Minia Journal of Engineering & Technology (MJET), Vol. 37, No. 1. January 2018

STUDY OF THE TORSION BAR PASSIVE SUSPENSION SYSTEM

Mohamed Khairy1, S. Allam1 and M. Rabie2

1Automotive Technology Department, Faculty of Industrial Education, Helwan University. 2Automotive and Tractor Dept., College of Engineering, Minia University.

E-mail of corresponding author: [email protected].

Abstract

A torsion bar passive suspension is a general term for any vehicle suspension that uses a torsion bar as its main weight bearing . The main advantages of a torsion bar passive suspension system are durability, easy adjustability of , and small profile along the width of the vehicle. It takes up less of the vehicle's interior volume than coil springs. The purpose of this study is to investigate the effect of the ride height of a vehicle which adjusted by the torsion bar on the vehicle body vibration in torsion bar passive suspension system. In this work the study, a front suspension of double-wishbone type suspension with upper torsion bar is assigned as quarter model and is considered for the performance index study. speed, sprung mass weight and presence of the hump are taken into consideration as the operation parameters. The results show the change of the torsion bar bolt position has sufficient effect on the sprung mass acceleration

Keywords: vehicle suspension systems, torsion bar, ride comfort.

1. Introduction

One of the major subsystems in a modern passenger car is the suspension system. The suspension system of a road vehicle refers to the assembly between the sprung mass and the . It transfers forces and moments from the contact patch to the . Vehicle suspension systems are designed to improve ride comfort, road- holding, handling, and directional performance [1]. A quality suspension must achieve a good behavior of the vehicle and a degree of comfort depending on the interaction between tire and road surface[2,3,4]. Traditional suspension system consists springs and dampers are referred to as passive suspension system. Although the coil springs are widely used in passengers nowadays, the torsion bars still have some application in the competition field as the coil springs. The most common place to find a torsion bar is in the suspension system of a car or truck, in machines used for production or in other precision devices[5]. The flexibility of the spring and when space is limited are the main reasons that a torsion bar is used. A torsion bar works by resisting the torque on it. When one end of the torsion bar is affixed to an object that cannot be moved, the other end of the bar is twisted, thus causing torque to build up. When this happens, the torsion bar is

- 170 -

Minia Journal of Engineering & Technology (MJET), Vol. 37, No. 1. January 2018 resistant to the torque and will quickly back to its position once the torque is removed. At one end, the torsion bar is fixed firmly in place to the chassis or frame of the vehicle. The other end of the bar may be attached to the suspension, or a spindle, depending on the specification of the vehicle[6]. The forces generated by the motion of the vehicle create torque on the bar, which twists it along its axis. Counteracting the torque is the fact that the torsion bar naturally wants to resist the twisting effect and return to its normal state. In doing so, the suspension provides a level of resistance to the forces generated by the movement of the vehicle. This resistance is the key principal behind a torsion bar suspension system. The effective spring stiffness of the bar is determined by its position, cross section, shape and material. If an arm is attached at right angles, to the free end, any movement of the arm will cause the rod or bar to twist the bars resistance to twisting provides a spring action

[7, 8]. The ride height of a vehicle is adjusted by the torsion bar, this is done by altering the angle of the torsion arms, or by using the adjustment bolts of the torsion bar stops. In this work presented here tries to develop an experimental test facility that can be investigate and analyze the effect of the ride height on the vehicle suspension performance at different conditions such as, road hump, sprung mass, and tire speed.

2. Experimental Methodology

To analyze the behavior of the torsion bar suspension system; double-wishbone type of suspension with upper torsion bar was used during the experimental tests. Figure (1) illustrates the arrangement of the quarter with torsion bar. The experimental setup is composed of electrical motor (5 hp and 1500 rpm) fitted with a drum has diameter 0.32 m used to rotating the tire has diameter 0.7 m via belt. speed can be controlled by inventor device to change the drum speed. To simulate the hump road effect, the drum tire has the freedom to move up and down direction by using electric motor (5 hp and 1500 rpm) via connecting rod attached with the drum tire. Electric motor speed can be controlled by inventor device to change the hump position. The high of the hump can be changed by using disc has some holes in certain position and rotates by the electric motor. The big end of the connecting rod connects to disc hole and the other attached to the drum. The high of the hump controlled by changing the position of contact of the connecting rod end with the hole disc. The vibrations were measured at two different positions and measured by ICP accelerometer has frequency range from 0.5 to 3000 Hz (model 333B32). The accelerometer signals are post-processed by LMS pimento a multi- channel device (model Asp 424). All the measured data were directly collected to PC computer, which is connected to the pimento device as XLS files and analyzed using the MATLAB. The accelerometer was calibrated and recorded as shown in figure (2).

