S T A N D A R D ASABE is a professional and technical organization, of members worldwide, who are dedicated to advancement of engineering applicable to agricultural, food, and biological systems. ASABE Standards are consensus documents developed and adopted by the American Society of Agricultural and Biological Engineers to meet standardization needs within the scope of the Society; principally agricultural field equipment, farmstead equipment, structures, soil and water resource management, turf and landscape equipment, forest engineering, food and process engineering, electric power applications, plant and animal environment, and waste management. NOTE: ASABE Standards, Engineering Practices, and Data are informational and advisory only. Their use by anyone engaged in industry or trade is entirely voluntary. The ASABE assumes no responsibility for results attrib- utable to the application of ASABE Standards, Engineering Practices, and Data. Conformity does not ensure compliance with applicable ordinances, laws and regulations. Prospective users are responsible for protecting themselves against liability for infringement of patents. ASABE Standards, Engineering Practices, and Data initially approved prior to the society name change in July of 2005 are designated as ‘ASAE’, regardless of the revision approval date. Newly developed Standards, Engineering Practices and Data approved after July of 2005 are designated as ‘ASABE’. Standards designated as ‘ANSI’ are American National Standards as are all ISO adoptions published by ASABE. Adoption as an American National Standard requires verification by ANSI that the requirements for due process, consensus, and other criteria for approval have been met by ASABE. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. CAUTION NOTICE: ASABE and ANSI standards may be revised or withdrawn at any time. Additionally, procedures of ASABE require that action be taken periodically to reaffirm, revise, or withdraw each standard. Copyright American Society of Agricultural and Biological Engineers. All rights reserved. ASABE, 2950 Niles Road, St. Joseph, MI 49085-9659, USA ph. 269-429-0300, fax 269-429-3852, [email protected]ASAE S211.5 JUL1998 (R2008) V-belt and V-ribbed Belt Drives For Agricultural Machines
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STANDARD
ASABE is a professional and technical organization, of members worldwide, who are dedicated to advancement ofengineering applicable to agricultural, food, and biological systems. ASABE Standards are consensus documentsdeveloped and adopted by the American Society of Agricultural and Biological Engineers to meet standardizationneeds within the scope of the Society; principally agricultural field equipment, farmstead equipment, structures, soiland water resource management, turf and landscape equipment, forest engineering, food and process engineering,electric power applications, plant and animal environment, and waste management.
NOTE: ASABE Standards, Engineering Practices, and Data are informational and advisory only. Their use byanyone engaged in industry or trade is entirely voluntary. The ASABE assumes no responsibility for results attrib-utable to the application of ASABE Standards, Engineering Practices, and Data. Conformity does not ensurecompliance with applicable ordinances, laws and regulations. Prospective users are responsible for protectingthemselves against liability for infringement of patents.
ASABE Standards, Engineering Practices, and Data initially approved prior to the society name change in July of2005 are designated as ‘ASAE’, regardless of the revision approval date. Newly developed Standards, EngineeringPractices and Data approved after July of 2005 are designated as ‘ASABE’.
Standards designated as ‘ANSI’ are American National Standards as are all ISO adoptions published by ASABE.Adoption as an American National Standard requires verification by ANSI that the requirements for due process,consensus, and other criteria for approval have been met by ASABE.
Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement hasbeen reached by directly and materially affected interests. Substantial agreement means much more than a simplemajority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that aconcerted effort be made toward their resolution.
CAUTION NOTICE: ASABE and ANSI standards may be revised or withdrawn at any time. Additionally, proceduresof ASABE require that action be taken periodically to reaffirm, revise, or withdraw each standard.
Copyright American Society of Agricultural and Biological Engineers. All rights reserved.
ASABE, 2950 Niles Road, St. Joseph, MI 49085-9659, USA ph. 269-429-0300, fax 269-429-3852, [email protected]
ASAE S211.5 JUL1998 (R2008)V-belt and V-ribbed Belt Drives For Agricultural Machines
V-belt and V-ribbed Belt Drives For Agricultural Machines
Adopted by ASAE June 1950; revised 1960, 1962; revision proposed bya joint committee representing the Rubber Manufacturers Associationand the Farm and Industrial Equipment Institute; approved by the ASAEPower and Machinery Division Technical Committee December 1968;reconfirmed December 1973, December 1978, December 1983; revisedMay 1986; revised editorially February 1987, September 1988; reaffirmedDecember 1990, December 1995, December 1996; revised editoriallyMarch 1998; revised July 1998; reaffirmed February 2003, February2008.
