MACHINE ELEMENTS

YEAR PROJECTMACHINE ELEMENTS IIStudent name: CANALES MORENO Isidro Fermin

Year: IIISpecialization: Mechanical Engineering

Transilvania UNIVERSITY OF BRASOV

1. STRUCURAL SCHEME, TORQUES AND ROTATION FOR EACH SHAFT

1.2 Structural scheme

Fig 1

1.2 Torque and rotations for each shaft

Engine

n = 1470 rot/min

Mt = 9.55*

Input shaft (I)

nI = n /iL= 1470 / 1.75 = 840 rot/min

TI = Mt * iL = 1011889.578 N*mm

Output shaft (II)

nII =

TII = TI * ir 1011889.578 *4.5=4.55475.95 N*mm

2

P, nMt

2. PROJECT PARAMETERS

2. INPUT DATA2.1 Pinion speed n1, rot/min n1 = 840 rot/min2.2 The torsion torque at the pinion of the gearing T1, N*mm

T1 = 1011889.578 N*mm

2.3 Gearing ratio udat udat = 4.52.4 Minimum functioning time of the gearing Lh, hours

Lh = 10000 hours

2.5 Functioning conditions of the gearing

Driver machine: electrical motorDriven machine: fansType of load: uniform

2.6 The loading cycles for the teeth

contact load : pulsatory cyclebending load : pulsatory cycle

2.7 Number of load cycles of the tooth flank, at a full rotation 1 for the pinion, 2

for the driven wheel

1,2 = 1

2.8 The reference rack profile

For inclined teeth n = 200; h*

an = 1,0; c*u = 0.25;

*fn = 0.38

3. CHOOSING THE MATERIALS, HEAT TREATMENTS AND THE LIMIT STRESSES 3.1 Choosing materials and treatments

We choose 17CrNi16 from STAS 791Treatment Ce+C+rHardness - external 60 HRC - internal 400 HBr = 1000 MPa02 = 635 MPa

3.2 Limit stresses, Hlim1,2, at contact and Flim1,2 at bending, MPa

Hlim1,2 = 1500 MPaFlim1,2 = 500 MPa

4. PRE-DIMENSIONING CALCULUS

3

4.1 Number of teeth z1, of the pinion, respectively z2 of the driven wheel.

it is choosen z1=14

it is choosen z2 = 63

4.2 Real gearing ratio u

4.3 The contact calculus factors [21,60]4.3.1 The elasticity factor of the wheels material zE,

4.3.2 The contact area factor zH

4.3.3 The covering factor z

4.3.4 Inclining factor of the teeth z

4.4 The factor for the bending calculus4.4.1 Number of teeth for the equivalent wheels

4.4.2 The displacement coefficient of the profile in the normal plane xn1,2

4.4.3 Shape factor of the teeth YFa 1,2

YFa1 = YFa1(zn1,xn1) = YFa1(16.581,0) = 3.55YFa2 = YFa2(zn2,xn2) = YFa2(74.657,0) = 2.25

4.4.4 Correction factor of stress YSa1 = YSa1(zn1,xn1) = YSa1(16.581,0) = 1.45

4

YSa 1,2 YSa2 = YSa2(zn2,xn2) = YSa2(74.657,0) = 1.75

4.4.5 Covering factor Y

4.4.6 Inclined factor for the teeth Y

4.5 Load correction factor4.5.1 The functioning regime factor ka

kA = 1.10

4.5.2 Dynamic factor kv kv = 1.084.5.3 Distribution (uneven) factor for load on the width of the teeth kH for contact and kF

for bending

kH = 1.5kF = 1.5

4.5.4 The uneven distribution factor of the frontal plane kH at contact and kF for bending 4.6 The allowable resistances HP1,2 at contact and FP1,2 for bending [MPa]