- 171 -

Minia Journal of Engineering & Technology (MJET), Vol. 37, No. 1. January 2018

Figure (1). Torsion bar passive suspension system test rig. 1- Electrical motor 2- Electrical motor for drum 3- Drum 4 - Hump system 5- Torsion bar 6- Quarter car suspension assembly 7- Tire 8- Accelerometer sensor position 9- Bolt of the torsion bar

- 172 -

Minia Journal of Engineering & Technology (MJET), Vol. 37, No. 1. January 2018

Accelerometer Calibration 10

9

8

7 2 6 5

4 Acceleration m/s 3 2 1 0 110 120 130 140 150 160 170 180 190 200 Frequency - Hz

Figure (2). Accelerometer calibration curve.

3. Results and discussions

This section presents the effect change of the vehicle high level on the ride comfort at different conditions such as tire speed, sprung mass weight and tire pressure. Figure (3a) and Figure (4a) demonstrate the effect of the vehicle high level (torsion bar bolt position) on the ride comfort at vehicle speed of 2.5 km/hr. (34.2 rpm) and 7.5 km/hr. (102.4 rpm), at 400 kg sprung mass weight respectively. Figure (3b) and figure (4b) show the root mean square (RMS) of the body acceleration according the following expression.

Where n is number of elements and x is the amplitude of acceleration. From the results shown in figure (3) it can be seen that the RMS of the body acceleration increases by about 16.07% with increase the torsion bar bolt position from 5 cm to 7 cm. while increases the bolt position from 5 cm to 9 cm causes increases the RMS to 43.58 %. The results shown in figure (4) indicate that, the increase of torsion bar bolt position from 5 cm to 7 cm increases the RMS from by about 11.58 %, increase of torsion bar bolt position to 9 cm increases the RMS to 15 %. The results presented in figure (3) and figure (4) indicates that, the increase of the vehicle level produces an increase of the vehicle vibration at both tire speed 2.5 and 7.5 km/hr. This could be attributed to the increase of the torsion bar bolt decreases the torsion bar twist angle, which in turn increase the stiffness of the torsion bar [9].

- 173 -

Minia Journal of Engineering & Technology (MJET), Vol. 37, No. 1. January 2018

-3 x 10 0.025 1.4 T =5 cm 400 Kg T=7 cm T=9 cm 1.2 0.02

1 2

0.015 ) 2 0.8

0.01 0.6

Acceleration m/s R.M.S ( m/s

0.4 0.005

0.2

0 0 50 100 150 200 250 300 350 400 450 0 Frequency - Hz T =5 cm T =7 cm T =9 cm

( a) ( b) Figure (3) effect of the vehicle high level on the ride comfort at 2.5 km /hr. tire speed and 400 kg sprung mass weight. (a) Body acceleration. (b) RMS .

-3 x 10 2

1.8

1.6

1.4

) 1.2 2

1

R.M.S (m/s 0.8

0.6

0.4

0.2

0 T =5 cm T =7 cm T =9 cm

(a) (b) Figure (4) effect of the vehicle high level on the ride comfort at 7.5 km /hr. tire speed. (a) Body acceleration. (b) RMS.

The effect of the vehicle high level (torsion bar bolt position) on the ride comfort at sprung mass weight of 400 and 530 kg, at 2.5 and 7.5 km/hr tire speed are recorded and plotted in figure (5) and figure (6) respectively. RMS of the sprung mass vibrations is shown in figure (7). These figures illustrate that, at tire speed of 2.5 km/hr, increase of the torsion bar bolt position from 5 cm to 9 cm increases the RMS of the sprung mass acceleration by about 43.58 present at 400 kg of sprung mass weight, and by about 45.46 percent at 530 kg of sprung mass weight. At 7.5 km/hr tire speed, increase of the torsion bar bolt position from 5 cm to 9 cm increases the RMS of the sprung mass acceleration by about 15 present at 400 kg of sprung mass weight, and by about 50.92 percent at 530 kg of sprung mass weight. It can be seen also, from this figures that, the effect of the increase torsion bar bolt position at 400 kg sprung mass weight on the vehicle vibration is lower than at 530 kg sprung mass weight at both tire speeds.

