The present invention relates to cooling arrangements for an amphibious
The design of road going vehicles has been refined over many years,
so that most manufacturers have agreed on an optimised layout for the various major
components, at least within classes of vehicles; e.g. passenger cars, or heavy goods
vehicles. In each of these cases, the engine is usually mounted at the front of
the vehicle, and is water cooled.
Manufacturers of amphibious vehicles may find it convenient and cost
efficient to adapt automotive components from road going vehicles to their products.
However, the different constraints of use on water must be factored into the design.
For example, the obvious location for an engine cooling radiator in
a road going vehicle is at the front of the vehicle, where a flow of cooling air
is easily obtained. Where the engine is front mounted, it is also easy to arrange
coolant flow from the engine to the radiator, and vice versa. A cooling air
opening is provided, whose area will typically be a compromise between air flow
capacity on the one hand; and aerodynamic drag generated by air passage through
said radiator, and the cooling duct leading therethrough, on the other hand. A cooling
fan is provided; which is usually driven from the engine crankshaft where the engine
is mounted along the main fore and aft axis of the vehicle; but is usually electrically
driven where the engine is mounted transversely.
For an amphibious vehicle, however, different constraints apply. Three
examples will now be given of prior art approaches to this problem, with reference
to the accompanying figures 1 to 4.
The French Hobbycar design (figs. 1 and 2) used a front mounted radiator
1, situated in a cooling duct 2 having an intake 3 and outlets 4 on each side of
the vehicle. This arrangement allowed the use of air cooling of the radiator on
land, and both air and water cooling of the radiator on water. It should be noted,
however, that this arrangement is suited only to low speeds on water, for the following
reasons. The radiator is exposed to mechanical damage, not only through collisions
with foreign objects; but also because the matrix and finning of the radiator are
designed only for air to pass over and through them respectively. Given the greater
density of water relative to air, the passage of water through an automotive radiator
at 15 knots (28km/h) or more could cause collapse of the radiator structure. Also,
the front mounting of the radiator in the Hobbycar necessitates long water pipes
or hoses to connect the radiator to the centrally mounted engine.
Rorabaugh and Costa (US patent 5,755,173) proposed an arrangement
whereby the radiator is mounted in a spoiler mounted above the rear deck of an amphibious
vehicle. This arrangement requires a spoiler to be included in the design of the
vehicle, which may not be aesthetically acceptable; and as with the Hobbycar design,
requires lengthy plumbing. It may be difficult to arrange a flow of cooling air
through such a horizontally mounted radiator.
The Alvis Stormer military amphibious vehicle (figs. 3 and 4) used
a front mounted radiator 5 mounted on a sloping forward deck 6, with a fan 8 mounted
on an internal partition 7. Air was drawn through deck 6 and radiator 5, then through
partition 7; and exhausted through deck 9 over engine 10. This arrangement suffers
from the fan being mounted remotely from the radiator, which is inefficient. It
will also be noted that the heat dissipated from radiator 5, along with that generated
from engine 10 and exhaust system 11, will tend to provide an uncomfortably warm
environment for the driver, seated at position 12 alongside engine 10. This may
be acceptable in a military vehicle, but would not be acceptable in a vehicle aimed
at the private leisure market.
The exhaust system of a road going vehicle is generally mounted underneath
the vehicle, with a catalytic converter (where fitted) being mounted as close as
possible to the exhaust manifold(s) to allow the fastest possible "light off", minimizing
noxious emissions from a cold start. The catalytic converter is designed to run
hot, but the rest of the exhaust system runs at cooler temperatures; so that the
rearmost silencer is almost always the first to corrode in a road going vehicle,
as it rarely reaches a high enough temperature to evaporate acidic water which collects
As the exhaust system of a road going vehicle is slung, underneath
the car, it is effectively air cooled as the vehicle is driven, although instances
have been known of catalytic converters overheating while vehicles idle in traffic
For an amphibious vehicle, there are different constraints on the
positioning of the exhaust. Clearly, the exhaust outlet(s) should be above the water
line, to ensure that water is not sucked into the tailpipe, resulting in engine
damage and immobilization of the vehicle. As the vehicle may be used in salt water,
it is highly desirable that the exhaust system should be protected as far as is
possible from water splashing over exhaust system components. It has been found,
for example in the field of oil exploration, that corrosion is most fierce in its
action in the "splash zone" where metal components are neither always submerged
nor always in the air, but alternate between wet and dry conditions.
