Production Technology of Agril. Machinery 3(2+1)

LESSON 23. CRITICAL COMPONENTS AND THEIR SELECTION

4.1.1 Meaning of critical

The term “critical” is related to decision-making or crisis or turning point.

4.1.2 What is a critical component?

The component responsible for creating a crisis by its wrong-working or faltering is called critical. A component may be critical in a machine, and so also a part. Thus, a critical component or say a critical part in a machine will cause the machine to dysfunction if the same is not properly designed, manufactured or repaired/maintained or selected. But most critical components or parts are available in market in ready-to-use form, the selection of which is, therefore, very important for the particular machine and conditions of operation. As for instance, the examples of these are bearings & housings, pulleys & belt, gears etc. Besides, the same critical components or parts may be fabricated also. These are, for example, lynch pins of tractor mounted implements. Thus, most of the critical parts and components are available in the market as standard material and no separate effort is, there-fore, required to design and fabricate them. One is, therefore, required to select the right one. A glimpse of such parts is presented in next section.

4.2. Standard Parts

4.2.1 Common bought-out parts

Almost all types of standard parts used commonly in common machines are also used in agricultural equipment.  A classification of the standard bought-out parts is presented in Fig.1. The criteria of selection of individual part are dealt in the subsequent sections through a few example cases.

4.2.2 Specific bought-out parts

Some parts used in agricultural equipment are not normally used in other machines but are specific to one more agricultural equipment. These have been in exhaustively listed in Table 1.  Some industries fabricate of them in their own units along with other components of implements and therefore they may not conform to standard dimensions.

Figure : 1

Table 1 . Bought-out / fabricated parts specific to agrl. Equipment

(This list is illustrative only.)

4.3.Selection criteria

In this lecture note, only a few parts have been selectively covered to explain criteria of selection. One may need to look into the following general criteria in selecting a critical component part.

i. Material

ii. Intricacy of design

iii. Quality of manufacturing

iv. Metallurgy, longevity, wearing, etc.

v. Space limitations

vi. Load and power

vii. Cost

4.4. Material:                                                                               

Material finds an important place in design of a critical component part of agriculture equipment. The performance and reliability of a component depends largely on the type and quality of material used in the parts and process of manufacturing. The quality of material refers to the following and is desirable for the design engineer to tread a course between functional quality requirement on one hand and cost consideration on the other although quality may over ride cost in some rare cases.

i. Strength

ii. Toughness

iii. resistance to wear and corrosion

iv. good scour (quality of material to allow easy flow)

v. lightness of weight, and

vi. low initial cost and subsequent upkeep requirement

In the present days, design is no longer and the consideration of time factor these days has necessitated the knowledge of the right materials and their use right from the beginning. It is also important to update one’s knowledge of new material being introduced every day in order to maximize on their use.

4.5. Specific cases

Here we deal with a few case examples to introduce the ideal of selection of critical components.

4.5.1 Bearing

For a bearing it is important to know in the first instant the nature of loads the bearing is to carry. According to the   type of loading namely axial, radial or mixed, the bearings have been classified as shown in Fig 2.

Selection of bearing

Bearing are classified in the manner as shown in Fig 2. The types of bearing and their nature of loading like radial, axial and mixed besides speed of operation have been give in this section. Moreover, it is also important to know the relationship between the load and life of bearing. The relationship is established by Eqs.1  & 2 and life calculation chart. Similarly the class of machines and their useful lives are presented in Table 2 for deciding the types of bearing to be used.

Fig.1. classification of bearings according to load

Revised life equations established by ISO 281 are:

Where,

L_a  =  Adjusting rating life, h

L_b   =  Basic operating life, h

a₁  =   life adjustment factor for reliability

a₂₃ =   Combined life adjustment factor for material and operating condition

n =   rpm

C =   Basic Dynamic Load Rating, Newton

P  =   Equivalent Dynamic Bearing Load, Newton

q=  exponent for life equation = 3 for ball bearing and 10/3 for roller bearing, and

C/P  =  Load ratio

Rise in operating temperature affects the hardness and bearing material. This affects C by the factor of temperature, f, as C.f.

