considerations on designing of telescopic boom aerial platform slewing-rings

8/9/2019 Considerations on Designing of Telescopic Boom Aerial Platform Slewing-rings

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BULETINUL INSTITUTULUI POLITEHNIC DIN IAI

Publicat de

Universitatea Tehnic Gh. Asachi, Iai,

Tomul LIV (LVIII), Fasc. 1, 2008Secia

CONSTRUCII DE MAINI

CONSIDERATIONS ON DESIGNING OF TELESCOPIC BOOM AERIAL

PLATFORM SLEWING-RINGS

BY

dr. ing. Rezmires Daniel, ing. Bocanet Vasile, : S.C Sirca S.A. Piatra Neamt

p.i. Monfardini Alfredo : S.C. Rima Spa - Italy

prof. dr. ing. : Racocea Cezar: TU Gh Asachi - Iasi

Abstract: During opetarion, telescoping boom aerial platforms slewing rings are quasi-statically loaded with axial,

radial stresses and bending moments. The external loads are expressed depending on the position in space of aerial

platfome charged by workers and their necessary tools and materials. The telescopic boom aerial paltform rolling

bearings sizing takes into account stability conditions described as permanent contact between the soil the chassis.

The design have to deliver a 3:1 safety factor, and the ability to withstand greater wind loads and greater nozzlereactions.

Key words: sizing, slewing rings, telescopic boom aerial platfome

This paper describes a method of sizing ball bearings with four contact points

used in the aerial platfome. Such a sizing algorithm has been conceived and

implemented within S.C. SIRCA. S.A. Piatra Neamt, slewing rings manufacturer,

and Rima Spa Italy, hydraulic equipment manufacturer. The program has been

developed using Borland Delphi - software.

1. Theoretical ConsiderationVehicle-mounted cranes [4], have been widely used for handling material,

specifically for the lifting of relatively heavy loads of material from one place, and

depositing it in position at another place. An aerial lift platforms is somewhat similar to

the vehicle-mounted cranes. It including a vehicle with a boom mounted thereon for

both horizontal swinging and vertical luffing movement. Typically, the platform

includes a floor and an upstanding protective enclosure or railing, to prevent falling of

the workman from the platform. A telescopic boom aerial platfom have to lift one or

more workmans and the additionally engaged material, using an hydraulic equipment

and in the same time it have to assure the positioning porcess by rotating and translation

movements. The movable part weight and the boom space position generates an

external load (axial and radial forces and bending moments) transferred to the support


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Rezmires Daniel, Bocanet Vasile, Monfardini Alfredo and Racocea Cezar Construcii138

slewing ring bearing. For this type of application have to check for slewing ring if

the contact pressures are below of the admissible load limit of the material used and if

the trunction of ellpises does not appear in the ball-raceways contact [1,2]. Also it is

necessary to verify the gear working conditions regardind the tooth contact resistance

and the bending moment, as well as the the numer of tapped holes, size and precisionclass of screws.

2. Logic of slewing ring programming and dimensioning

The final user of the telescopic boom aerial platforme slewing ring recives form

Sirca and Rima an questionnary regarding informations about : constructive geometry

of machine and hydraulic equipment, as well as data about the gear parameters ( type of

loaded gear - inner or outer, angle of teeth tilt, and so on).

All these are input data in the program developed for SIRCA S.A. and Rima Spa.

An interface example is shown in fig. 1.

Fig. 1. Input data.

The input data provided by the beneficiary lead to determining the operating

coverage area of the aerial platform boom (see Fig. 2). For all points indicateted in Fig.2

the forces and moments acting on the chassis and the slewing ring are computed

supposing a continuous digging process. When the chassis may be in danger of loosingits grip on the soil, the algorithm restrains and indicates the maximum value of the

stress which causes instability, by a feedback which generates information on a

possible over-sizing of the hydraulic system, or a down-sizing of the chassis. These

cases are shown in Fig 3 which indicates the point against which the stability condition

is calculated.


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de Maini Bul. Inst. Polit. Iai, T. LIV (LVIII), Fasc. 1, 2008 139

Fig. 2. Geometrical locus of active boom area.

