Trailer air brake device to allow towing of a military trailer with a civilian truck

[baxter462]

So, I've seen a lot of threads involving trailer brakes on military trailers when towed with a civilian truck. It seems like people are doing everything from axle swaps, retrofitting electric brakes on the existing trailer axle, replacing the air over hydraulic system on the trailer with and electric over hydraulic setup, installing a surge brake coupler, installing a trailer air brake system on their tow vehicle, etc. None of these options are ideal to me because I want to be able to tow any of my trailers, with any of my vehicles, including my M923A2. I also want family members/friends to be able to tow my M105A2 with their pickup trucks. This basically means that I had to find or create a solution so I could tow any trailer with any vehicle, without making any modifications to any of them. I ended up designing an "interface device" to accomplish this. I have started building it, and it is looking very promising. Here's a quick video of it thus far:

https://www.youtube.com/watch?v=QjG1yR_PXPY

Pretty much all that remains is to package it up nicely and thoroughly test it. I think it'll accomplish exactly what I need it to do. I'll be able to use any trailer with any truck, and just move this device around from vehicle to vehicle as needed. I am still trying to decide exactly how I want to package everything together to keep it portable and compact, but the hard part is finished. It functions very well with the testing that I've done so far.

Here are some of the features I designed into it:

• Converts 12V from vehicle lighting circuits to 24V for trailer
• Applies trailer's air brakes proportionally based on input from standard civilian brake controller
• Has an emergency breakaway switch so the device can be attached to the trailer if desired
• Will be packaged in such a way that will allow it to be secured in a pickup truck bed firmly enough to allow the air hoses to be forcibly disconnected in the event of a trailer breakaway to allow for emergency application of the trailer's brakes. Angled gladhand mounts were chosen to make disconnection easier and more likely to occur in the event of a breakaway
• Uses an 18AH onboard SLA battery that gets charged by the vehicle
• The power switch has three positions: On, Off,and Auto. In the Auto position, the vehicle's park lamp switch turns the device on and off. This is a convenience feature. Instead of having to manually turn the device on and off every time you enter/exit the vehicle, you can simply turn the park/head lamps on and off
• Has a manual shutoff valve on the line to the emergency gladhand to allow towing of single hose trailers, and to prevent draining the onboard tank when disconnecting the trailer

I'm excited, it is coming along nicely. I'll post updates as I make progress.

Now, for the disclaimers: No, I'm not producing and selling it, I am just building one for myself. Yes, I understand it isn't D.O.T. approved and there is liability involved in using it (although I personally think there is a lot less risk to this solution compared to most other available solutions. This actually meets the trailer brake requirements in my state because they just specify what needs to happen, not how it is being accomplished). Can you build one of your own? Of course you can. If I can build one, you can too.

 

[someoldmoose]

. . By crackeeeee ! ! ! Wut'll they think of next ? Actually, this, or somethin' like it, has been around for AGES. Had a independent air system on our Hydraulic brake dump trucks to tow the flatbed with the steam shovel on it. YES, a steam shovel.

Awesome info though ! Thanks

 

[red]

Nice, how much did the parts run to make it? The interface device is the hard part to figure out of the system.

 

[someoldmoose]

Better livin thru electronics red.

 

[baxter462]

Red,

I haven't kept very close track of the cumulative cost of the parts. I'd guess around $500. The E/P regulator is the single most expensive part. The one I am using is a new, old stock part I found cheap on eBay. It is actually discontinued by the manufacturer, but the updated version of it is around $350 or so. The old version I found seems to go for around $50 when you can find one.

Someoldmoose,

I know there have been a lot of methods developed over the years to tow trailers with air brakes with hydraulic brake equipped trucks, but that wasn't the only goal. It was to create a device that allowed it to happen without modifying the truck or trailer. Adding a system like you described to my tow vehicle is exactly what I am trying to avoid. I've seen some really nice kits for adding a supplementary air brake system to a pickup truck that used a 12v compressor, and a valve that taps into a hydraulic circuit of the brake system to adjust the air pressure output to the trailer, but that is far from being a portable device. My primary goal was "tow any trailer with any truck without making modifications to them."

 

[BadRobot]

It is a good idea and I want to do it too. However, a couple things come to my mind.
Will you need special or CDL license to operate air brake trailer?
Will you need DOT or inspection?
I am just curious. Thanks for the info.

 

[baxter462]

Those are good questions that I've been trying to find the answers to as well. I live in Utah, and so far it looks like I won't have to do anything, but I haven't gotten a definitive answer. The trailer brake laws here basically say the truck and trailer need to have a certain level of braking performance, but the laws aren't specific about the implementation of the braking system.

 

[someoldmoose]

Baxter, yer dead on. It was state of the art at the time. This set up is amazing.

Robot, laws vary from State to State. If yer using it commercial you will ALMOST certainly need a CDL. If recreational, gotta check with DMV in state where registered.

 

[Tinstar]

Check with your states DOT officers.
No matter what you come up with, they are the authority.
You will need something showing their approval.
They will explain what you need to do.

Without it, no matter how good the design, you will be fair game if anything ever happens.
Your tow all, unproven, not yet approved design could cost you everything, including your freedom.
Lawyers don't care how good it is, if you have an accident and The coupler is suspect.
DOT approval is there for a reason.

 

[baxter462]

Tinstar,

Thanks, that's the plan eventually. I appreciate the warning though. I obviously need to finish it up and validate it before seeking approval.

 

[THENICK]

Great job. I want one. Love it
SMILES ALL AROUND

 

[doghead]

Please include your state in your location, as our rules request.

 

[Eugen]

hey, the device looks great , where did you get the board from?
Thanks!