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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to dynamometers or dynamic testing apparatus
for measuring the performance of a vehicle. In particular, the present
invention concerns a dynamometer particularly suitable for measuring the
power characteristics of a motorcycle.
2. Description of the Prior Art
Ever since the development of the engine and the motor, man has sought
means to accurately measure the power characteristics thereof. Since the
horsepower delivered by a rotating shaft is defined as 2.pi.nT/33,000,
where n equals rpm and T equals torque in footpounds, output horsepower
can be determined by measuring the speed and the torque of the output
shaft. The speed can be measured directly by means of a tachometer.
Mechanical power measuring devices called dynamometers have been developed
to measure the torque.
There are basically two types of dynamometers: (1) those absorbing the
power and dissipating it as heat and (2) those transmitting the measured
power. In the transmission dynamometer, the torque is measured by means of
strain guage elements bonded to the transmission shaft. There are several
kinds of absorption dynamometers, one of which is the Prony Brake which
applies a friction load to the output shaft by means of wood blocks,
flexible bands or other friction surfaces. The fan brake and water brake
are other types of dynamometers which are known.
Many types of dynamometers have been specially developed for measuring the
power characteristics of automobiles. Some recent examples of automobile
dynamometers may be seen in U.S. Pat. Nos. 3,277,702; 3,491,587; and
3,651,690. Although some of the principles involved may be similar,
dynamometers developed for automobiles are not necessarily desirable for
use on motorcycles.
In the past, there has been little concern, other than by manufacturing
companies, for measuring the power characteristics of motorcycles.
However, with the greatly increased interest in and use of motorcycles,
there is an increasing demand for devices which accurately measure the
performance of these motorcycles. An example of a motorcycle dynamometer
may be seen in recently issued U.S. Pat. No. 3,733,894. Other motorcycle
dynamometers are commercially available.
Since cyclists are quite mobile and may be found in many different
locations, it is desirable that motorcycle dynamometers be as portable as
possible. It is also desirable that such dynamometers be self-sufficient,
relying as little as possible on outside power sources and auxiliary
apparatus such as plumbing for cooling water, etc.
Most of the commercially available motorcycle dynamometers leave a great
deal to be desired in accuracy. The apparatus for measuring either one or
both of the torque and speed of a motorcycle may not be totally reliable.
Furthermore, most of the motorcycle dynamometers available do not provide
the road wind normally encountered by a motorcycle under normal operating
conditions. Those that do, do so inadequately or by means of a relatively
small fan or blower which requires auxiliary power sources.
In addition, most motorcycle dynamometers of the prior art utilize some
form of load or torque arm for measurement of torque. Such devices are
relatively expensive and sometimes difficult to calibrate. Furthermore,
some of the motorcycle dynamometers of the prior art are hazardous to the
operator, cycle and bystanders.
SUMMARY OF THE PRESENT INVENTION
In the present application, a new and improved motorcycle dynamometer is
disclosed with features not present in the prior art. The disadvantages
present in much of the prior art are eliminated.
The dynamometer of the present invention comprises a support assembly or
frame on which a motorcycle may be supported; a power absorption roller
mounted on the support frame for engagement with at least one wheel of the
motorcycle and including a pump for producing a fluid pressure in response
to the torque produced by the wheel; a fluid reservoir connected to the
inlet of the pump by a first conduit; and to the outlet of the pump by a
second conduit; and pressure indicator means connected to the outlet side
of the pump for indicating the discharge pressure thereof. A unique speed
measuring and indicating apparatus is also provided whereby the speed and
fluid pressure, indicated by the pressure indicator, may be correlated
with the performance of the motorcycle. A blower for simulating road wind
may also be provided and in the present invention is uniquely connected to
the discharge of the power absorption pump for driving the blower. In
addition to simulating road wind, the blower serves to absorb much of the
energy of the high-pressure fluid, eliminating the need for cooling of the
fluid by any means other than normal convective cooling of the air
surrounding the machine.
The power absorption unit uniquely utilizes a pump of the rotary positive
displacement type and along with the accurately measuring speed indicator
provides power measuring accuracy not heretofore available in portable
motorcycle dynamometers. The simulated road wind provided by the blower
also contributes to a much more accurate measurement of power
characteristics since the entire power system is operating under very
realistic temperature conditions.
The motorcycle dynamometer of the present invention is totally portable and
completely self-contained. No auxiliary power sources or other auxiliary
apparatus is required for its operation. Thus, the dynamometer can be used
at almost any location.