Keywords: Belt, V-belt
1 Purpose1.1 The purpose of this Standard is to provide sufficient technical datafor the uniform physical application of belt drives to farm machines andmobile industrial equipment. Use of this Standard will contribute to thedesign of simple and economical drives.
2 Normative referencesThe following standards contain provisions which, through reference inthis text, constitute provisions of this Standard. At the time of publication,the editions indicated were valid. All standards are subject to revision,and parties to agreements based on this Standard are encouraged toinvestigate the possibility of applying the most recent editions of thestandards indicated below. Standards organizations maintain registers ofcurrently valid standards.ANSI/ASME B46.1-1995, Surface Texture (Surface Roughness,Waviness, and Lay)ISO 1000:1992, SI units and recommendations for the use of theirmultiples and of certain other unitsRMA/MPTA IP-20, Classical Multiple V-Belts (A, B, C, D, and E CrossSections)RMA/MPTA IP-21, Double V-Belts (AA, BB, CC, and DD Cross Sections)RMA/MPTA IP-22, Narrow Multiple V-Belts (3V, 5V, and 8V CrossSections)RMA/MPTA IP-26, V-Ribbed Belts (H, J, K, L, and M Cross Sections)
3 Scope3.1 This Standard establishes acceptable manufacturing tolerances,methods of measuring, and proper application for drives using V-belts orV-ribbed belts. They may be used individually or in matched sets.3.2 This Standard is unique to agricultural belt drives and should beused in lieu of standards for industrial drives published by the RubberManufacturers Association.3.3 This Standard does not specify the load-life characteristics of belts.3.4 This Standard does not include belts for automotive accessorydrives, flat conveyor belting, flat power transmission belts, orsynchronous belts.3.5 The term belt(s) used throughout this Standard means V-belt(s) andV-ribbed belt(s).3.6 In the interest of international standardization, metric-SI units,consistent with International Organization for Standardization Standard1000, SI Units and Recommendations for the Use of Their Multiples andof Certain Other Units, are included in tables 1a through 15a.
4 Definitions4.1 effective width of V-belt groove: A groove width characterizing thegroove profile. It is a defined value not subject to tolerance and is usually
Table 1 – Nominal dimensions of cross sections, in.
1)Classical and narrow V-belts are also available in the joined belt configuration asillustrated in figure 1.
2)Sg is specified pulley groove spacing (see table 7).
located at the outermost extremities of the straight side walls of thegroove. For all V-belt measuring pulleys and for most machined-typepulleys, it coincides with the actual top width of the groove withinreasonable tolerances.4.2 effective diameter of V-belt pulley: The diameter of the pulley atthe effective width of the pulley groove. (Formerly designated Effectiveoutside diameter.)4.3 effective diameter of V-ribbed pulley: The outside diameter of thepulley as a defined value at the specified pulley groove dimensions(without tolerances).4.4 effective length: The length of a line circumscribing a belt at thelevel of the effective diameter of the measuring pulleys with the belt at aprescribed tension.4.5 pitch width: The width of the belt at its neutral zone.4.6 pitch width of groove: That width of the pulley groove which hasthe same dimension as the pitch width of the belt used with this pulley.
Figure 1 – Belt types
ASAE S211.5 JUL76
4.7 pitch diameter of pulley: The diameter of the pulley at the pitchwidth of pulley groove.4.8 speed ratio and belt speed: Speed ratio is the ratio of the pitchdiameter of the pulleys; generally expressed as a number equal to orgreater than unity. Belt speed is the linear speed of the belt calculatedusing the pitch diameter of the driver pulley.4.9 installation allowance: A design length factor permitting theunforced installation of a belt (see tables 12 through 15).4.10 take-up allowance: A design length factor to permit sufficienttensioning over the life of the drive (see tables 12 through 15).4.11 measuring pulleys: Pulleys used for determining the effectivelength of a belt (see tables 5 and 6 for dimensions).4.12 ‘‘y’’ center distance: The center distance between measuringpulleys used to determine the effective length of a belt (see clause 7.1 forprocedure).4.13 clutching allowance: A design length factor to facilitate the beltdrive systems operation as a clutch (see clause 9.5).