- 174 -

Minia Journal of Engineering & Technology (MJET), Vol. 37, No. 1. January 2018

0.016 0.025 T=9 cm , w = 400 kg 2.5 km/hr T =5 cm , w = 400 kg 2.5 Km/hr T =5 cm , w = 530 kg T=9 cm , w = 530 kg 0.014

0.02

0.012 2 2 0.01 0.015

0.008

0.01 Acceleration m/s Acceleration m/s 0.006

0.004 0.005

0.002

0 0 0 50 100 150 200 250 300 350 400 450 0 50 100 150 200 250 300 350 400 450 Frequency - Hz Frequency - Hz ( a ) ( b) Figure (4) effect of the vehicle high level on the ride comfort at 2.5 km /hr tire speed.

0.03 0.035 T =5 cm , w = 400 kg T=9 cm , w = 400 kg 7.5 Km/hr 7.5 Km/hr T =5 cm , w = 530 kg T=9 cm , w = 530 kg 0.03 0.025

0.025

0.02

2 2 0.02

0.015

0.015

Acceleration m/s Acceleration m/s 0.01 0.01

0.005 0.005

0 0 0 50 100 150 200 250 300 350 400 450 0 50 100 150 200 250 300 350 400 450 Frequency - Hz Frequency - Hz (a) (b) Figure (5) effect of the vehicle high level on the ride comfort at 7.5 km /hr tire speed.

-3 -3 x 10 x 10 1.4 2

2.5 Km/hr 7.5 Km/hr 1.8 1.2 1.6

1 1.4

) 1.2

) 2

2 0.8

1

0.6 R.M.S (m/s

R.M.S (m/s 0.8

0.4 0.6

0.4 0.2 0.2

0 0 A B C D A B C D

Figure (7) RMS of sprung mass vibration at 2.5 and 7.5 km/hr of tire speed. (A) T =5 cm and w = 400 kg, (B) T =9 cm and w = 400 kg. (C) T =5 cm and w = 530 kg, (D) T =9 cm and w = 530 kg.

- 175 -

Minia Journal of Engineering & Technology (MJET), Vol. 37, No. 1. January 2018

The torsion bar bolt position effects on vehicle body vibration with and without hump at constant sprung mass weight 530 kg and different tire speeds are shown in figures (8, 9 and 10) From the results presented in these figures, it can be seen that, the increase of torsion bar bolt position from 5 cm to 9 causes increase the RMS of the body acceleration by about 45.46 % without presence hump with 2.5 km/hr tire speed. This increase diminishes with presence hump has 5 cm height to 29.28 %. Whereas, at 7.5 km/hr tire speed, the increase of torsion bar bolt position from 5 cm to 9 cm causes increase the RMS of the body acceleration by about 50.92 % without presence hump 2.5 km/hr tire speed. This increase diminishes with presence hump has 5 cm height to 32 %.

0.02 0.025 T =5 cm , No Hump T=9 cm , No Hump 2.5 Km/hr and 530 kg 2.5 Km/hr and 530 Kg 0.018 T =5 cm , H = 5 cm T=9 cm , H = 5 cm

0.016 0.02

0.014 2 2 0.012 0.015

0.01

0.008 0.01

Acceleration m/s Acceleration m/s

0.006

0.004 0.005

0.002

0 0 0 50 100 150 200 250 300 350 400 450 0 50 100 150 200 250 300 350 400 450 Frequency - Hz Frequency - Hz (a) (b)

Figure (8) effect of the vehicle high level on the ride comfort at 2.5 km /hr tire speed with and without hump.

