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UPM indoor tyre traction testing facility
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Journal of Terramechanics Journal of Terramechanics 44 (2007) 293–301 www.elsevier.com/locate/jterra
UPM indoor tyre traction testing facility A. Yahya *, M. Zohadie, D. Ahmad, A.K. Elwaleed, A.F. Kheiralla Department of Biological and Agricultural Engineering, Faculty of Engineering, University Putra Malaysia, 43400 Serdang, Selangor DE, Malaysia Available online 10 May 2007
Abstract Universiti Putra Malaysia (UPM) tyre traction testing facility was designed and developed to spearhead fundamental research on traction mechanics with high-lug agricultural tyres on tropical soils. This available facility consists of a moving carriage with a cantilever-mounted tyre that moves in either forward or reverse directions on rails well above a soil tank. The present facility set-up was able to operate in either: (a) towing test mode for tyre motion resistance studies, or (b) driving test mode for tyre net traction and tractive efficiency studies. The test tyre on the moving carriage under the towing test mode was made to rotate and engage onto the soil surface in the tank through a chain drive system. Under the driving test mode, the test tyre on the moving carriage was powered to rotate by a motor and a gearbox system with an additional pull provided by a cable-pulley mechanism connected to a tower with hanging dead weights. All controls on the moving carriage were activated from the main control console. Respective transducers were positioned at various localities within and interfaced to a data acquisition system to measure tyre horizontal and vertical forces, tyre sinkage, tyre speed and motion carriage speed. The data acquisition system was able to receive the measured signals in real time, display on the monitor screen and record into its CPU storage memory. Static calibration tests on various associated transducers showed excellent linearity with coefficients of determination (r2) of close to 1. The developed facility was successfully tested to determine motion resistance and net traction ratios for high-lug agricultural tyre at the recommended inflation pressure on sandy clay loam soil. 2007 ISTVS. Published by Elsevier Ltd. All rights reserved. Keywords: Soil bin; Tyre; Traction; Soil–machine
1. Introduction The tyre is an important form of running gear for offroad vehicles, and hence the study of its behaviour is of fundamental importance. Research studies indicate that about 20–55% of the energy developed to the drive tractor wheels is wasted in the tyre–soil interaction. This energy is not only wasted but the resulting soil compaction created by a portion of this energy may be detrimental to crop production [1]. Due to the complex problems of interaction between the vehicle’s running gears (wheel, track, etc.) and various type conditions of terrain surfaces, there have been intensive research efforts to obtain a better understanding of the vehicle system. *
Corresponding author. Tel.: +60 3 86567101/7126; fax: +60 3 86567099. E-mail address: [email protected] (A. Yahya).
Tyre design is almost entirely determined by experimental methods. These tests are conducted either on soil bin found in indoor testing facilities or by performing actual field tyre testing. In 1920, Dr. Mark L. Nichols, a soil dynamics pioneer, developed and used soil bins to study basic soil– machine systems and to identify and quantify soil behaviour that were fundamentally important to the solution of soil– machine problems. Nichols’s experience with small soil bins had led to the proposal for the construction in 1933 of the large soil bin facility that is now the National Soil Dynamics Laboratory, Agricultural Research Service, US Department of Agriculture (NSDL, ARS, USDA) located at Auburn, Alabama [2]. Available reported soil bins have different name depending upon the country and the language. ASAE [2] mentioned names frequently used such as soil bin, soil tank, soil canal, soil channel, soil box and model box. A survey by Wismer [3] found that 36 different facilities in 12 countries had 90 soil bins constructed. However, there
0022-4898/$20.00 2007 ISTVS. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jterra.2007.03.002
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may have been 150 soil bins in use around the world [2] with only several new soil bins built since 1983 [4,5]. Shmulevich et al. [6] stated that some single wheel testers were developed, mostly by government agencies in the USA and other countries. Some examples of the well established facilities are the National Soil Dynamic Laboratory (NSDL) of Auburn in USA, Cranfield University at Silsoe in UK, University of California at Davis in USA, University of Hohenheim in Germany and IMAG of Wageningen in Netherlands. The NSDL single wheel tester was developed as an indoor testing facility capable of performing all necessary tyre tests at very high level of control [7]. The single wheel tester developed at University of California in USA was designed to perform control field experiments. The Davis field single wheel tester is a combination of soil bin and field testing devices [8]. Shmulevich et al. [6] developed a mobile single wheel testing device to perform traction test on agricultural or across country tyres in the field. Most agricultural tractors that are manufactured and used within Asian region are factory installed with highlug agriculture tyres. The applications of Wismer–Luth [9] and Brixius [10] traction equations on these tyres have some limitations and constraints since these traction equations were formulated for general-purpose tyres. The validity of the equations on other type of tyres is presently not well documented. Although, several companies, institutes and universities had done tyre tests for long time, but specific tyre tests involving prediction of tractive performances for high lug agricultural tyres on tropical soils are very limited. Consequently, to meet the challenge, the indoor tyre traction testing facility at Department of Biological and Agricultural Engineering, Universiti Putra Malaysia was designed and developed to spearhead fundamental research on traction mechanics with high-lug agricultural tyres on tropical soils.
ing, Universiti Putra Malaysia (UPM) is shown in Fig. 1. The facility has a moving carriage that moves on rails well above a soil tank. The tested tyre is cantilever mounted to a support rig having linear bearings that are able to slide freely on a vertical polished and hardened shaft of the inner frame of the carriage. The design configuration permits vertical movements of the tyre as it rotates and propels on the soil surface, and at the same time allows for the measurements of the tyre sinkage in the soil. The forward and reverse movement of the carriage is made possible by means of a chain drive system that runs from the drive sprocket at one end and an idler sprocket at the other extreme end with support pulleys located evenly between these two ends. All controls on the moving carriage are located at the main control console closed to the set-up facility. The facility is equipped with the respective transducers to measure the horizontal force, vertical force, sinkage, and rotation of the test tyre and also the rotation of the drive sprocket of the chain drive system. The available data acquisition system is able to receive the measured signals in real time, control the information, display the information on a monitor screen, and finally record the information into a storage medium in real time. 2.2. Moving carriage assembly
2. UPM’s tyre traction testing facility
The moving carriage is a double frame type, with an inner frame that could slide vertically on rollers within an enclosed frame. The moving carriage can travel forward or reverse conditions on the carriage rails located well above the soil tank and can also be lifted or lowered by an electrical hoist fixed on the upper part. The tested tyre is mounted on the moving carriage. The moving carriage dimension is 1.30 m · 0.85 m with total weight of 104 kg. Fig. 2 shows the moving carriage assembly while Fig. 3a depicts the moving carriage with its auxiliaries.
