Re: 5000 brake booster (servo)

[cordeiro@adi.com (Alan Cordeiro)]

Hi Frank


>> Before I rebuilt mine, I considered getting
>> an ELECTRICAL 12 VOLT PUMP, with a cutoff switch and a pressure
>> accumulator. It would take the constant one or two horsepower
>> load off the engine and put it onto the battery. This pump would
>> only run when the pressure in the accumulator fell below
>> 2000 PSI. I can get manufacturers names if anyone wants.

>This is not a bad idea, tho you may find that the pump is hard to
>mount, and it may end up running most of the time.  Also, keep in mind
>that the accumulator is only used for the brakes, not the steering rack.

Perhaps I should clarify the options;

1. One large electrically driven pump, 2000 psi, and one fairly
large ( three or four times the present one ) pressure accumulator.
The pressure accumulator would have a pressure switch on it which
would turn off the pump once the set pressure was reached. Power
steering and brakes would be run off the accumulator.
Negatives would include loss of some brake boost when the
steering had been used vigorously for some time.

2. One pump, one large accumulator, and one small accumulator
(perhaps we could just use the present brake booster one ) for
the brakes.

3. Two pumps, two accumulators, (twice as many headaches, twice as many chances for leaks and problems, perhaps this devil we don't 
know is no better than the the devil we already know so well ).

Anyway, its food for thought, the best benefit may come from
removing the constant one or two horsepower load from the
driveshaft belt, and replacing it with an intermittant load
on the electrical system. I'd hesitate to put a larger
number on the constant horsepower draw of the present system,
but take your best guess.

The present pump system keeps the pressure constant at the 
brake booster by letting excess fluid overflow ( higher pressure
bypass valve on the accumulator ) back to the reservoir. The 
steering system high pressure circuit cleverly uses the the back
section of the pump as a built in accumulator for that circuit,
and has a high pressure bypass valve that just returns excess high
pressure oil back to the center chamber where it is re-circulated
( and heated up, thereby rapidly accelerating the demise of all
rubber components in the pump and power steering system ... ) back
to the high pressure side ...
( Needless to say, I've studied the pump and the design of the
hydraulic system  at considerable length, during my re-building
experiment ).

Alan Cordeiro
from by last rebuilding experiment