Single Circuit Brake - Safety Valves?

[Dbluff]

SS - In another posting i was pondering a theory that seems very probabaly. Hot roders and custom car builders use proportional valves for their brake systems to add a safety factor.

so has anyone checked into simple adding an inline proportional value on each side of the tee 30? Or even put one at each wheel?

So if a drop in pressure happens, ie wheel cylinder goes out, the valve simply will close and isolate that side of the system.

Here’s a standard quote from a proportional valve.

“ In the event of a failure, the emergency shut off valve detects a change in pressure and closes that portion of the brakes.”

Front Disc Brake and Rear Drum Brake Line Valve

Buy this front disk and rear drum brake line valve from the LEED Brakes store. This chrome proportioning valve is designed for high-grade performance.

leedbrakes.com

 

[Sumner]

I work in oil and gas production, and i've seen valves that do this before. As long a fluid travelling through them stays below a certain volume or velocity, they are open. If there is a broken line downstream of them with uncontrolled liquid release, they will close.

Swagelock has some, as well as other manufacturers as well. It would be interesting to find out if they would work. Heres an example.
They are called Excess Flow Valves

Stainless Steel Excess Flow Valve, 1/4 in. Swagelok Tube Fitting, 1 gal/min (3.8 L) Spring | Excess Flow Valves | Check Valves | Valves | All Products | Swagelok

products.swagelok.com

 

[rustystud]

The problem you will have with a "proportioning" valve is you need main pressure on the other side of the valve. I'll try and explain the operation of the valve so you will understand. Usually the valve is located just past the master cylinder with the front brake line on one side and the rear brake line on the other. If you loose pressure on either the front or rear brakes due to a ruptured line or seal, the pressure "differential" will push the "Proportioning" valve to one side blocking the port that has lost pressure. So trying to make this valve work on individual wheels would be a nightmare in plumbing. You would have to bring a rear brake line all the way up front to a front wheel to have the differential pressure needed to work. The same would apply to the rear wheels.

 

[Jbulach]

Not sure where the tee is now, but if you put it directly in the outlet of the master cylinder and had the appropriate rated excess flow valves screwed into it, could have potential to get you an emergency stop. It’s a shame Franks not still around…

 

[rustystud]

Not sure where the tee is now, but if you put it directly in the outlet of the master cylinder and had the appropriate rated excess flow valves screwed into it, could have potential to get you an emergency stop. It’s a shame Franks not still around…

It would work if you only wanted to isolate the rear brakes from the front brakes and not each individual wheel. So, if you had a non air-force truck this would give you some safety factor.
There are proportioning valves out there that can handle the flow needed on our Deuce's.
Which Frank are you talking about ?

 

[M35fan]

I'm trying to understand how these valves function. When excessive flow causes the valve to close, does it reopen once the brake pedal is released, or is there a manual reset? Is it possible for the valve to fail in such a way that it closes and prevents the use of your brakes?
Please excuse my ignorance. If this is a practical solution that would improve the safety of our trucks, I'm all for it. For me, converting to a dual circuit system is definitely part of my plan, when my budget allows it. This might be a cheaper option in the meantime.

 

[Sumner]

I believe once the pressure is released, it would open, until you press the brakes again, then it would close. I think it would have to be tried, and see whether they would ever close under normal operation, and tried in a simulated brake failure to see if they would function properly.
You would prob need two valves, one going to the front brakes, one going to the rear. Only problem is I haven’t found an affordable option for them, swagelok is quite expensive.

 

[rustystud]

I'm trying to understand how these valves function. When excessive flow causes the valve to close, does it reopen once the brake pedal is released, or is there a manual reset? Is it possible for the valve to fail in such a way that it closes and prevents the use of your brakes?
Please excuse my ignorance. If this is a practical solution that would improve the safety of our trucks, I'm all for it. For me, converting to a dual circuit system is definitely part of my plan, when my budget allows it. This might be a cheaper option in the meantime.

You must "manually" push in the button to reset the valve. That is of course after you fixed the pressure loss. You would only need the one valve too. It would split from front to rear. The two rear axles would be on the same circuit.