2.1. General description
2.3. Drive and control systems
The general arrangement of soil bin testing facilities at the Department of Biological and Agricultural Engineer-
The moving carriage driving unit is driven by a 3-phase 7.5 kW at 1500 rpm TECO-AEEBAN motor and a 13:1
Fig. 1. Schematic diagram of tyre traction testing facility.
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ratio Fenner type reducing gearbox through a chain-drive system (see Fig. 3b). The output shaft of the speed-reducing gearbox is connected to the drive shaft of the chain drive for the moving carriage through a flexible coupling. As the carriage driving unit moves, the 60 teeth sprocket on the carriage driving unit turns and the carriage speed encoder sends signal to the data acquisition system in microvolts and the readout on the control console displays the travel speed of the moving carriage. The tyre driving unit is powered from a 3-phase 0.75 kW at 1500 rpm Elektrim-SG9056-TH1 motor and a 60:1 TEM-ED20V 1-LUD speed reducing gearbox through a flexible coupling when running in the driving test mode (see Fig. 3c). For the test, the test tyre on the moving carriage is driven to pull the hanging dead weights on the cable-pulley mechanism of the pulling tower. The tower is provided with two pulleys; a pulley at the cross bar of the tower summit to support the hanging dead weight on the cable end and a pulley at the tower base to provide a 90 bent for the cable coming from the top pulley before going to the moving carriage (see Fig. 3d). The main control console controls the overall operations of running the whole soil bin facility (see Fig. 3e). The
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speed control knob on the console can set the moving carriage speed to any desired speed from 0.053 to 0.547 m/s. The emergency knob on the console when triggered could instantaneously cut the power supply to the moving carriage driving unit. Such available provision acts as a safety measure for the operator under emergency circumstances while running the test facility. The digital LED units on the front panel of the console displays the moving carriage speed and tested tyre rotation in real time. 2.4. Soil tanks and fitting equipment The soil testing facility is equipped with two 6.4 m · 0.6 m · 0.8 m size soil tanks having filled with sandy soil and sandy clay loam soil classifications (see Fig. 3f). The tank is located to enable the tested tyre to rotate on the soil surface at the centre position of the tank top. The soil in the tank is manually prepared to the desired test conditions before each test run. Initially, the soil surface is loosened to at least 150 mm depth with a hand hoe and then the surface is levelled with a hand leveller. A 3.75 kW Tai-pan gasoline soil compactor is driven on soil surface soil in the tank to get the desired soil density
Fig. 2. Moving carriage assembly.
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Fig. 3. Tyre traction testing facility main components: (a) moving carriage; (b) moving carriage drive unit; (c) test tyre drive unit; (d) the tower; (e) main control console and (f) soil tank.
in the test runs under towing test mode. The compactor weights 100 kg and equipped with a 485 mm · 480 mm vibration plate. By controlling the compactor speed and the numbers of passes, different soil strength can be obtained for the test runs. The compactor has to be replaced with hand rollers to compact the soil for the test runs under driving test mode. The rollers are made of concrete filled steel tubes of 0.5 m long with either 175 mm or
150 mm diameter sizes. The 175 mm diameter roller weighs 40.5 kg while the 150 mm diameter weighs 29 kg. Additional weights had been added to the rollers to get the desired soil strength for the test runs. An ELE H55-31485 proofing-ring penetrometer with a rated capacity of 1 kN was used to measure the cone index of the prepared test soil in the tank. A special graduated driving shaft and a cone base was fabricated to the size specification
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2.5. Data acquisition system The data acquisition system for the test facility is located in separate room closed to the soil tank facility. This dedicated system is made up of a HP 7500 Series B system that is RS interfaced to a HP Vectra 386 computer system. The computer system has an in-housed LABTECH NOTEBOOK data acquisition software to receive, monitor, display and store the measured signals from the respective transducers in ASCII code format. Quattro Pro Version 2.0 window is used to retrieve and read the stored data, and compute the average, standard deviation and variance of the needed tyre performance measurements. The block diagram of the data acquisition system with associate transducers is shown in Fig. 4. 2.5.1. Transducers Two KYOWA LU-100 KS B340 strain gage typed load cells that are located on a torque arm of the test tyre (see Fig. 5a) measure the horizontal and vertical forces on the tyre. These commercial load cells are able to measure both tension and compression loads at high reliabilty and mea-
surement stability. The horizontal and vertical load cells are connected to channels 2 and 3 of the data acquisition system and respectively records tyre motion resistance during the test runs under tow test mode and tyre torque during the test runs under driving test mode. An ONO SOKKI MP-981 encoder that is located on the main drive shaft of the carriage driving unit (see Fig. 5b) measures the moving carriage speed. The speed encoder is an ultra-small sized magnetic detector that can detect revolutions in digital values without making direct contact. In detecting revolutions, a detecting gear is installed on the revolving shaft and this detector is fastened at a fixed gap from the gear. The encoder detects signals equals to the numbers of teeth of the detecting gear per revolution of the rotating main drive shaft. The encoder is connected to channel 4 of the data acquisition system and records tyre actual travel speed. An ONO SOKKI MP-981 encoder that is located on the drive tyre (see Fig. 5c) measures the test tyre rotation. The set-up and measurement principles of the encoder are similar to the earlier described encoder for carriage speed measurement. The encoder is connected to channel 5 of the data acquisition system and records the tyre theoretical speed. A KYOWA DT 100A displacement transducer that is located on the moving carriage (see Fig. 5d) measures the test tyre vertical movement. The transducer body is held by a magnetic stand from the enclosed frame of the moving carriage and the transducer end rod is set to press on a special push bracket on the inner frame of the moving carriage. The transducer is connected to channel 1 of the main data acquisition system and records the tyre sinkage. 2.5.2. System software The LABTECH NOTEBOOK is an integrated and general-purpose software package and used for data acquisition
Displacement transducer
CH1
Horizontal Load Cell
CH2
Vertical Load Cell
CH3
Carriage Speed Encoder
CH4
Tyre Speed Encoder
CH5
Interface
for soft soil in accordance with ASAE Standard: ASAE S313.2 (ASAE 1996) [11]. Cone Index measurements were made close to the tyre path and were recorded at 250 mm penetration intervals to a depth of 150 mm. The average wheel numeric for the prepared soil was then calculated. Two extreme wheel numerics values of 19 and 29 had chosen for the actual study on tyre net traction ratio under power test mode. For the lower wheel numeric value, 29 kg roller was ran for two passes on the soil surface. However for the higher wheel numeric value, 40.5 kg roller with additional 40 kg dead weight was ran for four passes on the soil surface.
