Automatic brake diverter valve

[fissionspeed]

I'm currently planning out the brakes on the race truck, and for simplicity/drag reduction's sake I'm running a single pot master cylinder with no front brakes, just two drums in the rear. I'd like to have a little more redundancy, does a cost effective solution exist for automatically diverting brake pressure should one lose a brake line?

Supposedly the distribution blocks on some older vehicles had a toggle in them that would flop over to one side if asymmetric pressure were applied, diverting it all to the good side. But nobody I've spoken to has been able to verify that they perform as intended.

Thoughts?

[Stan Back]

Couldn't you just use a dual master cylinder?

[kiwi belly tank]

Production type master cylinders typically have a smaller bore size for the rear brakes so that wouldn't be desirable.
In what scenario do you think you might loose one rear brake that this would be a problem? Are you over thinking this?
Drum brakes are going to fade like a SOB if you find yourself needing to stop in a hurry like you're on fire or something! Why not just run stock disc brakes with retractor springs between the pads if you're worried about drag, you'll have a pedal on the second pump if you set it up right!
  Sid.

[71GSSDemon]

Wilwood and Tilton to name a couple companies, have dual master cylinder setups.  This is a separate master cylinder for front and rear using 1 pedal.  Couldn't these be sized to have a separate master cylinder and system for each rear brake?  I think is this what was meant above.

[fissionspeed]

Production type master cylinders typically have a smaller bore size for the rear brakes so that wouldn't be desirable.
In what scenario do you think you might loose one rear brake that this would be a problem? Are you over thinking this?
Drum brakes are going to fade like a SOB if you find yourself needing to stop in a hurry like you're on fire or something! Why not just run stock disc brakes with retractor springs between the pads if you're worried about drag, you'll have a pedal on the second pump if you set it up right!
  Sid.

I suppose I am overthinking just a bit, it does seem unlikely that a line would be knocked loose completely. I just figured redundancy is always good if it's easy to accomplish. What are these retractor springs?

[Stainless1]

retractor springs... something you would make to pull the pads away from the rotor so they do not rub.
If you move the pads away and never touch the pedal it accomplishes the same thing... Bike guys generally spread the pads so they don't touch... easy with a bike, the brake is exposed... Cars with brakes in the wheel, not so easy, thus put springs on them and they self spread.

[jimmy six]

 I was told this when I started in 1975......  "Brakes are to help in the loading and unloading a vehicle from the trailer.....Parachutes are for stopping the vehicle"......
Ive had a single Wilwood MC and a hand brake for the rear drums on 2 different race vehicles since 1975 and never ever had a failure.

[Stainless1]

The lakester has a single rear disc... we generally check that the caliper is spread after we test it... annually

[mc2032]

I just did a brake job on my 2019 Chevy Equinox with electric park brakes (4 wheel discs).  i had to retract the EPB to compress the calipers by using a simple jumper wire and 12v.  Could something like this set-up be an answer to lowering the brake drag?

[kiwi belly tank]

 On a car with easy access to the wheels it's just simpler to pull the wheels before a run & spread the pads then stay away from the pedal. I have 4 wheel brakes on a streamliner that makes that a major pain so I did retractors. My calipers are 1 ton dually front calipers on all four corners & the pads have a high center plate. I used two clutch pack springs from a TH400 & an Allison with one inside the other. The inside pad has a short pin to locate the springs & the outside pad has a bolt welded into it with a nut to adjust the spring tension after it's assembled. It has a pedal on the second hit.
The only reason to Not run a full set of brakes on the salt is the concern of brake drag. Braking is not a big deal on the salt unless you're going really fast & running out of real estate or you have an emergency like the muther is on fire & you need to get out of there in a hurry! A fire going out the back of your junk can burn up a chute in a heartbeat so it's well worth while building some protection into it before you have a holy $hit situation, you can't over build safety!
  I built a fire exit out the top of the body on my liner between the tail fins & lined it with carbon fire blanket material so the fire has somewhere to go. If you get high speed air into a fire you end up with a big a$$ cutting torch!
  Sid.

[manta22]

... If you get high speed air into a fire you end up with a big a$$ cutting torch!
  Sid.

This is another reason that favors a mid/rear engine configuration.

[datadoc]

Just a thought but why not pull a bit of vacuum on top of the master cylinder. That will pull the pads out of the way.

[kiwi belly tank]

Brake seals are designed to work with pressure from the fluid side so pulling a vacuum it would run the risk of getting air in the system.
  Sid.
 

[Dynoroom]

Just a thought but why not pull a bit of vacuum on top of the master cylinder. That will pull the pads out of the way.

Yep, Just like Roger Penske did in the 1960's & '70's endurance races, pulled vacuum to be able to swap brake pads during pits stops. Until it was banned as an "unfair advantage".