Dual Circuit Brake Engineering Thread

[Jakelc15]

Someyhing else to throw in the mix!
My plan on my 5 ton is to air brake the rear and use a master for the front.
Something like this
https://www.fayettedistribution.com/Trailer-Air-to-Hydraulic-Drum-Brake-1000-psi-p/8510-2kt.htm

FE41207 master cylinder and type 36 air disc brake can. No airpack. Replace brake pedal with actual air brake treadle valve.

 

[jacklegjim]

Thanks Rusty for the correction on the master cylinder info.
I have a couple of these master cylinders and one of them is a
60 40 configuration I also have 1.5” wheel cylinders for the front.
just so I understand what you are saying. Would I put the 60%
To the front? I have not been able to find much information
on these Bindex master cylinders so would the 60% port be closest
to the mounting flange or bigger port? Would it also be safe to assume if there are two
different port sizes that it is not a 50% 50% output?

 

[rustystud]

Thanks Rusty for the correction on the master cylinder info.
I have a couple of these master cylinders and one of them is a
60 40 configuration I also have 1.5” wheel cylinders for the front.
just so I understand what you are saying. Would I put the 60%
To the front? I have not been able to find much information
on these Bindex master cylinders so would the 60% port be closest
to the mounting flange or bigger port? Would it also be safe to assume if there are two
different port sizes that it is not a 50% 50% output?

The 60% port would go to the rear on the Deuce. Normally the 60% would go to the front due to caliper brakes needing more fluid. On the Deuce the 60% goes to the rear wheel cylinders. The 60% port should be the one nearest to the mounting flange Almost all dual brake master cylinders have a fluid differential between ports (or front and rear) . Normally most braking effort is applied to the front brakes but not on the Deuce since their are 4 wheel cylinders in back to the two in front. In the good old days a lot of trucks had a front brake disconnect on them ! Now we know that is totally wrong !

I edited my post due to information received from Peashooter. He is the expert on Deuce master cylinders and wheel cylinders.

 

[rustystud]

Someyhing else to throw in the mix!
My plan on my 5 ton is to air brake the rear and use a master for the front.
Something like this
https://www.fayettedistribution.com/Trailer-Air-to-Hydraulic-Drum-Brake-1000-psi-p/8510-2kt.htm

FE41207 master cylinder and type 36 air disc brake can. No airpack. Replace brake pedal with actual air brake treadle valve.

The "Breda" bus or "Tunnel" bus (made in Italy) for "Seattle Metro" was a dual brake configuration. Air brakes to the two rear axles, and hydraulic brakes to the giant front caliper brakes. It took awhile to get it to work properly, but after about 5 years we got it dialed in pretty good.

 

[peashooter]

The 87-88 dual circuit A2 trucks had master cylinders with the larger port sizes which meant they had internal residual pressure valves. It the port sizes are the 9/16 or 1/2" then the master cylinder doesnt have RPVs. Also the 87-88 trucks had 1-3/8" wheel cylinders all the way around and use a 60/40 split master cylinder. Normally the 60% goes to the front because the front would have disc brakes and require more fluid, but on our trucks the 60% is routed to the rear circuit because there are 4x wheel cylinders hooked to it and the 40% circuit goes to the front 2 cylinders.
Now on the m35 a3 trucks, the mc has no RPVs because it has a remote reservoir mounted high on the firewall and that height acts as a residual pressure valve. The A3 trucks use a 50/50 split master cylinder and have the larger 1-1/2" brake cylinders on the front 2 wheels and standard 1-3/8" on the rear 4 wheels.
I personally run a remote reservoir master cylinder that is a 60/40 split and has a built in differential pressure switch that will trigger the brake warning light if one of the circuits loses pressure(and creates a differential pressure with the good/working side). I run the 40% to the front wheels that have the larger 1-1/2" brake culinders with the standard size in the rear.

 

[jkcondrey]

Another question towards the system, I have the shorter style airpack. When i eventually go to the dual system, does it matter if the second pack is the same style, or can the longer style be used? Anyone got any idea?

 

[peashooter]

Another question towards the system, I have the shorter style airpack. When i eventually go to the dual system, does it matter if the second pack is the same style, or can the longer style be used? Anyone got any idea?

I cant say for sure, but i believe either will work. Since its a dual circuit system, its essentially 2 seperate brake systems that share the same fluid reservoir.
If it was me, I'd be okay using one of each style airpac if thats what i had on hand.