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Disk
CPU Display
Printer Fig. 4. Block diagram of the data acquisition system.
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Fig. 5. Various transducers of the data acquisition system: (a) horizontal and vertical load cells; (b) carriage speed encoder; (c) tyre rotation encoder and (d) displacement transducer.
system, monitoring and real time control. In the normal mode, data acquisition system may perform at sampling rates of 0.001–900 Hz. The display of data is available to user at real time on the monitor screen and the data could be permanently stored in a defined file in the storage medium of computer. The graphical interface ICONVIEW in the LABTECH NOTEBOOK software is used to in the system set-up for data monitoring and acquisition. The initial readings from the various mentioned transducers are recorded by the data acquisition system while the tyre is at the start position for each test run when the RUN command in the main menu screen of the software is triggered. The actual readings are taken while the tyre is rotating on the soil surface when the RUN command in the menu screen of the software is triggered. The ANALYSIS command in the main menu is used for post processing of the recording data after test run. Quattro Pro worksheet software is integrated together with LABTECH NOTEBOOK for determination of the means, standard deviations and variance, and also for retrieving and printing the initial and final readings. The user is able to return back to the main menu of the LABTECH NOTEBOOK by twice pressing the ESC key.
3. Calibration of transducers The static calibration was done to find the relationship between the voltage output from the force or displacement transducer with respect to a known applied force or applied displacement. All measurements were taken in micro-volts by the data acquisition system and the recorded measurements were retrieved using the Quattro Pro Version 2.0 for post processing. The general linear model procedure in PC SAS software package [12] was used to determine the linear relationship of the measured voltage with applied force or applied displacement. In all of the involved calibration tests, the obtained correlation coefficients were close to 1 with the respective transducers. 3.1. Load cells calibration The calibration process starts with the disconnection of the vertical load cell from the torque arm of the test tyre. A hanger was attached to the free clevis of the vertical load cell. An initial load is measured for the 30 s at one second sampling rate by the data acquisition system. The average, standard deviation and variance was calculated before
A. Yahya et al. / Journal of Terramechanics 44 (2007) 293–301
between dead weight and voltage output. The calibration curve for the horizontal and vertical load cells are shown Fig. 6a and b, respectively.
dead weights are loaded. Dead weight was loaded from 0 to 5402.5 · 10 6 kgf on the hanger at an interval of 1351.34 · 10 6 kgf and measurements were taken in micro-volts by the data acquisition system. The average, standard deviation and variance was calculated for each dead weight loading. Measurements were also taken for the unloading of dead weights. The procedure was repeated for three times before regression analysis was conducted with the obtained data. The vertical load cell was secured back to the torque arm of the test tyre upon the completion of the calibration test. As for horizontal load cell, a hanger was attached to the free clevis of the horizontal load cell after it had been connected from the torque arm of the test tyre. The same procedures as for the vertical load cell were repeated in the calibration of the horizontal load cell. Output of regression analysis was used to find the relationship
3.2. Displacement transducers calibration The displacement transducer had a plunger having a scale from 0 to 100 mm and was fixed onto moving carriage. Calibration of the transducer was done by measuring the initial reading when the plunger is at 0 mm scale for 30 s at one sampling rate by the data acquisition system. The plunger was then pushed to 10 mm scale and held for 30 s. Measurement was taken every second at sampling rate for 30 s. The same procedure was followed for every increase of 10 mm until the plunger reached the 100 mm scale. The same procedure was followed for the next two
b
250 200 150
y = 0.0394x R2 = 0.9997
100 50
250
Output Voltage (E-6 V)
Output Voltage (E-6 V)
a
200 150
y = 0.0408x R2 = 0.9862
100 50 0
0 0
2000
4000
0
6000
5000 y = 66.788x R2 = 0.9998
4000 3000 2000 1000
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Output Voltage (E-6 V)
6000
6000
500 400 y = 958.49x R2 = 0.998
300 200 100 0
0
20
40 60 80 Tyre Sinkage (mm)
100
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f
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2 Force (kN)
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4000
d 600
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0
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2000
Applied Load (E-6 kgf)
Applied Load (E-6 kgf)
c
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150 y = 577.41x R2 = 0.9926
100
1.5
50
0.5
0
0 0
0.1
0.2
0.3
Tyre Rotation (rev/s)
0.4
y = 0.3399x R2 = 0.9997
1
0
2
4
6
Penetrometer Reading (mm)
Fig. 6. Calibration curves for various transducers: (a) horizontal load cell; (b) vertical load cell; (c) displacement transducer; (d) carriage speed encoder; (e) tyre rotation encoder and (f) soil cone penetrometer.
