apart and against the brake drum
• Brake shoe: Steel mechanism with a lining that causes friction against the brake drum
• Return spring: A stiff spring connected to each of the brake shoes that returns the shoes to the open position when not spread by the s-cam or diaphragm.

At idle (foot off the brake and vehicle's air system charged), air pressure overcomes the diaphragm or the s-cam is in the closed position, resulting in a released brake system. As soon as you depress the brake pedal, the air pressure decreases, turning the s-cam and spreading the brake shoes against the drum. The compressor refills the reservoir tanks and when you allow the pedal to retract, the air pressure increases back to the original state.
Emergency air brakes complement standard air-brake systems and can be activated by pulling a button on the dash (near the one with the light that we saw in the introduction). Before you can drive a vehicle with air brakes, you must push in the emergency brake button to fill the system with air. As long as the emergency system is pressurized, the emergency brake will remain free. If the system has a leak, the pressure can decrease enough to engage the emergency brake. In addition, heavy trucks are often equipped with an exhaust brake that aids the braking process, but this relies on the engine, not the air-brake system.

That may be what How Stuff Works says, but it's flat WRONG for current trucks and RVs (I can't speak to rail cars).

[Wayne M]

Originally Posted by EricGT

This imo perfectly helps illustrate my thread about how difficult it is to drive a class a diesel. The above sounds like a lot to go over for the novice driver. I can understand the pros of a DP, but this sounds like a pretty big con to me. Should an emergency ever happen to me, I would hate to be lying there trying to give a crash course to my driver on how to drive my DP so he/she can get me and our kids to the hospital. Worse yet...what if I was knocked unconscious even? Atving is not exactly the safest recreation out there.

I'm sure some will chastise me for this. But there is something to be said for just having a no frills motorhome I guess.

Braking systems have one thing in common for sure and that is brake shoes. The complexity of brake shoes between a diesel and any other self propelled vehicle is the same. The shoes close around a drum, or disc, and cause the vehicle to come to a stop if pressure is continued to be engaged. As stated, both types of vehicles have a propensity for glazing the shoes. and as stated a good way to glaze the shoes is to continuously depress the brake when descending grades. Not only that, but in the non-air brake environment there is a concern of boiling the brake fluid and losing complete braking power. It is no more difficult to drive a 26,000 pound diesel than it is to drive a 26,000 pound gas vehicle. They both require a knowledge of the system(s).

Not chastising, just trying to explalin that there are common similarities that need to be studied and learned for both examples.

[adonh]

Originally Posted by cbeierl

That may be what How Stuff Works says, but it's flat WRONG for current trucks and RVs (I can't speak to rail cars).

So what is Correct for current trucks and RV's? I think that is what everyone wants to know.

[Wayne M]

Originally Posted by Wayne M

...........
Here is a quote from the linked manual.

"Spring parking brakes may be installed on an air brake–equipped vehicle for use as a reliable parking brake system. In the service brake system, the brakes are applied by air pressure and retracted by springs. In the spring parking brake system, the brakes are applied by spring pressure and retracted by air pressure."

So what part of that quote from the manual link that was posted is not understandable.

For the service brakes, push on pedal, air is compressed and the brake is applied. Release the pedal and air is released and the spring retracts the brake.

For the parking (emergency) brake, pull the parking (emergency) brake device and air is release completely from the spring parking brake system and the brakes are applied.

Two different sets of air lines. Two systems. Two different applications.

What am I missing?

[speedman42]

Using Air Brakes

I found this to be somewhat helpful. I think the common sense thing is take your time, dont be in a hurry or driving to fast, and watch far enough ahead to help prevent emergency actions.