Bearing  temperature,⁰C

Bearing temperature,⁰C          150                     200                     250                      300

Temperature factor, f               1.0                       0.9                      0.75                     0.6

 

Table2.Class of machines and their basic operating lives

S.NO	Class of machine	Basic operating life, h
1	Domestic & Agril.Machine	300-3,000
2	Electric hand tools & other intermitted machines	3,000-8,000
3	High operational reliability for short periods	8,000-12,000
4	Machine used 8h/d but not fully utilized	10,000-25,000
5	Machines used 8h/d and fully utilized	20,000-30,000
6	Machines used 24h/d like pumps, compressors etc.	40,000-50,000
7	Rotary  furnace , water works	60,000-1,00,000
8	Large electric machinery, pulp& paper making machinery	>1,00,000

Similarly the values of a, are also given by Table 3.

Reliability means the probability that a bearing will or exceed a specified life

Table 3. Reliability * versus a1

S NO.	Reliability,%	A	S NO.	Reliability,%	a	S NO.	Reliability,%	a
1	90	1	3	96	0.53	5	98	0.33
2	95	0.62	4	97	0.44	6	99	0.21

a: The value of a  is obtained in the following manner.

*Reliability means the probability that a bearing will attain or exceed a specified life.

For a selected roller bearing cylindrical bore of 18?5=90mm,22318CC/W33, W33 Feature is peripheral groove and 3 lubrication holes in the outer ring, value  are:d =inside bore = 90 mm;

іD₀=outside diameter=190mm;

Thus  d =average diameter =(90+190)/2=140mm.From Fig 4 corresponding to

dm=140mm,v =Satisfactory  oil viscosity =21 mm²аа/s at 500 rpm.

Hence ,k=v/v=35₍as given₎/21=1.61 and from Fig 5,fork=1.67,a₂₃=1.4

               

Thus,Lа=a₁.a₂₃‘10⁶/60n(C/P)q=0.33(1.4)’10⁶/60’500(4,77,000/50,000)10/3=28358h

Lengend:—Normal lubricants

 --..Lubricants WithEp additives , etc.

4.5.2 Gear selection

In agricultural   equipment, two types of gears are most common. These are spur and bevel gears. In these sections, selections of spur gear are presented.

a)Modules  of  gear

module  is  the  inverse  of  number  of  teeth  in  one  unit  diametric  pitch  of  gear. Two  spur  gears  will  match  only  when  they  match  in  their  modules . hence, module  is  an important  guiding  factor  of  matching  gear  pair.

According  to  recommendations  in  IS:2535-1969,the18  modules  of  gears  are:

                             1             2            4               8              16               32

                          1.25        2.5           5              10             20               40

                           1.5          3              6              12             25              50

The definitions of some terms are:

i. Z=NO .Of  teeth  of  a  gear  = Pitch  circle  Diameters  / module=dₒ/m

ii. Diametral   Pitch ,D_P =No. of  teeth  /No. of  inches  in  pitch  circle diameter=Z/dₒ=1/m

iii. Circular  pitch  , C_p    =Distance  of  consecutive  teeth  measured   along  pitch   circle =π .dₒ/Z

Thus , we  have  the  relation, D_P ×C_P=π

Or, m=dₒ/Z=C_P/π=        Sum  of  addenda  of  circle  Diameters  ,  d_a , of the  two  gears

                                                                             Z₁+Z₂

                             =  2×Centre  distance   of  two  gears

                                   Sum  of  teeth   of  the  gears

The 21  typical  gears  are   of  teeth

20       30         40        50        60       70        80        90        100        120          127

25       35         45        55        65        75        85       95         110        125

 5 (c) Selections   of V- belt  &  pulley

V-belts  are  mostly   used   in  powera

Commonly   used  belts  it  is  necessary   to  know  how  to  select  a  V-belt .

Selections   of  a   V -  belt  means

i. Selection  of  the  section   of  pulley  &  belt

ii. No. of  belts (and  belt  design)

iii. Belt   tensioning  and

iv. Care   and   conditions   of   use

However ,V-belts  should  satisfy    quality -  standards  in  BS-3790  or  DIN-2215 or  IS-2494 (for  V-belt  in  power  rating  )  & IS  :  3142  (for  cast  iron  pulley  sections).

