Dual Circuit Brake Engineering Thread

[7bdiver]

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If I remember correctly, the "79ish" Chevrolet pickup trucks have (had?) a proportioning valve in the brake system just below the master cylinder. There is a "rubber button" on the front of it and if the front or rear brake lines exploded, the functional part of the brake system would still be operational.

It's fuzzy, but I remember learning that the hard way repairing a truck. Easily found the busted rubber line, but I couldn't figure out how to bleed the brakes. Fluid wouldn't pass to the back axle. Problem was solved when one of the older guys pointed out the "button" on that valve - and PRESTO - fluid flowed again...

I looked at how the proportioning valves you were talking about worked. The ones with the reset. They're a combination valve. These would actually do the same thing as i was trying to achieve, and they're fairly cheap. They also have a warning light sender already on them to tell you when one circuit fails.

If you get the combination style proportioning valve, the center piston inside will shut off the leg that lost pressure in the event of back pressure loss. These are normally mounted right under your master cylinder on most vehicles. Very common on-the-shelf part.

So, put a T-splitter at your main outlet, run the two lines to your proportioning valve inputs. Now you have separate outputs from the valve to your front and rear.

They usually have two front outputs, just use one, plug the other. Presto, you have dual circuit brakes for like 35-50 bucks!

Might need to find one big enough for a deuce. I'm not sure how much adjustment they have. I assume a standard one would think your slamming on the brakes at all times.

Whew! No need to machine one from scratch.

I'll take some time to find one big enough and with the right size fittings already on it.

 

[Another Ahab]

I'll take some time to find one big enough and with the right size fittings already on it.

Excellent, 7bdiver. If you find a source, could you please post it up here?

That would be a treat!

 

[7bdiver]

I will.

Heres a lil drawing to explain the concept. Looking at the schematics online is not clear at all.

If one side loses pressure, the center piston will be shoved over by the pressure on the working side and shut the lost side down. It would have springs on each side. The reset button probably recenters it after youve fixed the leak.

 

[7bdiver]

Ok, I made a mistake folks. An off the shelf proportioning valve will not work due to the double inlet if it came from a T-junction. The brake fluid would always back-route at the T to the leak in that case. I will have to machine one of my original concept that will work from a single source.

 

[Another Ahab]

Ok, I made a mistake folks. An off the shelf proportioning valve will not work due to the double inlet if it came from a T-junction. The brake fluid would always back-route at the T to the leak in that case. I will have to machine one of my original concept that will work from a single source.

Well, at least now you know:

- That's good (solid) progress; all good!!

 

[Robo McDuff]

So fuses exist for pick-up trucks (to give them their real name), for forklifts and knuckle cranes, and for airplanes. Ferro, do trains use hydraulic velocity fuses?

Somehow it should be possible to use those existing fuses and fabricate them into something that is strong enough for a 5-ton. If it works for the 5-ton it should be easy to adapt it for the much smaller and lighter deuce as well.

 

[Mullaney]

Lookey there:

- Older Guys might sometimes seem like a PIA, but

- Every now and then, they're real useful!

(Full Disclosure: I am myself an O.G.)

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Another Ahab , I believe I have to agree with you... I acheived O.G. status about two years ago when I turned 60 and it isn't a bad place to be. Back when the "older guys" were showing me stuff I was in my 20's. Things worked really well back then.

Guessing because learning that I had two ears and one mouth helped me listen from time to time.

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7bdiver I would imagine there would be a waiting list for a truck size proportioning valve. The hydraulics in a lot of cranes have check valves. Some of the more simplistic have an in-line ball valve on the cylinder that keeps the boom in the air if a rubber line breaks. They have been known to just slowly drift down if not properly maintained, but even that is much better than a catastrophic failure when the load roars to the ground. (The Hiab 173 uses that valve type)

I wonder if a Ford F-750 or maybe a Chevy C-8500 has a proportioning valve - or are those like the Deuce A3 with dual circuit brakes "in the brake booster" rather than in the lines...?

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Robo McDuff It seems really odd Robo... In all the years working in hydraulics, I have never heard the words "hydraulic fuse" before. I went back and read your Post #24 . In that page, there was a Navy Aviation link with a really nice description and theory of operation.

Strangely, there is exactly ONE check valve on the M-936 that I have. Never seen a check valve that was in the middle of a rubber line... But the military had a plan I guess.

 

[7bdiver]

The stroke volume of the m35a2 master cylinder is about 3.75 ci. Thats a 1.56" stroke at 1.75" diameter.

I designed the dual cylinder part that would split the front and rear systems effectively, with bleeders, fittings, and all. It is spec'd to run on a little bit more volume than the master cylinder, to have some forgiveness room in there.

Basically, it has turned into another whole master cylinder. Though a good design. Its a little more complex and bulky than i would like.

I feel i would rather make in-line hydraulic fuses. They will be volume limiting, rather than the normal velocity limiting type you would find available. They wont be all that small either but they will be much easier to install. To match the master cylinder's max single-stroke volume output, they will be about 1.5" by 6" in size. 4" for the front, 6" for the back.