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replicates and from the output of these three replicates regression analysis was done. The calibration curve for the displacement transducer is shown in Fig. 6c. 3.3. Carriage speed encoder calibration Initial zero carriage speed was recorded before various carriage speeds was used to move the carriage. The measurement was taken in micro-volts by the data acquisition system at one-second sampling rate for 30 s. The carriage speed was then increased from 0 to 0.549 m/s at an interval of 0.12 m/s. At each increment of carriage speed, measurements was measured and recorded by the data acquisition system. The calibration was proceeded for the next two replicates and from the output of these three replicates regression analysis was done. The calibration curve for carriage speed encoder is shown in Fig. 6d.
to 70 in the tyre motion resistance test. A total of 42 test runs were carried out at the same nominal inflation pressure and wheel numeric level of 19 and 29 for a travel reduction of 0 to 40% in the tyre net traction test. Fig. 7 represents the tyre motion resistance ratio curve at a nominal inflation pressure of 221 kPa while Figs. 8 and 9 represent the tyre net traction ratio curves at a nominal inflation pressure of 221 kPa and wheel numerics of 29 and 19, respectively. The results showed that the logarithmic model is the best to describe the tyre motion resistance ration and net traction ratio for a high-lug agricultural tyre. Detail descriptions of experimental procedure, analysis and interpretation of data were reported by Elwaleed [13]. This paper reports the development and operations of UPM indoor tyre traction testing facility. Only description of the facility and its operations are presented to demonstrate the capability and value of the facility.
3.4. Tyre rotation encoder calibration Motion Resistance Ratio
0.3
Initial zero tyre rotation was measured before various tyre speeds was used to rotate the tyre. The measurement was taken in micro-volt by the data acquisition system at one-second sampling rate for 30 s. Tyre operating speed was then increased from 0 to 0.324 m/s at an interval of 0.07 m/s. At each increment of tyre speed, the measurement was measured and recorded by the data acquisition system. The calibration was proceeded for the next two replicates and from the output of these three replications regression analysis was done. The calibration curve for tyre rotation encoder is shown in Fig. 6e.
0.2 T F = -0.0682Ln(Cn ) + 0.3719 R2 = 0.8597
0.15 0.1 0.05 0
0
10
20
30 40 50 Wheel Numeric
60
70
Fig. 7. Tyre motion resistance ratio at 221 kPa.
Net Traction Ratio
3.5. Soil cone penetrometer calibration The soil cone penetrometer was held vertically and forces were applied from an Instron machine. The force applied was added and the changes of gauge reading were recorded manually. This was done for two more replication and regression was done to obtain the relationship between applied force and gauge reading. The calibration curve for soil cone penetrometer is shown in Fig. 6f.
0.25
0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0
P/W = 0.083Ln(s) + 0.55 R2 = 0.9384
0
0.05
0.1
4. Facility performance
0.25 0.15 0.2 Travel Reduction
0.3
0.35
0.4
Net Traction Ratio
Fig. 8. Tyre net traction ratio for wheel numeric of 29 at 221 kPa.
Extensive tests were conducted using the indoor tyre traction testing facility of Biological and Agricultural Engineering Department at Universiti Putra Malaysia to determine the motion resistance and net traction ratios for high-lug agricultural tyre on sandy clay loam soil. A Bridgestone 5–12, 4-ply, lug-M or high-lug agricultural type was used as test tyre. The soil tank was filled with sandy-clay-loam soil and was manually prepared for each test run. Penetration readings of the prepared soil using ELE H55-3-1485 proofing-ring penetromer were determined randomly at six different sites throughout the soil surface. A total 33 test runs were carried out at a nominal inflation pressure of 221 kPa for a wheel numeric range of 0
0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0
P/W = 0.061Ln(s) + 0.56 R2 = 0.9062
0.05
0.1
0.25 0.15 0.2 Travel Reduction
0.3
0.35
0.4
Fig. 9. Tyre net traction ratio for wheel numeric of 19 at 221 kPa.
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5. Conclusions UPM single wheel tyre facility has been designed and developed to test high lug agricultural tyres at towed and driving modes for their motion resistance, net traction and tractive efficiency at different soil conditions. The facility can be used for testing the effects of other parameters such as dynamic loading, ballasting, travel speed, and tyre inflation pressure on tractive performances of the tyre. Acknowledgements This research project is classified under RM7 IRPA Project No. 01-02-04. The authors are very grateful to the Ministry of Science, Technology and the Environment of Malaysia for granting the fund for this research project. The authors are also grateful to Dr. R.P. Hettiaratchi of the Department of Agricultural and Environmental Science, University of Newcastle upon Tyne for his constructive guidance during the development of this facility. References [1] Burt EC, Lyne PW, Meiring P, Keen JF. Ballast and inflation effect on tyre efficiency. Trans ASAE 1983;26(5):1352–4.
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[2] ASAE. Advances in soil bin dynamics. American Society of Agricultural Engineering, 2950 Niles Road, St. Joseph, Michigan, USA, vol. 1; 1994. [3] Wismer RD. Soil bin facilities: characteristics and utilization. In: Proc. 8th international conference, international society for Terrain-Vehicle systems, vol. III. England: Cambridge; 6–10 August 1984, p. 1201–16. [4] Wood RK, Wells LG. A soil bin to study compaction. ASAE paper No. 83–1044. ASAE, St. Joseph:Michigan; 1983. [5] Onwualu AP., Watts KC. Development of a soil bin test facility. ASAE paper No. 89–1106, ASAE, St. Joseph: Michigan; 1989. [6] Shmulevich I, Ronai D, Wolf D. A new field single wheel tester. J Terramech 1996;33(3):133–41. [7] Burt EC, Reaves CA, Baily AC, Pickering WD. A machine for testing tractor tyres in soil bins. Trans ASAE 1980;23(3):546–7. [8] Upadhyaya SK, Mehkschau J, Wulfson D, Glancey JL. Development of a unique, mobile, single wheel testing device. Trans ASAE 1986;29(5):1243–6. [9] Wismer RD, Luth HJ. Off-road traction prediction for wheeled vehicles. Trans ASAE 1974;17(1):8–10. [10] Brixius WW. Traction prediction equation for bias ply tyres. ASAE paper, No. 87-1622. ASAE, St. Joseph: MI; 1987. [11] ASAE Standards S313.2. Soil cone penetrometer. In: Hahn RH, Purschwitz MA, Rosentreter EE, editors. ASAE Standards. MI: ASAE, St. Joseph; 1997. p. 821–2. [12] Steel RGD, Torrie JH. Principles and procedures of statistics, a biometrical approach. New York: McGraw-Hill Book Co., Inc.; 1996. [13] Elwaleed AK. Motion resistance ratio, net traction ratio and tractive efficiency of Riceland type tyre. MS Thesis, Biological and Agricultural Engineering Department, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Selangor DE, Malaysia; 1999, unpublished.