1. Selection  of  section  of  pulley  and   belt

V-belts  and  pulley  come  in  standard  sections of  A,B,C,D and E. And  some special  sections  among  five  are  also  manufactured  in  belts  by  some  manufacturers. The  sectional  geometries   of  the   belts  and  pulleys and  are  presented   in  Fig 6 while  the  dimensions  in  Table 4

 

section

Belt attributes

Pulley attributes

W mm

Ip mm

H mm

Belt speed m/s

Belt wt.kg/m

B mm

t mm

e mm

f mm

? mm

dp mm

g mm

W for belt width; ᴵp for belt pitch width; H for belt height; b for addendum; t for groove height; e for pitch of groove end distance; ? for groove angle; dp for pulley diameter min; g for groove top width

A              13        11         8           30            0.112          3.3       12        15±0.3         9 to         0.4

34

75 to 124

13

38

³125

13.3

B            17          14         11         30              0.193         4.2       15        19±0.4    11.5to 14.5

34

125 to199

16.6

38

³200

16.9

C             22         19         14          30             0.33           5.7       20         25±0.5    16 to 19

26

200to 299

22.7

28

³300

22.9

D            32          27         19          30            0.675            8.1     28       37±0.6     23 to 27

36

355to 499

32.3

38

³500

32.6

E             38           32        23          30             1.030           9.6      33      44.5±0.7   28 to 33

36

500to 629

38.2

38

³630

38.6

The selection of pulley &belt both in any one category of A,B,C,D,E& any special category will depend on the factors like

• Power to be transmitted

• Speed at which to be transmitted, and

• The working conditions.

Of course, the former two are more important because power=torque, T’ angular motion ?.the angular rotation can be in terms of rpm(rotation of pulley per minute). For selection of the belt cross.

Fig 7 may be referred. From this figure, for a 5 kW of power transmission, we can select C-section V-belt to 175 rpm(on the ordinate)or B-section belt for rpm between 175 to 775 rpm(A&B on the ordinate) or A-section belt for rpm between 77 to 5,000rpm(p & q on the ordinate). And the further calculation of number of belts will decide whether the pulley will be of single groove.

Once section is graphically selected from fig. 7, the power which one belt of the selected section can transmit can be also selected from the power versus rpm given in Table 5 for given (standard) pulley diameters (pitch circle). Normally, the prime-movers are electrical motors; hence, the rpm are 720, 960, 1440 or 2880.

Table 5 Power transmission of belt

Pulley size in mm	Pulley section		Capacity to transmit power ,Kw, at  Pulley   rpm
			720		960		1440	2880
75	A		0.62		0.76		0.98	1.36
80	A		0.75		0.92		1.21	1.75
90	A		0.94		1.17		1.57	2.38
100	A		1.11		1.39		1.88	2.94
112	A		1.32		1.67		2.28	3057
125	A		1.54		1.95		2.68	4.26
125	B		2.00		2.46		3.23	4.39
132	B		2.25		2.79		3.70	5.08
140	B		2.41		3.01		4.00	5.58
160	B		3.03		3.79		5.08	7.10
180	B		3.57		4.51		6.04	8.31
200	B		4.21		5.29		7.12	-
200	C		5.50		6.78		8.75	-
212	C		6.16		7.61		9.86	-
224	C		6.63		8.21	10.65		-
250	C		8.00		9.92	12.84		-
280	C		9.28		11.49	14.79		-
355	C		12.89		15.82	19.7		-
355	D		20.52		24.51	24.58		-
375	D		22.52		26.88	-		-
400	D		25.00		29.70	-		-
450	D		29.76		35.09	-		-
500	D		34.25		39.89	-		-
560	D		39.33		44.84	-		-
450	E		27.20		30.68	-		-
500	E		32.13		35.34	-		-
600	E		41.60		-	-		-
630	E		44.25		-	-		-
710	E		50.40		-	-		-
750	E	52.97		-		-		-

 

Number of belts

The procedure to calculate the number of belts once the belt & pulley section is determined previously from fig 7 can be explained in the following steps with the of an example of driving a centrifugal at 2400 rrpm being run 18 hours a day by a 22 kW, 2880 rpm, 3-phase electrical (A.C) motor at 600mm centre distance. The steps involved to calculate the number of belts are:

