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Unread 04-15-2010, 07:45 PM   #1
sherlocktk
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How to make your Jeep STOP when flat towing (WITH PICS)

6 months ago I was contemplating a tow dolly or to flat tow to move the jeep around. There is nothing fun about a 800 mile journey in a CJ, I would much rather be in my Truck. I needed a solution that would not take up too much space and let me control the vehicle in a "stopping" situation. I ended up choosing a flat tow, mostly becasue all I need to store then is the tow bar and whatever I need for the braking system.

I decided to hook up the Jeep for a flat tow test, without brakes, just to see what happens, and its mostly fine, until you really need to stop, it then makes the truck wiggle all over the place, and make the ABS work harder than I have ever had it working. This confirmed my need for brakes, I just was still waiting on parts.

My options were a brake buddy/blue ox, but thoes were lots of $$ and were not controllable from the truck. I wanted a proportional system, similar to electric trailer brakes. I "invented" my own system.

Pre-requisites:
Vehicle with electric brake controller
an "infinite" air source I used my air compressors in my jeep
Air storage tank (I had a total of 4ga, but 1ga would work fine)
Air hookup in cab of jeep
7 pin trailer connector with +12 acc working

Parts List:
2 inch bore 10' stroke double acting air cylinder. (automationdirect.com) ($85)
electropneumatic transducer 900x 0-10v 2-100psi (ebay) I have a Control Air 900x, but there are a few Manufactures. I paid $160 for a good condition used.
1 trailer magnet (Does not matter what kind/size) $40
Air Regulator (home Depot) $10
1/4 poly tubing for air plumbing/fittings/T's (automationdirect.com) $25 ish
1 emergency brake engager (etrailer.com)
Miscelaneous hardware to mount cylinder to brake pedal/tub of jeep This will vary depending on the model of jeep you have.

Function and Hookup:
My "air cylinder" is a Dual acting, meaning you can apply air pressure on one side to make it expand and the other side to make it retract. In order to make the cylinder retreate properly I hooked up an air regulaor set to about 10 psi on the "retract" side, as to be absolutely sure the brakes would not be barely dragging. in a 2 inch cylinder 2x the air pressure is the pounds of fouce, so I always had 20 lbs that was making the pedal stay "up". My Electric Regulator puts out 2 psi at 0 volts signal so I needed to have a pressure >2 psi to ensure the pedal was in the "up" position.

The brake controller needs a magnet in order to think its hooked up. I tried a simple 30 watt light, and it thought there was a short in the system. A magnet instead, and I got a simple "c" on the contorller meaning all was working well. This was the easiest way to fix that problem.

I have a teknosha prodigy brake controller, I ran it in no "boost" mode. Max setting of 4.3 volts. The electric regulator was very linear in its response, so 1 volt 10 psi, 2 volts 20 psi etc. at 60 psi the brake pedal was on the floor, and the jeep's tires would skid at that point. At 1 volt I could feel the brakes, just barely and once I got to 2 volts the jeep definately stopped itself under "normal driving conditions" If I hit the brakes hard the jeep definately reacted to that and helped get everythign to a stop.

It was nice in the windy areas where it started moving left to right to just tap that brake lever inside, and it would straighten right out. This feature right here makes this system SO much better than a brake buddy. Its also much more compact. I really like being able to control the brakes inside the tow vehicle. I used this setup on a 1600 mile trip and it worked great in the mountains and the flats on the interstate. It does have a 1/10 second lag time, (needing to pressurize the cylinder) but it was good to me, Im sure increasing the diameter from 1/4 poly tube to 3/8 would fix this entirely.


Electrical Diagram:

Notice the 2 diodes needed to make it work. Make sure the diodes are a 10 watt or so so it can handle the 3 amps the whole thing takes.

Air Diagram:


Coming Soon in an edit

Installation Pictures:


How the Air cylinder attaches to brake pedal


Air input is on the left, Air Output is on the right. You can see the trailer brake magnet here to "trick" the brake controller that its hooked up.



