Adding a power brake booster.

The VH44 and other similar types have two pistons in them. One is operated by hydraulic pressure from the master cylinder and switches the vacuum operated (2nd) piston into action as required.
So; the two are hydraulically plumbed in series. Theoretically, you can mount the VH44 anywhere on the vehicle.

On my VC Regal 8 Safari (miss it dearly) it had discs on the front with the booster plumbed only into the front brakes.

Jarrod.

The firewall mounted car systems are the equivalent of the old Bedford "whistler" booster with a rod and pivots from the footpedal...............I would not drive any hydraulic braked vehicle on the road that wasnt dual circuit from the booster ,and preferably dual line all through ,as is the case with all the firewall mounted car and LT systems......Ive had the pedal go to the floor too many times in the days when there was always an escape route......

No eBay APP ID and/or Cert ID defined in Kunena configurationDave

It is an in-line unit that boosts your normal pressure. It is not the type that has a connection to the master cylinder.

Here is a simple explanation.
techtalk.mpbrakes.com/boosters/remote-mo...sters-vacuum-booster

This is what I have put in 4 vehicles (you can get larger size if required). Standard single line booster for all original brake plumbing. I am still looking for the dual outlet one.


lang

Thanks, Guys!
OK, got the gist of it now. Lang, one of those links you sent show a dual circuit, dual diaphragm booster for early muscle cars. I'm thinking along John.K. 's line, maybe the bigger VH90 or evenVH80 may be big enough.
The one fitted to the Gamecock is of the earlier "Hydro boost" or "Hydrovac" , which is irrelevant anyway as it wont fit.
Don't have one to trade in, so may be able to work something out with supplier.
One thing though, with those earlier VH44 type of booster, commonly fitted to Ford, Valiant , Holden whatever, were they mostly fitted to only the front brake (if drum) circuit? OR, were they single line from the master cylinder to the booster and then either went to a "block" where they were distributed evenly to all four wheels?
I'm thinking along what John.K. said about the dual circuit lines from the booster to the wheel cylinders.
Just kicking this around, but IF the booster were only hooked up to the front brakes, as has been done apparently, wouldn't you have problems with uneven brake shoe wear?? Seems to my way of thinking, you would either be constantly replacing front shoes, or have the fronts locking up, neither a good scenario. Probably some sort of brake proportioning valve may negate this, even should it be fitted after. Seems a lot of ginning around .
Another thing I was told earlier tonight, when "dual circuit" brake plumbing came into general acceptance, it was NOT uncommon for a vehicle to be plumbed "diagonally", i.e. left front/right rear and right/front/left rear.
Going back to the issue with single input (into booster) and even if there was such a way to plumb it so you had DUAL outlet, you could still lose all braking if something went amiss between the master cyl and the booster!
Another thing, somewhere along the system, or within it, I would have thought that you would probably have to have a brake proportioning valve of some sort. Maybe they got away without them early in the piece by having different bore diameter wheel cylinders? OR, different size brake lines?

Dave

My thoughts on your comments.

The unit takes the single line from the master cylinder with a single line out to go back in to the system before it splits front and rear.

Nearly all early vehicles overcame different needs by having fixes:
1. Different size drums front and back
2. Different size wheel cylinders front and back
3. Stepped wheel cylinders to give different push to leading and trailing shoes.
4. Different size shoes front and back or different size shoes on a single wheel

The proportioning valves with a lever connected to the back axle that opened up the rear lines as the truck squatted with extra load was a reasonably modern addition for general production vehicles. Almost everything has them now - try driving a 4x4 ute empty with it disconnected, the back wheels will lock with little provocation.

Just my opinion but I think you are making a rod for your own back seeking a double line braking system. Vehicles went for 75 years without them. Stories of total brake failure sound good but I believe most are after many warnings (leaks, squeaks. soft pedals, poor performance) and the rest from aged rubber - lines and cylinder cups.

Although trucks are not immune from blown hoses etc like everyone else many of the "I have had brakes fail on me" stories are self-inflicted wounds from being slack on controlling their speed on long hills and taking the brakes beyond their design limits. You will be having a brand new system which will outlast all of us before it starts to deteriorate. Dual system does not work any better. it is the boost, from whatever system, that will improve an old wheel cylinder/brake shoe set-up.

I think your beaut little truck can survive and brake nicely on a boosted single system but this is not just about getting a truck on the road it is an adventure so please continue to keep us informed as you try to get the best (or most interesting) engineering solutions. What about double discs all round with electric brakes? We want photos of that project.

Lang

Ok my 2 cents worth

Scratching my feable and at the moment overloaded brain
I think Dave your onto it and what your trying to achieve is what we all should be trying to achieve

I recall that you have a diesel motor out of a Landrover or some such thing in this machine ? Hence the vacumm pump
If this is correct you will need a vacuum tank as and it will need a non return valve to hold vacuum if the motor stalls
Or even if you are driving normally and apply the brakes a few times in close succession like tight maneuvering as the little vacuum pump wont be able to keep up

So hope that makes sense

Next is dual circuit power boosted brakes
With out getting to overly complicated
There are dual circuit master cylinders out there, whether they have the correct bore stroke ratio I dont know, you will need to investigate that your self

If you found one that was suitable you could simply put two inline power boosters in, one on the front end and the other on the ass end

If this route was taken I feel you would need to vacuum tanks

If you couldn't find a suitable dual master cylinder is there any reason you cant have 2 separate master cylinders off the pedal ? I think it should be fine provided they are joined properly to the pedal

Some things to consider

If you split the brakes up you will need to redo your maths on volume and bore and stroke of wheel cylinders to master cylinder
As the volume of fluid getting shifted is a lot less per stroke

Dunno if this helps or hinders but its things I would consider

Paul

Maybe easier to just connect a booster to the front brakes, surely they take the main brunt of stopping generally. It would simplify your connections Dave.

My experience of these old trucks is locking the brakes on any wheel is about as likely as winning lotto...twice......Most of the older Jap trucks with hydraulic brakes had two small but completely separate vacuum boosters .

Thanks for all the help, fellows!
Sometimes it is easy to overlook a very simple explanation, even when it is so obvious.
I have been corresponding with a few people away from this forum and have been given what would seem to be a logical answer.
These vehicles were supplied to Govt departments like Parks and Gardens, City Councils etc, in several states by the Rootes Group, they were basic, cheap and did the job for what they were designed for.
They also came in several variations. Entry level may have been say, 13" wheels to lower the loading height for tippers, basic gauges in the cab, NO vacuum assist with brakes and so on.
Next level up and sold to a different clientele, had 15" OR 16" wheels (depending on year ), had more comprehensive dash layout, heaters, AND Hydrovac assisted braking. Many of the sewerage slurry tankers, and similar adaptations would fall in there.
Makes sense when you stop and think about it.

So, Mrsmackpaul and PDU, lang and John.K. everybody else who offered advice, thanks again!
Whilst I have the shed off and its easy to get to, I am going to suss out a very basic vacuum assist like several of you guys threw out there. Maybe a simple single line from the original resleeved master cylinder to a VH 80 or VH90 type chassis mounted booster, a single line back to the junction where it splits into front and rear, a chassis mounted vacuum tank ( plenty available as after market on flea bay!) with a check valve and a line from the vacuum pump on the engine to the vacuum tank.
Several schematic diagrams available on the net, look pretty simple.
Let you know how it goes, Cheers, Dave

Good luck Dave. I for one reckon you have chosen the best compromise path KISS

Lang