Another negative effect of water splashing over an exhaust system
is that components of said system may be subjected to extremes of temperature and
local quenching, resulting in cracking and premature failure of said components.
The Hobbycar exhaust silencer (13, fig. 6) is located in a dedicated
compartment to the rear of the vehicle (exit 14, fig. 5). This is a good arrangement
for a low speed amphibious vehicle, but raises concerns regarding the efficiency
of exhaust cooling for a higher speed amphibian. As the surrounding body panels
are made of composite plastic material, they may be damaged by a hot exhaust.
The Alvis Stormer was fitted with a side exit exhaust (fig. 4). This
arrangement is unsuitable for a present day design from a health and safety viewpoint,
as exhaust gases would be directed from the vehicle towards pedestrians on adjacent
pavement areas. Rorabaugh and Costa do not disclose an exhaust arrangement. Yet
another design of a cooling arrangement is known from Le Blanc (US-A-4,607,562).
Water cooled exhausts are known for boats; but they are heavy, and
will not work on land unless they carry additional coolant; which further increases
An object of the invention is therefore to overcome the aforesaid
According to the invention, there is provided an amphibious vehicle
with the features of claim 1.
The advantage of the arrangement according to the invention is that
engine heat is kept away from the driver and passenger areas; and that most water,
often sea water, can be kept away from both the radiator(s) and exhaust silencer(s);
and that air is passed efficiently through the radiator(s) to cool the exhaust silencer(s);
enabling exhaust gases to be vented to the rear of the vehicle.
It is convenient to use a transversely front mounted power train from
a typical family car to drive the front wheels of amphibious vehicles; particularly
as the associated steering gear can also be conveniently used Such a transplant,
however, has drawbacks which will become evident from further consideration of the
design and use of amphibians.
In order to achieve substantial penetration of the potential leisure
market for amphibians, it is necessary to offer substantial speed on water. If the
amphibian is capable of planing, where the vehicle rides substantially over the
water, rather than through it; it may be capable of speeds on water of 15 knots
(28km/h) or more. For this purpose, the weight of the engine should be placed towards
the rear of the vehicle to assist achievement of the tail down attitude on water
which is necessary to commence and maintain planing.
However, if the engine is placed at the extreme tail of the vehicle,
it may be difficult to package the engine accessories and marine drive in the restricted
space available; and also to ensure that engine systems such as the combustion air
intake, ignition system, and engine management system, are kept dry.
Front wheel drive power trains generally have driveshafts located
behind the engine block. If such a power train is mounted behind a vehicle's rear
wheels, in its original orientation, drive must be transferred from the driveshafts
forward to the wheels, past the engine. This solution would be expensive and complex.
Alternatively, the power train could be reversed, with the transmission
ahead of the engine; but additional gears would then be required to reverse the
direction of rotation of the halfshafts. It is therefore convenient to mount the
power train ahead of the rear axle. This also has a marketing advantage, as the
vehicle can be marketed as a mid-engined sports car for road use. However, a rear
mounted engine may be a viable alternative.
