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Manumatic transmission was a great idea. As the name
implies, it is a half-way house between a manual and a fully
automatic gearbox, doing away with the clutch pedal but
retaining the gear lever. To quote the description in the
manual ‘With the aid of the Manumatic Transmission
System, a perfect gear change requires no other action than
the appropriate movement of the gear lever’.
In principle the system was very simple. An electric switch
mounted on the gear lever was operated when the knob was
held and caused the clutch to disengage. When the change had
been completed, the lever would be released and the clutch
would be re-engaged.
But while the theory is straightforward, putting it into
practice complicates the issue a bit. The trouble is that,
when you change gear, it’s not just a question of
banging the clutch in and out like a switch. Though, coming
to think about it, there are some (Egyptian taxi drivers
spring to mind as one example), who may not agree. But for
the rest of us, some attempt has to be made to co-ordinate
throttle and clutch to achieve a nice, smooth change, and
this is the part that taxed the engineers in the 1950s.
 Fig.
SA. 1 gives an idea of the apparatus that was required to do
this. It is reproduced from the workshop manual, which takes
four pages to describe how everything works and a further 33
on how to mend the system when it goes wrong. The editorial
blue pencil would undoubtedly be wielded with a vengeance if
I went into detail, so I will try to be brief...
For a start, the clutch is of the centrifugal type, so that
when the engine is idling it is disengaged, but then
steadily engages as the engine revs rise. This means that,
to start from rest, you grasp the ever, which disengages the
clutch, pop it into first and release the lever again. The
car will not move until you pass down the accelerator pedal,
which causes the centrifugal clutch to engage. and off you
go.
When you get bored with first gear, you grasp the lever
again to select another one. And here is the clever bit.
This can be done with the accelerator pedal in any position
- the system incorporates two vacuum operated throttle
servos which control the opening and closing of the throttle
independently of the pedal’s position. One of these is
controlled by the clutch servo and closes the throttle when
the gear change commences.
 The
other is controlled by a solenoid operated valve in circuit
with a synchronising switch on the clutch cover. If the
engine speed falls below the driven plate speed, the
throttle opening servo kicks in to increase the engine speed
and ensure that nice, smooth take-up which all except those
Egyptian taxi drivers aspire to. And to make absolutely
certain, a pedal valve is incorporated in the control unit
which ensures a progressive engagement of the clutch. Fig.
SA.2 Shows how all these bits and pieces fit together and
indicates what is happening when the car is at rest and in
gear.
The last picture clearly shows the black control box mounted
behind the engine on top of the bell housing, together with
the linkages from the two servos to the throttle.
 In
nearly 20 years of attending Magnette events I have never
seen a Manumatic car, and the Register has details of only
three or four that are know to exist, none being road
worthy. Records show that a total of only 494 were produced,
most of which were exported to North America.
So why was such a clever system such a flop? A clue is given
by Peter Woods’ own car, which he bought for a snog
from a main dealer in Oxford because the transmission was
faulty. The cure was simple - two of the wires in the
control unit had been swapped over by a puzzled fitter and
when they were swapped back, all was well..
The basic trouble with the system was its complexity; it
incorporated a large number of components of unique design,
which had an almost infinite capacity for failing. This
seems to have been combined with an inability of BMC dealers
to diagnose the faults properly when they occurred. So it is
hardly surprising that the system rapidly got a dreadful
reputation, second-hand values plummeted and many of the
original cars were converted back to standard form by
frustrated owners.
Written by Paul Batho
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