SI NO	Step		Calculation
1	Determine the belt & pulley section from fig 7 corresponding to p=22kW of power and n=2880 rpm		B section of belt & pulley for n=2880 rpm & p=22kW
2	Calculate speed ratio, r,from r=N1/N2=Dp/dp		R=2880/2400=1.2
3	Select the motor pulley from amongst the standard preperred diameters (PCD) of 85,90,100,106,112,118,140,150,160,170,180,190,200, 224,212,236,250,265,280,315,355,375,400,425,450,500, 530,560,600mm and some non-preferred ones of 75,80,125,132,670,710,750,800,850,900,950 &1000.		We select Dp=smaller pulley for motor       =150 mm
4	Compute C2=service factor from Table 6		C2=1.2 from table 6 against light-duty,star-delta start & over 16 hours of works/day
5	Pitch diameter of slower pulley,Dp=r xdp		Dp=1.2 x 150 =180 mm
6	Check drive center distance C, suitable if 0.7 (Dp+dp)<2.0 (Dp+dp)		C=600mm as chosen is OK.
7	Select belt length (pitch) from Lp=2C+1.57(Dp+dp)+(Dp-dp)2 / 4C		Lp=2x600+1.57(180+150)=180-150)2  / 4x600)=1718mm; and from Table 7,the nearest standard length isn1720 mm=L
8	Cc,Ca C=C+(L-Lp)/2 if l>lp Or C=C-(L-Lp) /2 if L<Lp K=(L- /2 (Dp+dp)) /4 Ca=K+(K2-(Dp-dp)2 /8))		Cc=600 +(1720-1718)/2=601 mm and Ca= 600.76mm
9	For arc of contact correction factor, C1,take the value of C1 from Table 8 corresponding to (Dp-dp)/c	(180-150)/600=0.05 C1 =0.99 Corresponding  to .05 from Table 8
10	For  correction factor, C3,of belt length, choose C3  from Table 9 corresponding to L	C3 =0.94 from  Corresponding  to L=1720mm
11	Power rating pern belt, Pn Pn is taken from Table 10 corresponding to r, n & dp	Pn = 5.55+0.50=6.05 kW for r=1.2; n=2880 rpm and dp=150mm from Table 10
12	No. Of belts,Z Z=(pxC2)/(pnxC2xC3)	Z=(22x1.2)/6.05x0.99x0.94)=4.69 -5(taking next whole number)

 

Thus 5 units of B 66/1760 belts will be required to transmit 22kW power.

3. Belt tensioning

Proper belt tensioning would not allow slip of belt on the pulley under maximum load condition. The procedure to ensure proper belt tensioning is as follows:

Step1. Apply the recommended load for the belt section and calculate deflation of belt, Ea, under the recommended load by the relation E_a=(ExC)/100

Where,  E=Deflation/ 100mm of centre-to-centre distance.Take this value from

Table11

C=Centre-to-centre distance,mm;

The load is applied at the centre of belt span perpendicularly.

Step2. Adjust the drive until until the calculated deflation ‘E_a’ is obtained.

Step 3. In case of belt under long-time use,E_a increases to 1.3E_a for which retensioning is required.

Table 6 Service factor, C₂, for belt drives

Class of duty	Type of driven machine	C2
		Type of prime mover
		SOFT START			HEAVY START
		PER DAY DUTY HOURS			PER DAY DUTY HOURS
		<10	10 TO 20	<16	<10	10 TO 16	>16
Light  duty	Agitators (uniform),blowers,exhausters & fans (<7.5 kW),centrifugal compressors, pumps,belt conveyors (uniform)	1.1	1.1	1.2	1.1	1.2	1.3
Medium of duty	Agitators,mixers (Variable), blowers,exhausters,fans (>7.5 kW),(Noncentrifugal),rotary compressors, pumps,belt conveyors (non uniform),generator,exciter,power shaft,machines tools,wood working machines, screws (rotary)	1.1	1.2	1.3	1.2	1.3	1.4
Heavy of duty	Bucket elevator, compressors, pumps (reciprocating), conveyor (heavy duty),hoists,mills,pulverisers, punching machine,press, shear,screw (vibrating)	1.2	1.3	1.4	1.4	1.5	1.6
Extra heavy duty	Crushers (gyrator – jaw roll), mills (ball-rod-tube)	1.3	1.4	1.5	1.5	1.6	1.8

 

Note: 1. Correct  the tabulated C₂ value by the factors.