An embodiment of the invention will now bet described with reference
to the accompanying drawings, in which:
- Figure 1 is a perspective view of the front of the known "Hobbycar" amphibious
- Figure 2 is a similar view of the vehicle shown in figure 1, but without the
- Figure 3 is a diagrammatic sectional side view of the known Alvis Stormer amphibious
- Figure 4 is a diagrammatic sectional plan view of the vehicle of figure 3;
- Figure 5 is a perspective rear view of the vehicle of figure 1;
- Figure 6 is a perspective rear view of the vehicle of figure 1, without the
outer bodywork; and,
- Figure 7 is a diagrammatic sectional side view of the amphibious vehicle according
to the invention.
Referring to figure 7, engine 101 of amphibious vehicle 100 is located
in an engine compartment 102. The engine is cooled by a radiator 103, which is mounted
in a cooling compartment 104, which is separate to the engine compartment, and is
sealed off therefrom. In this case, the vehicle is mid-engined, so the cooling compartment
is located at the upper rear of the vehicle bodywork.
The radiator is cooled by one or more fans 105. The fan(s) may be
driven electrically, hydraulically, or by mechanical drive means from the engine
or elsewhere in the power train, as may be mechanically convenient. Cooling air
is drawn into cooling compartment 104 through radiator 103 by said fan(s), and exhausted
aft of the radiator through an opening 106. The cooling air passes over exhaust
silencer(s) 107 on its way to opening 106, helping to cool the silencer on its way.
Although this may appear illogical, it should be noted that the coolant temperature
of the radiator is essentially limited to its boiling point under pressure of around
120 degrees Centigrade (248 degrees Fahrenheit). Beyond this point, the cooling
system will become dysfunctional. By contrast, the exhaust system temperature has
no such limitation. Hence even ambient air which has been heated by passage through
the radiator may still be used to cool the exhaust. More than one coolant radiator
and more than one exhaust silencer may be required within the cooling compartment,
to provide sufficient cooling and exhaust silencing capacity respectively.
In order to protect the engine ignition system from ingress of water,
the apertures 108 and 110 through which coolant hoses 109 and exhaust pipe(s) 111
respectively leave the engine compartment are sealed by metal and rubber composite
seals 112 and 113. These are known from, for example, the Amphicar amphibious vehicle,
and do not form part of the invention. As the temperatures of the coolant hoses
109 will be lower than those of exhaust pipe(s) 111, seals 112 may be made simply
The mounting of radiator 103, fans 105, and exhaust silencer 107 are
by means of conventional brackets and resilient mountings, already known in the
automotive engineering art. These mountings do not specifically form part of the
The engine catalytic converter(s) (not shown) should preferably be
mounted within engine compartment 102. Catalytic converters are designed to run
at high temperatures; both the converters themselves, and their electrical connections
(e.g. for lambda sensors), should be kept away from water.
For a road going vehicle, engine compartment 102 will be open to the
road below, allowing additional cooling of the engine block, transmission, catalytic
converter, and any other mechanical and electronic components mounted in this area.
The engine compartment of an amphibian vehicle, however, must be sealed below the
engine; not only to stop the engine getting wet, but also to maintain buoyancy.
The engine compartment may therefore require a further cooling system or systems,
separate to that for the radiator and exhaust; which may comprise further cooling
air ducts and fans. On the other hand, it may not be necessary to provide positive
sealing around openings between engine compartment and cooling compartment as described
Although cooling fans are used in the preferred embodiment, if the
engine is of low power rating, and the radiator is large, it may be possible to
delete the fans; and to cool the radiator by natural passage of air over the radiator,
known as "ram air".
In addition to the engine water cooling system, further cooling systems
may be required in an amphibian, for engine oil, transmission oil, and power take
off oil. (The power take off being used to drive a marine propulsion means, e.g.
a jet drive.) Also, if the engine has forced induction, an intake air intercooler
may be required to maintain the efficiency of the engine by cooling the intake air
after it has passed, through the supercharger, turbocharger, or other forced induction
means. These further cooling systems may be located either in the engine compartment,
or in the separate cooling compartment described above. The placement of these systems
will be determined firstly by packaging requirements, and secondly by issues of