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UDC 629.1 - 42.001.4
IS0
I NT ERN AT1 ON AL ORGANIZATION FOR STAN DA RD IZATl O N
IS0 RECOMMENDATION
R 789
TEST CODE FOR AGRICULTURAL TRACTORS
1st EDITION
July 1968
c
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 789, Test Code for agricultural tractors, was drawn up by Tech-
nical Committee ISO/TC 22, Automobiles (Section ISO/TC 22(T) - Agricultural Tractors), the
Secretariat of which is held by the Association Française de Normalisation (AFNOR).
Work on this question by the Technical Committee began in 1964 and led, in 1965, to the
adoption of a Draft IS0 Recommendation.
1
In January 1966, this Draft IS0 Recommendation (No. 942) was circulated to all the IS0
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature, by
the following Member Bodies :
Argentina Italy Spain
Belgium
Japan Sweden
Brazil
Korea, Rep. of Switzerland
Canada Netherlands U.A.R.
Chile Poland United Kingdom
Czechoslovakia Portugal U.S.A.
France Romania U.S.S.R.
Hungary South Africa, Yugoslavia
Israel Rep. of
One Member Body opposed the approval of the Draft :
Germany
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
L
which decided, in July 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 789-1968 (E)
IS0 Recommendation
R 789 July 1968
TEST CODE FOR AGRICULTURAL TRACTORS
1. SCOPE
This IS0 Recommendation deals with the testing of agricultural tractors.
The tests measure certain performance characteristics of the tractors, in order to assess the working
qualities of these tractors.
A complete test should include
technical tests made at testing stations, that is tests made under conditions that, in
(a)
principle, are identical regardless of the station;
(b) tests made under farm working conditions.
Because it is not possible to standardize the conditions in which tractors are used in farming, only
tests in category (a) are included in the present document.
Only these can be carried out in accordance with uniform rules intended to give results which can be
compared in all countries, and even then some differences may arise between tests in various coun-
tries due to differences in fuel quality, atmospheric conditions and local regulations controlling minor
details of construction.
2. FIELD OF APPLICATION
This IS0 Recommendation applies exclusively to mass-produced tractors.
Any prototype tractor tested should be subject to special agreement between the manufacturer and
the testing station with regard to adjustments and the corresponding tests to be made.
3. CODE
It is necessary to list and define the operations involved in the preparation of the tractor for the tests
and the requirements for the preparation of the specification sheet, and then to consider the tests
themselves.
3.1
Preparation of the tractor for the tests and preparation of the specification sheet
The operations involved in the preparation of the tractor relate to the requirements concerning
sampling the tractor to be tested, running-in the tractor before tests commence, making prelim-
inary adjustments and ballasting the tractor.
The instructions for the preparation of the technical specification sheet are then given.
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ISO/R 789-1968 (E
3.1.1 Sampling. The tractor submitted for the test is taken from series production by the manu-
facturer with the agreement of the testing station.
The tractor should be a production model in all respects, strictly conforming to the speci-
fication sheet submitted by the manufacturer; this sheet should accurately define the model
tested.
The test report should state how the tractor was selected.
3.1.2 General condition of the tractor before testing commences and preliminary adjustments.
The tractor should be new and run-in by the manufacturer before test, under his responsi-
bility and in accordance with his usual instructions, and in collaboration with the testing
station.
The test report should state the place and duration of running-in.
The adjustment of the carburettor or the injection pump and the setting of the governor
should conform to the tolerances for agricultural use specified by the manufacturer.
For spark ignition engines fitted with a means for the operator to vary the ratio of the
fuel/air mixture, all tests should be made and reported with the settings recommended for
4
normal operation.
The manufacturer may make carburettor, governor, ignition and injection adjustments during
the period prior to testing. These adjustments should not be changed during the tests.
3.1.3 Ballasted tractor. Wheel or track equipment and ballast weights which are commercially
available and approved by the manufacturer for use in agriculture may be fitted. For tractors
having pneumatic tyres, ballast in the tyres may also be used; the overall static weight on
each tyre, including ballast in the tyres and the inflation pressure, should be within the
limits specified by the tyre manufacturer (inflation pressure should be measured with the
tyre valve in the lowest position; when this is not practicable (liquid ballast), the measured
value of the pressure should be turned into the value corresponding to the lowest position of
the valve).
