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Q.
Where are "ROVERDRIVES" manufactured?
A. In British Columbia,
Canada in a factory with ISO 9000 certification.
Q.
Why did you decide to add overdrives to your product
line?
A. Our sister company WISE
OWL INNOVATIONS INC is a leading supplier of parts
for Series Land Rovers in North America. Over the years
Wise Owl sold many overdrives made by SANTANA and FAIREY.
When supplies of these products dried up, and it was
obvious that there was still a demand for overdrives,
it was decided to make one of our own.
Q.
What models of Land Rover can be fitted with a "ROVERDRIVE"?
A. At present we make the 'SX' model for 4 and
6 cylinder Series Land Rovers and the DX model for coil
sprung Land Rovers fitted with the 230 transfer case.
At the present time, application of the DX model is
restricted to 4 and 5 cylinder diesel engine as tests
on V8 models have not been completed.
Q.
What are the benefits of fitting a "ROVERDRIVE"?
A. The "Roverdrive" is like having
an extra gear on the Land Rover. When it is engaged
it reduces engine speed by 28%. This reduces wear and
tear on the drive train. The reduction in RPM makes
the Land Rover quieter and more pleasant to drive. Used
sensibly the "Roverdrive" will reduce fuel
consumption significantly.
Q.
Can it only be used when you are in top gear?
A. No. You can also use it in other gears where
it will give you some additional useful ratios for climbing
hills. We suggest it not be used in first or second
gear as the torque loading on the overdrive is higher.
Q.
Is the "ROVERDRIVE" similar to the SANTANA
and FAIREY units?
A. No. It is very different. At Rocky Mountain
we have never copied other peoples designs. We always
strive to introduce products that are improvements over
the existing state of the art. In the case of overdrives
it was obvious that the existing designs of Series overdrive
have weaknesses which have shown up over the years.
These old designs use a spur gear train with coarse
teeth which can be very noisy especially as the units
get older. They also use large numbers of needle roller
thrust bearings which never stand up well to the axial
loads imposed on them. The splined couplings used to
connect the overdrive to the transmission are only marginally
strong enough for the torque transmitted and are placed
in an area which is not lubricated well. And the overdrive
reservoirs are pretty small - especially on the Fairey
- which is unsatisfactory in hot climates and the
units tend to blow oil out of the vents on the top.
Q.
How does a "ROVERDRIVE" differ?
A. In a number of ways. Most important is that
we use an epicyclical gear train. This reduces the overall
size of the unit considerably. Using an epicyclical
allowed us to draw on the experience of automatic transmission
manufacturers who have perfected the art of passing
high horse power through compact gear trains very quietly.
Our overdrive is very similar to a stage in an automatic
transmission except that it uses a sycromesh toothed
clutch and not a friction clutch to engage the speeds.
The "ROVERDRIVE" is very quiet. You cannot
easily detect if the unit is engaged or not by listening
to it.
Q.
How did you overcome the problem of having a
limited supply reservoir and the problem of leaking
seals and vents?
A. We think our solution is elegant. We did away
with a dedicated oil supply for the overdrive. When
you first install a "ROVERDRIVE" you put a
litre of oil into the housing. After that, as the vehicle
is driven, a constant supply of oil circulates into
the overdrive and returns to the transfer case. Let
me explain: On the nose of our
overdrive where it fits into the transfer case is a
rectangular hole which points upwards. As the Land Rover
is driven a constant stream of oil from the transfer
case gearing splashes into this hole. At the bottom
of the hole a spiral groove in the output shaft draws
the oil into the overdrive housing. Here the oil flows
through a single large ball bearing into the overdrive
reservoir where it lubricates the gears, bearings and
syncromesh assembly. As surplus oil builds up in the
overdrive it overflows down an annular passage between
the input and output shafts and lubricates other components
before returning to the transfer case. Oil circulates
constantly removing heat from the overdrive. There are
no dynamic seals to wear out and no breather to blow
oil out of the case.
Q.
Not having a dedicated oil reservoir must make the unit
quitecompact?
A. Very compact. It is only seven inches in diameter
and conical in shape. Much smaller than other overdrives
and the conical castings are easy to cast and machine
which keeps costs down.
Q.
How does the shift mechanism operate?
A. In exactly the same way as other mechanical
overdrives. The shift lever emerges from the side of
the transmission tunnel. To shift into overdrive you
depress the clutch and push the lever forward.
To disengage the overdrive you depress the clutch and
move the lever back.
Q.
I have difficulty understanding how the epicyclical
unit works. Can you explain this to me?
A. It is not very complicated. The drawing
here shows a cross section of the unit.
 Inside
the "Roverdrive" is a rotating planet carrier
'E' which is driven by the gearbox
output shaft. Three shafts 'G' are
held in the planet carrier and rotate with it. Three
planet gears 'H' rotate about the
shafts 'G' on bearings 'I'.
Sun gear 'J' is placed in the center
of the three gears 'H' and annulus
gear 'L' is placed on the outside
of gears 'H'. Annulus gear 'L'
is connected directly to the output shaft of the overdrive
on which is machined a large gear to replace the topmost
gear in the transfer case. Bolts 'FF'
hold the overdrive together inside casing 'U'.
When the overdrive is
not in use a clutch locks sun gear 'J'
to the three planet gears 'H' and
as a result the annulus gear 'L'
is forced to rotate at the same speed as planet carrier
'E' and there is no overdrive effect.
Note that in this mode none of the gears is actually
working - all the components are rotating at the same
speed about the center.
When the overdrive is
in use a clutch locks the sun gear 'J'
to housing 'U' and the sun gear can
no longer rotate. As planet carrier 'E'
rotates about sun gear 'J', planet
gears 'H' are forced to rotate about
shafts 'I' and the effect is to cause
annulus gear 'L' to rotate 28% faster
than planet carrier 'E' thus giving
an overdrive effect.
Q.
The gears and clutches must be pretty highly stressed?
A. Not really. As the torque is divided among
the three gears the stresses are much lower than would
be the case with a single gear train. And as the three
gears are placed 120 degrees apart all side stresses
in the assembly are contained. The whole overdrive
assembly rotates supported by one large deep groove
ball bearing. It is a very simple concept. Epicyclical
overdrives are not new of course. Many British cars
in the sixties were fitted with them. But as far as
we know the "ROVERDRIVE" is the first epicyclical
overdrive for a Land Rover that employs a simple mechanical
shift mechanism. There are no electrical solenoids,
relays or microprocessors. A lot of thought and testing
have gone into it and we have applied for patents
on the concept.
Q.
How difficult is it to install?
A. Not difficult. On Series vehicles and Defenders
it is very straightforward as there is a lot of space
adjacent to the transfer case. On Discoverys and Range
Rovers, some trimming of the body work is required
to provide clearance.
Q.
What about service and maintenance?
A. We have given a lot of thought to making
this product as simple as possible and anyone with
good mechanical aptitude can install and service the
unit. It can be completely dismantled using common
hand tools. We chose to use simple metric ball bearings
which can be purchased from regular bearing suppliers.
This is an overdrive made in the tradition of the
older Land Rovers. You can take it anywhere
knowing some electrical or electronic problem will
not cause a failure.
3396
Marine Drive, West Vancouver, BC CANADA, V7V 1M9
Telephone (604) 913-7910 Fax (604) 921-7290
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