 

[jacklegjim]

I have spent hours trying to get the info that is here in just a few posts
thanks for sharing your knowledge.
One of my master cylinders does not have the seats in the ports.
I have a few old rebuild kits for these and it has the rpv and large seats
that won’t work on mine but, it also has the smaller seats.
Do they just press into port or is there a procedure for installing them.
I only have one set of the correct seats so I don’t want mess this up.
I think I am going to buy another remote reservoir that way I will have a
spare master cylinder and reservoir.
The first conversion I did I used parts from an A3
and it had air brake line from the reservoir to the master cylinder.
The air brake line is what I went back with I just assumed it was ok because
that is what was on it. If air brake line is ok to use I will drill and tap
the remote reservoir plate on the master cylinder 3/8 NPT because it configured
for a double flare hard line. Are you aware of a source for a differential pressure switch that will work. I have found one for a 70’s ford truck
that may work but I was hoping to find something in current production.
I have a parts brake down of the master cylinder that shows a pressure differential block with a switch that attaches to the ports but, I have not seen
this in any of my research.

 

[peashooter]

Yes, you can use air-brake hose to connect the remote reservoir to the master cylinder.
I'm not sure how the seats are installed, I'll leave that to RustyStud to answer. I also dont know where to find any good fitting differential valves.
In my case I decided to use a 1.75" bore 60/40 split master cylinder with the remote mount top plate and a built in pressure differential switch. There were only a couple vehicles that used these for just a couple years. Fortunately an aftermarket company started making them again a few years ago and they are sold under the following brands and part numbers (I've bought many of them over the years and they were all USA made as of a year ago anyway):
-RAYBESTOS MC390625
-CENTRIC 130.84002
-AC DELCO 18M1112

I think they only make these every now and then so they are frequently out of stock for a month or 2 at a time.

Also if you change your front wheel cylinders to the larger A3 style 1-1/2" diameter bore, then you need to modify the link pins by cutting the slot deeper (1/8" I think). Otherwise with new pads, the drums will drag on them, heat up and stop the truck. There is a thread on this somewhere.

 

[rustystud]

Yes, you can use air-brake hose to connect the remote reservoir to the master cylinder.
I'm not sure how the seats are installed, I'll leave that to RustyStud to answer. I also dont know where to find any good fitting differential valves.
In my case I decided to use a 1.75" bore 60/40 split master cylinder with the remote mount top plate and a built in pressure differential switch. There were only a couple vehicles that used these for just a couple years. Fortunately an aftermarket company started making them again a few years ago and they are sold under the following brands and part numbers (I've bought many of them over the years and they were all USA made as of a year ago anyway):
-RAYBESTOS MC390625
-CENTRIC 130.84002
-AC DELCO 18M1112

I think they only make these every now and then so they are frequently out of stock for a month or 2 at a time.

Also if you change your front wheel cylinders to the larger A3 style 1-1/2" diameter bore, then you need to modify the link pins by cutting the slot deeper (1/8" I think). Otherwise with new pads, the drums will drag on them, heat up and stop the truck. There is a thread on this somewhere.

Hey Aaron, glad you jumped in on here. As far as the residual check valves go, they are pressed in. You can use a screw and slid-hammer to remove them if you need to.
For all the rest of you here. Peashooter is one of the most read-up and knowledgeable on the "Master cylinder" and "Wheel cylinders" of the Deuce then anyone I know. I would heed his advice.

 

[jkcondrey]

Well I just ordered that master cylinder, next I will try to get the fitting size adapted down to the correct line size and order another airpack and tank. If I remounted the reservoir in the cab would that be high enough to act as residual pressure? I was thinking on the left side on the kick panel area or just behind the seat on the b pillar.

 

[jacklegjim]

What master cylinder brake pedal bracket are you using?

 

[peashooter]

Well I just ordered that master cylinder, next I will try to get the fitting size adapted down to the correct line size and order another airpack and tank. If I remounted the reservoir in the cab would that be high enough to act as residual pressure? I was thinking on the left side on the kick panel area or just behind the seat on the b pillar.

Remember the dual circuit systems have a special 2 chamber tank, or you can add a 3rd tank like you mentioned. If you get the outboard side A3 style tank it may be a quicker nstall though. I think you will be fine with the reservoir located anywhere at or above the original position. The important thing is to have it at least a foot above the wheel cylinders.

 

[jkcondrey]

As for the bracket I’m thinking of mocking it up in card board first, then some thin sheet steel. After getting it located I’ll have it done in 1/4 steel. Of course that plan will change I’m sure lol. I probably will go with three tanks. There’s not a lot of spare parts places close by though, so it may be a summit racing or similar size tank.

