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modern dual circuit air over hydraulic brakes

patracy

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The residual valving is more for the lower MC mounting height from what I understand. Mount the MC up higher on the firewall and it wouldn't be needed. I ordered the last MC they had as well. It appears the difference is actually a safety switch to light up the brake light in the event there's a failure.
 

patracy

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Good deal. Thinking about it more I like your idea too. I may have to see how yours turns out!
I think I've decided how I'm going to go about it now. I was considering the air brake canister. But I'd have to really redo the air plumbing to do that. Also you really get into needing to separate tanks. Since I'm really only looking for a way to get better brakes, I'm going to go with the MC we bought, but mount it up on the firewall and hang a pedal. Then feed the outputs to the original airpack, as well as a second air pack. I know this is probably more expensive and more involved than the air brake can setup. But this keeps me having a "physical" connection to the brakes. Also in the event of a air failure, there would be a delay until that can reverted to "parked". Also this would mean that I still would have SOME brakes even without any air at all. (Meaning I can apply AND release them under my control) And honestly, this is more in tune with what the military did with the M35A2C's.

Now thinking it out more. I'm going to be adding in power steering to my truck as well, but I'm not going with a HF54 or any power steering box. But rather a servo and a assist cylinder. So my firewall and steering column will get crowded. So I plan to offset the MC over to the side. I'm thinking about using a keyed shaft to setup the pivot point for the pedal. I can then setup the actuator rod anywhere left of right of the peddle. I'll probably mount the second airpack in the area where the stock MC goes.

I thought about just buying a entire F700 hydroboost setup. But I'm clueless how you'd get that to actuate air brakes for the trailer. Unless someone has an idea for that? Maybe a treadle valve could work off that lever arm setup I mentioned to control the trailer air brakes? Course a hydroboost setup is only good for those of us that have PS pumps.

Anyhow, I think I've talked. (Maybe overthought) Myself out of the air brake can idea.
 

cbrTodd

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Patracy, you can have a "hydroBoost" system and activate the air brakes on a trailer with a "high pressure activated electrical switch" that then activates a "Relay valve" (like a R-14) that then supplies the air to the trailer.
This would activate the trailer brakes, but unless I am missing something there would be no modulation of the trailer brake force applied. A light tap of the truck brakes would give full trailer brakes, wouldn't it? I thought the air pack had at least some ability to modulate the amount of trailer brake application based on the amount of brake pedal travel, but I will admit I am not an air pack expert.

Not trying to criticize as I have a Hydromax 2 unit and a F700 brake pedal assembly sitting on the shelf to install after I do the 6BT swap and then have a power steering pump. I am genuinely interested in finding a solution that will work. I was under the impression that using a standard electronic brake controller and then an expensive electric to hydraulic brake power unit on the trailer would be my only option to keep proper brake application with stock axles on an M105 trailer.
 

patracy

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This would activate the trailer brakes, but unless I am missing something there would be no modulation of the trailer brake force applied. A light tap of the truck brakes would give full trailer brakes, wouldn't it? I thought the air pack had at least some ability to modulate the amount of trailer brake application based on the amount of brake pedal travel, but I will admit I am not an air pack expert.

Not trying to criticize as I have a Hydromax 2 unit and a F700 brake pedal assembly sitting on the shelf to install after I do the 6BT swap and then have a power steering pump. I am genuinely interested in finding a solution that will work. I was under the impression that using a standard electronic brake controller and then an expensive electric to hydraulic brake power unit on the trailer would be my only option to keep proper brake application with stock axles on an M105 trailer.
That is what I thought as well. I mean, on tractors you also have the trailer brake control valve on the column to allow you to modulate the rear brakes. It just seems like full apply on any braking could lead to some unsafe trailering.
 

rustystud

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The switch you would need is the same one the big trucks and buses use that have "brakes-by-wire" application. It has a "varistor" inside that puts more current with more pressure. Of course you would then need the relay valve that is also variable.
Actually thinking about this and the cost, you would be better off buying the "kit" instead.
 

patracy

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banditt1979

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20220923_170310.jpg

Got mine with a broken cap. Since its a closeout and they don't have any more I would have to return it, doesn't look like there is any other option on rock auto. Hoping I can pick up a cap from the local parts store. The reservoir is metal so shouldn't be an issue running some lines to it and installing a remote tank somewhere.
 

rustystud

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I haven't been able to find anything like that? I did find this though, which is a hydraulic over air valve which would allow proportioning the air.


I found a link on google under shopping and the valve was priced at over a thousand dollars. So I'm going to lean back towards the MC on a mount on the firewall and run dual air packs.
Yes ! That is the type of valve I was talking about. There are several makes out there. Didn't know how much they cost though !
 

patracy

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View attachment 880251

Got mine with a broken cap. Since its a closeout and they don't have any more I would have to return it, doesn't look like there is any other option on rock auto. Hoping I can pick up a cap from the local parts store. The reservoir is metal so shouldn't be an issue running some lines to it and installing a remote tank somewhere.
Since it's metal, is there the four mounting holes for the resv. to the MC body like mine? You could make a metal lid and secure it down with all thread all the way through maybe? (You'd need sealing washers on the inside of the resv). Or maybe just remove it completely and make a plate to bolt down to those 4 bolt holes and drill the ports and tap them NPT and make your own remote setup?
 

banditt1979

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Since it's metal, is there the four mounting holes for the resv. to the MC body like mine? You could make a metal lid and secure it down with all thread all the way through maybe? (You'd need sealing washers on the inside of the resv). Or maybe just remove it completely and make a plate to bolt down to those 4 bolt holes and drill the ports and tap them NPT and make your own remote setup?
Good ideas. The rubber boot under the cap still seals well. Dorman responded to me saying they don't sell the cap separately but if I return the assembly I'll lose out on the good deal. I may also rig up some hose clamps to wrap around it for the short term, bigger issue for me will be modifying the A2 mc bracket.
 

banditt1979

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So the main brake line coming off the single circuit mc is 5/16" and uses 1/2-20 fittings. Looking at the pictures below the lines off the dual mc are 1/4" and use 7/16-24 fittings. If we use mc adapters that adapt to 1/2-20 inverted flare fittings, we wouldn't have to change the adapters on the air packs. If we reduce the mc fittings to 7/16-24, we would need to do the same to the inlet side of the air packs.

So for the mc to use 5/16" brake line, we would need adapters that go 9/16-18 to 1/2-20 IF, then 1/2-20 to 1/2-20 IF.

To use 1/4" brake line as the diagram suggests, we need mc adapters that go 9/16-18 to 7/16-24 and 1/2-20 to 7/16-24, then additional 7/16-24 adapters at the inlet side of the air packs. Not sure what the threads are at the air packs, I'll try and measure my spare in a few.

I found the adapters to go to 7/16" at the mc. Edelmann #258450 for the 1/2", #258403 for the 9/16". At least I think these would work. They are called master cylinder adapters in the description. If someone has better info or I need to be corrected, please let me/us know.

Screenshot 2022-02-06 at 09-50-41 PEASHOOTER BRAKE SCHEMATIC REV 2 Public-1 pdf.png

PEASHOOTER BRAKE SCHEMATIC A2 DUAL CIRCUIT REV 1 PUBLIC.jpg

In the second picture there is a combination valve with the 2 lines in and 2 lines out. I had previously sourced this part as ac delco #15835212 but now looking for it, and any ac delco combo valve, they are unavailable at this time. This one was set up for the 7/16-24 IF brake lines. I will try to find another that has the 1/2-20 IF threads so if needed we could just use 5/16" brake lines all the way out.
 
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