4.7 The distance between the axis at pre-dimensioning 4.7.1 Wide coefficient a, d

a =0.25

d =

4.7.2 Distance between the axis from the

5

strength condition at contact awH, mm4.7.3 Distance between axis from the strength condition at bending awF, mm

4.7.4 Adopting the distance between the axis at predimensioning aw, mm

aw = max (awH,awF) = max (269.13,173.56) = 269.13mm ;We adopt from STAS 6057 the following aw = 275 mm

5. GEARING FORCES CALCULUS

5.1 Forces calculus

5.1.1 Tangential force Ft, N;

6

5.1.2 Radial force Fr, N;

5.1.3 Axial force Fa, N;

5.2 Choosing the sense of rotation and applying forces

Fig. 5

6. CALCULUS OF THE SHAFTS

6.1 Pre-dimensioning calculus:

7

6.2 Choose of bearing mounting for input and output shafts:

d(b)I,II = dI,II – (2…8)mm

Shaft D(db) D B a Cr X Y Symbol Cr

I 35 72 17 31 28.5 0.35 0.57 7207BII 50 90 20 39 37.4 0.35 0.57 7210B

6.3 Check of the input shaft for composed stresses.

6.3.1 Horizontal plane

Fig. 6.1

6.3.2 Vertical plane

A B

RAH RBH

Fr1

Fa1

[H]

8

Fig. 6.2

6.4 Determining of the reactions in the 2 bearings

Fig. 6.3

6.5 Stresses identification

9.6.1 Torsion

RAV

l1

A B

RBV

Ft1

[V]

l1

AB

Mih

Miv

Mt

T

9

9.6.2 Bending

6.6 Equivalent stress

7. CHOOSING AND CALCULUS OF THE PARALLEL KEY

Fig. 7.1

we choose from STAS 1004-81: b=16; h=10

From crushing σs= , σas=120MPa,

l = lc + b = 136 + 16 = 152 we modify by our design l = 63 mm.d b h

10

I 28 8 7II 44 14 9

II’ 50 16 10 7.1 CHOOSING THE ENDS OF THE SHAFTS

Fig. 7.2

Input shaft:daI = dsI – (3…5) mm = 32 - 3 = 32 mmWe choose from STAS 8724/2-71; l = 58

Output shaft:daII = dsII – (3…5) mm = 48 - 3 = 39 mm

8. CHECKING THE ASSEMBLY WITH THE BALL-BEARINGS AFTER THE DYNAMIC LOAD CAPACITY

Fig. 8

da lI 28 42II 44 54

11

RAH RBH

8.1 Establishing the supplementary axial forces

8.2 Establishing axial forces in the bearings:

Bearing A- establishing axial forces in the bearings

the ball-bearing is found in the 1st area

where we can neglect the influence of the axial force over the equivalent dynamic load.

- Equivalent dynamic load

where V=1- Durability of the bearing

- Dynamic capacity load

- Durability ensured by the ball bearing

- Ensured functioning time

9&10. CHOOSING AND JUSTIFYUING THE OILING SYSTEM AND SEALING SYSTEM

Oiling the gearings:

12

Gears of gears are lubricated by oil bath bubbling. InTo this end a gear wheel is inserted into the oil pan upthe height of a tooth but at least 10 mm and never exceeding 6 timesmodule.If multi-stage gear units (when the wheels do not reachbath), the anointing is done by means of gears of stray ortablespoons discs or spraying.Lubrication of the gears balbotare apply to working regularlywith speeds of up to 15 m / s. May Maire peripheral speeds, lubrication isrun oil injectors. Oil pressure is usually 0.1-At 0.8.To grease commonly used mineral oil viscosity 3-60degrees ^ C E50As the peripheral speed is lower, and even contact pressureroughness is higher, the more they use thicker oils.The multi-stage gearboxes, lubrication oil is chosen with aviscosity corresponding to step forward greatest moment.For the volume of oil bath oil is considered a horse 0.25-0.5 lpower. Oil change period is 1000-5000 hoursoperation (if it is sealed and the oil is angrenajufiltered after every 2500 hours). Filtering canuse magnetic filters. On reducing new oil change after 200 -300 hours of operation.