 

[goodwithwood35]

I will be using a separate, isolated regular M35 tank, I was able to pick up an extra one, along with the straps. It will easily fit on the passenger side next to the existing tanks. I have an extra “long style” airpack that will be rebuilt prior to the install, along with new cunifer brake lines all around. I have the remote reservoir master cylinder, not the kind with the built in pressure switch, but I have the A3 external switch and the lines, also the parking brake switch, and the dash warning light. Remote reservoir, and an extra A2 style master cylinder mount bracket. There is a lot of similarities between the geometry of the A2 and “dual circuit” brackets, and they are cast steel (not iron), so I will be modding my extra one as a weldment while still having the old one installed, so I don’t go “to the land of no return” and can play around with the fitment of the MC and the PTO lever. I’ve also 3D printed Peashooter’s CAD file, to use as a mock-up. This will be a lengthy project for sure, so it will be a while till I get to it. She’s about to go on a 500 mile road trip, so it will have to wait a while after that too.

Meanwhile, I got piles of hope and glory in my shop for several projects. I keep saying one day they’ll dwindle down!


Sent from my iPhone using Tapatalk

 

[jkcondrey]

Well I have the master cylinder on the counter trying to find a way to downsize the ports on it to match the tubing for the airpacks. I'm not having a lot of luck. One port is 11/16-18 and the other is 3/4-18, with inverted flares. I have found some adapters for one but they only go to -an fittings on the other side. I found that the 11/16-18 thread is used on tie rod ends for old fords. I have emailed a couple of companies about getting fittings made to adapt, but have been turned down. I think I may try a local machine shop to see if they can turn something out for me to get down to the lines for the airpack connection. You can get dies and taps for those larger ports, but premade adapters are crazy scarce. This particular master may be more easily bought, but the port sizes are tough to find parts for as mentioned earlier in the thread. Guess I will keep trying.

 

[yolner]

Yeah not a lot out there for those sizes. Only options I see are inverted to AN and back to inverted or something custom made.

 

[jkcondrey]

Well I ordered some taps and dies for the oddball ports. Going to try to machine them out myself with some help at a friends shop. Plan on getting them to size and them tapping the centers to fit the 1/2-20 lines to the airpacks.

 

[tobyS]

I don't know if this is the place to bring up brake piston sizing or if the discussion has occurred (please reference to it if you know).

I'm making sure some surplus brake cylinders that I got from GL are ready to go. Here is a link to related thread where I posted pictures of 6 new brake cylinders and the various springs inside of them. The discussion was about alternatives, so I may have slightly hijacked the thread when I found I had three types of springs inside them. Here is a link;

https://www.steelsoldiers.com/showthread.php?180384-Civilian-wheel-cylinders/page2

So after going through the cylinders and reconditioning them with fresh lube and paint, I read that the front of an M35A3 is not the same as the A1 or A2. My (6) cylinders all were 1 3/8" piston diameter, but I read that A3 has 1.5" on the front.

My project is a 4x4 so I will not have 6 cylinders... being reduced to 4. My question is, has anyone changed the rear to the larger 1 1/2" size piston on an A3, as a 4x4?

Has there been a discussion of using the larger piston size (1 1/2" Rab. WC37317) on the older A2 or A1 (fronts)? The piston size seems to tie in to a brake engineering thread. Thanks for your help.

 

[peashooter]

I don't know if this is the place to bring up brake piston sizing or if the discussion has occurred (please reference to it if you know).

I'm making sure some surplus brake cylinders that I got from GL are ready to go. Here is a link to related thread where I posted pictures of 6 new brake cylinders and the various springs inside of them. The discussion was about alternatives, so I may have slightly hijacked the thread when I found I had three types of springs inside them. Here is a link;

https://www.steelsoldiers.com/showthread.php?180384-Civilian-wheel-cylinders/page2

So after going through the cylinders and reconditioning them with fresh lube and paint, I read that the front of an M35A3 is not the same as the A1 or A2. My (6) cylinders all were 1 3/8" piston diameter, but I read that A3 has 1.5" on the front.

My project is a 4x4 so I will not have 6 cylinders... being reduced to 4. My question is, has anyone changed the rear to the larger 1 1/2" size piston on an A3, as a 4x4?

Has there been a discussion of using the larger piston size (1 1/2" Rab. WC37317) on the older A2 or A1 (fronts)? The piston size seems to tie in to a brake engineering thread. Thanks for your help.

Yes, they will work fine but the link pins need modification, see these threads:
https://www.steelsoldiers.com/showthread.php?117663-Wheel-Cylinders&p=1538032&viewfull=1#post1538032

https://www.steelsoldiers.com/showt...ck-locked-up&p=1625924&viewfull=1#post1625924