In addition to being portable, self-contained and more accurate, the
dynamometer of the present invention eliminates the hazards present in
dynamometers of the prior art. The unique wheel engaging rollers and
safety tie-down reduce the possibility of the motorcycle leaving the
support frame. In addition, other safety features such as a ramp which
doubles as a safety shield for the power wheel is provided. Many other
objects and advantages of the invention will be apparent from a reading of
the specification which follows in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective representation of a dynamometer, according to a
preferred embodiment of the invention;
FIG. 2 is a schematic representation of the dynamometer of FIG. 1
illustrating a motorcycle placed thereon for measuring the power
characteristics thereof;
FIG. 3 is a plan view of an instrument panel which may be utilized with the
present invention; and
FIG. 4 represents an evaluation chart which may be used to convert
horsepower and speed data into rpm and torque (footpounds) for a
particular motorcycle engine.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring first to FIG. 1, the dynamometer of the present invention may
generally comprise a support assembly or frame 1, power absorption
apparatus 2, fluid reservoir 3, indicating apparatus 4, blower apparatus
5, and speed indicating apparatus 6. These components are uniquely
arranged in a completely portable and self-contained unit.
The support assembly 1 includes a platform 7 on which the motorcycle, to be
tested, will be supported, e.g., as in FIG. 2. The platform may be
provided with an axle 8 and rear wheels 9 by which the entire unit may be
moved from place to place. Front support legs 10 may also be provided with
platform 7. Hingedly attached at 11 to the forward part of platform 7 is a
front support or apron 12 on which the front wheel of the motorcycle would
be supported. Rails 13, between which the front wheel would be positioned,
and a chain 14 may be provided to assure that the motorcycle does not
leave the support assembly 1.
A ramp 15 is hingedly connected at 16 to the rear of the platform 7 and
serves as a means by which the motorcycle may be moved from the ground to
its position on the support assembly 1. The ramp 15 may be elevated to a
substantially upright position, as in FIG. 2, to provide a safety shield
during testing of the motorcycle. Both ramp 15 and apron 12 may be pivoted
to substantially upright positions for movement of the entire unit from
one place to another. During such periods, the blower 5 would be placed on
the platform 7 for movement therewith. The unit is light enough that it
can be carried in a pickup truck or on most motorcycle trailers. A hand
truck may be provided for moving the unit.
The platform 7 may be provided with a slot or well 17 in which rollers of
the power absorption apparatus 2 and speed indicating apparatus 6 may be
mounted. The roller 18 of the power absorption unit is preferably of the
drum type and is mounted on a shaft 19 (see FIG. 2) supported by the
platform 7 for frictional engagement with the rear or driving wheel 20 of
the motorcycle 21 which is being tested.
As best seen in FIG. 2, the power absorption unit also includes a pump 22
which is directly connected to the shaft 19 for rotation thereby in
response to the torque developed by the motorcycle wheel 20. The pump 22
is preferably of the rotary positive displacement type sometimes referred
to as a "gear pump." The inlet of the pump 22 is connected by a first
conduit 24 to an oil, or other hydraulic fluid, reservoir 3. The outlet 25
of the pump 22 is connected, eventually, by a second conduit 26 to the
reservoir. Thus the pump 22 receives fluid from the reservoir 3 and
discharges it at a substantially higher pressure at 25 for return to the
reservoir 3 through conduit 26. The pressure produced by the pump 22 is
dependent on the torque developed by motorcycle wheel 20.
A throttling valve 27 may be connected in the conduit 50 by which loading
of the power absorption apparatus can be controlled by controlling an
appropriate amount of fluid directed back to the reservoir 3. A pressure
gauge 28 is connected to the conduit 26 to measure the discharge pressure
of pump 22. A conduit 51 is connected to the downstream of the pump but
upstream of the control throttle valve. This line 51 returns the fluid to
the reservoir 3 through the relief valve 52. If the pressure exceeds a
safe level at the pump outlet, the relief valve automatically opens to
dump the fluid directly back to the reservoir 3.
The blower apparatus 5 is for the purpose of producing an air stream 29
(see FIG. 2) which simulates the road air or wind which would be
encountered by the motorcycle 21 under normal road operating conditions.
Such an air stream 29 will effectively cool the power system of motorcycle
21 in a manner similar to road wind. Although many types of blowers may be
used, a squirrel cage type 30 has been found to be especially desirable.