9.1 Oiling the ball-bearings.

Choose rulemnti lubricants for bearings with lubrication intervals and determination ismade depending on the size, speed, load and temperature of the bearing.In general, liquid lubricants, to those consistent with a number of advantages such ashigher physical and chemical stability, speed and ability to use high temperatures andvery low temperatures ola, easier removal of heat that can occur in camp, oppositelower resistance in rolling bodies. As disadvantages can be mentioned: the difficultsealing camp, while losses through leaks, etc..Lubrication with grease is advantageous as it leads to constructions limped tobearings, seals easier and lower cost, better protection from external agents rulemtilor,smaller loss of lubricant, etc..In the case of liquid lubrication, for small shi average speed, oil level should reachapproximately to the center of ball or roller rulementului lower.In normal operating conditions are used for lubricating waxes. The amount of greaselubrication of a bearing frame rulemnti required generally depends on the shaft speed.11. DESIGN OF CHAIN DRIVE

11.1 NUMBER OF TEETH OF THE SMALL WHELL

11.2 NUMBER OF TEETH OF THE BIG WHELL

13

11.3 THE PITCH

from STAS 5174-66

11.4 THE AVARAGE SPEED

11.5 THE ADMISIBLE USEFULL FORCE

11.6 THE ADMISIBLE USEFUL POWER

the number of chain rows

14

We choose p=p2=15.875 mm

11.7 THE PRELIMINARY DISTANCE BETWEEN THE AXIS

11.8 THE NUMBER OF LINKS

11.9 THE LENGTH OF THE CHAIN

11.10 THE RECALCULATED DISTANCE BETWEEN THE AXIS

11.11 THE FORCE FROM THE PASSIVE BRANCH OF THE CHAIN

from STAS 5174-66

P1 P2 P3

Zr 4 2 2

15

11.12 THE USEFULL FORCE

11.13 THE FORCE FROM THE ACTIVE BRANCH OF THE CHAIN

11.14 THE SAFETY COFFICIENT AT BREAKING

from STAS 5174-66

11.15 THE FORCE THAT ACTS ON THE SHAFTS

12. Choosing the materials and manufacturing system

Materials used in construction reducersBuilding Materials gears: steelsSteels are used to improve the otelutrile carbon steels with 0.4-0.6% C and 0.35-0.45% C low alloy Mn, Cr, Cr-Mo, Cr, Ni etc. Unalloyed and low alloy steels, Cr, Cr =Mo, Cr-Ni, a possible cyanide

IronsIrons are used to slow functioning gears, wheels rarely work exchange, etc.. Whensilence is required severe conditions may be used ordinary gray cast iron withspheroidal graphite.

Materials used for the execution tree:In general, trees that are not heat treated carbon steel is made from ordinary: OL 50,OL 60, 500-78 StasIndifferent trees bearing capacity can use high quality carbon steel: XC 35, XC 45,XC 60, according to STAS 880-66.If trees are required to ask pternic small chrome alloy steels are used, Cr or Cr-Mn-Ni

Materials used for the execution of carcassesCarcasses, because rigidity is the dominant criterion, are made of cast iron or cast steel. Most carcasses are made by casting iron medium strength FC 200, FC 250.

16

Technical safety regulations

La locul sau in exploatarea reductoarelor va trebui sa se tina seama de urmatoarele prevederi cu privire la normele de tehnica securitatii muncii:

The operation of reduction gears in place will have to take account of these provisionson work safety technical rules: Reducer to be securely bolted to the workbench Do not use gears  lacking parts (parts of housing, eteansare caps etc) Will not change the oil during operation  Will not check the oil level during operation  Will replace defective parts with other corespuzatoare

17