Split Brakes

[mudguppy]

...ELECTRIC BRAKE BOOSTER VACUUM PUMP :eBay Motors (item 330370881621 end time Nov-22-09 11:24:27 PST)

um, it may not be the seller's fault, but i want to you be aware that there is no such thing as "18 - 22 psi of vacuum". you can't create more vacuum than there is in the atmosphere. and since atmospheric pressure is ~14.7psi at sea level, we usually represent full vacuum (FV) as -15psi or just put "FV".

so, assuming that the seller has mixed up his units, it could be 18 - 22 in of H20 or mm of Hg. either way, it's not that much.

OR,

the psi value could have been derived by measuring the output if used as a compressor to create 18 - 22 psi. this could be the case. if so, then it might make FV.

just remember about reliability: when your [ebay] vac pump dies, you have no brake boost. when your engine dies (w/ hydro boost), you still have brake boost by keeping the engine in gear (manual trans).

 

[Chinookpilot77]

I hear you about the psi...however, almost all the other ones I looked at were in inches of mercury, not water, and not mm. I was just linking those for examples, not the ones I found to actually use. 22-24"hg seems about the standard in hot rod vacuum pumps. I actually found two relatively cheap, so I was thinking about using both for redundancy.

The 5 ton pumps do bolt on under the IP. Does your pump reach over the the genny or just extend out to use the compressor? I assume you meant compressor?

I am still kicking around ideas. I dont think it'd be too horribly difficult to just add another deuce MC and booster....but then I worry about valving and equal braking around the four wheels...the install might be ok, but then setting it up and adjusting everything could be a giant PITA. Keep the ideas coming Mudguppy, this is some good poop.

Check out the specs here mudguppy, this is the one I'm thinking about. (maybe two set up with a check valve for redundancy) http://cgi.ebay.com/Thomas-Industri...m5636585eddQQitemZ370278948573QQptZBIQ5fPumps

 

[mudguppy]

24" Hg is 11.8 pounds of vacuum - that's pretty good.

no, i meant alternator - i just didn't know where the 5 ton pump bolted on to. so when you said the spot above the alternator is spoken for, i thought that is where the 5 ton pump went and that is why you can't use it.

my pump is mounted, i guess more to the side, of the IP. the [single] belt goes on pump to the front crank and fan grooves and clear across to the front alternator groove. the rear alt belt goes around just the crank and fan - a little odd having two different belts around different accessories, but it seems to work well and i carry spares of each belt.

so, why don't you use a 5 ton pump? sounds like the easiest setup...?

since my pump will be gear driven off the cummins, i'm thinking my best option will be to just get a '99+ F450/550 MC (large volume 4 wheel disc system) and just hydro-boost off of the power steering pump. a simple adjustable proportioning vavle can be installed in-line on the rear circuit to fine-tune the rear. i truly believe the most difficult part will be hanging the pedal assy on the firewall. but i think this will be straight forward since i have my dodge 2500 as a donor for clutch/brake pedal assy.

i have considered hanging a second pump off the motor (in the A/C compressor spot?) for either redundancy or individualized hydraulic circuits. but with individual circuits, loss of a belt leads to loss of either brake boost or steering - not sure which one i want to be w/out. redundant pumps would require check valves, a pressure relieve valve, and a good bit of extra hoses. plus all the added volume would mean an even bigger cooler for the system. too complicated.

i think i'll go w/ the first option. and if my source comes through with machined rotors and caliper brackets in time, i'll just do the entire disc brake conversion at the same time.

 

[Chinookpilot77]

Thats another problem I've run into, I want to find a large vacuum assist for 4 wheel discs, but still use my drums. I figure between a dual diaphragm booster and using one meant for discs will help create the pressure to the wheel cylinders while still using drums from a larger system at the wheels. Disc MC's have larger volume and create higher pressures than do drum MC's, so I'm thinking I can probably get away with a 1 ton truck's donor parts. My deuce will never be loaded, and I think she's only around 10k now that she's bobbed. Nothing a 1 ton brake system can't handle I wouldn't think.

I just need to find an MC that isn't divided disc front, drums rear.

Sound reasoning you think?

And honestly, for some reason, I think this system would be just as reliable, and an easier install. I dont have to open the engine up for possible leaks, I dont have to take out the radiator or remove any parts at all, other than the stock brake system once the new one is up and running.

