Trailer Air Brakes for a Heavy Duty Pickup

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pmramsey

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Trailer Air Brakes for a Dodge Pickup

Yes, the big pickups can pull an M105, 30 KW gen-sets, a pair of 10 KW gen-sets, and even a 2.5 ton M1082A1 trailer but how well can the vehicle stop it and can it be done safely. This is especially important since I do not run a dully Dodge. Its a 2500 diesel with an extra heavy suspension.

What follows is my solution. It is an external, mobile, airbrake system, that rides in the bed of the truck. I first began with a good, new, 12-volt aircompressor. It was mounted on an aluminum cut off from a 10 KW generator mount from a Humvee.

The stock air tank on the compressor is too small for the job, so an air-tank off a duce was mounted alongside the standard tank. We gained capacity for the 3.5 CFM pump. We installed a 12-volt plug running under the cab from the engine compartment and terminated between the truck bed and cab. (See photo for location)

Standard military air-hoses were installed running from the tanks, one line being service and the other emergency. Air pressure is controlled at the compressor. See gage on the photo) We can manually adjust the air flow from the tanks allowing faster or slower braking depending upon the empty weight of the trailer and the load.

Everything else is run through a controller mounted on the truck dash. We can turn the system on and off, monitor the total air pressure in the system, and the actual air available at any one moment in time.

We are ready to roll when the pressure peaks and the compressure shuts off at 120 psi. The cpmpressor turns on when the air pressure drops below 85 psi. Yes, there is a night light on the controller but there is not a horn or warning buzzer.

We have less than $300 invested in the thing and it has worked flawlessly for the past three years. We do keep a small piece of green tarp over the thing when not in use.
 

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doghead

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How is the air/brakes applied? Id it simply on or off, or proportionally controlled, or automatically applied with the brake pedal?
 

pmramsey

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How is the air/brakes applied? Id it simply on or off, or proportionally controlled, or automatically applied with the brake pedal?
I removed the electric trailer brake controller mounted in the Dodge and replaced it with the air brake controller. The air brakes are engaged when the truck brakes are applied. The trailer brake response time is adjusted manually at the compressor and it is done according to the trailer and its load. I like the trailer slowing faster than the Dodge which causes the trailer to be a drag on the truck. The trailer brakes are timed to be a bit slow coming off its brakes as the truck gently pulls the trailer off its brakes.

There must be caution. My truck is a six-speed and I use the brakes only for coming to a full stop or in an emergency. The air brakes on the trailer do not know this. Therefore, I tap the truck brakes to engage the trailer air brakes before down shifting. It makes for a smoother ride and better stops. Braking and down shiftng in a turn towing a heavy trailer and without the aid of duel rear tires has never been a wise choice. Nothing changes with this air brake system in that regard.
 
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runk

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Did you custom build the controller ? If it's commercial, part numbers please !
I've found some brake controllers that will interface with my ford, and would appear to drive a PWM air valve in place of the hydraulic valves they are designed for, but no confirmation that one will actually work.
I used a battery in series with the power connection to my 12V compressor to accommodate the startup current so I could use the built in aux trailer power source on the ford. But just ended up with a manual "OH SH!T" valve to actuate the brakes. While that met the legal definition of trailer brakes, it was not much use, and I'd like to upgrade before I pull the 103 with the Ford again.
A related thread-
http://www.steelsoldiers.com/trailers/14427-converting-trailer-brakes-air-electric.html
 

sweet trav

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do you want to make a unit and ship it to me???:mrgreen:

actually, I was wanting to install onboard air for airing up and down tires for offroading...could that all be combined into one unit?

btw-that's a great setup...my dad and i were talking about the same thing today while we were looking over my m105a2.
 