The blower 30 is preferably driven by a fluid motor or drive unit 31, the
power fluid of which is supplied through conduit 26 from the discharge of
pump 22. After the fluid circulates through the fluid drive 31, it returns
to reservoir 3 through the last portion of conduit 26. It should be noted
that part of the energy present in the fluid on the discharge side of pump
22 is thus utilized to drive the blower 30. This is a particularly unique
feature of the present invention since those dynamometers of the prior art
which are provided with fans or blowers require auxiliary power sources
such as an electric motor.
In addition to simulating road wind and utilizing much of the energy
present within the system to do so, the blower apparatus 5 serves an
additional function. By absorbing the energy within the fluid and
consequently reducing its pressure, it is not necessary to throttle all of
the fluid before returning to the reservoir 3. In systems which require
throttling all the fluid before returning it to a reservoir, excessive
heat is generated which must be dissipated by some type of a cooling
device. This requires a heat exchanger connected to a source of water or
other cooling medium. This additional equipment and auxiliary apparatus is
thus eliminated with the dynamometer of the present invention. The heat
that is generated by the throttling part of the oil is rejected from the
surfaces of the reservoir and other parts without installing special
equipment for this purpose.
The speed indicating apparatus 6 of the present invention includes a roller
32 which is mounted in the platform well 17 for engagement with the wheel
20 of motorcycle 21. The distance between rollers 18 and 32 (which may be
adjustable) is designed to receive the wheel 20 so that the angle between
radial lines projecting from the axis of wheel 20 to the axes of rollers
18 and 32 is preferably between 60.degree. and 120.degree.. In fact,
90.degree. has been found to give particularly good traction while
avoiding excessive tire wear.
The speed measuring apparatus also includes a speedometer 34, the cable 33
of which is directly connected to the roller 32. SInce, unlike motorcycle
dynamometers of the prior art, speed is measured by an independent roller
32, the measurement thereof is not affected by the slippage which is
inherent in the torque-transmitting roller 18. It will be noted that the
speedometer 34 may be mounted, along with pressure gauge 28 and valve 27,
on an instrument panel 35.
As best seen in FIG. 3, the instrument panel 35 may also be provided with a
chart 36 having horizontal lines representing pressure, vertical lines
representing speed and inclined lines representing horsepower for a
particular pressure and speed. The load on the motorcycle being tested may
be controlled by adjustment of the control or throttling valve 27 so that
several test points may be plotted on the chart 36 for the pressure and
speed developed for each setting of the control valve 27. These test
points may be plotted to produce a curve 37 from which the horsepower
developed at any speed may be determined.
If a more complete analysis of engine operation is desired, a
"speed-torque" chart 38, such as shown in FIG. 4, may be utilized. The
lower portion of the chart 38 is a plot of speed versus engine revolutions
in some distance of movement, e.g., 50 feet. The upper portion of the
chart is plotted for revolutions per minute of the engine, horsepower and
torque thereof. To determine the engine revolutions in 50 feet, all that
is required is the gear ratio of the motorcycle and the wheel diameter. In
the alternative, the number of engine revolutions may be counted as the
motorcycle is rolled 50 feet.
STATEMENT OF OPERATION
In operation, a motorcycle 21 may be rolled up the ramp 15 and placed with
the rear wheel 20 supported between and engaging the rollers 18 and 32.
The forward roller 32 shall have been previously adjusted to provide
between 60.degree. and 120.degree. between radial lines from the center of
wheel 20 through the axes of rollers 18 and 32. In fact, 90.degree. has
been found to give particularly good traction while avoiding excessive
tire loading. The front wheel rests on apron 12 and is restrained by
safety chain 14. The rear ramp may be elevated by the operator who sits on
the motorcycle in conventional riding position.
The motorcycle power is then applied through the roller 18. The speed of
the motorcycle engine is controlled by the throttle valve 27 and measured
by the front roller 32. The torque which is produced by the motorcycle is
proportional to the pressure generated in the pump. Minor torque is
produced by friction drag in the pump and is not reflected in the pressure
output, but this is normally less than 1% and is negligible error. Thus,
knowing the displacement of the hydraulic pump, a relatively precise
torque value can be determined by measuring the output pressure.