Oh, and if the vacuum fails for whatever reason, there is still a mechanical linkage there that will allow me to stop. I ran a deuce 100 miles or more with no air assist, its not fun or easy, but she'll stop with enough force on the pedal!

 

[mudguppy]

... Nothing a 1 ton brake system can't handle I wouldn't think.

I just need to find an MC that isn't divided disc front, drums rear.

Sound reasoning you think?...

i'm with you all the way. and the big 3 went to 4 wheel disc as an option toward late 90's and standard early 00's. so finding a 4 wheel disc MC should be pretty simple...

i just searched for a MC and brake booster - about $80 for a new '00 F350-F550 MC and $150 for a reman'd hydro brake booster (w/out core). throw in some tubing, fittings, proportion valve and get to bending!!

 

[Chinookpilot77]

I have a guy that does hydraulic work and said he'll fabricate up full stainless steel braided lines for my deuce. I checked the specs and they are 6000 psi brake lines. also, I checked the stretch factor on those and its only 1.7%. I am going to have him make me a full set when I switch over to the vacuum booster and MC. wish me luck, the project starts soon!

 

[mudguppy]

shoot, let me know what costs look like - i may be placing an order w/ 'your guy'.

 

[stumps]

This guy: Classic Tube - PreBent and Custom Stainless and OE Brake Lines and more..., makes up stainless steel flexible hoses that meet all of the DOT tests. He wants about $18 each for the deuce front hoses.

I think it would be a good idea to have the DOT testing on anything you add to the braking system that isn't OEM.

-Chuck

 

[Chinookpilot77]

Understood Chuck, thank you. I am just going to "assume" that these hoses will out perform anything designed for the road since they were designed for the flight control hydraulic system of a helicopter and the specs I have found far out perform anything designed for the road. I'd use somebody like that, but I am going 100% braided, no straight steel anywhere.

I do however need to know how much pressure a stock deuce is putting down at the wheel cylinders. I heard 1800psi somewhere, but that seems high to me. most drum brakes only require around 300? disc brakes around 1000.

 

[mudguppy]

i also heard a max of 1800psi from the airpak.

 

[stumps]

Is there some particular reason you want to go braid the whole way?

It would seem to be to be more rugged to use SS tubing for the runs that could be affixed to the frame, and braid only for the flexible sections. My reasoning has to do with expansion of the tubing. Even the best braided tubing expands much more than steel tubing. Any expansion will appear to you as a spongy pedal.

-Chuck

 

[mudguppy]

i, too, have tried to talk him into using SS tube for the straight/longer runs...

basically, when i redo mine, there will only be 4 braided / flex lines: 1 at each knuckle and 1 for each frame-axle drop down. i just think the tube is a lot more rugged. and, sometimes bending tube can be fun.

 

[stumps]

I intend to replace the original rubber/dacron hoses with SS braided hoses from the link I posted. The only thing holding me up from ordering is I don't know for certain the details of the current hose fittings. I am pretty sure that they are straight 3AN or 4AN female, but I would rather not break my system down more than the once.

Anybody know for sure what fittings are on the standard deuce front brake hoses?

-Chuck

 

[Chinookpilot77]

Is there some particular reason you want to go braid the whole way?

It would seem to be to be more rugged to use SS tubing for the runs that could be affixed to the frame, and braid only for the flexible sections. My reasoning has to do with expansion of the tubing. Even the best braided tubing expands much more than steel tubing. Any expansion will appear to you as a spongy pedal.

-Chuck

The only reason I'm thinking of doing 100% braid is cost and ease of installation. The lines will be free, so I'll give them a shot. Less connectors, no bending of tubes. Aviation grade hydraulic line is spec'ed to swell less than 1%. They are filled with kevlar weave and then wrapped in stainless braid. Bursting pressure rated over 6000psi.

All that being said, if the lines dont work out, or they do swell more than is acceptable on the pedal, I'll do straight runs on the frame, and just keep braided on the drop down and the axles themselves. Ill keep you posted.

I'm starting to second guess my use of a f450 vacuum booster though...we'll see how it works out. I can always change to a hydro boost if this isn't enough. time will tell.

 

[Chinookpilot77]

Any idea if the deuce uses residual pressure valves to keep some back pressure on the drums? if so, what weight are they in LBS?

