The principal aim of tractor testing is to make available to buyers the data on power output and performance of the tractor. The test would provide a general identification and description of the tractor and its usual accessories.
Preparation for Tests:
The tractor is selected at random from the production unit as directed by the testing station with its usual accessories and in a condition as generally offered for sale.
2. Running-In and Preliminary Adjustment:
(a) The tractor should be new and run-in by the manufacturer before test.
(b) The test report should state the place and duration of running-in.
(c) The manufacturer may make adjustments in governor, ignition and injection during the period the tractor is prepared for tests.
3. Ballasted Tractor:
Wheel equipment and ballast weights which are commercially available and approved by the manufacturer for use in agriculture, may be fitted.
4. Specification Sheet:
The tractor manufacturer should supply the specifications of the tractor. These specifications should be verified by the testing station End should be reported.
5. Repairs and Adjustments during Tests:
All repairs or adjustments made during the test should be noted.
6. Fuels and Lubricants:
Fuels and lubricants should be selected from the range of products commercially available.
7. Other Adjustments:
(a) For measurement of length, width and other dimensions, the tractor should be parked on a firm horizontal surface with steering wheels in a position to allow the tractor to travel in a straight line.
(b) The pressure in pneumatic tyres should be adjusted to the value recommended by the tractor manufacturer for field work.
Type of Tests:
Main tests are of the two types:
(A) Essential test and
(B) Optional test
(A) Essential Test:
In essential tests there are a number of tests:
1. Main power take-off test
2. Belt or pulley shaft test
3. Engine test
4. Drawbar test
5. Centre of gravity
6. Visibility for the driver’s seat
7. Turning space
8. Turning circle
9. Hydraulic power lift
10. Brake test and
11. Air cleaner oil pull-over test
1. Test at the Main Power Take-Off:
(a) Test at Maximum Power:
This test is done with the help of a suitable dynamometer. The tractor is operated for a period of about two hours after the engine has warmed up. Several readings are taken at almost equal intervals during the two hour test. Temperature and pressures are also noted invariably.
The maximum power quoted in the report should be the average of the readings taken during the two hours test. If the power variation exceeds 2% from average value, the test should be repeated. If the same condition persists in further tests, it should be recorded in the report.
(b) Test at Varying Speeds at Full Load:
The torque, power, speed and hourly fuel consumption are noted and suitable curves are plotted.
(c) Tests at Varying Load:
In the governor controlled zone, the torque, speed and hourly fuel consumption should be noted, corresponding to the power of the engine. Engine speed at no load is also recorded. The readings are taken at no load, one quarter load, half load, three quarter load, and full load, corresponding to maximum power and at 85% of the torque.
2. Belt or Pulley Shaft Test:
The tractor pulley is coupled to a dynamometer by a belt. The belt slip should not exceed about 2%. The hourly fuel consumption, specific fuel consumption and engine power should be recorded corresponding to engine speed.
3. Engine Tests:
In this test, sufficient data should be obtained to relate specific fuel consumption with power, torque and engine speed throughout the working period. The results should be presented graphically.
4. Drawbar Test:
Drawbar pull is determined by means of suitable dynamometer, inserted at the hitch between the tractor and the pulling load. For drawbar testing, the load on the back of the tractor has to be varied and hence a loading car is used. Loading car is a device on which any amount of load can be applied.
In drawbar testing, the important things to be noted are:
(a) Drawbar pull
(b) Wheel slip
(c) Fuel consumption and
(d) Time for a given test.
Drawbar performance curves are obtained by applying a large number of known loads in each forward gear and measuring the distance travelled and the time taken for a fixed number of wheel revolution. Fuel consumption is measured directly by means of special apparatus.
5. Position of Centre of Gravity:
The slope of the land has got effects on tractive effort and stability of the tractor. To evaluate this effect, the centre of gravity of the tractor should be determined with and without ballast with fuel tank full, and lubricating oil up to desired mark. A weight of 75 kg is put on the seat of the driver to replace the driver.
6. Visibility from the Driver’s Seat:
This test is done to find whether sufficient visibility is there from the seat of the driver or not.
7. Turning Space:
The diameter of the smallest circle, described by the outermost point of the tractor at a speed not exceeding 2 km/hour is called turning space. The diameter of the circle described by the outermost part of the tractor is measured with accuracy. Tests should be done turning right and left, with and without using the steering brakes.
8. Turning Circle:
The diameter of the circle described by the median plane of the outermost steered wheel while moving at speed not exceeding 2 km/hr. with the steering wheel in full locks, is called turning circle. The turning circle is also measured with accuracy. It is desirable to move the tractor slowly with steering wheels in full lock. The speed should not exceed 2 km/hr.
9. Hydraulic Power Lift:
The engine is run with the governor control lever fully open. The specifications of the hydraulic fluid should confirm the specifications of the manufacturer. Power lift and the hydraulic pump are tested to see whether these items are functioning well according to the requirements.
10. Brake Test:
Brake test is done in cold conditions as well in hot condition. A brake is considered cold when its temperature is lower than 80°C. An artificial horizontal track is prepared, which gives good grip for the tyres. It is desirable to test the brake at maximum speed or at 25 km/hr., whichever is lower. Test should be done in ballasted and un-ballasted conditions.
11. Air Cleaner Oil Pull-Over Test:
The tractor shall be put on a level ground. The air cleaner should be cleaned and filled with normal oil. The engine shall be operated at full governed speed for 15 minutes with continuous acceleration and decelerations. The air-cleaner assembly shall be weighed before and after the test.
The loss of weight of oil will be recorded. If there is no oil pull-over with the tractor in level position the tests shall be repeated with tractor tilted 15° to either side and then 30° forward and backwards with direction of travel.
12. Noise Measurement:
Noise is measured with a sound level meter. This test is done in order to determine that the noise of the tractor is under reasonable limit or not. Some special tests are also done depending upon the requirement.
(B) Optional Test:
Optional test includes noise measurement and some special tests.