Since the speed is measured accurately by the free running roller 32, the
horsepower being applied to the test stand by the rear wheel of the
motorcycle can be accurately calculated. The chart shown in FIG. 3 is an
example. For each pressure and speed there is a unique horsepower which
can be cross-plotted as shown in this figure. The shape of the curve is
proportional to the torque speed curve for the motorcycle and the
horsepower level at each speed can be read. This is normally all that is
required in motorcycle evaluation. However, if actual engine speed and
torque is desired, a second chart shown in FIG. 4 can be used.
Knowing the tire size and gear ratio, or the engine revolutions in a given
distance (50 feet or so) the speed can be related to the engine RPM as
shown in FIG. 4. Then, knowing the horsepower output (from FIG. 3), the
engine torque can be determined as illustrated. To utilize the chart 38
for any speed in miles per hour, a line 39 may be projected to a point 40
representing the engine revolutions in 50 feet. From this point, a line 41
is projected vertically to a point 42 representing the horsepower read
from horsepower curve 37 (FIG. 3) which was previously plotted from the
test. A line 43 is then projected horizontally for a reading of engine
torque in footpounds at point 44. It will also be noted that the engine
RPM can be read where the vertical line 41 crosses into the upper portion
of the chart 38. Thus, the acutal engine performance can be evaluated.
As the pressure is being generated by the motorcycle torque, most of the
pressurized fluid goes through the hydraulic motor to operate the blower.
As the motorcycle produces more torque, more pressure is produced which
forces more fluid through the blower drive and makes the blower produce
more air. Thus, as the motorcycle works harder, the blower blows harder
simulating realistic road air conditions. This is important since the
temperature of the entire system -- carburetor, engine, exhaust,
transmission, tires, etc., -- all affect power output. Meanwhile, the
pressure (and the load on the motorcycle engine) is controlled by valve 27
to produce the desired test speed by short circuiting or bypassing a
portion of the oil directly back to the reservoir. The displacement of the
pump and the fluid drive are carefully selected to give the best
compromise between cooling and controllability.
The relief valve 52 is inactive unless excessive torque is applied,
overpressuring the unit. The relief valve is set to flow adequately in the
event of overpressure to protect the gauge and other pressure sensitive
elements in the system. While a portion of the oil is throttled back to
the reservoir causing heating in the oil, the resulting heat is not
excessive to the point that special cooling elements are required. Steady
operations at 50 to 75 horsepower will cause temperatures no greater than
160.degree.F in the installation described herein when operated properly.
Proper operation requires selection of the proper gear for the motorcycle.
Typically, the test should be made in a gear that will produce enough
pressure to operate the blower vigorously. Low gear produces the highest
pressure (high torque) and high gear produces a low pressure (low torque).
Thus, normally, a middle gear gives best results, the lower the better
until the relief valve is actuated, making it impossible to further
control the load on the motorcycle. Operation at a fairly high pressure
forces the majority of the oil through the blower drive, resulting in
minimum heating. The valve 27 is operated nearly closed, resulting in
minimum throttling of the fluid thus minimum heat generation in the oil.
Normally, during operation, the data is recorded (pressure and speed) for
plotting on the graph and evaluation at a later time. As best seen in FIG.
3, the instrument panel 35 may also be provided with a chart 36 having
horizontal lines representing pressure, vertical lines representing speed
and inclined lines representing horsepower for a particular pressure and
speed.
CONCLUSION
From the foregoing description and statement of operation, it can be seen
that the motorcycle dynamometer of the present invention offers many
features and advantages not provided in the prior art. The dynamometer is
put together in a highly portable, completely self-contained unit,
requiring no auxiliary power sources or other auxiliary apparatus.
A unique blower arrangement is provided for simulating the road wind and
cooling the motorcycle power train which also serves another function. The
blower is driven by a fluid motor powered by fluid routed from the power
absorption apparatus so that much of the energy of the high pressure fluid
produced therein can be utilized. This also prevents having to throttle
all the fluid, which would result in excessive heating up the oil
reservoir. Thus, energy is conserved and the necessity of an oil cooler is
eliminated.
Speed is taken from an independent roller not affected by the slippage
inherent in torque transmission apparatus, resulting in accuracy of speed
measurement. Measurement of torque is also accurate due to the design of
the power absorption unit.
Although the dynamometer of the present invention has been primarily
designed for testing motorcycles, it is not so limited. It could be
adapted for testing the performance of any wheeled vehicle. Furthermore,
many variations of the invention can be made by those skilled in the art
without departing from the spirit of the invention. It is therefore
intended that the scope of the invention be limited only by the claims
which follow.
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