Journal of Terramechanics Journal of Terramechanics 44 (2007) 293–301 www.elsevier.com/locate/jterra
UPM indoor tyre traction testing facility A. Yahya *, M. Zohadie, D. Ahmad, A.K. Elwaleed, A.F. Kheiralla Department of Biological and Agricultural Engineering, Faculty of Engineering, University Putra Malaysia, 43400 Serdang, Selangor DE, Malaysia Available online 10 May 2007
Abstract Universiti Putra Malaysia (UPM) tyre traction testing facility was designed and developed to spearhead fundamental research on traction mechanics with high-lug agricultural tyres on tropical soils. This available facility consists of a moving carriage with a cantilever-mounted tyre that moves in either forward or reverse directions on rails well above a soil tank. The present facility set-up was able to operate in either: (a) towing test mode for tyre motion resistance studies, or (b) driving test mode for tyre net traction and tractive efficiency studies. The test tyre on the moving carriage under the towing test mode was made to rotate and engage onto the soil surface in the tank through a chain drive system. Under the driving test mode, the test tyre on the moving carriage was powered to rotate by a motor and a gearbox system with an additional pull provided by a cable-pulley mechanism connected to a tower with hanging dead weights. All controls on the moving carriage were activated from the main control console. Respective transducers were positioned at various localities within and interfaced to a data acquisition system to measure tyre horizontal and vertical forces, tyre sinkage, tyre speed and motion carriage speed. The data acquisition system was able to receive the measured signals in real time, display on the monitor screen and record into its CPU storage memory. Static calibration tests on various associated transducers showed excellent linearity with coefficients of determination (r2) of close to 1. The developed facility was successfully tested to determine motion resistance and net traction ratios for high-lug agricultural tyre at the recommended inflation pressure on sandy clay loam soil. 2007 ISTVS. Published by Elsevier Ltd. All rights reserved. Keywords: Soil bin; Tyre; Traction; Soil–machine
1. Introduction The tyre is an important form of running gear for offroad vehicles, and hence the study of its behaviour is of fundamental importance. Research studies indicate that about 20–55% of the energy developed to the drive tractor wheels is wasted in the tyre–soil interaction. This energy is not only wasted but the resulting soil compaction created by a portion of this energy may be detrimental to crop production [1]. Due to the complex problems of interaction between the vehicle’s running gears (wheel, track, etc.) and various type conditions of terrain surfaces, there have been intensive research efforts to obtain a better understanding of the vehicle system. *
Corresponding author. Tel.: +60 3 86567101/7126; fax: +60 3 86567099. E-mail address: [email protected] (A. Yahya).
Tyre design is almost entirely determined by experimental methods. These tests are conducted either on soil bin found in indoor testing facilities or by performing actual field tyre testing. In 1920, Dr. Mark L. Nichols, a soil dynamics pioneer, developed and used soil bins to study basic soil– machine systems and to identify and quantify soil behaviour that were fundamentally important to the solution of soil– machine problems. Nichols’s experience with small soil bins had led to the proposal for the construction in 1933 of the large soil bin facility that is now the National Soil Dynamics Laboratory, Agricultural Research Service, US Department of Agriculture (NSDL, ARS, USDA) located at Auburn, Alabama [2]. Available reported soil bins have different name depending upon the country and the language. ASAE [2] mentioned names frequently used such as soil bin, soil tank, soil canal, soil channel, soil box and model box. A survey by Wismer [3] found that 36 different facilities in 12 countries had 90 soil bins constructed. However, there
0022-4898/$20.00 2007 ISTVS. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jterra.2007.03.002
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may have been 150 soil bins in use around the world [2] with only several new soil bins built since 1983 [4,5]. Shmulevich et al. [6] stated that some single wheel testers were developed, mostly by government agencies in the USA and other countries. Some examples of the well established facilities are the National Soil Dynamic Laboratory (NSDL) of Auburn in USA, Cranfield University at Silsoe in UK, University of California at Davis in USA, University of Hohenheim in Germany and IMAG of Wageningen in Netherlands. The NSDL single wheel tester was developed as an indoor testing facility capable of performing all necessary tyre tests at very high level of control [7]. The single wheel tester developed at University of California in USA was designed to perform control field experiments. The Davis field single wheel tester is a combination of soil bin and field testing devices [8]. Shmulevich et al. [6] developed a mobile single wheel testing device to perform traction test on agricultural or across country tyres in the field. Most agricultural tractors that are manufactured and used within Asian region are factory installed with highlug agriculture tyres. The applications of Wismer–Luth [9] and Brixius [10] traction equations on these tyres have some limitations and constraints since these traction equations were formulated for general-purpose tyres. The validity of the equations on other type of tyres is presently not well documented. Although, several companies, institutes and universities had done tyre tests for long time, but specific tyre tests involving prediction of tractive performances for high lug agricultural tyres on tropical soils are very limited. Consequently, to meet the challenge, the indoor tyre traction testing facility at Department of Biological and Agricultural Engineering, Universiti Putra Malaysia was designed and developed to spearhead fundamental research on traction mechanics with high-lug agricultural tyres on tropical soils.
ing, Universiti Putra Malaysia (UPM) is shown in Fig. 1. The facility has a moving carriage that moves on rails well above a soil tank. The tested tyre is cantilever mounted to a support rig having linear bearings that are able to slide freely on a vertical polished and hardened shaft of the inner frame of the carriage. The design configuration permits vertical movements of the tyre as it rotates and propels on the soil surface, and at the same time allows for the measurements of the tyre sinkage in the soil. The forward and reverse movement of the carriage is made possible by means of a chain drive system that runs from the drive sprocket at one end and an idler sprocket at the other extreme end with support pulleys located evenly between these two ends. All controls on the moving carriage are located at the main control console closed to the set-up facility. The facility is equipped with the respective transducers to measure the horizontal force, vertical force, sinkage, and rotation of the test tyre and also the rotation of the drive sprocket of the chain drive system. The available data acquisition system is able to receive the measured signals in real time, control the information, display the information on a monitor screen, and finally record the information into a storage medium in real time. 2.2. Moving carriage assembly
2. UPM’s tyre traction testing facility
The moving carriage is a double frame type, with an inner frame that could slide vertically on rollers within an enclosed frame. The moving carriage can travel forward or reverse conditions on the carriage rails located well above the soil tank and can also be lifted or lowered by an electrical hoist fixed on the upper part. The tested tyre is mounted on the moving carriage. The moving carriage dimension is 1.30 m · 0.85 m with total weight of 104 kg. Fig. 2 shows the moving carriage assembly while Fig. 3a depicts the moving carriage with its auxiliaries.