Fig. 3 Stability point.

The program draws the axial and bending memoent stresses diagrams as well as

the useful load diagram against the geometrical locus of the slewing ring which

corresponds to the operating cycles for which the equipment stability condition is met.

Fig.4 shows, cumulatively, the analysis results.


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Rezmires Daniel, Bocanet Vasile, Monfardini Alfredo and Racocea Cezar Construcii140Fig. 4. Evolution of stresses and moments acting on the slewing ring, resulted in telescopic aerial

platform stability conditions.

Interpreting fig.4 results is relatively time-consuming, and for that reason the

data are sorted out depending on their occurrence frequency. This algorithm enables usto approximate the loading cycles, in percentages. Fig. 5 gives the previous data

expressed in percentages, taking as sorting criterion the bending moment acting on the

slewing ring.

Fig. 5. Data sorted out in order to establish loading cycles.

The analysis carried out for the case under investigation lead to the conclusion that for

this case can be used an 2IE.064.00 slewing ring [3], and the utile load can be moved.

According to Fig. 5, the proposed configuration of the telescopic boom aerial platforme

can take up more than 100 Kg = 1KN. For safety we have to tack into account an useful

load grather like the nominal load mutiplied with the safety factor sf=3. For simplicity

we draw the limit load chart to verify that the bearing resist to the maximum axial force

and bending moment gives by the algorithm. Of course the considered case occur to a

super sizing bearing dimensions and an reconsideration have to be tacked into accout

with gear working conditions.

Fig. 6. Limit load chart of the investigated slewing ring. Fig. 7. Bearing geometry

In fig. 6, Pu is the point of use for the case under consideration [3], Peq is the value of

stresses and moments affected by a safety factor established by the beneficiary, and 10.9

is the classes of M16 screws usable. Fig 7 shows the bearing geometry.


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de Maini Bul. Inst. Polit. Iai, T. LIV (LVIII), Fasc. 1, 2008 141

3. ConclusionsThe algorithm used indicates the multitude of situations that may occur in the

dimensional designing of a slewing ring, in correlation with the working environmentand the equipment for which it is destined. The analysis stages have been presented. The

developed algorithm has the following advantages:

Establishes maximal operational cycles for an aerial platforme Establishes the outer loads that act on the slewing ring Ensures a feedback relation between the hydraulics of the equipment and its

overall size leading to some constructive optimising situations

Helps in mapping the aerial platforme operation by using a potential system ofsensors which may be attached to the mobile effectors ensemble.

Received May 20th 2006 Technical University of IassyDepartment of Machine Design and Mechatronics

R E F E R E N C E S

1. Harris T.A. .,Rolling bearing analysis 3rdedition . John Wiley & Sons Inc., New York, 1991.2. Rezmires, D., Research on Dynamics and Kinematics Optimization of the Spherical Roller

Bearings, Iasi, PhD Thesis, 2003 (daniel-rezmires.tripod.com)

3. http://www.rimaspa.com/4. Howard I, s.a., Cranes and Derricks, McGraw Hill, 2000, USA

CONSIDERAII PRIVIND PROIECTAREA RULMENTILOT PENTRU PLATFORME AERIENE

(Rezumat)

In timpul operatiei de pozitionare a unei platforme aeriene telescopice rulmentii de sprijin sunt

solicitati cvasistatic cu forte axiale, radiale si momente de incovoiere. Sarcinile externe sunt exprimate functie

de pozitia spatiala a elementului de pozitionat raportat la centrul geometric al rulmentului, de parametrii

functionali ai sistemului hidraulic care antreneaza in miscare elementele mobile ale utilajului, cat si de

geometria constructiva (fixa sau variabila) a sistemului de sprijin. Dimensionarea rulmentilor pentru

platforme ia in considerare respectarea conditiilor de stabilitate, adica de pastrarare a contactului permanent

dintre sasiul utilajului si sol cat si conditii de natura economica.

considerations on designing of telescopic boom aerial platform slewing-rings

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