Packard Forum Index » General

Quote: "The boost of the dual is considerably more--almost equal to a 10-- than the single according to a guy who published numbers. Was just wondering how that translates to real world. I would think that it should make a big difference since the BTV was approx 5 1/2 albeit with a smaller diameter cylinder which throws another variable in."


I don;t see what single line cylinder vs dual line cylinder has to do with the amount of boost ASSUMING same diameter MC's are used.


Bottom line: my F explorer conversion is just as good as any other modern day car with dual line MC in terms of feel and sensitivity and stopping power. Just as good as my very pristene low mileage original 01 Dodge ram 1500 and pristene original low mileage 89 Caprice or ANY other modern cars i've driven with power brakes.

I am talking boosters only. Believe the masters are the same on the last few conversions mentioned here - 1" dual or tandems.. Yours and Turbo's were are in a different location with different pedals and power units so not quite sure if same feel or response would happen there. Jerry also used the same universal booster and cylinder but IIRC, his is with a different pedal ratio.

Boosters I am asking about is the universal 7" single diaphragm Craig used and is happy with vs the 7" dual diaphragm the other guys used--and is the one I'm thinking of using. Force out data is so different, am asking some questions.

Example: Assuming same pedal input, according to the comparison chart, at 15" vacuum and 100% efficiency, 7 single is 289 additional pounds force out whereas the 10 single (which 7 dual is supposed to be almost equivalent to) is 589. With all else being equal, a fairly substantial difference. Reason I asked about vacuum was each additional inch raises force out by approx 25 pounds so 20" vacuum on same units, same conditions would be 385 and 785. Again, substantial difference. Any real world would be less because units are only 80-90% efficient.

If the pedal is sensitive on those duals or with little travel or effort before brake action that might be an issue if I go that way rather than use the single. If the feel and action is good to the guys that have it, then will probably stick with that unit and ratio since I have it and not think much more about any changes. With the shorter unit though, some advantages. Could possibly revise the levers and get the rod down in a more original position and probably all under the floor with no bulge. Much as I'd like the shorter single benefits, am still concerned. Most of the guys writing brake articles recommend duals if possible.

I know the only real way is to measure actual line pressure between BTV and the others but am aways off from being able to do that. Don't want to buy a single just for that purpose but will probably wind up doing it just because I am curious. The master is going to make a huge difference as well. 3/4" master puts out less volume but almost twice as much psi as a 1", all else equal. BTV with ram and even smaller bore should even increase that psi.

With the conversions so fresh, just wondered how they feel compared to BTV--or even modern cars. I know that is not oranges to oranges comparison since principles are so different but just curious.

Oh! We are talking DUAL diaphragm vs SINGLE diaphragm boosters. SOrry.

I agree with the first post you deleted.. That is pretty much the way the formula was described- I got all that data from heredeanoshiro.com/brakes/brakearticle.html#booster

The small BTV is able to put out the extra force because of the small equivalent master. Just how much that extra force is has got me curious so as to explain how they got away with the 1:1. Also the volume Chevy vs Packard with same unit but different ratios.

There is not that much volume needed if shoes properly adjusted so maybe that is how. Chevy just puts out what was needed but more force & maybe smaller cylinders. Had toyed with a smaller master and single 7 here. Decided to keep things easy to find instead with the 1"--but the single 7 is still under consideration because of the benefits in packaging..

Here's the only Conversion comparison to BTV that is in service i can tell about:

Off the parts store shelf Ford Explorer, NINE inch diameter power unit. 1" master cylinder, 12" overall length of brake pedal lever with power-unit stem attaching to brake pedal lever FOUR inches from pedals hinge point.

I like it. BTV so slightly better in terms of foot effort and 'feel' so as to be negligable.

So maybe u can use that criteria to determine adjustments in sizes to your particular situation.

Yes, i deleted the post because i thot it no longer applied due to suddenly realizeing that we are talking about DUAL DIAPHragm boosters, not single diaphragm.

I'll add it back rite here:

Here's the way i think it works:

Engine vacuum is only used to exhaust or diminish the atmospheric pressure in the front 1/2 of the power unit. THus NORMAL atmosphereic pressure is doing all of the work on the pedal side of the power unit.

APROXIMATE conversion: 2 in hg of vacuum = 1 #/in**2.
SO 2 inches of vacuum = 1 psi of force.
i.e divide the vacuum gauge reading by 2 and that will yield the PSI force on the power unit.

Therefore: 15 in-hg of vacuum = 7 pounds/sq.in of force.
SO:
10" diaphragm = 3.14(5**2) = 78 sq inches x 7 psi = ~560 pounds of force OUT.
7" diaphragm = 3.14(3.5**2) = 38 x 7 psi = ~ 280 ponds out.

5.5" diaphragm = 3.14(2.7**2) = 24 x 7 = ~175 pounds out.

Well, rod change doesn't look viable.

Now looks like about the only advantage size wise changing to single 7 booster is to maybe recess it some more. Not sure that's a big consideration as bulge is felt but minimally visible under carpet.

Hope bhappy or walkerman or anyone else with a dual 7 diaphragm booster can give me their impressions on the performance and if they would do anything differently now that they had a chance to drive a bit.

Still looking for any info on how far the clutch comes over from Left kickpanel to see if it falls in that 3 1/2 or so inches available.

HH56 wrote Quote:

I hope we get driver feedback too. But, be that as it may, why don't you take my single 7in as a "nominal" install. The foot pedal pressure is very satisfactory to me at least. The line pressure resultant from easy to hard foot pressure is very satisfactory (to me) from a drivability point of view. I can lock up all four wheels brakes with hard, but no undue pressure. I would not change anything on my current install, but of course I am used to the relocated pedal.

Since your pedal-multiplier setup does not significantly change the "foot feel" of the brake pedal location, I do not see where anyone would have an objection to it.

One point I do not see addressed is the original toe plate. My 7in booster setup used the stock toe plate with only minor relation of the mounting holes. How does yours work? Specifically, is the original toe plate used in modified form or does your conversion replace same?

Craig

I'm sure that everyone, especialy HH56 is more than just tired of my opinions. But if a single line MASTER CYLINDER will free up more room to allow for power unit size adjustemnets and positioning then i would not hesitate to use the single line Master Cylinder. Not hesitate at all.

In fact all of this has me looking for a single line MC for my already completed and operating conversion.

Brake pedal will have a single hole for a bolt that will be hidden by pad, but otherwise support and plate are new.

Decided not to use the old plate because without slicing and dicing, the depressed and angled area didn't work with where things had to go.

Making the bracket will require some fabrication and welding so not the easy bolt in yours is. Am sure I went overboard a bit also, so am still trying to simplify a couple of things. If I can build it though, anyone else with a decently equipped shop can too--they just need to be a better welder than I am or take it to a professional..

Anyway, just an exercise in possibility and option for someone who wants to keep a mostly original interior look. Don't expect there will be many takers.