2.1. General description
2.3. Drive and control systems
The general arrangement of soil bin testing facilities at the Department of Biological and Agricultural Engineer-
The moving carriage driving unit is driven by a 3-phase 7.5 kW at 1500 rpm TECO-AEEBAN motor and a 13:1
Fig. 1. Schematic diagram of tyre traction testing facility.
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ratio Fenner type reducing gearbox through a chain-drive system (see Fig. 3b). The output shaft of the speed-reducing gearbox is connected to the drive shaft of the chain drive for the moving carriage through a flexible coupling. As the carriage driving unit moves, the 60 teeth sprocket on the carriage driving unit turns and the carriage speed encoder sends signal to the data acquisition system in microvolts and the readout on the control console displays the travel speed of the moving carriage. The tyre driving unit is powered from a 3-phase 0.75 kW at 1500 rpm Elektrim-SG9056-TH1 motor and a 60:1 TEM-ED20V 1-LUD speed reducing gearbox through a flexible coupling when running in the driving test mode (see Fig. 3c). For the test, the test tyre on the moving carriage is driven to pull the hanging dead weights on the cable-pulley mechanism of the pulling tower. The tower is provided with two pulleys; a pulley at the cross bar of the tower summit to support the hanging dead weight on the cable end and a pulley at the tower base to provide a 90 bent for the cable coming from the top pulley before going to the moving carriage (see Fig. 3d). The main control console controls the overall operations of running the whole soil bin facility (see Fig. 3e). The
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speed control knob on the console can set the moving carriage speed to any desired speed from 0.053 to 0.547 m/s. The emergency knob on the console when triggered could instantaneously cut the power supply to the moving carriage driving unit. Such available provision acts as a safety measure for the operator under emergency circumstances while running the test facility. The digital LED units on the front panel of the console displays the moving carriage speed and tested tyre rotation in real time. 2.4. Soil tanks and fitting equipment The soil testing facility is equipped with two 6.4 m · 0.6 m · 0.8 m size soil tanks having filled with sandy soil and sandy clay loam soil classifications (see Fig. 3f). The tank is located to enable the tested tyre to rotate on the soil surface at the centre position of the tank top. The soil in the tank is manually prepared to the desired test conditions before each test run. Initially, the soil surface is loosened to at least 150 mm depth with a hand hoe and then the surface is levelled with a hand leveller. A 3.75 kW Tai-pan gasoline soil compactor is driven on soil surface soil in the tank to get the desired soil density
Fig. 2. Moving carriage assembly.
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Fig. 3. Tyre traction testing facility main components: (a) moving carriage; (b) moving carriage drive unit; (c) test tyre drive unit; (d) the tower; (e) main control console and (f) soil tank.
in the test runs under towing test mode. The compactor weights 100 kg and equipped with a 485 mm · 480 mm vibration plate. By controlling the compactor speed and the numbers of passes, different soil strength can be obtained for the test runs. The compactor has to be replaced with hand rollers to compact the soil for the test runs under driving test mode. The rollers are made of concrete filled steel tubes of 0.5 m long with either 175 mm or
150 mm diameter sizes. The 175 mm diameter roller weighs 40.5 kg while the 150 mm diameter weighs 29 kg. Additional weights had been added to the rollers to get the desired soil strength for the test runs. An ELE H55-31485 proofing-ring penetrometer with a rated capacity of 1 kN was used to measure the cone index of the prepared test soil in the tank. A special graduated driving shaft and a cone base was fabricated to the size specification
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2.5. Data acquisition system The data acquisition system for the test facility is located in separate room closed to the soil tank facility. This dedicated system is made up of a HP 7500 Series B system that is RS interfaced to a HP Vectra 386 computer system. The computer system has an in-housed LABTECH NOTEBOOK data acquisition software to receive, monitor, display and store the measured signals from the respective transducers in ASCII code format. Quattro Pro Version 2.0 window is used to retrieve and read the stored data, and compute the average, standard deviation and variance of the needed tyre performance measurements. The block diagram of the data acquisition system with associate transducers is shown in Fig. 4. 2.5.1. Transducers Two KYOWA LU-100 KS B340 strain gage typed load cells that are located on a torque arm of the test tyre (see Fig. 5a) measure the horizontal and vertical forces on the tyre. These commercial load cells are able to measure both tension and compression loads at high reliabilty and mea-
surement stability. The horizontal and vertical load cells are connected to channels 2 and 3 of the data acquisition system and respectively records tyre motion resistance during the test runs under tow test mode and tyre torque during the test runs under driving test mode. An ONO SOKKI MP-981 encoder that is located on the main drive shaft of the carriage driving unit (see Fig. 5b) measures the moving carriage speed. The speed encoder is an ultra-small sized magnetic detector that can detect revolutions in digital values without making direct contact. In detecting revolutions, a detecting gear is installed on the revolving shaft and this detector is fastened at a fixed gap from the gear. The encoder detects signals equals to the numbers of teeth of the detecting gear per revolution of the rotating main drive shaft. The encoder is connected to channel 4 of the data acquisition system and records tyre actual travel speed. An ONO SOKKI MP-981 encoder that is located on the drive tyre (see Fig. 5c) measures the test tyre rotation. The set-up and measurement principles of the encoder are similar to the earlier described encoder for carriage speed measurement. The encoder is connected to channel 5 of the data acquisition system and records the tyre theoretical speed. A KYOWA DT 100A displacement transducer that is located on the moving carriage (see Fig. 5d) measures the test tyre vertical movement. The transducer body is held by a magnetic stand from the enclosed frame of the moving carriage and the transducer end rod is set to press on a special push bracket on the inner frame of the moving carriage. The transducer is connected to channel 1 of the main data acquisition system and records the tyre sinkage. 2.5.2. System software The LABTECH NOTEBOOK is an integrated and general-purpose software package and used for data acquisition
Displacement transducer
CH1
Horizontal Load Cell
CH2
Vertical Load Cell
CH3
Carriage Speed Encoder
CH4
Tyre Speed Encoder
CH5
Interface
for soft soil in accordance with ASAE Standard: ASAE S313.2 (ASAE 1996) [11]. Cone Index measurements were made close to the tyre path and were recorded at 250 mm penetration intervals to a depth of 150 mm. The average wheel numeric for the prepared soil was then calculated. Two extreme wheel numerics values of 19 and 29 had chosen for the actual study on tyre net traction ratio under power test mode. For the lower wheel numeric value, 29 kg roller was ran for two passes on the soil surface. However for the higher wheel numeric value, 40.5 kg roller with additional 40 kg dead weight was ran for four passes on the soil surface.