3.1.4 Specification sheet. The tractor manufacturer should supply a specification sheet of the
tractor consisting of the items listed in the specimen report in Annex C, as well as any fur-
ther data required to carry out the tests. These specifications should be verified by the test-
ing station, particularly those connected with an IS0 Recommendation which is of import-
ance to the tractor user.
Y
3.2 The tests
The purpose of the tests is to determine the operational characteristics of the tractor in different
conditions. The following requirements should be taken into account.
3.2.1 General requirements
REPAIRS AND ADJUSTMENTS DURING TESTS
3.2.1.1
Ail repairs or adjustments made during the tests should be noted, together with
comments on any practical defects or shortcomings about which there is no doubt.
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ISO/R 789-1968 (E’
3.2.1.2 FUELS AND LUBRICANTS
Fuels and lubricants should be selected from the range of products commercially
available in the country where the equipment is tested but should conform to the
minimum specifications approved by the tractor manufacturer.
They should be identified in the following manner :
(U) fuels : legal name, type and grade, density at 15 OC or at 20 OC,
octane or cetane numbers. (The temperature chosen should
be stated in the report).
(b) lubricants : types, viscosity. If different lubricants are used, precise
information should be given as to where they are used
(engine, hydraulic transmission, etc.).
If the fuel or lubricant conforms to a national or international standard, this should be
mentioned and the standard stated.
3.2.2 Types of tests listed
3.2.2.1 COMPULSORY TESTS
The tests listed below are compulsory from the point of view of this IS0 Recommen-
dation.
Main power take-off tests (see clause 3.2.3).
(1)
Engine tests (see clause 3.2.4.1) which should be made compulsory only in
(2)
the following circumstances :
when the tractor is not commercially available with a power
(U)
take-off,
when the power take-off is not capable of transmitting the full
(b)
power of the engine (see clause 3.2.3.6),
when the power take-off is not mechanically connected to the
(c)
engine.
Drawbar tests (see clause 3.2.6).
(3)
Determination of turning space (see clause 3.2.7.1).
(4)
Determination of turning circle (see clause 3.2.7.2).
(5)
Determination of position of centre of gravity (see clause 3.2.7.3).
(6)
For all these tests, accessories such as the hydraulic lift pump or air compressor may be
disconnected only if it is practicable for the operator to do so as normal practice in
work.
3.2.2.2 OPTIONAL ADDITIONAL TESTS
Engine tests (see clause 3.2.4.2).
(1)
Belt or pulley shaft tests (see clause 3.2.5).
(2)
Determination of special characteristics (see clause 3.2.7.4).
(3)
3.2.3 Tests ut the main power take-off
3.2.3.1 GENERAL REQUIREMENTS
The torque and power values in the test report should be obtained from the dynamo-
meter without correction for losses in power transmission.
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In all tests, the shaft connecting the power take-off to the dynamometer should not
have any appreciable angularity at the universal joints.
If, in the laboratory, use is made of an exhaust gas discharge device, it should not
change the engine performance.
No correction should be made to the test results for atmospheric conditions or other
factors. During maximum power tests, the ambient temperature should be between
15 and 27 "C and atmospheric pressure should not be less than 725 mm of mercury. If
this is not possible because of conditions of altitude, the real pressure should be noted
at the top of the test report.
In all tests, the fuel temperature should be as close as possible to that observed in the
fuel feed system of the tractor under similar load conditions in normal work.
The specific consumption figures in the test report should be given as weights of fuel
per unit of work.
of
To obtain hourly consumption by volume and the work performed per unit volume
fuel, a conversion of units of weight to units of volume should be made using the
density value at 15 OC.
When consumption is measured by volume, the specific consumption should be
calculated using the density corresponding to the appropriate fuel temperature.
The various tests should be carried out continuously, the governor control lever being
placed in the position recommended by the tractor manufacturer for obtaining
continuous maximum power.