The idea is to put one on each side of the distribution block (the t-fitting) on the frame where your hoses go front/rear.

I'm trying to locate parts online that you can just put together, but its not easy.

Here's the basic principle. I'm putting this in front of a local hydraulics shop to see how they might build it with their experience.

 

[Another Ahab]

Here's the basic principle. I'm putting this in front of a local hydraulics shop to see how they might build it with their experience.

A report on that (and their comments), will be greatly appreciated!

 

[7bdiver]

I forgot to say that I did find a way to make an off-the-shelf proportioning valve work.

All you have to do is put put a check valve on each line going into the proportioning valve, after you split the line from the air pack. Then make return lines that t-off from each output line and bypass the proportioning valve going back to the single line from the air pack. The return lines would need check valves too. Done, split system.

Might end up being cheaper than a from-scratch fuse. Thats quite a few more fittings tho.

But, that way, you all could split your systems for about 75 - 120 bucks.

Is that something you'd rather do, or go with the fuses?

 

[frank8003]

Hydraulic fuse and more

and the explantion in Stack Path

Hydraulic fuses add safety and control to circuits

A hydraulic fuse serves the same function as a fuse or circuit breaker in electrical circuits. When an electrical circuit is overloaded, the excessive current either burns the...

www.hydraulicspneumatics.com

Hydraulic fuse is a general term given to three different types of devices — velocity fuses, quantity fuses, and pressure fuses.

 

[7bdiver]

From what I can tell, Parker Hannifin are the only ones that actually make the quantity style fuse. They seem to be a very rare item indeed, and theyre for aerospace applications. They are what we'd want, but are very likely out of budget. If they would even sell them to us. Maybe I'll call to find out.

 

[Robo McDuff]

I would have to ask the Dutch DoT if I can include this in my system. Problem is, in the EU, ANY change to the brake system has to be registered and approved. If not, in case of a brake-related accident, the insurance company will say that we made not-approved changes to the system and as such any insurance is void. Does not matter if the change actually improved the braking, they will use anything to avoid having to pay.

 

[ldmack3]

From what I can tell, Parker Hannifin are the only ones that actually make the quantity style fuse. They seem to be a very rare item indeed, and theyre for aerospace applications. They are what we'd want, but are very likely out of budget. If they would even sell them to us. Maybe I'll call to find out.

Since they are for either 5606 or Skydrol are either one compatible with DOT 3 or 5?

 

[7bdiver]

My understanding is that dot 5 is compatible with all common seals. I doubt they are using anything that would be a worry.

 

[7bdiver]

After pouring over the internet for a couple weeks now, it looks like no one manufactures a valve like what I want. There's nothing out there but damn velocity fuses.

The closest was Parker's quantity fuse. Used to be watterman. Model G8381-8 type1. But they are still a little big, the smallest one limiting to 5 ci before shutoff. Still a neat design that can be scaled. I modeled one I could machine that would be 2 ci. But... i still don't really like it because you will lose that much fluid each time you pump the pedal.

Instead, I modeled one that will shutoff upon simple pressure loss, only losing mere cc's. I cannot fathom why no one makes this valve. There are drawings of the concept everywhere. So, will machine my f-ing own. This would only take very basic milling tools and is still pretty small in size.

It's no dual circuit system, but these fuses will shut off anything that fails below them. Better than nothing. Mainly, they are small, easy to install, and easy to make.

I based it off this drawing I found on the internet, but mine is way easier to machine. I'll do an actual spec drawing when I get around to it.

There would be a spring in the back of the piston. (Not shown). Also, a magnetic reed switch could be put on it to blink at you if it's experiencing a leak or failure on that line.

 

[7bdiver]

I want to hear some opinions on people's preferences. This would be to swap out the brake system on your deuce, get rid of the master cylinder and airpack altogether. What system would you feel safer with? All dual circuit sized for a medium truck of course.

1) Off the shelf dual circuit vacuum boosted master cylinder. This would run off a vacuum pump, just like what's on most diesel pickup trucks these days.

2) Off the shelf hydraulic boosted dual master cylinder. This would use hydraulic pressure off your engines hydraulic pump if you have one. technically you could use an electric pump so it would still operate even if the engine dies. I believe this is done in some large trucks already. But... that would have to constantly be running.

3) Run a pressure boosted master cylinder off your original compressor. I have not been able to find one with a hard link to the pedal yet.

I would like the idea of an air pressure boosted system because if the engine dies, you still have residual pressure in the tanks. I don't know why this seems to not be a thing, it's simply the opposite of a vacuum booster. I can't stand how the current system has the airpack divorced from the master cylinder. It should be linked through with a single push rod like a traditional vacuum booster!

Why are all the air pressure boosted master cylinders, like busses use, the remote mounted type with no pedal linkage!? I do not understand where things went wrong with the design of these things. Put the pressure booster in front of the master cylinder so the pedal push rod runs through both! Why does this not exist? Frustrating to say the least. I am considering building my own pressure cylinder with poppet valve to mount in front of an existing master cylinder. Designed to the same diameter as the deuce airpack for the same feel. Would have the same size function and look as a normal ass brake booster.