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Unread 04-16-2010, 01:01 AM   #2
slow_motion
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id never be able to hook something like that to my jeep simply bc lack of knoledge...
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Unread 04-23-2010, 10:18 AM   #3
extsp2
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sweet setup.
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Unread 04-29-2010, 09:55 PM   #4
colojeepguy
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It'd be a lot simpler to just buy a truck with strong enough brakes to stop your Jeep.
Just sayin...
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Unread 04-29-2010, 09:59 PM   #5
g-off70
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would have never thought of something like this. great setup
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Unread 04-29-2010, 11:05 PM   #6
sherlocktk
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Quote:
Originally Posted by colojeepguy View Post
It'd be a lot simpler to just buy a truck with strong enough brakes to stop your Jeep.
Just sayin...
The biggest truck in the world will not help with swaying back And forth (except the new 2010 ford sd) this system really helped in the cross wind. Also most states say trailer over xxx lbs need brakes. This was to give more control than a brake buddy at a fraction of the price
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Unread 04-30-2010, 09:05 AM   #7
colojeepguy
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I've flat towed a CJ5 with an F250 for 11 years. Probably 1500-2500 miles every summer, over 11,000 ft mountain passes in Colorado, through denver traffic on I25, weekend stop-and-go traffic on I70. I've never experienced my truck wiggling all over the place even in a panic stop.
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Unread 04-30-2010, 09:21 AM   #8
sherlocktk
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The only places it wiggled around was with 50mph side gusts from las vegas to so cal. and that was only on the return trip on the way to moab. On the way out I did not even need the brakes at all.
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Unread 05-06-2010, 07:41 PM   #9
thantos858
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Quote:
Originally Posted by sherlocktk View Post
The biggest truck in the world will not help with swaying back And forth (except the new 2010 ford sd) this system really helped in the cross wind. Also most states say trailer over xxx lbs need brakes. This was to give more control than a brake buddy at a fraction of the price
Flat towing is not a trailer. The sway will happen even with brakes and is normally caused by high center of gravity, unstable load or something wrong with the towed object. Ive had a loaded 120 barrel tank trailer start to sway because of wind. I personally wouldn't trust something like that to push the brake pedal to stop it instead I would of gotten one of the electric/hydraulic kits and tapped into the jeeps braking system.
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Unread 07-09-2012, 09:28 PM   #10
white_2003
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This is a great idea!!! But instead of air I grabbed an Allen Bradley controller (microligix) a small power supply a robo cylinder and an analog card. But the basic idea was the same using a potentiometer as my base setting to the analog card and a simple PID loop in the microligix controller (proportional integral derivative) using scaling with parameters. Yes I know this isn't a programmers forum so bear with me as I get a geeky and overly excited to make this work with "spare parts" lol but it works very effectively. Maybe NOT the most cost effective but I like using the daily grind as an excuse to build jeep parts lol. And thank you for this very impressive idea.
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Unread 07-09-2012, 09:47 PM   #11
sherlocktk
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How much pressure can that cylinder exert. I thought about a linear ram or something before I went Pneumatic but I wanted instant brakes without ramp up

I like.the full electric idea too. Post it up when you get done
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Unread 09-09-2012, 10:13 AM   #12
neonhomer
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You would almost be better off with one of those electropneumatic trailer brake units. It takes the electric brake signal, and uses a small master cylinder and actuator to transfer the electric into hydraulic force. You could then plumb that into your rear brakes of the towed vehicle.

Either that or some kind of actuator on the emergency brake cable... and use those to stop the vehicle.
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Unread 09-13-2012, 08:29 AM   #13
wilson1010
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Quote:
Originally Posted by colojeepguy View Post
I've flat towed a CJ5 with an F250 for 11 years. Probably 1500-2500 miles every summer, over 11,000 ft mountain passes in Colorado, through denver traffic on I25, weekend stop-and-go traffic on I70. I've never experienced my truck wiggling all over the place even in a panic stop.
This is totally the correct answer^^^

I flat towed many rigs and many trailers without brakes. I cannot imagine a need for this other than to tow with an undersized tow rig. My K2500 Suburban towed an XJ for years and I never one time experienced any wiggle on braking or any diminished stopping distance. Same for the various F250's I've had.

Nice technical exercise though.
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Unread 09-13-2012, 06:09 PM   #14
MPond
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Quote:
Originally Posted by wilson1010 View Post
This is totally the correct answer^^^

I flat towed many rigs and many trailers without brakes. I cannot imagine a need for this other than to tow with an undersized tow rig. My K2500 Suburban towed an XJ for years and I never one time experienced any wiggle on braking or any diminished stopping distance. Same for the various F250's I've had.

Nice technical exercise though.
Here we go again...

Wilson - Your statement is absurd. You cannot make a case that your 3/4-ton Suburban's stopping distance isn't diminished by a 4000 lb. vehicle behind it without brakes. That just doesn't hold water.

I flat-tow my Jeep with my 2500 Suburban and my 3500 Silverado Dually, both without a problem, but you most certainly do have an increased stopping distance. And saying otherwise is nothing but ridiculous.

And brakes or not, if you have to brake hard in a curve, such as a freeway interchange, any light-duty truck (1500, 2500 or 3500) is going to have some wiggle with a 4000 vehicle behind it and zero tongue weight.

You may have been lucky if you've never had to brake hard in a curve, but that doesn't make you right.
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Unread 09-13-2012, 07:10 PM   #15
wilson1010
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Quote:
Originally Posted by MPond View Post
Here we go again...

Wilson - Your statement is absurd. You cannot make a case that your 3/4-ton Suburban's stopping distance isn't diminished by a 4000 lb. vehicle behind it without brakes. That just doesn't hold water.

I flat-tow my Jeep with my 2500 Suburban and my 3500 Silverado Dually, both without a problem, but you most certainly do have an increased stopping distance. And saying otherwise is nothing but ridiculous.

And brakes or not, if you have to brake hard in a curve, such as a freeway interchange, any light-duty truck (1500, 2500 or 3500) is going to have some wiggle with a 4000 vehicle behind it and zero tongue weight.

You may have been lucky if you've never had to brake hard in a curve, but that doesn't make you right.
Wringing your hands over a few extra pounds?

I have had to brake in every kind of curve and every kind of situation. I have probably towed with more vehicles of any kind than you and your father have owned combined, son. Your theories are always intersting, but, not real world helpful. Back to the books.
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