Stable operating conditions should be attained at each load setting before beginning
test measurements.
The test report should include presentation of the following curves made for the full
range of engine speeds available :
power as a function of speed;
(1)
equivalent crankshaft torque as a function of speed;
(2)
hourly and specific fuel consumption as a function of speed;
(3)
specific fuel consumption as a function of power.
(4)
In addition to the performance measurements required above, the following should also
be noted :
the temperature of the fuel measured at a suitable point between the tank
(1)
and the engine, and the oil temperature measured at a suitable point in the
oil flow;
the coolant temperature measured at the outlet of the cylinder block or
(2)
cylinder head before the thermostat and, in the case of air-cooled engines,
the engine temperature at a point specified by the manufacturer;
the air temperature measured at two points :
(3)
for tractors fitted with a suction device, one approximately 2 m
(a)
in front of the tractor and approximately 1.5 m above the ground
and the other at the engine air intake;
for tractors fitted with a blowing device, one approximately 2 m
(b)
behind the tractor and approximately 1.5 m above the ground
and the other at the engine air intake;
(4) atmospheric pressure;
(5) relative air humidity.
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ISO/R 789-1968 (E)
3.2.3.2 TESTS AT MAXIMUM POWER
The tractor should operate for a period of two hours subsequent to a sufficiently long
warming-up period for power to become stabilized.
The maximum power quoted in the report should be the average of the readings made
during the two-hour period; if the power variation exceeds f 2 oh from the average, the
test should be repeated. If the variation continues to exceed f 2 ‘L, it should be
mentioned in the report.
At least six readings should be made during the two-hour test period.
3.2.3.3 TESTS AT VARYING SPEEDS AT FULL LOAD
The hourly fuel consumption, torque and power should be measured as a function of
speed and the results should be set out as in the table in Annex C. To plot the curves
listed in clause 3.2.3.1 the tests should go down to an engine speed at least 15 below
the speed at maximum torque.
3.2.3.4 TESTS AT VARYING LOAD
In the zone controlled by the governor, the torque, speed and hourly fuel consumption
should be noted as a function of power. In addition, the no-load engine speed should
be recorded.
The data required to complete the section entitled “varying load” in the specimen
table in Annex C should be recorded at the following loads :
I - 85 of the torque obtained at maximum power;
II - unloaded;
III
- half the load defined in I;
IV - a load corresponding to maximum power;
V - one quarter of the load defined in I;
VI
- three quarters of the load defined in I.
3.2.3.5 STANDARD SPEED OF THE POWER TAKE-OFF
If the engine speed recommended by the manufacturer for the tests specified in
clause 3.2.3.2 does not correspond to a power take-off speed conforming to
IS0 Recommendation R 500, Power take-off and drawbar for agricultural tractors
(540 rev/min), and to IS0 Recommendation R .* (1000 rev/min), then the perfor-
mance at the IS0 recommended power take-off speed should be one of the points
observed during the full load test (see clause 3.2.3.3).
The power and the hourly and specific fuel consumption at this engine speed should be
measured.
The power take-off performance at the engine speed which corresponds to standard
belt speed should be determined in the same manner.
3.2.3.6 SPECIAL CASES
The tests specified in clause 3.2.3 are made when the total available power can be
transmitted by the main power outlets.
If this is not the case, the power take-off test should consist of a two-hour test at the
rating specified by the manufacturer with a 20 overload applied every five minutes
for a period not exceeding one minute.
If the engine does not withstand the 20 overload, the test should be carried out at
full engine power.
*
At present at the stage of draft proposal.
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3.2.4 Engine tests
3.2.4.1 COMPULSORY SUBSTITUTE TESTS
(made instead of power take-off tests)
The engine should be equipped with all the accessories required for continuous oper-
ation of the tractor; these should be installed in the same relative position as when
fitted in the tractor.
All the provisions in clause 3.2.3 should apply to compulsory tests of the engine with
the exception of those in clauses 3.2.3.5 and 3.2.3.6. A test should be carried out at
the engine speed corresponding to the standard speed of the power take-off in
accordance with IS0 Recommendations R 500 and R .*, unless the tractor has no
power take-off.