Idk, I've been fussing a lot, waiting for it to get above freezing out so I can start messing with things. Sadly, my truck can't fit through the door in my shop at the moment.

 

[rustystud]

I want to hear some opinions on people's preferences. This would be to swap out the brake system on your deuce, get rid of the master cylinder and airpack altogether. What system would you feel safer with? All dual circuit sized for a medium truck of course.

1) Off the shelf dual circuit vacuum boosted master cylinder. This would run off a vacuum pump, just like what's on most diesel pickup trucks these days.

2) Off the shelf hydraulic boosted dual master cylinder. This would use hydraulic pressure off your engines hydraulic pump if you have one. technically you could use an electric pump so it would still operate even if the engine dies. I believe this is done in some large trucks already. But... that would have to constantly be running.

3) Run a pressure boosted master cylinder off your original compressor. I have not been able to find one with a hard link to the pedal yet.

I would like the idea of an air pressure boosted system because if the engine dies, you still have residual pressure in the tanks. I don't know why this seems to not be a thing, it's simply the opposite of a vacuum booster. I can't stand how the current system has the airpack divorced from the master cylinder. It should be linked through with a single push rod like a traditional vacuum booster!

Why are all the air pressure boosted master cylinders, like busses use, the remote mounted type with no pedal linkage!? I do not understand where things went wrong with the design of these things. Put the pressure booster in front of the master cylinder so the pedal push rod runs through both! Why does this not exist? Frustrating to say the least. I am considering building my own pressure cylinder with poppet valve to mount in front of an existing master cylinder. Designed to the same diameter as the deuce airpack for the same feel. Would have the same size function and look as a normal ass brake booster.

Idk, I've been fussing a lot, waiting for it to get above freezing out so I can start messing with things. Sadly, my truck can't fit through the door in my shop at the moment.

Are you referring to the "Hydra-Boost" type booster ? There on the frames for safety reasons. These are either vacuum boosted or pressure boosted units, depending on enginee type ie: Diesel/Gas.
Is that what your asking ?
I've gone back and reread several pages to get up to speed here, and it seems your just trying to prevent fluid loss after a brake failure, correct ? Really the Dual Brake booster system is about as good as it gets here. Since the Deuce should only be running 55 MPH this system should be totally adequate.

 

[Another Ahab]

Idk, I've been fussing a lot, waiting for it to get above freezing out so I can start messing with things. Sadly, my truck can't fit through the door in my shop at the moment.

Cabin Fever

On top of the COVID Carnival, it'll all for sure make a body antsy.

 

[peashooter]

I want to hear some opinions on people's preferences. This would be to swap out the brake system on your deuce, get rid of the master cylinder and airpack altogether. What system would you feel safer with? All dual circuit sized for a medium truck of course.

1) Off the shelf dual circuit vacuum boosted master cylinder. This would run off a vacuum pump, just like what's on most diesel pickup trucks these days.

2) Off the shelf hydraulic boosted dual master cylinder. This would use hydraulic pressure off your engines hydraulic pump if you have one. technically you could use an electric pump so it would still operate even if the engine dies. I believe this is done in some large trucks already. But... that would have to constantly be running.

3) Run a pressure boosted master cylinder off your original compressor. I have not been able to find one with a hard link to the pedal yet.

I would like the idea of an air pressure boosted system because if the engine dies, you still have residual pressure in the tanks. I don't know why this seems to not be a thing, it's simply the opposite of a vacuum booster. I can't stand how the current system has the airpack divorced from the master cylinder. It should be linked through with a single push rod like a traditional vacuum booster!

Why are all the air pressure boosted master cylinders, like busses use, the remote mounted type with no pedal linkage!? I do not understand where things went wrong with the design of these things. Put the pressure booster in front of the master cylinder so the pedal push rod runs through both! Why does this not exist? Frustrating to say the least. I am considering building my own pressure cylinder with poppet valve to mount in front of an existing master cylinder. Designed to the same diameter as the deuce airpack for the same feel. Would have the same size function and look as a normal ass brake booster.

Idk, I've been fussing a lot, waiting for it to get above freezing out so I can start messing with things. Sadly, my truck can't fit through the door in my shop at the moment.

If starting fresh and i had the money, id probably go the Hydro-Max route like Jesse did in the below links. This gets you simplicity from no airpacks, gives dual circuit, hydraulic pump off the engine, differential pressure warning switch, residual pressure valves, remote reservoir, and a 24v backup pump so you still have boosted brakes if the engine cuts out.

Hydro-Max Brake Assist *pics added* (long read)

For the amount of times that 12v boost motor is going to run, why worry about getting a 24v motor? Slap a couple of wires to a switch or whatever from one battery and call it a day. It really is only a momentary draw and not like something always eeking away juice from one battery.

www.steelsoldiers.com

Hydro-Max Brake Assist *pics added* (long read)

The 1 3/4" master cylinder is going to build more pressure when used with the Hydro-Max 2 booster. It's the most powerful combination of parts, and the stock master cylinder is 1 3/4", so should have enough fluid volume. Gonna give it a try anyway...

www.steelsoldiers.com