5 Cross sections5.1 Nominal dimensions of belt cross sections for agricultural machinesare shown in tables 1 and 2. Because of different constructions andmethods of manufacture, the cross-sectional shape, dimensions, andincluded angle between the sidewalls may differ among manufacturers.However, all belts of a given cross section shall operate interchangeablyin standard grooves of the same cross section, but belts of differentmanufacturers should never be mixed on the same drive (see tables 7through 9).
6 Available lengths6.1 The length ranges for agricultural belts are shown in tables 2 and 2a.
Figure 2 – Relationship between sheave or pulley outside diameter and thecorresponding effective diameter
Figure 3 – Diagram of a fixture for measured belts
Table 3 – Effective length tolerance, in.
Effective length range Effective length tolerance
Up through 51 60.40Over 51 to and incl. 98 60.50Over 98 to and incl. 124 60.60
Over 124 to and incl. 157 60.80Over 157 to and incl. 197 61.00Over 197 to and incl. 248 61.25Over 248 to and incl. 315 61.60Over 315 to and incl. 390 62.00
Table 4 – Limits of difference in effective length for matching sets, in.
Effective length range
Matching limits for one set
Normaltensile
modulus
Hightensile
modulus1)
Up through 54 0.16 0.08Over 54 to and incl. 111 0.24 0.12Over 111 to and incl. 236 0.39 0.20Over 236 to and incl. 390 0.63 0.24
1)Examples of high tensile modulus belts are those containing aramid, fiberglass,or steel cable reinforcement.
Figure 4 – Measuring belt ride, V-belt
Table 3a – Effective length tolerance, mm
Effective length range Effective length tolerance
Up through 1300 610Over 1300 to and incl. 2500 613Over 2500 to and incl. 3150 616Over 3150 to and incl. 4000 620Over 4000 to and incl. 5000 625Over 5000 to and incl. 6300 632Over 6300 to and incl. 8000 640Over 8000 to and incl. 10000 650
Table 4a – Limits of difference in effective length for matching sets, mm
Effective length range
Matching limits for one set
Normaltensile
modulus
Hightensile
modulus1)
Up through 1375 4 2Over 1375 to and incl. 2820 6 3Over 2820 to and incl. 6000 10 5Over 6000 to and incl. 10.000 16 6
1)Examples of high tensile modulus belts are those containing aramid, fiberglass,or steel cable reinforcement.
*Measuring pulley dimensions for HA and HB grooves are different than those recrecommendations so that precision measuring pulleys will not need to be replaced
1)Values for HA, 13F belts in RMA/MPTA combination A/B or 13C/16C grooves.
1998 „R2008… 79
Table 6 – Data for use in measuring effective lengths
Crosssection
Pulleyoutside
diameter,reference
in.
Pulleyeffective
circumference,in.
Pulleygrooveangle
a60.25
deg
Pulleygroovespacing
Sg ,in.
J 3.183 10.000 40 0.09260.001
L 6.366 20.000 40 0.18560.002
M 9.549 30.000 40 0.37060.0003
Table 6a – Data for use in measuring effective lengths
Crosssection
Pulleyoutside
diameter,reference
mm
Pulleyeffective
circumference,mm
Pulleygrooveangle
a60.25
deg
Pulleygroovespacing
Sg ,mm
Diameballrod d60.0
mm
FPJ 95.5 300 40 2.34 1.50(60.03)
FPL 159.2 500 40 4.70 4.00(60.05)
FPM 254.6 800 40 9.40 7.00(60.08)
Table 7 – Pitch diameter location, 2a p in.
Cross section Standard groove Deep groove
HA 0.25 0.531)
HB 0.35 0.71HC 0.40 1.01HD 0.60 1.43
1)Values for HA, 13F belts in RMA/MPTA combination A/B or 13C/16C grooves.