3.2.4.2 OPTIONAL ADDITIONAL ENGINE TESTS
These tests can be carried out to supplement the main tests. In each case, any accessory
which is not necessary for the continuous operation of the engine, such as the
hydraulic lift pump or air compressor, should be disconnected.
When an optional additional engine test in undertaken, the provisions in clause 3.2.3
should be modified, so that measurements are also made under part-load conditions at
reduced engine speed.
Sufficient data should be obtained to relate specific fuel consumption to power,
torque and engine speed throughout the working range of the engine. The results
should be presented graphically on one chart showing torque (ordinate) and speed
(abscissa) curves of equal specific fuel consumption and equal power. The values of
speed and torque should be shown respectively as percentage values of the maximum
torque and of the nominal speed of the engine.
The provisions given in clause 3.2.3.5 should apply.
3.2.5 Belt or pulley shaft tests
3.2.5.1 GENERAL CONDITIONS
The tractor pulley should be coupled to that of the dynamometer by a belt. This belt
should be flexible and have appropriate power and torque transmission characteristics.
Belt slip should not exceed 2 and the necessary tension to obtain this condition
should be as small as possible.
The tests at the pulley shaft should be conducted by directly coupling the tractor
pulley to the dynamometer shaft.
All of the provisions in clause 3.2.3, with the exception of those in clauses 3.2.3.5
and 3.2.3.6, should apply equally to the belt tests and to the pulley shaft tests.
3.2.5.2 STANDARD BELT SPEED
If the engine speed recommended by the manufacturer for tests carried out in conform-
ity with clause 3.2.3.2 does not correspond to the standard belt speed in the country
where the tests are being made, the operational characteristics of the engine at a speed
corresponding to the standardized belt speed should be measured during the full load
test.
The test report should indicate the power, hourly fuel consumption and specific fuel
consumption in relation to engine speed.
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ISO/R 789-1968 (E)
3.2.6 Tests at the drawbar
3.2.6.1 TEST TRACKS
The tests at the drawbar should be conducted according to the following requirements,
in order to provide comparable results in all countries :
for tractors with pneumatic tyres, the tests should be carried out on a
(a)
clean, horizontal and dry concrete or tarmacadam surface containing a
minimum number of joints;
tests of steel-wheeled tractors and track-laying tractors should be carried
(b)
out on flat, dry, horizontal, mown or grazed grassland, or on a horizontal
track having equally good adhesion characteristics.
A moving track (treadmill) may also be used subject to the condition that results
produced are comparable with those obtained on the surfaces mentioned above.
The type of test track should be clearly stated in the test report.
3.2.6.2 TESTS ON OTHER SURFACES
Additional optional tests may be carried out on other surfaces. It is recommended
L
that the following conditions be taken into account :
firm soil conditions that produce good adhesion (which could be the
(a)
track used in clause 3.2.6.1) : as a guide to suitable working conditions, it
is suggested that the ground should have a minimum shear strength of
0.5 kgf/cm2, measured iri situ by a method to be detailed in the test
report, at a depth of 5 to 7.3 cm and at a moisture content between 15 and
25 (dry basis);
loose, cultivated soil conditions : for example, a soil ploughed to a depth
(b)
of 20 cm and cultivated after a few days to a depth of 8 to 12 cm. It is also
recommended that the moisture content be between
12 and 15 (dry
basis) and that the shear strength, measured in situ by a method to be
detailed in the test report, should be between 0.20 and 0.35 kgf/cm2.
3.2.6.3 GENERAL BASIC REQUIREMENTS CONCERNING TEST TRACKS
During all the tests at the drawbar, the governor control lever should be placed in the
position recommended by the manufacturer for work at the drawbar. The line of
draught should be horizontal and the height of the drawbar should remain fixed in
relation to the tractor during all tests.