   Speed ratio of                1.00 To 1.24            multiply                   C₂                            by

        -do-                          1.25 to 1.74            multiply                   C₂                            by

        -do-                          1.75 to 2.49            multiply                   C₂                            by

        -do-                          2.50 to 3.49            multiply                   C₂                            by

        -do-                          3.50 and                 multiply                   C₂                            by

2.Soft start prime movers are AC are star-delta,shunt wound DC motor, IC engines with >-4 cyclinder, etc.

3. Heavy start prime movers are AC Direct-on-line start, DC series & compound wound, IC engines <4 cyclinders.

 

Table 7   V-belt sizes of polyester cord

S.No	Section	Length(inch / mm
1	A	A23/620,A24/645,…….,A76/1966(by Step of 1”/25mm),A78/2017,A80/2068,……,A84/2195(by step of 2”/50mm),A85/2195,A86/2220,……,A98/2525(by step of 1”/25mm);A100/2516,A102/2626,…..,A112/2880(by step of2”/50mm);A114/2932,A115/2982,A118/3033,A120/3064,A124/3186,A125/3211,A126/3236,A128/3267,A130/3338,A134/3440,A136/3490,A138/3541,A140/3696,A144/3793,A154/4430and A174/4456
2	B	B26/703,…..,B120/3091 by step f 1”/25mm except bill/2775;B122/3142,B124/3194,B125/3218,B126/3244,B128/3294,B129/3320,B130/3345,B132/3396,B134/3447,B135/3472,B136/3498,B138/3548,B140/3599,B141/3624,B142/3624,B143/3675,B144/3701,B145/3726B146/3752,B148/3802,B150/3853….B156/4006 by step of 2”/50mmB157/4031,B158/4056,B160/4107,B162/4158,B164/4209,B165/4234,B166/4259,B168,4310,B169/4336,B170,4361,B173/4437,B175/4488,B178/4564,B180/4564,B185/4742,B186/4767,B190/4889,B192/4920,B195/4996,B196/4996,B197/5047,B200/5123,B204/5225,B205/5250,B210/5377,B215/5504,B218/5580,B220/5631,B225/5758,B238/6088,B240/6139,B275/7028,B278/7014
3	C	C46/1224,C48/1275,C49/1301,C51/1351,C5/1453,C60/1580,C63/1656,C68/1783,C71/1859,C75/1961,C77/2012,C78/2037,C81/2113,C85/2215,C86/2280,C87/2266,C88/2291,C89/2317,C90/2342,C91/2367,C92/2393,C93/2418,C94/2444,C95/2469,C96/2494,C97/2590,C98/2545,C99/2571,C100/2596,C101/2621,…..C130/3358 by step of 1”/25mm except C121,C132/3409,C134/3459,C135/3485, C136/3510, C137/3561,C138/356,C139/3557,C140/3612,C142/3663,C144/3713,C145/3739,C146/3769,C18/3815,C150/3866,C152/3917,C153/3942,….C158/4069 by step 1”/25mm,C160/4120,C162/4171,C163/4196,C164/4222,C165/4247,C166/4272,C168/4223,C169/4349,C170/4374,C173/4450,C175/4501,C176/4526,C178/4577,C180/4628,C183/4704,C184/4730,C185/4755,C186/4780,C190/4882,C191/4907,C192/4933,C195/5009,C196/5034,C197/5060,C200/5136,C204/5237,C205/5263,C208/5339,C210/5390,C215/5517,C218/5592,C220/56444,C224/5748,C225/5771,C228/5847,C230/5898,C236/6050,C238/6101,C240/6152,C246/604,C248/6355,C250/6406,C252/6457,C255/6533,C258/6609,C260/6680,C262/6711,C268/6863,C270/6914,C277/7092,C280/7092,C280/7168,C284/7270,C285/7295,C290/7422,C298/7625,C300/7676,C305/7803,C308/7879,C328/8387,C330/8438,C340/8692,C358/9149,C360/9200
4	D	D109/2848,D112/2924,D114/2975,D116/3025,D5118/3078,D120/3127,D122/3178,D124/3229,D128/330,D130/3381,D132/3432,D134/3483,D136/3533,D140/3635,D144/3736,D148/3838,D150/3880,D152/3940,D155/4016,D158/4092,D160/4143,D162/4194,D168/4346,D170/4397,D173/4473,D176/4550,D177/4575,D178/4600,D180/4651,D185/4778,D188/4854,D190/4905,D195/5032,D218/5616,D220/5667,D224/5769,D225/5794,D228/5540,D230/5921,D235/6058,D238/6124,D240/6175,D248/6378,D300/7699,D252/6480,D255/6556,D256/6581,D258/6632,D260/6683,D264/6784,D268/6889,D270/6937,D276/7089,D278/7140,D280/7191,D285/7318,D287/7369,D290/7445 298/7648,D300/7699,D314/8055,D320/8207,D328/8410,D330/8461,D336/8613,D340/8715,D358/9172,D360/9223,D368/9426,D380/9731,D390/9985,D394/10087,D396/10137,D398/10188,D408/10442,D418/10698
5	E	E180/4664,E195/4689,E210/4815,E220/5065,E238/6137,E240/6188,E268/6899,E270/6950,E298/7661,E28/8423,E358/9185,E374/9592,E392/10049,E394/10100,E396/10150,E418/10709

