Dual Circuit Brake Engineering Thread

Dual circuit would be a nice update. I have nothing useful to add on the engineering of it other then to say this could be a good parts source. http://www.brakeplace.com/ Had luck finding oddball brake parts for farm equipment and the like.

Years ago when I wanted to have split brakes on a hot rod so I could do burn outs. I took a master cylynder off of an old John Deere. It had split left and right brakes. I replumbed it for front and rear brakes. I welded a tab on the front of the left pedal. If I hit the right pedal it aplied the front brakes "Instant burn out" if I hit the left pedal it applied front and rear brakes. It was originaly mounted similar to the Deuce cylynder. It was not boosted though. A modern John Deere or Case should have the same set up but boosted now. That might be an alternative to look into.

parts is parts

I have an '87 ex-air force deuce with the dual brake system.
Maybe I could get some pics from underneath for ya if it would help.
Gimp, if you could let me know how to put the truck on it's side so I would have better lighting while taking pics of these parts, that would be great.

A modern John Deere or Case should have the same set up but boosted now. That might be an alternative to look into.[/QUOTE]


I doubt you will find what you are looking for there. Most tractor brake systems are integrated right in the hydraulic sysem. (no separate fluid) Some exeptions are around I am sure, but I would sure just try and copy the late M35 deuce which had dual circuit or the A3

The manual listed above is for modified M44A2's NOT A3's.

Huh?

Pic of modified M44A2's .

Had to do a lot of resizing....So it might be real small.

That's not split. It comes out of booster, to a 'T', and heads front and rear. That's how they are now.

Want to figure out how to really do it, ask M35 Tom as he has put two MC's in a truck for true split circuit brakes.

The mounts for the winch controls are on the side of the master cyl. The A3 master cyl doesn't have the winch control mounts because it's winch is hydraulic.

spicergear said:

That's not split. It comes out of booster, to a 'T', and heads front and rear. That's how they are now.

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That is a bad pic from the manual. It uses a dual resevoir master cylinder and the 2nd airpack is added. It is a split system.

This is a post I did in another thread:

"Here's what I think I know about the A3 system.

The air packs are the standard deuce ones.

I believe a valid part number for the master cylinder is: Bendix 11999 or Raybestos MC39577

This crosses to a NAPA TS108038, TS108002 and UP39577.

This is a dual circuit master cylinder with 1 3/4" bore used on Ford B600 buses in 1984-1985, about $150.

The pressure differential switch "seems" to be the exact same one used on.... wait for it...... an early '70s AMC Javelin! I've not found a part number or source for this, but just about any differential switch would work. It's plumbed between the master cylinder and air packs.

One of the air tanks has a baffle installed, dividing it into two separate tanks. I think using the stock air setup would be fine, you could lose boost but you'd still have brakes"




Here's the split brake supplemental manual for modified trucks:

http://www.xm381.com/xm381/TMs_files/TM 9-2320-209-14&P.pdf

The main non-standard parts that come to mind, that aren't over the counter, are; master cylinder mounting bracket, brake pedal "arm", differential switch, split air tank.

The differential brake switch seems to be the same one used on a AMC Javelin but could be sourced from another vehicle or omitted. It is not a proportioning valve, it's a switch. It lights the dash brake light if you blow a line and seals off the blown line.

You could omit the split air tank too, you'd loose boost redundancy if you loose air pressure but would not loose the brakes. A third air tank could also be used instead of the split tank.

I've not yet converted my truck, it's on the "to do" list.

This is what I think I know.

gimpyrobb said:

The mounts for the winch controls are on the side of the master cyl. The A3 master cyl doesn't have the winch control mounts because it's winch is hydraulic.

Click to expand...

Look at the useable on codes on page F-5 M35A2 W/W and M35A2C W/W are included. If you look in the A3 manual 9-2320-386-24P, The A3 uses p/n 2233867 for the Master CYL, 12448508 for the Bracket, and 2232244 for the resevoir. Those are different part numbers than what this manual is calling for an A2.

mikew said:

The differential brake switch seems to be the same one used on a AMC Javelin but could be sourced from another vehicle or omitted. It is not a proportioning valve, it's a switch. It lights the dash brake light if you blow a line and seals off the blown line.

Click to expand...

The valve I listed is P/N 5934092. That is the same one you show as a differential valve in the same manual. The NSN is 2530-01-257-7705, which is a proportioning valve made only by AMG. This info comes straight from WEBFLIS. FYI

I suspect the the differential valve. p/n 5934092 is only available from AMG... but take a look at this AMC differential switch, it sure does look identical!

That being said, I've not been able to find a source for the AMC one either.

Now, if the AMG one is simply a differential SWITCH that lights the dash lamp on failure (which the supplemental TM seems to indicate) it could be omitted or replaced with any differential switch.

As far as I know, true proportioning valves are only used on vehicles with front disk and rear drum brakes.

mikew said:

As far as I know, true proportioning valves are only used on vehicles with front disk and rear drum brakes.

Click to expand...

This is correct. True proportioning valves break up the distribution of brake pressure. Since disc brake vehicles do anything from 60 to 80% of their braking on the front, they proportion more pressure to the front.

An all drum brake equipped vehicle like the deuce probably has a "distribution block", which divvies up fluid to individual circuits, as opposed to proportioning it.

Someone who has the hummer manuals look up this distribution block/proportioning valve for one of them. I just got off the phone with a parts distributer who has the same NSN listing and they say it also fits the Hummer and they are $135.20. That would only leave the master cylinder mount left to be able to buy a whole system in parts.

For those trying to follow along:


A PROPORTIONING VALVE is a valve installed into a brake system that limits the pressure to the rear brakes. When a vehicle is braking, its weight shifts toward the FRONT of the vehicle. This weight shift reduces the traction of the rear tires and limits the amount of stopping power that they generate. The result of this, were it to continue, would be the rear wheels locking, the vehicle becoming unstable, and a spin could/would occur.


“The best braking performance is achieved when the front brake lock just before the rear brakes”. (Automotive Brake systems 4th Ed, Pearson Prentice Hall)


A device that provides means to correctly PROPORTION the hydraulic force delivered to the front and rear brakes is essential to proper braking.


That device (or process) could be as simple as a smaller piston or orifice out of the section of the Master Cyl that provides hydraulic force to the rear, a “balance bar between two master cyls (one for the front brakes, one for the rear, or a valve that regulates pressure. It can also be down with different sized wheel cylinders front vs rear.

It should be noted that one vehicles weight and weight distribution is VERY different than an others. Also vehicles with disc brakes are VERY different then vehicles with DRUM brakes.

An off-the-shelf proportioning valve is not a one-size-fits-all type of device.

ADJUSTABLE Proportioning valves are available from various performance parts suppliers such as Summit.

oddshot

For those trying to follow along:

A PRESSURE DIFFERENTIAL SWITCH is a device installed in a DUAL CIRCUIT brake system that senses a failure (a sudden leak) in one or the other circuit. If one circuit develops a leak, the fluid pressure in this device pushes the spool valve off its centered position, and closing the contacts of an electrical switch that will light a warning ling on the dash … alerting the driver to something he already knows … there has been a loss of one circuit … and his brake pedal is suddenly a bit closer to the floor and a bit mushier then normal.

Much like the switch in the cap of a master cylinder reservoir that senses fluid level, the driver who pays attentions to these things has no need of either a pressure differential switch or a fluid level indicator.



oddshot