0.03 0.03 T =5 cm , No Hump T=9 cm , No Hump 7.5 Km/hr and 530 Kg 7.5 Km/hr and 530 Kg T =5 cm , H = 5 cm T=9 cm , H = 5 cm

0.025 0.025

0.02 0.02

2 2

0.015 0.015

Acceleration m/s Acceleration m/s 0.01 0.01

0.005 0.005

0 0 0 50 100 150 200 250 300 350 400 450 0 50 100 150 200 250 300 350 400 450 Frequency - Hz Frequency - Hz (a) (b)

Figure (9) effect of the vehicle high level on the ride comfort at 7.5 km /hr tire speed with and without hump.

- 176 -

Minia Journal of Engineering & Technology (MJET), Vol. 37, No. 1. January 2018

-3 -3 x 10 x 10 2.5 3.5 2.5 Km/hr 7.5 Km/hr

3 2

2.5 )

) 1.5 2 2 2

1.5 R.M.S (m/s R.M.S (m/s 1

1

0.5 0.5

0 0 A B C D A B C D

Figure (10) RMS of sprung mass vibration at 2.5 and 7.5 km/hr of tire speed. (A) T =5 cm and no Hump, (B) T =9 cm and no Hump. (C) T =5 cm and H = 5 cm, (D) T =9 cm and H = 5 cm. 4. Conclusions

A front suspension of double-wishbone type suspension with upper torsion bar has been studied to investigate the effect of ride height on the sprung mass dynamic under different conditions. This included tire speed, sprung mass and during pass a hump. From the results obtained from experimental study, it is seen that;  Increase the torsion bar bolt position from 5 to 9 cm increases the sprung mass acceleration with 2.5 km/hr tire speed, this effect was diminished as the tire speed increased to 7.5 km/hr at the same conditions.  Increase the sprung mass weight from 400 to 530 kg decreases the sprung mass acceleration at the same torsion bar bolt position and tire speed.  Increase of the sprung mass weight with increase the torsion bar bolt position increases the sprung mass acceleration.  The sprung mass acceleration as increased the torsion bar bolt position from 5 to 9 cm during passing the hump.

References

1- Yogesh Sanjay and Sripad R Nimbalkar “Design and Development of Quarter Car Suspension Test Rig Model and its Simulation” IJESAT. Volume-3, Issue-3, 157-170 (2014). 2- Andronic Florin, Manolache-Rusu Ioan-Cozmin and Pătuleanu Liliana “Pasive Suspansion Modeling Using MATLAB, Quarter Car Model, Imput Signal Step Type” New Technologies and Products in Machine Manufacturing Technologies, PP 258-263(2015) 3- Kamalakannan, K., ElayaPerumalb A., Mangalaramananc, S., Arunachalamd K. “Performance Analysis and Behaviour Characteristics of CVD (Semi Active) in Quarter Car Model”.-Jordan Journal of Mechanical and Industrial Engineering, Volume 5, Number 3.- , ISSN 1995-6665. P.261- 265(2011). 4- Augustaitis, V. K., Gičan V., Šešok N., Iljin I. “Computer-aided generation of equations and structural diagrams for simulation of linear stationary mechanical dynamic systems” Mechanika 1.-Kaunas: Technologija, ISSN 1392-1207. p.255-263. (2011). 5- Rajashekhar Sardagi and Kallurkar Shrikant Panditrao “Design and Optimization of Passenger Car Torsion Bar” Journal of Mechanical and Civil Engineering, e-ISSN: 2278-1684, p-ISSN: 2320-334, PP 15-18

- 177 -

Minia Journal of Engineering & Technology (MJET), Vol. 37, No. 1. January 2018

(2015). 6- Vikas V.Ya lasangi and A.M .Nan iwadeka r “Analysis of Torsion Bar of Light Motor Vehicle Car Using Alternative Material” International Journal of Engineering Science and Computing, Volume 6. Issue 7. PP 1849-1851 (July 2016) 7- Kumbar R. B et al “An Overview of Disarray in Finite Element Analysis of Composite Torsion Bar” IJSRSET. Volume 1. Issue 6. Print ISSN: 2395-1990 (2015). 8- Laxminarayan Sidram Kanna et al “Feasibility of hallow stability bar” IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE), e-ISSN: 2278-1684, p-ISSN: 2320-334X, PP 76-80, (2014). 9- Gerald R. Kress and Paolo A. Ermanni “Carp Torsion Bar: Load Introduction Problem “16th International Conference on Composite Materials. Japan (2007).

- 178 -