105 Dual booster brakes

[Dana Loomis <dloomis@domain.elided>]

In AD V8 #1130, Bob Wilkinson said:
>Perhaps this should be off-list, but mayby I'm not the only ignorant one.
>What is the reason for the RHD dual booster systems?  I've seen pictures,
>and have assumed that some space limitation prevents a booster in its usual
>place--behind the dual MC.  How does it work?  Is there one MC, feeding
>hydraulic fluid to two boosters?  Or a dual MC, one to each booster?  I'm
>assuming that the boosters are hydraulic-in, hydraulic-out, not mechanical
>in/out like ordinary ones??  

I'd submit that this is exactly the kind of discussion that should NOT go
off list.  

My supposition is that the complex dual booster system was conceived as a
stopgap solution for models destined for relatively limited production. It
was a way of providing power assist to the front and rear brakes of cars
that had both the early type of under-floor master cylinder and dual
circuit brakes.   Essentially the same system was used on 1969 (only) US
model cars and RHD cars from about 1970 onward. The boosters were of the
Lockheed type, acted in-line with the hydraulic system and were mounted
remotely from a dual circuit master cylinder under the floor, with one
servo for the front circuit and another for the rear.  

This system was dropped from the US model through a 1970 redesign of the
pedal system that affected all LHD Alfas.  The new system involved the more
familiar top-pivoting pedals and a mechanical booster mounted between the
brake pedal and the master cylinder.  All cars with this system also had
dual circuit braking, but I don't know whether the move to dual circuit
brakes on European models was required by regulation or a voluntary change.  

Presumably the older system with floor mounted pedals and dual hydraulic
boosters was kept on RHD cars because the intake system made it impossible
to simply transplant the new LHD pedal box, booster and master cylinder to
the opposite side of the car.  Sales expectations for RHD markets probably
didn't justify re-engineering it all, so Alfa kept a system that worked (at
least when new) and solved the space problem.   Interestingly enough, a
number of British cars, including the MGC and the Rover 2000 used a similar
setup, so it probably seemed rational enough to owners in RHD markets. 

Dana Loomis
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided