Use Electric Parking Brake for Toad Break-away ? ? ?

Find out what cables actually apply the brake and if full 12Vdc is needed to actuate the brake, insert a rellay that when the solenoid is off the original signals pass through and when the brake away system is activated the conection is diverted to an electronically controled and timed application of the braking system that does not send a signal to the computers but only to the bake actuator, that way you have a brake system when pulling and your normal brake actuation when not being towed.

Way back when the world was flat and the brakes failed on my WB bus comming down a mountain, I used the parking brake to get me home, cost me new rear drums, shoes and a new master cylinder but I made it down and home.

navegator

sh410 wrote:


In addition, the breakaway system will activate without any action by the driver. In your case, how will the solenoid by activated?

I will activate the solenoid with a standard breakaway switch.

The only question now... how long is the breakaway trip cable? Longer or shorter than the safety cables?

If the answer is "shorter", then the breakaway system would only have to slow the toad so it does not run into the back of the MH.

In that case the question of two-vs-four wheel breakaway brakes seems moot. IOW, rear-only brakes would be more than enough to slow the toad and avoid hitting the MH.

If the safety cables can dependably keep the toad from breaking totally away, then I don't see the need for a breakaway system at all.

I have stopped trailers (twice) when they came off the hitch and were retained by the safety cables. Something to be avoided, but not a big deal either. In both cases, there was no damage.


UPDATE: The install instructions for the SMI system call for the breakaway cable being SHORTER than the safety cables. SO.. the breakaway is activated upon tow bar failure but while safety cables are still intact.

Not on mine. The length of the breakaway cable will activate the brake on the toad before the safety chains become into play. I'm sure others will agree. The safety chains are the secondary attachment to the TV in order to maintain control until you can safely stop without damage to the toad or TV.

If you had an event like you describe, having the to bar dig into the road -- it could be disasterous.

In addition, the breakaway system will activate without any action by the driver. In your case, how will the solenoid by activated?

sh410 wrote:


"The purpose of safety chains is to prevent the trailer from separating from the tow vehicle in event of a hitch failure, such as a hitch ball that has loosened. The chains should be crossed in an "X" fashion below the ball mount, with enough slack to allow unrestricted turning, but not enough to allow the coupler to hit the ground."

I assume that "breakaway" is when everything (tow bar AND safety chains) have failed and the toad is on its own.

If the tow bar has failed but the safety chains are still intact, then I assume that is not a "breakaway" and the breakaway braking system would not be activated ? ? ? ?

The difference is merely how long you make the breakaway cable. I believe that most/all installations call for the cable to be longer than the safety chains - hence not activated unless the safety chains have (also) failed. Right ? ? ?

From the California Department of Motor Vehicles web site.


"The purpose of safety chains is to prevent the trailer from separating from the tow vehicle in event of a hitch failure, such as a hitch ball that has loosened. The chains should be crossed in an "X" fashion below the ball mount, with enough slack to allow unrestricted turning, but not enough to allow the coupler to hit the ground."

sh410 wrote:
I must be missing something. My understanding is that the breakaway system is to apply the brakes on the toad in the event of a breakway. The safety chains are to maintain control of the toad until you can get safely stopped. The idea of a breakaway toad crashing either into a ditch or to someone else is frightening.

None of the breakaway systems are supposed to activate until both the tow bar AND the safety chains have failed. I suppose one could hook it up so that the breakaway engages while the safety chains are still intact. In fact, that's an interesting idea. :h

My jeep emergency brake engages only the rear wheel service brakes. I think that's plenty since all hell will "break loose" anyway. A little longer stopping distance (4w vs 2w) in this case is highly theoretical anyway, since the toad will probably well off the road.

As you can tell, after all this discussion, I think I will proceed with this idea. I will not hook in electrically, but instead install a mini-solenoid that will push the switch just link my finger does.

I have tested what happens when I trigger the brake while in motion. The results are good. The brakes engage very firmly and it comes to a rapid stop. No complaints from the various systems.

So all I need is a break-away switch (about $7) and a solenoid (about $15).

I must be missing something. My understanding is that the breakaway system is to apply the brakes on the toad in the event of a breakway. The safety chains are to maintain control of the toad until you can get safely stopped. The idea of a breakaway toad crashing either into a ditch or to someone else is frightening.

Homegrowing a safety system gives you the benefit of the liability if it fails.

sealg,
First off, you can get a break-away system for much less than $200 to $400 like you just mentioned. Readybrake's Readystop breakaway system, which will work with just about ANY vehicle or setup, is around $100.

I must say, though, your solution does sound interesting, and you've definitely done your homework with this very well. Kudos to you for that. My only concern with this, that may or may not be a concern, depending on how your Jeep truly is designed:

Break-away systems are designed to brake ALL FOUR wheels via the regular brakes. Not just the rear brakes like an emergency brake does. Engaging just the rear brakes at highway speed, in an unmanned vehicle....Well, that just seems like even MORE of a recipe for a huge disaster, even more so than if all 4 wheels were being braked. Much higher chances of it spinning and going who knows where, I would think.

Mowermech does make a good point, that the results of a break-away incident are not going to be pretty regardless, but I'd still want all 4 wheels to be braked in this case.

I know you said that your Jeep's emergency brake engages all 4 disc brakes. If that is true, then your solution should be OK (as long as you wire it right).

However, I would make absolutely 100% sure that it works that way (braking all 4 wheels) before going forward with this. Some comments previously about emergency brakes supposedly only braking the back wheels, makes me wonder if your Jeep's emergency brake does truly brake all 4 wheels.

With all respect to the OEM engineer plus lots of gratitude for enhancing this discussion....

I think we need to keep some things in mind.

• The idea is to use the car's electronic park brake for a breakaway situation - not everyday toad braking.
  
  
• If deploying in a breakaway results in fault codes etc -- well, so what? Keep in mind, the toad will probably be totaled anyway, so a few fault codes will be of little consequence ! ! (is that "toadaled" ?)
  
  
• Plus, wrt screwing with the computers - Activating the park/emergency brake with a solenoid to trip the switch avoids tapping into any electronics and is no different that hitting the switch with your finger.
  
  
• This will probably never be used and if it is, it will not be used more than once. :o
  
  
• A car with the rear brakes applied as it careens off the road is likely to be no more out of control than one with four brakes applied. A crash is a crash.
  
  
• Aggressive application of the rear brakes in a breakaway would certainly stop the car as long as it stays right-side-up. That easily meets the intent of a breakaway system and I speculate it would satisfy any regulatory requirement for breakaway.
  
  

So in the points above, are there errors in logic ?


ps: It bugs me to pay $200 to $400++ for a breakaway system that will never be used anyway. Using this solution, the total cost will be less than $20 plus my time (which is free as I am retired).

I agree. AND, I agree with the auto engineer! I avoid messing with the computers in the newer vehicles if at all possible. I had to replace one of the master computer modules in our PT Cruiser because the right front turn signal quit working.
Thank goodness for extended warranties! That thing is EXPENSIVE! Don't do ANYTHING that might compromise one of them!