1Introduction

2Structural features of the crane

2.1Low weight of crane

Uvod

Mala masa dizalice

Ultra-light telescopic cranes are designed for peopleworking at height where they perform differentmaintenance jobs: e.g. glass facades of buildings, frescos inthe religious facilities, transmission lines, lighting poles etc.It is also possible to use them to manipulate different typesof small goods in manufacturing facilities, warehouses,energy facilities etc. The maximum setting-up height is 30m.

The drive can be manual, hydraulic, electric orcombined. The most common drive is a combined electro-hydraulic one, because of the possibility of automaticcontrol and driving with security the crane's functions.Driving the crane can be achieved from the ground or fromthe working crane's basket [1]

The basic crane's features arise from its use, and theseare:

l (less than 3 tones)minimum pressure on the basesmall dimensions of the foldable transport position, inorder to pass through narrow passages/doorsapplication of fine-granular high-strength steel.

The crane must have a minimum mass from severalreasons:

Possibility of pulling by car.

.

ow weight

Konstrukcijske značajke dizalice

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87

T. Ergić, Ž. Ivandić

ISSN 1330-3651UDC/UDK 621.873.01 : 519.863

ULTRA-LIGHT TELESCOPIC CRANE/PLATFORM MECHANISMS FEATURE ANALYSIS

Todor Ergić, Željko Ivandić

Based on the research of mechanical properties of fine-granular high-strength steels and the obtained results, the design of prototype ultra-light telescopic cranewas performed. The article presents the analysis results of the crane drive mechanism. The geometric synthesis of shapes and sizes of four joint was performedbased on the maximum and minimum slope of each arm and on the minimum weight. Feedback of optimal shape of each mechanism's stick was implemented bythe variant solutions evaluation methods. The detailed calculation of stress and strain in each mechanism's stick was performed by finite element method.

Keywords: Ultra-light telescopic crane/platform, mechanisms, mechanisms' synthesis, optimization

Preliminary notes

Temeljem istraživanja mehaničkih svojstava sitnozrnatih visokočvrstih čelika i dobivenih rezultata izvršeno je projektiranje prototipa ultralake teleskopskedizalice. U članku su prikazani rezultati analize pogonskog mehanizma dizalice. Izvršena je geometrijska sinteza oblika i dimenzija četverozgloba na temeljumaksimalnog i minimalnog nagiba pojedine ruke i minimuma masa. Ocjena optimalnog oblika pojedinog štapa mehanizma provedena je metodamavrednovanja varijantnih rješenja. Detaljan proračun naprezanja i deformacija u pojedinim štapovima mehanizma izvršen je metodom konačnih elemenata.

Ultralaka teleskopska dizalica/podest, mehanizmi, sinteza mehanizama, optimiranjeKljučne riječi:

Prethodno priopćenje

Analiza značajki mehanizama ultralake teleskopske dizalice/podesta

Analiza značajki mehanizama ultralake teleskopske dizalice/podesta

Technical Gazette 16, (2009), 874 -91

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Minimal pressure on the ,Entering into rooms, whose structure is notdesigned for the increased load.

To reduce the mass of crane, in addition to specificconstruction operations, the fine-granular high-strengthsteels StE 680 and StE 960 were selected [1]. Based on theresearch of mechanical, metallographic, tribological andother properties and based on the results, the design oftelescopic crane/platform was carried out.

The crane is self-propelled because it possesses owndrive for starting in the workspace. The crane is autonomousbecause it does not require the external power source. For itstransport from one worksite to another it a tow truck isnecessary which is in the form of a passenger car withlimitation of drawn mass size.

From the minimum conditions of mass, dimensions andform a special problem is set to the crane's drive. From theanalysis of forces in the crane's arms, a solution with four-joint with electro-hydraulic drive controlled by electronicswas found.

The mechanism, whose scheme is shown in Figure 1, isa mechanism for rotating the basket and the upper arm(Figures 2 and 3). The mechanism shown in Figure 4 is usedto start the lower arm.

backgroundbackground

2.2Drive of crane

3Analysis of mechanism

3.1The connection between the geometric parameters ofthe mechanism

Pogon dizalice

Analiza mehanizma

Veza između geometrijskih parametara mehanizma

3.1.1Analysis of four-joint mechanismAnaliza četverozglobnog mehanizma

Drives for the rotation of the upper arm and the baskethave the form of four-joint mechanism.

The connection between geometric sizes of four-jointmechanism can be concluded from Figure 1. Geometricsynthesis of shapes and dimensions of the four-joint isperformed on the maximum and minimum inclination ofeach arm, and on minimum masses [2, 3]. , and arelengths of sticks of mechanism.