 

[CARNAC]

NSN 2530-01-257-7643 Dual Circut Master Cylinder

All 3 listed below are the exact same part.

Bendix part # 2232693
AM Generals part # 5934071
TACOM's part # 12357047

Another useful tidbit is the Bore Diameter is 2.742 inches min and 2.747 inches max

Emmado,

Made it to page 3 on this thread and the eyeballs gave out.

1. Where can I find the dual circuit installation instructions or MWO for this for the A2 or would I just go by the A3 directions?

2. So basically these are the parts for the A3 that are needed to split the system in my A2?

TIA

CARNAC

 

[G-Force]

The Bendix number is an obsolete number according to Bendix. The Bendix number for the A3 master cylinder is still a good number according to the Bendix website but there are no specs available. You would have to contacrt Bendix about it I would guess. The only difference is that the A3 is a remote reservoir and the A2 is not.
Also, the A2 brake system uses 1 3/8" wheel cylinders and the A3 system uses 1 1/2" from what I have researched so far.

 

[DanMartin]

Where can I find the dual circuit installation instructions or MWO for this for the A2 or would I just go by the A3 directions?

SMARPI 9-2320-209-14 is a good start....


See below:

 

[jesusgatos]

...the A2 brake system uses 1 3/8" wheel cylinders and the A3 system uses 1 1/2" from what I have researched so far.

Dammit. Wish I knew that before I just installed all new wheel cylinders in mah deuce.

 

[Unforgiven]

I have considered this carefully. There is a reason todays vehicles have dual systems. I have personally experienced failure of one side of such a system (a hose that showed no visible signs prior to failure) and was happy to have the split system. My '59 Anglia has a single system, and I will keep it as such for authenticity in the restoration, but then, it has a 36hp flathead four and a three speed and only weighs 1664#s. How many deuces is that?

The deuce brake system is typical of the era and not hard to understand. The airpack is a bit more complex, but its just a booster, similar to a vauum or hyroboost in effect.

I value all the comments made regarding inspections, maintenance and proper technique and second them strongly, especially on something as old and as big as a deuce. This is why I have all new hoses, WCs with new shoes and hard lines were applicable. After rebuilding the airpack and ordering a new MC, I'm reasonably pleased that the health of the stock single system on my M36 will be up to snuff.

However, Mudguppy is spot on on the redundancy factor. I'm a mining engineer; we have systems on top of systems on top of systems underground.

The comments from Stumps about MC failure point back to my concept of using two stock deuce MCs. The only common point of failure at that point is the mechnical brake pedal/actuation. 'Course, the fact that there a brand new MC sittin on the work bench is driving that motivation a bit too. Guess I could sell the extra MC and buy the dual.

I still think the dual MC is more convenient with less fabrication. Would love to have the Bendix Number is anyone finds it. I was on the Raybestos site looking at the Ford F800 MCs and some chevys. Matching pressure calcs/capacity at the MC and WCs through the system should ensure original design integrity.

MC piston stroke is the one question I am considering. Ignoring differnces in line lengths, etc for a moment. if you use the same MC to activate 4 WCs instead of 6 (focusing on the rear axles), you only need 2/3 the fluid volume to fully brake. Worse only 1/3 for the front. Would the stock MC be too big for service in a split system X 2? I've got a brake/hydraulics ref in the shop I'll need to dig up and dust off the cobwebs, but off the top of my head, I think this is an issue. Would you lose pedal travel before full lock up with two deuce MCs supplying the same spec WCs or does the valving in the two airpacs accomodate that? I'll have to study some more. You could alter the pedal mechanical ratio however to accomdate. Some calcs are in order I think...

If you're going to custom mod a dual master cylinder setup, why stop there? Heck, make it a 3 master cylinder setup. Run extra hard lines to the rear-rear if needed. That way you don't have to worry about proportioning valves at all. And you would have triple redundant brakes.

Just install a pivot system on the brake pedal to negate the "hair trigger" effect from pumping 3x the fluid for the same pedal push.

Or you could run your two master cylinder kit into left & right instead of front/back. Sure it's goofy. But in an emergency it would work. Well, it would work if you have tons of upper body strength to keep the thing on the road. That also would not require any proportioning.

I kind of like the triple master cylinder idea though.

I have no idea how all the air assist stuff works. I'm planning to read up on it real soon. But surely you could tee off the air lines & put a larger air tank on?