 

Note:V-belt A 50/106 means an A section V-belt of 50” inside length & 1306 mm nominal pitch length.

Table 8 Correction factor, C₁, of arc of contact

(DP-dP)/C	?=Arc of Contact,degree	C1		(DP-dp)/C	?=Arc of Contact, degree	C1
0.00	180	1.00		0.55	148	0.92
0.05	177	0.99		0.60	145	0.91
0.10	174	0.99		0.65	142	0.90
0.15	171	0.98		0.70	139	0.89
0.20	169	0.97		0.75            136                           0.88
0.25	166	0.97
0.30	163	0.96		0.80	133	0.87
0.35	160	0.95		0.85	130	0.86
0.40	157	0.94		0.90	127	0.85
0.45	154	0.93		0.95	123	0.83
0.50	151	0.93		1.00	120	0.82

 

Table 9 Length Correction Factor, C₃

C3	Length for belt section, mm							C3	Length for belt section, mm
	A	B	C	D	E				A	B	C	D	E
0.80	630							1.02	1940	2500	4060
0.81		930						1.03				6890
0.82	700		1560	2740				1.04	2050	2700
0.83		1000						1.05	2200	2850	4600	7620
0.84	790		1760					1.06	2300
0.85		1100						1.07				8410
0.86	890			3130				1.08	2480	3200	5380
0.87		1210	1950	3330				1.09	2570			9140
0.88	990							1.10	2700	3600	6100
0.89								1.11
0.90	1100	1370	2190	3730				1.12	2910		6860	10700
0.91			2340					1.13	3080	4060
0.92		1560	2490	4080				1.14	3290		7600
0.93	1250							1.15		4430
0.94			2720	4620				1.16	3540	4820		12200
0.95		1760	2800					1.17
0.96	1430		3080					1.18		5000		13700
0.97		1950	3310	5400				1.19		5370
0.98	1550		3520					1.20		6070		15200
0.99	1640	2180						1.21			9100
1.00	1750	2300		6100				1.24			10700

 

Table 10 Power rating of belt,P_n, for smaller pulley(or faster pulley) (θ =180⁰)

Section A belt

Speed of Faster Pulley,(rpm)	Power in KW for pitch diameter, dp, Of smaller pulley, mm									Add power in kw  for r         of
	75	80	85	90	100	106	112	118	125	1.01 to 1.04	1.05 to 1.12	1.1 3to 1.24	1.25 to 1.51	1.52 & above
720	0.53	0.60	0.68	0.75	0.90	0.99	1.07	0.16	1.26	0.01	0.03	0.05	0.07	0.09
960	0.66	0.76	0.86	0.95	1.14	1.25	1.37	1.49	1.61	0.01	0.04	0.06	0.09	0.12
1440	0.91	1.04	1.17	1.31	1.58	1.73	1.90	2.07	2.24	0.02	0.06	0.10	1.14	0.17
2880	1.42	1.67	1.91	2.14	2.59	2.76	3.11	3.36	3.63	0.04	0.12	0.20	0.27	0.35

