Great idea for dual circuit brakes

I was brainstorming a little tonight while watching the thunderstorm. An idea for an easy to setup and inexpensive but reliable "dual" circuit brake system for all Deuce's. For those familiar with the stock braking system you'll see the AIR PAK powers both the front axle and rear wheel cylinders. What if, one were to disconnect the line for the front wheel cylinders and instead power the front wheel cylinders with an old Bendix 2 ton vacuum booster off an old Chebby truck. In the case of you Multifuel guys a vacuum pump would have to be mounted. But for my GMC which already has a 455 GASSER in it, hooking up a vacuum booster would take less than a day. It would mount next to the original master cylinder and work off the same linkage. The GMC's have 2 wheel cylinders per wheel as apposed to the M35's single cylinder setup. Seeing as how most of the braking happens up front, I think it would work quite well to stop the vehicle. CERTAINLY better than yanking on the E brake in the case of total brake failure with the single circuit setup.

Opinions? I think the tricky part would be finding a booster that emits the same pressure and moves the same amount of fluid as the original setup. Or, I suppose the front shoes could be adjusted to grab easier.

I'm not sure I understand your concept, but wouldn't you need to fabricate a linkage to engage the front booster?
As far as the brake pressure, you could use a adjustable proportioning valve in the line. I have used a few of them on different projects, they work well.

Without changing the master cyl to a 2 chamber one, it is still a single circuit system.

Gimpy, you are correct. I was under the assumption that some of the Bendix vacuum boosters are "actuated' via an external type linkage but it seems they have to receive hydraulic pressure from the master cylinder to apply pressure to the wheel cylinders. I am not sure but I see more than 1 output on my master cylinder, it is plugged with a threaded fitting. It would be great if these had two outputs on them from the factory, could be nobody's ever thought to check on the GMC's.

A dual circuit system is actually 2 master cyls in one. This is LONG, but describes it well.

PART 5 - How the Master Cylinder works

4x4e350 said:

I'm not sure I understand your concept, but wouldn't you need to fabricate a linkage to engage the front booster?
As far as the brake pressure, you could use a adjustable proportioning valve in the line. I have used a few of them on different projects, they work well.

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No linkage necessary,,, its all hydro and vacuum ( just had 2 rebuilt last year for some farm trucks) just tee into the MS and feed the rest....at the very least it would shorten the common circuit to just the MS, airpac and the booster.........I Like the out of the box thinking ! ( which really means your a sick individual)

i was thinking of a similar idea but instead i was going to use a airpak and master cylinder from a military generator trailer and mount it in the rear and hook it in to the service line for the glad hand and isolate the rear axle to it. any body ever tried this.

adamax said:

i was thinking of a similar idea but instead i was going to use a airpak and master cylinder from a military generator trailer and mount it in the rear and hook it in to the service line for the glad hand and isolate the rear axle to it. any body ever tried this.

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your even more insane, but thats cool

adamax said:

i was thinking of a similar idea but instead i was going to use a airpak and master cylinder from a military generator trailer and mount it in the rear and hook it in to the service line for the glad hand and isolate the rear axle to it. any body ever tried this.

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that would still be single circuit brales, just less reliable!

Drum brakes do not have bias. No proportioning is necessary. If anything, heavy trucks should have bias towards the rear. That way the truck driver still has control over the steering in case of brake lockup. It's better for the rears to lock up first & still have some steering control. This is opposite from what lighter cars/trucks have.

A3 dual circuit master cylinders are now available through Eastern Surplus. They are expensive, but probably the easiest solution since they are designed exactly for this purpose (to upgrade A2 trucks to A3 dual-circuit trucks).

Spicergear Hydromax is what I'm going with (whenever the hot Vegas weather breaks). I'm going to keep the stock air packs & wire them into the Hydromax safety backup system via an air solenoid. That way if the backup system ever kicks in it'll engage the air packs full-strength & hopefully bring me to a quick halt. Better safe than sorry.

Other than the pedal assembly, the Hydromax systems can be sourced out for just a few hundred $ on Ebay & elsewhere.

this would still be dual circuit just in a round about way you would have 2 seperate master cyl the original one for the front 2 axles and a seperate one for the very rear axle,if you had a fluid failure on one of the front 2 axles the rear one would still work and stop you in an emergency,and vice versa for the rear, if you had an air failure there should be enough reserve in the tanks for at least one stop. correct me if im wrong.

The system I am brainstorming is to use the disk brake systems thhat clamp on to the rockwell axles.

