How to control trailer air-brakes?

[racing4funn]

I have a tractor that has the separate trailer control to the right of the steering wheel but that’s for braking the trailer separate. How would I adjust the trailer to truck ratio? Meaning I need more trailer to truck or the other way? What if the trailer’s air supply line attached behind the cab for a 5[SUP]th[/SUP] wheel setup or what if its at the rear on a panicle. Are both of those locations controllable?

 

[Ferroequinologist]

Normally, you don't touch the trolley valve at all. The only time I use it is when I'm checking to make sure the trailer brakes work during my pre-trip. Trailer air is supplied by simply pressing the brake pedal in the cab. Yes, both the brake connection behind the cab and at the rear of the truck can be actuated by the trolley valve. Using this valve the wrong way while traveling down the highway can lead to a lose of control and death to you or anyone riding beside your trailer. Trailer brakes locking up are the root cause of jackknifed trucks.

I would HIGHLY recommend watching videos, reading the operators manual for your truck, and riding along with someone that has a CDL or big truck experience.

 

[sandcobra164]

I agree with Ferro in regards of use of the trolley brake resulting in most of the jack knifed trailers. It may sound crazy but alot of Owner Operator truck drivers use the trolley brake when using leased trailers to keep from using their trucks brakes. That's penny pinching at it finest. The trolley brake was designed as Ferro indicated, to ensure you have your trailer locked securely in the 5th wheel jaws.

 

[racing4funn]

I didnt say I was going to use the trolley brake. My post is for adjusting the brake ratio while braking between the the truck and trailer. IE more trailer brake because its loaded or less because its unloaded.

 

[jw4x4]

I have never seen any that are adjustable as far as the ratio goes. As for the trolley brake, about the only time it is used while moving is if the trailer starts swerving and a quick jab of the trolley brake can get the trailer tracking straight again. NOT recommended for newbies.

 

[Ferroequinologist]

Ah, ok. It seemed to me that you were asking if that valve was used to adjust the braking percentages.

There is no adjustment between truck and trailer brakes other than your foot. You could probably climb under and adjust one set tighter than the other, but I don't think it is an issue at all. If everything is working properly than the brake system will stop the truck and trailer correctly loaded or empty, based on how hard you push the pedal and how long your stopping distance is. The only thing I do different between empty and loaded is adjust my stopping distance.

 

[racing4funn]

Ah, ok. It seemed to me that you were asking if that valve was used to adjust the braking percentages.

There is no adjustment between truck and trailer brakes other than your foot. You could probably climb under and adjust one set tighter than the other, but I don't think it is an issue at all. If everything is working properly than the brake system will stop the truck and trailer correctly loaded or empty, based on how hard you push the pedal and how long your stopping distance is. The only thing I do different between empty and loaded is adjust my stopping distance.

Weird. A trailer tire locks up easier unloaded and the trailer braking can do more with when its loaded. Maybe the air system makes it more linear on the trailer than what Im use to on electric trailer brakes.

 

[jw4x4]

That's not weird. Think about it. When unloaded, there is less weight pushing the tire down on the pavement, thus it locks up easier. When loaded, the added weight makes it harder to lock up the tires.

 

[Triple C]

Yep, that's the way it works, if your slack adjusters are properly adjusted, you're good. And your implication is correct, it is a lot harder to control an empty trailer in a panic stop than a loaded one. A loaded one will take longer but will almost always track better. Good question too.

 

[quickfarms]

You need to make sure all of the truck and trailer brakes are working correctly and properly adjusted. It is part if the pretrip inspection.

You did not mention what tractor and trailer it is. A lot of older military equipment uses air actuated hydraulic brakes. Most civilian stuff that you find in operation now is straight air brakes. You also need to know the type if air brakes , you have wedge, S cam and S cam maxi, just to name the common ones.

 

[jwaller]

You can turn the handle on the valve at the base of the pogo stick to regulate how much air goes to the trailer. I use this to help me from locking it up when it's unloaded.

 

[racing4funn]

Yep, that's the way it works, if your slack adjusters are properly adjusted, you're good. And your implication is correct, it is a lot harder to control an empty trailer in a panic stop than a loaded one. A loaded one will take longer but will almost always track better. Good question too.

Slack adjusters? Maybe I need to know more about these..

 

[racing4funn]

You did not mention what tractor and trailer it is. A lot of older military equipment uses air actuated hydraulic brakes. Most civilian stuff that you find in operation now is straight air brakes. You also need to know the type if air brakes , you have wedge, S cam and S cam maxi, just to name the common ones.

Its a m931A2 pulling a commercial dozer trailer.

 

[doghead]

There are many good reasons why people need CDL/training. This is one of them.

 

[zout]

Well stated DH - here is a basic air system diagram - there are brake air system proportioning valves in the system - relay valves etc etc etc. If your slacks are properly adjusted to DOT specifications - if your brake system has S cams and the bushings are not worn out - the are designed to brake properly with no intervention.

here is a freebie diagram

 

[racing4funn]

There are many good reasons why people need CDL/training. This is one of them.

Well if you knew me or knew what you were talking about then Im might care what you think. Ive known everything thats listed on this thread (stupid answers like explaining to me why a empty trailer locks its wheels or what trailer only braking is for) I just dont bother telling them because again like you they dont know me and unlike you are trying to be helpful... I was asking specifics on a truck that I dont know.
If it will make you feel better then delete the thread!

 

[racing4funn]

here is a freebie diagram View attachment 445138

Thanks.. Understanding the machinist of it and how it works is what Im interested in.. Not being a dumb drivers that knows to hookup and push a air button

 

[bearboley]

Let me help you, Everyone missed this. His only experience is with electric brakes, 99% of electric brake controllers operate off of time. The longer the pedal is held the more current that is applied to the electric brakes at the wheel. When empty you turn the voltage down so the tires don't slide. That is his way of thinking. Air brakes on the other hand are controlled by the air pressure applied by the foot valve. The harder you push the more pressure that is put on the relay valve the more air pressure that is applied from the air reservoir tank the air chambers. Its regulated with your foot and your natural ability to do so. Some may say "well if I hook my 105 trailer to may deuce it will slide the brakes empty" and they would be correct because it is a air over hydraulic system and functions just like the electric brake. The longer you hold the pedal in the deuce the more air that is applied to the master cylinder, the harder the brakes are applied. Closing the valve on the trail air some will help that by limiting the air flow. Clear as mud

 

[porkysplace]

Well if you knew me or knew what you were talking about then Im might care what you think. Ive known everything thats listed on this thread (stupid answers like explaining to me why a empty trailer locks its wheels or what trailer only braking is for) I just dont bother telling them because again like you they dont know me and unlike you are trying to be helpful... I was asking specifics on a truck that I dont know.
If it will make you feel better then delete the thread!

Well since you don't know what a slack adjuster is , it pretty clear you don't know much about air brakes or have a desire to here answers you don't agree with .
Do you have a CDL?

 

[Triple C]

In a commercial setting, your DOT mechanic would normally set your slack adjusters (assuming you are on the road a lot which means you will probably be having a service monthly) or you are running auto adjusters. In our hobby though we have neither luxury. I am not a mechanic but essentially all you are doing is taking up the slack that comes along with wear on the brake lining. Here is link that explains it better than I can. http://www.ehow.com/how_5503112_adjust-slack-adjusters-trailer-brakes.html