The values of , and together with the angles , ,, and determine the geometry of supports, is the

length of the drive cylinder. The angle is the entry valuewhich comes from the working conditions and purpose ofthe crane/platform. During the calculation of geometry,some of these values result from the calculation of otherphysical features and they are included as the known values.

l l l

a b d

h

1 2 3

1

1

α β

β δ ψ

β

88

Ultra-light telescopic crane/platform mechanisms feature analysis T. Ergić, Ž. Ivandić

Tehni ki vjesnikč 16, (2009),4 87-91

The values and , together with angles and ,determine the geometry of supports. The length of drivecylinder is The angle is input value which comes fromworking conditions and purpose of the platform/crane.From Figure 2 it is possible to write the connection betweenthe geometric values of the drive mechanism.

c c

h

1 2

1

α φ

α.

Figure 1Slika 1

Scheme of four-joint mechanism. Shema četverozglobnog mehanizma

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al, (5)

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cos32 ���

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3.1.2Analysis of lower arm driveAnaliza pogona donje ruke

Figure 2Slika 2

Scheme of lower arm driveShema pogona donje ruke.

1 1

1 2

cos cos 0

sin sin 0

l h c

l h c

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sin

sin

l ch

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3.2Forces in elements of mechanismSile u elementima mehanizma

For dimensional control it is necessary to determine themaximum force in some sticks of mechanisms dependingon the inclination angles of lower and upper arm. Forcesand are in B and D of four-joint mechanism. is themoment in the point B from its own gravity, inertial forces,conductive and wind action on the structure. and arethe forces acting on the drive cylinders.

F

F M

F F

B

D B

C1 C2

� �1 1sinB

BM

Fl � �

�� �

, (10)

B11

D sintancos

sintancosFF �

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��

��, (1 )1

��

cos

coscos 1BDC

����

FFF . (1 )2

89Technical Gazette 16, (2009),4 87-91

Analiza značajki mehanizama ultralake teleskopske dizalice/podestaT. Ergić, Ž. Ivandić

a) b)

Figure 3Slika 3

Force changes in B mechanism (a) and in D mechanism (b) for the arm liftingPromjena sile u B mehanizma (a) i D mehanizma (b) za podizanje ruke. u

a) b)

Figure 4Slika 4

Force changes in the cylinder 1 for the rotation of the upper arm (a) and in the cylinder 2 for the rotation of the lower arm (a)Promjena sile u cilindru 1 za zakretanje gornje ruke (a) i u cilindru 2 za zakretanje donje ruke (a).

Figure 5Slika 5

Forces in the mechanism for rotating the basketSile u mehanizmu za zakretanje korpe.

90 Tehni ki vjesnikč 16, (2009),4 87-91

The method of determining the maximum forces actingon individual elements of the crane is performed dependingon the taken angles of the crane arm. Inertial forces are notdirectly taken into account because the velocity of basketmotion is very small. Furthermore the engaging ofindividual actuators is regulated electronically so that theacceleration is very small. The dynamic effects on the craneare taken into account through the dynamic plug-in

EN 280:2001 (6.1.4.4) [4]. Theresults of analysis of the forces that act on individualelements of the crane's mechanism are shown in Figure 3and Figure 4.

The form of each stick is determined from theconditions of minimum crane's dimensions with the fact thatthe selection of optimal form is carried out by evaluation

prescribed by the standard

methods of variant solutions [5, 6].Detailed calculation of stresses in some sticks of

mechanism is performed by finite element method.Some problems appeared in applying the finite element

method. For example, with known elements and applyingknown theoretical relations how to determine all valuesrequired for the analysis of described continuous system.Ten-nodal isoparametric tetrahedral 3D elements are usedto describe the elements of construction and generation ofmesh elements [7]. Examples of analysis of some elementsof the mechanism are shown in Figures and . Figure 3shows the strains of basket by different ways of loading.Figures 4 and 5 show the stresses and strains for one of thecrane segments. Figure 6 shows the schedule of stresses andstrains quantities of the crane's upper and lower base.

6 7

Ultra-light telescopic crane/platform mechanisms feature analysis T. Ergić, Ž. Ivandić

Figure 6Slika 6

Analysis of stresses in the sticks of the mechanism of the upper arm a - in a straight stick, b – in a curved stickAnaliza naprezanja u štapovima mehanizma gornje ruke a – u ravnom štapu, b – u zakrivljenom štapu

: ) ): ) ).

a) b)

Figure 7Slika 7

Disposition of stresses in the basket rotation mechanism a - in a straight stick, b – in a curved stickRaspored naprezanja u mehanizmu zakretanja korpe a – u ravnom štapu, b – u zakrivljenom štapu

: ) ): ) ).

a) b)

4Analysis of resultsAnaliza rezultata

Figures 3 and 4 show the forces variation in the sticks ofmechanism for the platform drive. From these figures it isevident that the forces in the B and D mechanismdecrease with increasing the slope angle. Thus can beconclude that it is better to lift first the lower arm, and then torotate and draw the upper arm. The forces on the drivingcylinders of mechanisms are also lower and if it is possiblethe work can be performed electronically only by the raised

of

lower arm. From Figure 4 is also visible that the force in thecylinder of the lower arm increases rapidly and goes to thesingularity if the slope angle amounts to <0. Furthermore,it is evident that the mechanism does not work singularly.Singularities are located outside of the mechanism so for theupper and the lower arm work that for the basket rotation.Forces in the mechanism for rotating the basket

The possibility of going into the singular area ofmechanism is limited by cylinder's stroke, end-switches andelectronic control of the platform operating.