 

Section B belt

rpm	dp= 125	132	140	150	160	170	180	190	200	Speed ratio r is same
720	1.61	1.79	1.99	2.24	2.48	2.73	2.97	3.21	3.45	0.03	0.08	0.13	0.18	0.23
960	2.02	2.24	2.50	2.82	3.13	3.44	3.75	4.05	4.35	0.03	0.10	0.17	0.24	0.30
1440	2.72	3.03	3.39	3.8	4.26	4.68	5.09	5.50	5.90	0.05	0.15	0.25	0.36	0.46
2880	3.96	4.44	4.95	5.55	6.11	6.62	7.08	7.48	-	0.10	0.30	0.50	0.71	0.91

 

Section C belt

rpm	dp= 300	212	224	236	250	265	280	31 5	355	400	Speed ratio r is same
720	4.65	5.18	5.70	6.22	6.81	7.44	8.06	9.49	1105	1275	0.07	0.21	0.35	0.49	0.63

 

Section D belt

rpm	dp = 355	375	400	425	450	475	500	530	560	600	Speed ratio r is same.
720	16.26	17.90	19.90	21.85	23.75	23.59	27.38	29.44	31.42	33.91	0.25	0.75	1.25	1.75	2.22
960	19.26	21.16	23.45	25.63	27.70	29.65	31.47	33.50	35.32	-	0.33	1.00	1.67	2.33	3.00
1440	21.22	23.03	-	-	-	-	-	-	-	-	0.50	1.50	2.50	3.50	4.50

 

Section E belt

960	5.76	6.42	7.08	7.72	8.46	9.24	10.00	11.72	13.58	15.51	0.09	0.28	0.47	0.66	0.85
1440	7.49	8.36	9.21	10.03	10.95	11.91	12.82	14.76	16.67	-	0.14	0.42	0.71	0.99	1.27
2800	8.05										0.27	0.82	1.37	1.92	2.47

 

rpm	dp= 450	500	560	630	670	710	750	800	850	900	950	100	r= 1.01 to 1.04	r= 1.05 to 1.12	r= 1.27 to 1.57	>157
720	26.44	31.69	37.56	43.78	47.0	49.97	52.67	55.66					0.38	1.92	3.07	3.45
960	29.77	35.29	40.94	46.07	-	-	-						0.52	2.60	4.16	4.68

 

Table 11 Deflection, of belt per 100mm of C

Belt section	Applied Load on belt (Newton)	dp=Small pulley diameter (mm)	Deflection, E, per 100mm of C (mm)	Belt section	Applied Load on belt (Newton)	dp=Small pulley diameter (mm)	Deflection, E, per 100mm of C(mm)
A	25	75≤dp ≤100 100<dp≤1 32 dp>132	1.90   1.70   1.50	C	100	200≤dp ≤265 265<dp ≤355 dp>355	2.30   2.10   2.00
B	50	125≤dp 160≤ 160<dp ≤200 dp>200	2.30   2.10   1.90	D	150	355≤dp ≤450 450<dp ≤670 dp>670	2.20   2.10   2.10

 

4. Conditions of use

1. Belts of a matched set of required number of correct length and section of the same make and not in a mix-up of new and old should be used.

2. Pulleys of uniform and smooth (Ra<6.3µ) free of oil & grease and monted close to the bearings should be used.

3. Pulleys higher than 30m/s of speed be dynamically balanced.

4. Belts should be stored at 13 to 25C in dry & light-free place & used in temperature medium not exceeding 60C.

5. Idler pulley to provide requisite tension should be flat placed externally on slack side and should be grooved, placed internally on the slack side of diameter at least equal to the smaller pulley such that a=contact angle same for both the puleys.

 

Critical Components and their Selection

Dr.H.S.Biswas

Head, Technology Transfer Division, Central Institute of Agricultural Engineering, Bhopal

PRODUCTION TECHNOLOGY OF AGRICULTURAL EQUIPMENT

SEPTEMBER 4-24.2002