FACULTY OF MECHANICAL ENGINEERING

MACHINE ELEMENTS PROJECT

PROJECT : Horizontal Cylindrical Single Step Speed Reducer

ContentsContents21.STRUCTURAL SCHEME, TORQUES AND ROTATIONS FOR EACH SHAFT41.1.Structural scheme41.2.Establishing the rotational speed and the torques for each shaft52. PRE -DIMENSIONING OF THE GEAR61. Input data61.1.Rotation of the pinion61.2.The torque at the pinion61.3.The gear ratio61.4.The imposed lifetime61.5.Functioning conditions61.6.Loading cycles61.7.The no. of loading cycles in the case of one complete rotation for the pinion61.8.The reference racks profile62.Choosing the materials treatments and limit stresses72.1.Choosing the materials treatments and the hardness72.2.Limit stresses for contact:73.Pre-dimensioning of the gear73.1.Number of teeth for the pinion and wheel z1, z273.2.The real gear ratio73.3.The contact calculus factor83.4.The bending calculus factors83.5.Load correction factors93.6.Allowable stress for crushing, respectively for bending in MPa103.7.Pre dimensioning of the distance between the axes11GEAR FORCES CALCULUS13Calculus of forces13Calculus scheme and establishing of the forces direction134.Shaft calculus14Pre-dimensioning calculus144.1. Choosing the bearing assembling for the input and output shaft155. Choosing and verifying the assembling through key between the driven wheel and output shaft206. Choosing and verifying the bearings assembling of the input shaft217. Choosing and justifying the sealing devices238. DESIGN OF THE BELT249. JUSTIFICATION ON CHOSE OF MATERIALS AND CONSTRUCTIVE SOLUTIONS FOR THE MAIN PARTS OF THE MECHANISM2810. RULES OF SAFETY AT WORK29

1.STRUCTURAL SCHEME, TORQUES AND ROTATIONS FOR EACH SHAFT1.1. Structural scheme

Figure1.1M - electric motorP - power of the electric motorn rotation of the motors shaftMtn torque at the motors shaftiL ratio of the chain drive transmissioniR speed reducers ratioI input shaft of the speed reducerII output shaft of the speed reducerTI torque at the input shaftnI rotational speed of the input shaftTII the torque at the output shaftnII the rotational speed of the output shaft1 pinion2 wheelA,B,C,D bearingsW.M. working machine

1.2. Establishing the rotational speed and the torques for each shaftThe motors shaft

Rotational speed: n = 930 rot/minThe torque:

The input shaft

The torque:

Rotational speed: The output shaft

The torque:

Rotational speed:

22. PRE -DIMENSIONING OF THE GEAR1. Input data

1.1. Rotation of the pinion

1.2. The torque at the pinion

1.3. The gear ratio

1.4. The imposed lifetime

1.5. Functioning conditions The motor: ASYNCHRONUS MOTOR The machine: SMALL SHOCKS The load: UNIFORM

1.6. Loading cycles Contact: Pulsating Bending: Pulsating

1.7. The no. of loading cycles in the case of one complete rotation for the pinion

1.8. The reference racks profileFor inclined tooth profile.

2. Choosing the materials treatments and limit stresses

2.1. Choosing the materials treatments and the hardnessMATERIAL: 18MnCr20 TREATMENT: CEMENTATED

2.2. Limit stresses for contact:

3. Pre-dimensioning of the gear

3.1. Number of teeth for the pinion and wheel z1, z2

=7It is chosen z1 = 17 teeth

3.2. The real gear ratio

3.3. The contact calculus factor

3.3.1. The elasticity factor

3.3.2. The contact zone factor

3.3.3. The gearing factor

3.3.4. The tooth inclination factor

3.4. The bending calculus factors

3.4.1. The number of teeth for the equivalent wheels

3.4.2. The profiles displacements coefficients

3.4.3. The teeth shape factors

3.4.4. The stress correction factors

3.4.5. Covering grad factor

3.4.6. Factor of the inclined tooth

3.5. Load correction factors

3.5.1. Working condition factors

3.5.2. Dynamic factor

3.5.3. Uniform distrib. factor of the load on the tooth width crushing and bending stresses

3.5.4. Uniform distribution factor of the load in frontal plan crushing and bending stressesThe condition is accomplished.

3.6. Allowable stress for crushing, respectively for bending in MPa

Where: - lubricating factor - speed factor - roughness factor of the active flanks for rectified tooth gear with torque factor of the material measurement factor =1.21 - no cips admitted=1.25

For generally used speed reducersAllowable stress for bending

correction factor(relative sensibility factor at the tension concentrator from the tooth addendum) = 1.0 for roughness of the application zone of the teeth durability factors for bending for the wheels size factorusual industrial transmission

3.7. Pre dimensioning of the distance between the axes

3.7.1.Width coefficient:

3.7.2. Distance between the axes from the condition of the bending stress

3.7.3. Distance between the axes from the condition of the contact stress

3.7.4. Adopting the distance between the axes in pre dimensioning It is chosen

3.7.5. Preliminary width of the wheels =50 mm

GEAR FORCES CALCULUSCalculus of forcesRadial force:

Axial force:

Calculus scheme and establishing of the forces direction

4.Shaft calculus

Pre-dimensioning calculus

Input shaft

Output shaft

=40 MPa It is adopted :=32mm =40 mm

4.1. Choosing the bearing assembling for the input and output shaft

Bearing choosingdDTCCoReference speedLimit speedDesignation

I30551735.84490001200032006 X/Q

II35621842.95485001100032007 X/Q

c- dynamic loadCo-static load

4.2. Verifying the input shaft at composed loadsDetermining the reaction from the 2 planes

In horizontal plane :

In vertical plane

The reactions from the two camps

Drawing the bending moments diagram in the 2 planes

Bending moments

Total bending moments

Identifying the loads-compression of Fa1

-torsion

-bending

5. Choosing and verifying the assembling through key between the driven wheel and output shaft

5.1. Determing the length calculus

lstas=60mm

Because there are chosen 2 keys A8 x10 x32 STAS 1004-8 1

6. Choosing and verifying the bearings assembling of the input shaft

Verifying the bearings assembling Choosing the bearings radial-axial with conic roles on one row in

Verifying the bearings assembling after the dynamic loadSetting the suplementary axial forces

B bearing

Equivalent dynamic load

Durability of the bearing

Needed dynamic load capacity

Durability assured by the bearing

Functioning time

7. Choosing and justifying the sealing devices

dm1=drul1-(23)=30-2=28 mmdm2=drul2-(23)=35-3= 32mm

There are chosen two simerings : A28x40 and A32x40 STAS 7950/2-72

Nr

hD

I28740

II321050

7.1. Heads of the shaft calculusNr(mm)lb

I24368

II284210

8. DESIGN OF THE BELT

8.1 Calculus power at driving shaft :

P=7.5 KW ==7.89 kw =0.850.95 transmission efficiency 8.2 Driving wheel speedn1=930 rot/min 8.3 Driven wheel speed n2=801.72 rot/min8.4 Transmission gear ratioi== 8.5Workin regime of the transmissionLh=8500h8.6Type of beltIt is chosen belt type SPZ 8.7 Primitive diameter of the wheelD1=140mm8.8 Primitive diameter of the big wheelDp2=iD1=1.16*140=162.4 mm

8.9 Primitive diameter of the belt wheels

Dpm=(Dp1+Dp2)/2=(140+162.40)/2=151.2mm

8.10 Distance between axes :

Preliminary

0.7(Dp1+Dp2) A 2(Dp1+Dp2)

0.7(140+162.4) A 2(140+162.4) 211.68 A 604.8 => A=400 mm

8.11 Angle between belt arms:=2arcsin=2acrsin=3.28.12 Winding angle on small wheel=180-3.56=176.448.13 Winding angle on big wheel2=180+==183.568.14 Primitive length of the belt Lp=2*A*sin + *= 2*400*sin + *=1275.3 mm => it is adopted 1400 mm Distance between axes ( definite)

8.15 Pheripheral speed of the beltv=*Dp1*n1/60000= *140*801.72/60*1000=5.87m/s

8.16 Functioning coefficient Cf=1.2(816h) neglijable variations of the work regime

8.17 Length coefficientCL==0.96 8.18 Winding coefficient C=0.998.19 Nominal powertransmited by the beltPo=2,87 kw 8.20 Nr of belts coefficientCz=0.908.21 Number of beltsZo=Cf*P/Cl*Po*C=1.2*7.89/0.96*0.99*2.87=3.47Z=Zo/Cz=3.47/0.90=3.84 => z=4 belts8.22 Number of transmission wheels :Constructively we choose x=28.23 Bending frequency of the belt:f=103*x*v/Lp=103*2*5.87/1400=8,38 H8.24 Periferic transmitted forceF=103*Pc/v=103*7.89/5.87=13448.25 Tensile strength of the belt :F=(1.52)F=1.6*1344.12=2314.6 N8.26 Distance between axes modifying levels :

X 0.003 Lp ; X 42Y 0.015 Lp ; Y 218.27 Simbolization and designation of the belt:SPZ 1400 STAS 7192 8.28 Simbolization and designation of the wheel of the belt :RCT 140 A 38 STAS 1162

9. JUSTIFICATION ON CHOSE OF MATERIALS AND CONSTRUCTIVE SOLUTIONS FOR THE MAIN PARTS OF THE MECHANISM

For proper operation of the speed reducer the input shaft, the output shaft should be stiff enough for good transmission of power, for reduced wear of the teeth. For this reason it is chosen l 18MnCr20 for the shafts. Also there are chosen angular contact ball bearings, because the are taking over medium radial loads and, small to medium axial loads acting on one way. The are mounted in X. Axial clearance of the bearings are adjusted during the fixing of the assembling, through relatively displacement of the rings. The cap and the body of the speed reducer will be manufactured from regular materials, low alloy steels for general construction usage from STAS 500/2. The separation plane between the body and the cap should have relatively small roughness to ensure a good sealing so that dust and other impurities can not get inside the speed reducer. Screws should be resistant enough to ensure a good fixing of the bearings, in this way reducing the radial and angular movements of the shafts. Also for proper sealing there are chosen proper Oil Retaining Rings.10. RULES OF SAFETY AT WORK At work or in the operation of the gears you will need to take into account the following provisions relating to rules of safety at work. 1. The device has to be fixed with screws to the workbench. 2. Do not use reducers that have missing parts, components. 3. Do not change the oil during operation. 4. Do not check the oil during operation. 5. Defective or worn parts will replace the corresponding ones. 6. There are no adjustments to the play from ball bearings during operation. 7. Follow the exchange of oil ranges and bearings. 8. It aims to overcome the operating hours to load.