β

are shown inFigure 5.

The method of determining the maximum forces actingon individual elements of the crane is performed dependingon the taken angles of the crane arm. Inertial forces are notdirectly taken into account because the velocity of basketmotion is very small. Furthermore the engaging ofindividual actuators is regulated electronically so that theacceleration is very small. The dynamic effects on the craneare taken into account through the dynamic plug-in

EN 280:2001 (6.1.4.4) [4]. Theresults of analysis of the forces that act on individualelements of the crane's mechanism are shown in Figure 3and Figure 4.

The form of each stick is determined from theconditions of minimum crane's dimensions with the fact thatthe selection of optimal form is carried out by evaluation

prescribed by the standard

methods of variant solutions [5, 6].Detailed calculation of stresses in some sticks of

mechanism is performed by finite element method.Some problems appeared in applying the finite element

method. For example, with known elements and applyingknown theoretical relations how to determine all valuesrequired for the analysis of described continuous system.Ten-nodal isoparametric tetrahedral 3D elements are usedto describe the elements of construction and generation ofmesh elements [7]. Examples of analysis of some elementsof the mechanism are shown in Figures and . Figure 3shows the strains of basket by different ways of loading.Figures 4 and 5 show the stresses and strains for one of thecrane segments. Figure 6 shows the schedule of stresses andstrains quantities of the crane's upper and lower base.

6 7

91Technical Gazette 16, (2009),4 87-91

Analiza značajki mehanizama ultralake teleskopske dizalice/podestaT. Ergić, Ž. Ivandić

5ConclusionZaključak

Based on the analysis it can be concluded that thedifferent variants of work can be performed by the crane.The paper presents an example of development andstructural analysis of the drive mechanisms of ultra-lightcrane. The aim of this study was to get the optimal design oflight crane, as well as detailed analysis of the stresses ofeach crane's mechanism elements. Some innovative anddesign solutions (Figure 8) with optimized variant solutionswere used in the design process.

This article resulted fromtechnological project supported by the Ministry of Science,Education and Sports of the Republic of Croatia TP-05-152-05. The authors thank all participants in the project whoprovided presentation of project solution in this article.

Acknowledgment:

6LiteratureLiteratura

[1]

[2]

[3]

[4]

[5]

[6]

[7]

Novosel, M.; Krumes,

Mermertas, V. Optimal design of manipulator with four-barmechanism//Mechanism and Machine Theory 39 (2004),545-554Wittwer, W. J.; Chase, W. K.; Howell, L. L. The directlinearization method applied to position error in kinematiclinkages//Mechanism and Machine Theory 39 (2004), pp.681-693Euronorma EN 280 2001

(2009), pp. 281-291

//

aka zavarivanja i zavarivanju srodnih tehnika u izradizavarenih konstrukcija i proizvoda, Slavonski Brod, 2007.pp. 147-156

// 12 International research/expertconference "Trends in Development of Machinery andAssociated Technology" Editors:

D. Posebni čelici, Slavonski Brod,1998.

..

..

:Ivandić, Ž.; Ergić, T.; Kokanović, M. Conceptual Model andEvaluation of Design Characteristics in ProductDevelopment//Strojarstvo. 51, 4 .Kljajin, M.; Ergić, T.; Ivandić, Ž.; Karakašić, M.; Katalenić,Z. Praktično rješenje robota za zavarivanje prikladno zarazličite konstrukcije proizvoda 4. Međunarodnoznanstveno-stručno savjetovanje Tehnologična primjenapostup

.Krumes, D.; Ergić, T.; Penava,A.; Marković, R.; Rosandić, Ž.Desing of Ultra-Light Mobile Elevating Working Platform(MEWP) Prototype.

S. Ekinović, S. Yalcin, J.Vivancos, Istanbul, 2008, pp. 973-976.

th

Figure 8Slika 8

Production and testing of prototypes in the workshopIzrada i testiranje prototipa u radionici.

Authors' addressAdrese autora

Josip Juraj Strossmayer University of OsijekFaculty of Mechanical Engineering in Slavonski Brod

35000 Slavonski BrodCroatia

doc. dr. sc.doc. dr. sc.

Todor ErgićŽeljko Ivandić

Trg Ivane Brlić-Mažuranić 2