Vacuum actuating valve on early Commer

Hi, Can anybody tell me how the valve works to allow engine Vacuum to enter the Booster? The truck is a 1951 Commer QX R7 with the Clayton Delwandre systerm. It is a double valve and I can see how it helps apply the brakes but I cannot see how the engine end of the valve comes off its seat to connect the engine Vacuum. Obviously it comes off its seat some how to allow the Vacuum in, but I am at present thinking the valve is not held forward but centred when the brakes are not being used. Any help on this would be much appreciated, I do have a maintainance manual but it is confusing as to how this works. Cheers Hommie

Might it work something like a PBR where the vacuum is controlled by the small piston under pedal (hydraulic) pressure?
(input side, before the output piston)
I had to have one in bits and the book there to work that one out.

Jarrod.

Hi Jarrod, Good news I've managed to work it out last night after a long look at the lever mechanism fulcrum set up in the front of the housing. It certainly is an amassing set up the way it works, it pulls and then pushes the vacuum valve to introduce the Vacuum and then opens the atmospheric valve to release. Thanks for getting back to me on my problem. All good now Cheers Hommie

Guess n the reason U aint gunna find much info on the workings
is cos of saftey....... they probly dun wanna see people playing with the gizzmo
and prefer U buy a new one ..... coz if it fails ......... U'll B 1st to kno bout it
cya
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