Brake booster issues on FC

[123rover50]

Got the first kit , thanks Murray.
Now I am confused about boosters.
Why do we change to the disco one?
Is there a difference in the line pressure?
Does anyone know what the line pressure of these boosters is?
Does the front and rear run the same pressure or is one greater?

On the 6x6 I have no room for the mastervac so am running a VH40 for the front discs and a VH44 on each back axle. I now know this is not enough as the 44 only puts out 900 odd psi and the 40 does 1400 psi or so.
I was wondering how this pressure compares with the original boosters.

Help appreciated.
Keith

[Lotz-A-Landies]

Got the first kit , thanks Murray.
Now I am confused about boosters.
Why do we change to the disco one?
Is there a difference in the line pressure?
Does anyone know what the line pressure of these boosters is?
Does the front and rear run the same pressure or is one greater?

On the 6x6 I have no room for the mastervac so am running a VH40 for the front discs and a VH44 on each back axle. I now know this is not enough as the 44 only puts out 900 odd psi and the 40 does 1400 psi or so.
I was wondering how this pressure compares with the original boosters.

Help appreciated.
KeithKeith

Doesn't the VH44 have a range of pressures depending upon suffix?

http://www.pbr.com.au/products/heavy/documents/PBRHydropowers.pdf

[123rover50]

Keith

Doesn't the VH44 have a range of pressures depending upon suffix?

http://www.pbr.com.au/products/heavy/documents/PBRHydropowers.pdf

That is interesting. The brake bloke I talked to seemed to think they only do one now.
I have bought a pressure gauge and will be making some adapters and just seeing what my line pressures are. I will compare the 6x6 with the disco, 110 and the unboosted series for comparison.
By the way , welcome back, hope all is OK.
Keith

[Lotz-A-Landies]

I couldn't say whether it's an improvement or not, but just part of the Australian content requirement for the tender when they purchased the Perenties. Although they are easy to find as they were also on Fords and Commodores about the same vintage.Wasn't the PBR mastervac a larger diameter booster than the one being used on the civvy 110 at the time? Rover only increased the 110 booster in later models.

Keith

Am I correct in assuming you're using the in-line boosters because of the lack of space in front of the firewall? If that is the case will comparing the Disco and Defender/110 with yours be relevant.

Diana

[123rover50]

Wasn't the PBR mastervac a larger diameter booster than the one being used on the civvy 110 at the time? Rover only increased the 110 booster in later models.

Keith

Am I correct in assuming you're using the in-line boosters because of the lack of space in front of the firewall? If that is the case will comparing the Disco and Defender/110 with yours be relevant.

Diana

Thats right, the big Ford master only just squeezes in.
No one can tell me what the line pressures are for the disco and 110 so I am doing that just to compare.
It was mentioned that changing to the disco master from the 110 master was more a function of volume of fluid than pressure as the discs apparently need the higher volume.

[Judo]

Thats right, the big Ford master only just squeezes in.
No one can tell me what the line pressures are for the disco and 110 so I am doing that just to compare.
It was mentioned that changing to the disco master from the 110 master was more a function of volume of fluid than pressure as the discs apparently need the higher volume.
I'm some way off starting my conversion, so I'm interested to see how you go with this research. :)

[isuzurover]

...
No one can tell me what the line pressures are for the disco and 110 so I am doing that just to compare....

All the hydraulic pressures and forces are easy to calculate if you have all the piston diameters and dimensions of valves and booster diaphrams (and whether single or double).

[123rover50]

Thats all too hard for this old buggar. 50 years since I left school.
I would rather build stuff:)

But you would think these figures for stock vehicles would be available.:(

[Lotz-A-Landies]

Thats right, the big Ford master only just squeezes in.
No one can tell me what the line pressures are for the disco and 110 so I am doing that just to compare.
It was mentioned that changing to the disco master from the 110 master was more a function of volume of fluid than pressure as the discs apparently need the higher volume.
I've been thinking about going air over hydraulic from something like a 5 tonner UD or similar.

Has anyone had any experience with those systems?

[123rover50]

OK, made up the pressure tester today then rigged up my little camera onto movie mode and sat it on the tripod.
Started the engine and these figures are at idle speed.
The rear drums on the 110 read 1300 psi.
The rear discs on the 92 TDI Disco read 1800 on the first pump then 900 then 700. I guess because at idle it has no reserve.

These figures on my 6x6 are of no use to anyone else as I have remote boosters, not the mastervac.

Rear drum axles each with a standard PBR VH44 read 900 psi on both.
Front disc axle with a standard PBR VH 40 read 2000 psi on the first pump with 30" HG on the gauge, then 1600 with 28" HG, then 1500psi with 20" HG on the third pump.
The vh40 is rated at 1400 psi so I imagine they are all rated at 20'HG.

So with my setup the 900 psi is too low for drums or discs so my problem is do I put one VH40 for both rear axles or replace each VH 44 with a VH40 for each axle.

Keith

PS. Thanks Murray the third kit arrived today.

[123rover50]

Yep got a tank. Once it got down to 20"HG it pretty well stayed there even at idle. That gave the 1500 psi on the front. As you say it weighs over 5 ton and the 900,s on it give more resistance to stopping than the 7.50,s would.
The pressure in the disco dropped faster with each application.
Asked around about the VH90,s but seem to be like Rocking Horse Poo:(
On that table their max pressure is 1460 like the VH40 but with a much lower input pressure. I understand the master has to be bigger in the bore for more capacity hence the lower pressure.
I dont really want to change the master yet.
I can get a high pressure VH40 for the front discs then put that standard VH40 on the back. That should give me higher pressures all round.

[123rover50]

I wont hijack your thread any more Murray but just for comparison I put the gauge in the 1954 86" I am rebuilding.
With about the same pedal pressure I was using before I got just on 1000 psi unboosted, std SWB master.
Thats more than the VH44 gets:o
Keith

[Lotz-A-Landies]

I wont hijack your thread any more Murray but just for comparison I put the gauge in the 1954 86" I am rebuilding.
With about the same pedal pressure I was using before I got just on 1000 psi unboosted, std SWB master.
Thats more than the VH44 gets:o
KeithHi keith

Was discussing this with cookey who's just started manufacturing a disk brake conversion for the front of the series LR. He suggested that you need at least 1200 psi to have reasonable braking.

Maybe you could migrate the VH44 to the clutch line and have a soft clutch pedal!

In regards to the actual setup for the FC, I've been considering making a pivot and crank arrangement on a six cyl pedal box to turn the mastervac 90 degrees to the pedal direction, the booster would be bracketed off the LHS off the clutch pedal box and the master cylinder beyond that above the radiator. The idea came when I looked under the bonnett of an XF Jaguar, where in the RHD models there is a cross shaft across the top of the engine with the mastervac sitting on the LHS in front of the passenger.

Diana

[123rover50]

That sounds a good idea. Something that I had not considered at the time.

[bobslandies]

Hi Keith,

Have a look inside the dash of a bus or forward control truck. Often the brake master cylinder / vacuum booster assembly is at 90 degrees to the pedal inside the dash. My old Coaster was like that and I thought that may be adaptable to a LR Forward Control.

Bob