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Disk
CPU Display
Printer Fig. 4. Block diagram of the data acquisition system.
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Fig. 5. Various transducers of the data acquisition system: (a) horizontal and vertical load cells; (b) carriage speed encoder; (c) tyre rotation encoder and (d) displacement transducer.
system, monitoring and real time control. In the normal mode, data acquisition system may perform at sampling rates of 0.001–900 Hz. The display of data is available to user at real time on the monitor screen and the data could be permanently stored in a defined file in the storage medium of computer. The graphical interface ICONVIEW in the LABTECH NOTEBOOK software is used to in the system set-up for data monitoring and acquisition. The initial readings from the various mentioned transducers are recorded by the data acquisition system while the tyre is at the start position for each test run when the RUN command in the main menu screen of the software is triggered. The actual readings are taken while the tyre is rotating on the soil surface when the RUN command in the menu screen of the software is triggered. The ANALYSIS command in the main menu is used for post processing of the recording data after test run. Quattro Pro worksheet software is integrated together with LABTECH NOTEBOOK for determination of the means, standard deviations and variance, and also for retrieving and printing the initial and final readings. The user is able to return back to the main menu of the LABTECH NOTEBOOK by twice pressing the ESC key.
3. Calibration of transducers The static calibration was done to find the relationship between the voltage output from the force or displacement transducer with respect to a known applied force or applied displacement. All measurements were taken in micro-volts by the data acquisition system and the recorded measurements were retrieved using the Quattro Pro Version 2.0 for post processing. The general linear model procedure in PC SAS software package [12] was used to determine the linear relationship of the measured voltage with applied force or applied displacement. In all of the involved calibration tests, the obtained correlation coefficients were close to 1 with the respective transducers. 3.1. Load cells calibration The calibration process starts with the disconnection of the vertical load cell from the torque arm of the test tyre. A hanger was attached to the free clevis of the vertical load cell. An initial load is measured for the 30 s at one second sampling rate by the data acquisition system. The average, standard deviation and variance was calculated before
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between dead weight and voltage output. The calibration curve for the horizontal and vertical load cells are shown Fig. 6a and b, respectively.
dead weights are loaded. Dead weight was loaded from 0 to 5402.5 · 10 6 kgf on the hanger at an interval of 1351.34 · 10 6 kgf and measurements were taken in micro-volts by the data acquisition system. The average, standard deviation and variance was calculated for each dead weight loading. Measurements were also taken for the unloading of dead weights. The procedure was repeated for three times before regression analysis was conducted with the obtained data. The vertical load cell was secured back to the torque arm of the test tyre upon the completion of the calibration test. As for horizontal load cell, a hanger was attached to the free clevis of the horizontal load cell after it had been connected from the torque arm of the test tyre. The same procedures as for the vertical load cell were repeated in the calibration of the horizontal load cell. Output of regression analysis was used to find the relationship
3.2. Displacement transducers calibration The displacement transducer had a plunger having a scale from 0 to 100 mm and was fixed onto moving carriage. Calibration of the transducer was done by measuring the initial reading when the plunger is at 0 mm scale for 30 s at one sampling rate by the data acquisition system. The plunger was then pushed to 10 mm scale and held for 30 s. Measurement was taken every second at sampling rate for 30 s. The same procedure was followed for every increase of 10 mm until the plunger reached the 100 mm scale. The same procedure was followed for the next two
b
250 200 150
y = 0.0394x R2 = 0.9997
100 50
250
Output Voltage (E-6 V)
Output Voltage (E-6 V)
a
200 150
y = 0.0408x R2 = 0.9862
100 50 0
0 0
2000
4000
0
6000
5000 y = 66.788x R2 = 0.9998
4000 3000 2000 1000
Output Voltage (E-6 V)
Output Voltage (E-6 V)
6000
6000
500 400 y = 958.49x R2 = 0.998
300 200 100 0
0
20
40 60 80 Tyre Sinkage (mm)
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0.2
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2 Force (kN)
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4000
d 600
7000
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e
2000
Applied Load (E-6 kgf)
Applied Load (E-6 kgf)
c
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150 y = 577.41x R2 = 0.9926
100
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50
0.5
0
0 0
0.1
0.2
0.3
Tyre Rotation (rev/s)
0.4
y = 0.3399x R2 = 0.9997
1
0
2
4
6
Penetrometer Reading (mm)
Fig. 6. Calibration curves for various transducers: (a) horizontal load cell; (b) vertical load cell; (c) displacement transducer; (d) carriage speed encoder; (e) tyre rotation encoder and (f) soil cone penetrometer.