I would use a seperate non power master cyl. from any race car setup and plumb an entirely seperate sustem to the disk brakes. then I just need to have the pedal actuate two braking systems and play with the bias adjusters till it was dialed in.

It is not perfect but you will still stop in an emergency failure of the factory system.

Drawbacks

-Expensive
-takes fab skills (lots of tubing work and routing.)
-you can't use lockout hubs
-standard bolton rockwell disk brake kit (like Boyce's) won't clear oil pan on front need -smaller disk.
-will be a pain in the butt to dial in. Imagine a full day of panic stopping a deuce.
-never used untill you blow out your brakeing system. Unless you dial it in perfect

adamax said:

this would still be dual circuit just in a round about way you would have 2 seperate master cyl the original one for the front 2 axles and a seperate one for the very rear axle,if you had a fluid failure on one of the front 2 axles the rear one would still work and stop you in an emergency,and vice versa for the rear, if you had an air failure there should be enough reserve in the tanks for at least one stop. correct me if im wrong.

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Nope, the signal to activate the emergency line is sent from the airpack. NOT a dual circuit.

mightymanx said:

The system I am brainstorming is to use the disk brake systems thhat clamp on to the rockwell axles.

I would use a seperate non power master cyl. from any race car setup and plumb an entirely seperate sustem to the disk brakes. then I just need to have the pedal actuate two braking systems and play with the bias adjusters till it was dialed in.

It is not perfect but you will still stop in an emergency failure of the factory system.

Drawbacks

-Expensive
-takes fab skills (lots of tubing work and routing.)
-you can't use lockout hubs
-standard bolton rockwell disk brake kit (like Boyce's) won't clear oil pan on front need -smaller disk.
-will be a pain in the butt to dial in. Imagine a full day of panic stopping a deuce.
-never used untill you blow out your brakeing system. Unless you dial it in perfect

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The big draw back is that the pinion brakes are spinning 7x faster than the axles and creating MUCH heat. Good luck with brake fade. There is a reason nobody uses pinion brakes on a street truck.

gimpyrobb said:

Nope, the signal to activate the emergency line is sent from the airpack. NOT a dual circuit.



The big draw back is that the pinion brakes are spinning 7x faster than the axles and creating MUCH heat. Good luck with brake fade. There is a reason nobody uses pinion brakes on a street truck.

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I agree this is why it would pretty much be be an emergency/augment system but 3 disks would sure beat the parking brake in a crisis.

I am fairly certian it would beat out one side of a dual circut system as well. But that would need to be tested to know for sure.

gimpyrobb said:

Nope, the signal to activate the emergency line is sent from the airpack. NOT a dual circuit.



The big draw back is that the pinion brakes are spinning 7x faster than the axles and creating MUCH heat. Good luck with brake fade. There is a reason nobody uses pinion brakes on a street truck.

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One of the reasons pinion brakes aren't for street use is they are intended for use with a spool or locker . If you use them on an open diff and one tire looses traction you will have no braking action.even though the pinion spins 6.72 times faster than the wheels it uses 6.72 times less force to stop the driveshaft than the wheel due to the gear reduction of the diff. this is why you can stop or slow down a truck using engine braking .The clutch has way less surface area than the wheel brakes but the gear reduction makes it possible....
BUt very simply put dual brake systems have a dual master or two mastercylinders if you pull actuating fluid or pressure from a single line mastercylinder you will still have single circuit brakes

Points taken, I've thought of using a pinion brake on the intermediate axle as an emergency brake. I agree, with a open diff, only one will would skid but the bull gear on the intermediate passes through to the rear axle as well. At that rate, we'd effectively lock 2 sets of tires in a worst case scenario. I feel that would provide quite a bit of stopping power. The fact that the diffs input spins 6.72 times faster than the wheels would make the brake stronger in the initial phase. If used only once in an emergency, hopefully it wouldn't fade. We all know the cable actuated drum parking brake is not very effective and using the pinion brake only in an emergency situation, I think it'd work pretty good. I also know the axles don't prefer pinion brakes but I'd rather trash an axle in an emergency than trash the live's of someone else if I did experience a brake failure. Regular cars don't like 13,000 pounds crashing into them.

Before you guys "think" pinion brakes are a good idear, please speak to someone that uses them. Most I have spoken to don't like them. That is why I am biased against them.

gimpyrobb said:

Before you guys "think" pinion brakes are a good idear, please speak to someone that uses them. Most I have spoken to don't like them. That is why I am biased against them.

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Is that their only system? If so I would tend to agree now as an addition to stock brakes....