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pmramsey

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VA
Did you custom build the controller ? If it's commercial, part numbers please !
I've found some brake controllers that will interface with my ford, and would appear to drive a PWM air valve in place of the hydraulic valves they are designed for, but no confirmation that one will actually work.
I used a battery in series with the power connection to my 12V compressor to accommodate the startup current so I could use the built in aux trailer power source on the ford. But just ended up with a manual "OH SH!T" valve to actuate the brakes. While that met the legal definition of trailer brakes, it was not much use, and I'd like to upgrade before I pull the 103 with the Ford again.
A related thread-
http://www.steelsoldiers.com/trailers/14427-converting-trailer-brakes-air-electric.html
Frankly, I knew far less than I needed to know but that is nothing new for me. The entire controller is at best a cob job. I first looked at the electric controller already mounted on the Dodge. Once I saw how the electric controller interfaced with the Dodge's brakes, we then worked backwards to the controller box that you see as the "air brake" controller. I have no idea what the box came off of or what it was used for in the past. I knew a manual electric switch running to the compressor in the bed of the truckwas needed and I knew I needed the truck brake pedal to release air from the air tanks to the trailer brakes. The air pressure running the trailer is controlled manually at the compressor. We found that in most cases, 45 lbs psi is the best all around pressure going to the trailer. Too much air caused the brakes to grab and caused the trailer to even hop a bit. Too little pressure and the trailer was stopping slower than the truck braking. (Not good) It was all trial and error. I have used as much as 120 lbs psi when getting the brakes to release on a trailer that has been sitting with its brakes "locked" for a long period of time. However, the pressure would be lower once the brakes had been broken free and ready to move out onto the road.

The gage on the "controller" sitting on the dash has a simple needle that measures the total pressure in the tanks. The needle was set to turn on the compressor when pressure in the tanks fell below 85 lbs psi.

Sorry, there is no slick, convenient part number on this project. I am sure there may be something on the market but I do not know what it may be.
 

pmramsey

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do you want to make a unit and ship it to me???:mrgreen:

actually, I was wanting to install onboard air for airing up and down tires for offroading...could that all be combined into one unit?

btw-that's a great setup...my dad and i were talking about the same thing today while we were looking over my m105a2.
I do keep a 50-foot air hose with gage on the Dodge and it couples to the emergency side of the compressor output. I use it for checking tire pressures and I even use it to run a small partical blaster for removing rust scale on small rust areas on trailers. It works about as good an hooking up to a Deuce air system. However, far better sources for air pressure to do any serious sand blasting is readily available.
 

pmramsey

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Given my low level of experience, I would not want to build something for someone else. Sorry...
 

doghead

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Subscribed to what? the thread was dead and deleted....

I brought it back for a reference for IF4x4. Follow his thread!
 
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I wonder if a hall effect switch connected to the brake pedal, then wired up to an air solenoid. When you press down the brake pedal the hall effect switch opens the air solenoid sending air to the trailer brakes. Then all you would need is a 12volt air compressor/tank to provide the air.

Something like this

Electric Solenoid Air Valve - Horn Accessories - Automotive Exterior - 3FHX2 : Grainger Industrial Supply

Limit Sensor, Sourcing, Normally Open - Limit Switch Body and Contacts - Switches - 5CJG3 : Grainger Industrial Supply
 

doghead

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Depends how effective you want it to be. Depends on the load. Depends on your speed.

You do NOT want to skid the trailer behind you, or it may "pass" you.
 

doskiez

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I plan on building one of these systems for breaking/ on board air for my truck soon. I was going to utilize one of the higher end Vivair compressors, 5 gal storage tank and a solonoid air valve sourced from somewhere like grainger. I would have a switch in the dash to turn on or off the air brake system and the solonoid valve would trip whenever the brakes were applied. my current trailer brake controller is an all on or all off (no proportioning) type controller so I am used to that type of setup. That being said I was going to use a regulator on the air supply to the brakes to adjust braking pressure instead of a proportioning valve.
I have a F350 diesel dually 6 speed truck that I use to pull an M105 for local firewood deliveries it behaves fine as is and I haven't had any issues stopping it while fully loaded but it would be nice to have the trailer brakes operating and take some of the load off the truck.
 

quickfarms

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The braking force of the brakes is regulated by varying the air pressure from the foot valve. The harder you press down in the pedal the higher pressure in the service line, this pressure actuates a relay valve that releases air from the trailer air tanks to actuate the brakes.

There is also a proportioning that regulates the order and force applied to the brakes on each axle.

The emergency line charges the system and releases the spring brakes, if equipped.

If you use a solenoid valve the brakes with either be released or fully applied. You need some way to variably apply the brakes that is synchronized with the towing vehicle.

There is a regulation that states the application of the trailer brakes must be automatic.

In theory this is a great idea but it is also a very dangerous idea that could expose you to a lot of liability if you are involved in an accident.
 
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