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replicates and from the output of these three replicates regression analysis was done. The calibration curve for the displacement transducer is shown in Fig. 6c. 3.3. Carriage speed encoder calibration Initial zero carriage speed was recorded before various carriage speeds was used to move the carriage. The measurement was taken in micro-volts by the data acquisition system at one-second sampling rate for 30 s. The carriage speed was then increased from 0 to 0.549 m/s at an interval of 0.12 m/s. At each increment of carriage speed, measurements was measured and recorded by the data acquisition system. The calibration was proceeded for the next two replicates and from the output of these three replicates regression analysis was done. The calibration curve for carriage speed encoder is shown in Fig. 6d.
to 70 in the tyre motion resistance test. A total of 42 test runs were carried out at the same nominal inflation pressure and wheel numeric level of 19 and 29 for a travel reduction of 0 to 40% in the tyre net traction test. Fig. 7 represents the tyre motion resistance ratio curve at a nominal inflation pressure of 221 kPa while Figs. 8 and 9 represent the tyre net traction ratio curves at a nominal inflation pressure of 221 kPa and wheel numerics of 29 and 19, respectively. The results showed that the logarithmic model is the best to describe the tyre motion resistance ration and net traction ratio for a high-lug agricultural tyre. Detail descriptions of experimental procedure, analysis and interpretation of data were reported by Elwaleed [13]. This paper reports the development and operations of UPM indoor tyre traction testing facility. Only description of the facility and its operations are presented to demonstrate the capability and value of the facility.
3.4. Tyre rotation encoder calibration Motion Resistance Ratio
0.3
Initial zero tyre rotation was measured before various tyre speeds was used to rotate the tyre. The measurement was taken in micro-volt by the data acquisition system at one-second sampling rate for 30 s. Tyre operating speed was then increased from 0 to 0.324 m/s at an interval of 0.07 m/s. At each increment of tyre speed, the measurement was measured and recorded by the data acquisition system. The calibration was proceeded for the next two replicates and from the output of these three replications regression analysis was done. The calibration curve for tyre rotation encoder is shown in Fig. 6e.
0.2 T F = -0.0682Ln(Cn ) + 0.3719 R2 = 0.8597
0.15 0.1 0.05 0
0
10
20
30 40 50 Wheel Numeric
60
70
Fig. 7. Tyre motion resistance ratio at 221 kPa.
Net Traction Ratio
3.5. Soil cone penetrometer calibration The soil cone penetrometer was held vertically and forces were applied from an Instron machine. The force applied was added and the changes of gauge reading were recorded manually. This was done for two more replication and regression was done to obtain the relationship between applied force and gauge reading. The calibration curve for soil cone penetrometer is shown in Fig. 6f.
0.25
0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0
P/W = 0.083Ln(s) + 0.55 R2 = 0.9384
0
0.05
0.1
4. Facility performance
0.25 0.15 0.2 Travel Reduction
0.3
0.35
0.4
Net Traction Ratio
Fig. 8. Tyre net traction ratio for wheel numeric of 29 at 221 kPa.
Extensive tests were conducted using the indoor tyre traction testing facility of Biological and Agricultural Engineering Department at Universiti Putra Malaysia to determine the motion resistance and net traction ratios for high-lug agricultural tyre on sandy clay loam soil. A Bridgestone 5–12, 4-ply, lug-M or high-lug agricultural type was used as test tyre. The soil tank was filled with sandy-clay-loam soil and was manually prepared for each test run. Penetration readings of the prepared soil using ELE H55-3-1485 proofing-ring penetromer were determined randomly at six different sites throughout the soil surface. A total 33 test runs were carried out at a nominal inflation pressure of 221 kPa for a wheel numeric range of 0
0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0
P/W = 0.061Ln(s) + 0.56 R2 = 0.9062
0.05
0.1
0.25 0.15 0.2 Travel Reduction
0.3
0.35
0.4
Fig. 9. Tyre net traction ratio for wheel numeric of 19 at 221 kPa.
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5. Conclusions UPM single wheel tyre facility has been designed and developed to test high lug agricultural tyres at towed and driving modes for their motion resistance, net traction and tractive efficiency at different soil conditions. The facility can be used for testing the effects of other parameters such as dynamic loading, ballasting, travel speed, and tyre inflation pressure on tractive performances of the tyre. Acknowledgements This research project is classified under RM7 IRPA Project No. 01-02-04. The authors are very grateful to the Ministry of Science, Technology and the Environment of Malaysia for granting the fund for this research project. The authors are also grateful to Dr. R.P. Hettiaratchi of the Department of Agricultural and Environmental Science, University of Newcastle upon Tyne for his constructive guidance during the development of this facility. References [1] Burt EC, Lyne PW, Meiring P, Keen JF. Ballast and inflation effect on tyre efficiency. Trans ASAE 1983;26(5):1352–4.
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[2] ASAE. Advances in soil bin dynamics. American Society of Agricultural Engineering, 2950 Niles Road, St. Joseph, Michigan, USA, vol. 1; 1994. [3] Wismer RD. Soil bin facilities: characteristics and utilization. In: Proc. 8th international conference, international society for Terrain-Vehicle systems, vol. III. England: Cambridge; 6–10 August 1984, p. 1201–16. [4] Wood RK, Wells LG. A soil bin to study compaction. ASAE paper No. 83–1044. ASAE, St. Joseph:Michigan; 1983. [5] Onwualu AP., Watts KC. Development of a soil bin test facility. ASAE paper No. 89–1106, ASAE, St. Joseph: Michigan; 1989. [6] Shmulevich I, Ronai D, Wolf D. A new field single wheel tester. J Terramech 1996;33(3):133–41. [7] Burt EC, Reaves CA, Baily AC, Pickering WD. A machine for testing tractor tyres in soil bins. Trans ASAE 1980;23(3):546–7. [8] Upadhyaya SK, Mehkschau J, Wulfson D, Glancey JL. Development of a unique, mobile, single wheel testing device. Trans ASAE 1986;29(5):1243–6. [9] Wismer RD, Luth HJ. Off-road traction prediction for wheeled vehicles. Trans ASAE 1974;17(1):8–10. [10] Brixius WW. Traction prediction equation for bias ply tyres. ASAE paper, No. 87-1622. ASAE, St. Joseph: MI; 1987. [11] ASAE Standards S313.2. Soil cone penetrometer. In: Hahn RH, Purschwitz MA, Rosentreter EE, editors. ASAE Standards. MI: ASAE, St. Joseph; 1997. p. 821–2. [12] Steel RGD, Torrie JH. Principles and procedures of statistics, a biometrical approach. New York: McGraw-Hill Book Co., Inc.; 1996. [13] Elwaleed AK. Motion resistance ratio, net traction ratio and tractive efficiency of Riceland type tyre. MS Thesis, Biological and Agricultural Engineering Department, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Selangor DE, Malaysia; 1999, unpublished.