The manufacturer should comply with the following instructions :
i
(a) the height of the drawbar should not be such that the direction
of the tractor cannot be controlled when it develops maximum sustained
pull;
,
if W is the static weight exerted by the front wheels on the ground,
(b)
Z is the wheelbase,
P is the maximum drawbar pull, and
H is the height above ground of the line of draught,
then PH should never exceed WZ X 0.8;
at the beginning of the drawbar tests, the height of the tyre tread bars
(c)
should not be less than 65 of the height of the bars of the tyres when
new;
measurements of the drawbar pull, speed and slip should not be started
(4
before operational conditions are stabilized.
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ISO/R 789-1968 (E)
3.2.6.4 RESULTS TO BE RECORDED
For each gear combination tested, curves showing power, forward speed, slip and
specific fuel consumption should be determined as a function of the drawbar pull and
included in the test report.
The coolant temperature, that of fuel and engine oil, the air temperature, the humidity
and the atmospheric pressure should be measured.
In the case of the wheeled tractors, values of the performances on the test tracks as in
clause 3.2.6.1 (a) should not be mentioned if the wheelslip exceeds 15
With tracklaying tractors, the maximum sustained pull should be stated as a footnote
beneath the table giving drawbar power values.
Measurement of fuel consumption may be omitted in tests of unballasted tractors and
during tests of ballasted tractors at speeds less than 2.5 km/h.
If the tractor is equipped with a torque convertor unit fitted with a “lock-out” device
which is controlled by the driver, the drawbar tests should be carried out in succession
with the convertor in operation and with the convertor “locked-out”.
For tractors driving four wheels, the slip of front and rear wheels should be separately
measured and reported.
During all tests the forward speed should be maintained within the limits of safety of
testing equipment.
3.2.6.5 TEST PROCEDURE
(a) Tests with additional weight
(1) Maximum power
Test A - Test report
A first test series should be performed on the tractor when ballasted in
accordance with the provisions of clause 3.1.3. The tests should cover at
least all combinations of speed from the lowest to the combination iminedi-
ately higher than that which makes it possible to develop maximum drawbar
power.
(2) Ten-hour test
A ten-hour test should be made as follows :
For wheeled tractors on pneumatic tyres ballasted as specified in clause 3.1.3,
the test should consist of two periods.
- Test B - Test report
Five hours in the gear specified by the manufacturer, in agreement with
the testing station (this speed should be one normally used for basic
agricultural work such as ploughing). The drawbar load applied should be
75 of the pull at maximum power in the gear being used.
Values of power, pull, forward speed, slip and fuel consumption should be
included in the test report.
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ISO/R 789-1968 (I
In the case of tractors fitted with a hydrokinetic torque convertor that can
be “locked-out” by the driver, the five-hour test should be carried out with
the torque convertor in operation, within the limitations specified by the
manufacturer in his published instructions. If the limiting conditions are
reached, the test should be completed with the torque convertor out of
operation. The respective duration of the two parts of the test should be
noted in the test report and the fuel consumption separately stated.
- Test C - Test report
Five hours at the drawbar pull coincident with 15 wheelslip measured
during the tests specified in clause 3.2.6.4. The gear used should be the
fastest gear in which the required pull can be obtained when the engine is
operating under the control of the governor.
In the event of the tractor not developing sufficient power to reach drawbar
pull coinciding with 15 wheelslip, the test should be conducted at
maximum available drawbar pull, keeping at this well-defined value of the
pull.
It may be necessary to add supplementary ballast to reduce tyre wear and
to facilitate control of the tractor.
No measurements need be taken for inclusion in the test report other than
those of pull and forward speed.
In the case of tractors fitted with a hydrokinetic torque convertor that can
be “locked-out” by the driver, the five-hour test should be carried out with
the torque convertor in operation, within the limitations specified by the
manufacturer in his operating instructions. If the limiting conditions are
reached, the test should be completed with the torque convertor out of
operation.
At the end of the ten-hour test, the oil consumption should be measured
and expressed in units of weight/hour.
For tracklaying and steel-wheeled tractors the ten-hour test is made as
specified in test B.
The oil consumption should be measured as described in test A.
(b) Tests without additional weight
Test D - Test report
The lowest speed combination P allowing the maximum power to be developed
and the highest speed combination Q allowing maximum pull to be developed
should be considered.
