I just rebuilt my land cruiser's booster, so I am recent on the topic of
boosters.
They are usually bolted between the pedal assembly and master cylinder
assembly, thus someplace on the firewall. What they consist of usually is a
big rubber diaphragm with several valves controlling where the vacuum
"flows". The diaphragm chamber connects through a stiff (don't want the hose
to collapse) line to the intake manifold. As soon as light pressure on the
pedal and pedal pushrod is applied vacuum begins to suck on the diaphragm
which pulls the pushrod forward into the master cylinder to aid you to stop.
When you release the pedal, the vacuum is usually opened up to fresh air,
through a small air filter and the valve to the engine is closed as to not
create a vacuum leak. Obviously they work so well due to the fact that
usually you are not accelerating while braking thus a vacuum is present in
the intake manifold so why not take advantage of it. There are a few
accessories on my Toyota that are vacuum powered. The wipers change speeds
as throttle position changes :P
I also know some other designs actually use 2 chambers, one in front and one
behind the diaphragm. Somehow they play with the pressure difference
throughout the pedal stroke to give you a very smooth nice pedal. Personally
I want a car I can stop when the engine dies :P. When the coil on my Toyota
went south at 65mph on the freeway, it was a very scary experience putting
my entire weight on the pedal, and just slowly brushing off speed.
Oh and the cruiser is a dual circuit design, I see no reason why it
shouldn't work, as long as it is a single piston, dual circuit master
cylinder. (and not some dual master cylinder design with pedal linkages)
Good luck.
Toby
69 Sprite
69 Midget
71 Land Cruiser
http://www.tobysengineparts.com
Thanks for the replies. My uneducated guess would have been for hard ( fear
and loathing :) ) driving where a heel and toe style of driving could be
used without having to stamp on the pedal.
My also uneducated theory would be that any weakness in the system would be
detected early. :(
What does a servo do? Increase the hydraulic pressure in the system using
mechanical advantage or vacuum or what? Looking at the description in VB's
catalogue, it does connect to the 'inlet manifold'. It also states that it
is for single line brake systems. I would want to convert the car at some
point to dual line, for maximum safety. Eventually the car would be for the
kids' use. That's the plan, anyway.
Robert Duquette
Ottawa ON Canada
http://www3.sympatico.ca/robertduquette
RobertDuquette@Sympatico.ca
'65 RHD BRG Sprite
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