The tests should be made at least from the combination closest to P which gives
a speed greater than that corresponding to P up to the combination closest to Q
which gives a speed less that corresponding to Q.
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ISO/R 789-1968 (I
3.2.1 Complementary measurements
3.2.1.1 TURNING SPACE
These measurements are made on one or other of the surfaces mentioned in clause
3.2.6.1 according to the kind of tractor under test. The track-setting should be one
commonly used in the country in which the test is made and should be stated. Tests
should be made turning right and left, with and without use of the steering brakes.
3.2.1.2 TURNING CIRCLE
Proceed as in clause 3.2.7.1, measuring the left and right diameters, with and without
use of the steering brakes.
3.2.1.3 POSITION OF CENTRE OF GRAVITY
To enable the effects of gradients on tractive effort and stability to be evaluated, the
position of the centre of gravity of the tractor should be determined with and without
ballast, with full tanks and the driver replaced by a weight of 75 kg on the driver’s seat.
3.2.1.4 SPECIAL CHARACTERISTICS OF THE TRACTOR
Supplementary measurements to determine special characteristics of the tractor may
be made, providing all the compulsory tests have been carried out.
The results should be reported in an annex to the test report.
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ISO/R 789-1968 (E)
Annex A
ANNEX A
VOCABULARY
GENERAL REMARKS
The tractor should stand on a rigid horizontal surface. Dimensions of length and width are then
I.
measured on horizontal lines and those of height on vertical lines.
The vehicle should be stationary with its wheels and components in the positions they would be
2.
in if it were travelling in a straight line, unless otherwise stated.
3. The pressure in pneumatic tyres should be adjusted to the value recommended by the tractor
manufacturer for field work.
If additional ballast or equipment is fitted so that this pressure is too low to be in accordance
with the tyre manufacturer’s recommendations, then pressure should be adjusted to conform
to these recommendations.
4. The definitions of the dimensions apply to new vehicles normally equipped.
DEFINITIONS
Agricultural tractors
A. 1
Self-propelled vehicles with wheels, having at least two axles, or tracks, having two tracks and
designed to carry out the following operations, primarily for agricultural purposes :
- pulling trailers,
- carrying, pulling or propelling agricultural tools or machinery and, where necessary,
supplying power to operate them with the tractor in motion or stationary.
An agricultural tractor may be equipped with a removable charging platform, which permits it,
in particular, to carry agricultural products, placed on the tractor.
A.2 Track
A.2.1 Preliminary definition : median plane of the wheel
The median plane of the wheel is equidistant from the two planes containing the periphery
of the rims at their outer edges.
A.2.2 Definition of track
The vertical plane through the wheel axis intersects its median plane along a straight line
which meets the supporting surface at one point.
If A and B are two points thus defined for the wheels on the same axle of the tractor, then
the track width is the distance between points A and B. The track may be thus defined for
both front and rear wheels.
Where there are twin wheels, the track is the distance between two planes, each being the
median plane of one pair of wheels, at right angles to the axis of the pairs of wheels.
For tracklaying tractors, the track is the distance between the median planes of the tracks.
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ISO/R 789-1968 (E)
Annex A
A.2.3 Additional definition : median plane of the tractor
Take the extreme positions of points A and B for the tractor rear axle, which gives the maxi-
mum possible value for the track. The vertical plane at right angles to the centre point of the
segment AB is the median plane of the tractor.
A. 3 Wheelbase
Distance between the vertical planes passing through the segment AB as defined above one for
the front wheels and one for the rear wheels.
A.4 Ground clearance
Distance between the supporting surface and the lowest point of the tractor, the tractor being
loaded to its maximum permissible weight.
A5 Length
Maximum distance between the two vertical planes at right angles to the median plane of the
tractor and touching its front and rear extremities.
All parts of the tractor and, in particular, ail fixed components projecting at the front or rear
(drawbar, etc.) are contained between these two planes.
Hitch components at front and rear removable without implements are not included in the
length.
A.6 Width
Maximum distance between two vertical plane
...