7 Method of measuring belts7.1 The effective length of an agricultural belt is determined using ameasuring fixture (fig. 3), consisting of two pulleys of equal diameterhaving standard groove dimensions (see tables 5, 5a, 6, and 6a). One ofthe pulleys is fixed in position while the other is movable along agraduated scale with a specified force applied to it. The belt is rotatedaround the pulleys at least twice to properly seat it in the pulley groovesand to determine the midpoint of the center distance range. Effectivelength of the belt is determined by adding twice the average centerdistance measured on the fixture to the effective circumference of themeasuring pulley specified in tables 5, 5a, 6, or 6a.7.2 The belt ride dimension is checked by measuring the distance fromthe top of the belt to the top of the measuring pulley groove (figs. 4, 5,and 6). Belt ride shall be within the maximum limit given in tables 5, 5a,6, and 6a. For V-belts the belt ride dimension is the only method ofdetermining proper belt fit in the groove.
8 Specifications for pulleys used with V-belts and V-ribbed belts8.1 Pulley groove dimensions8.1.1 Refer to the appropriate RMA/MPTA standard for pulley groovedimensions as follows below. Please observe that the ASAE V-beltdesignations are prefixed with an H, indicating heavy duty construction,and the belts are not to be replaced with RMA/MPTA Standard belts eventhough they are dimensionally equivalent. (This terminology does notapply to V-ribbed belts).Classical Belt Drives RMA/MPTA STD IP20Sections Sections A, B, C, D
HA, HB, HC, HD 13C, 16C, 22C, 32C13F, 16F, 22F, 32F (see clause 8.1.2)
V-Ribbed Belt Drives RMA/MPTA STD IP26Sections J, L, M Sections J, L, M
FPJ, FPL, FPM PJ, PL, PM
Adjustable Speed Belt DrivesSee tables 8, 8a, 9, and 9a along with figures 9 and 10.
NOTE 1: Please consult RMA or MPTA if there is uncertainty concerningthe latest available standard.
NOTE 2: Select deep groove pulleys for ‘‘quarter turn’’ or other situationswhere belts enter pulley groove at an angle.
8.1.2 Pitch diameter location (dimension 2ap in pulley groove tables) isdependent on belt construction and pitch diameter location of the belt.Refer to table 7 for recommended values of 2ap for HA, HB, HC, HD,13F, 16F, 22F, and 32F sections.
8.2 Construction8.2.1 Pulleys used with agricultural V-belts or V-ribbed belts shall bemade of a material which is resistant to abrasion between the groove walland the belt. The material should be sufficiently close-grained to allowthe machining or forming of a smooth groove sidewall.8.2.2 Machined pulleys shall have surface finishes equal to or smootherthan the following values:
ASAE S211.5 JUL80
Maximum surface roughness height(arithmetic average)1)
Machined surface area µin. µm
Pulley groove sidewall 125 3.2Adjustable pulley sidewall 63 1.6Flat pulley rim O.D. 250 6.3Rim edges. rim O.D. 500 12.7
1)The measuring methods defined in ANSI/ASME B46.1 shall be used to deter-mine these values.
8.2.3 Pulleys formed from sheet metal shall be made so that the groovewidth and angle are uniform throughout the circumference of the pulley.The gage of the sheet metal used should be such that the groove will notdeflect under the load imposed by the belt.
8.2.4 Adjustable-speed pulleys should be so designed that the movabledisk is perpendicular to the axis of rotation at all times withoutappreciable runout or wobble. Failure to accomplish this results in anonuniform groove width, which materially reduces belt life and may setup undesirable vibration of the machine on which it is used (see tables8 and 8a).
9 Recommended design practices9.1 Pulley diameters . In designing belt drives, it should be recognizedthat the use of larger pulley diameters will result in lower bearing loadsand can result in the use of smaller and less expensive belt crosssections.
Table 8 – Dimensions for pulleys using adjustable speed belts, in.
9.2 Idlers9.2.1 Idlers may be necessary on agricultural belt drives to providetake-up or to increase the arc of contact to obtain the required drivecapacity. If an idler is needed, it should be located on the slack side ofthe drive. Other factors that affect the location of the idler are itseffectiveness in belt take-up and its effect on arcs of contact.9.2.2 An idler should have its axis of rotation perpendicular to the planeof the belt strand on which it runs. The idler mounting should be strongenough to maintain this relationship at all times.9.2.3 If grooved idlers are used, the groove dimensions should be asshown in tables 9 and 9a.9.2.4 Minimum diameters recommended for idlers are shown in tables10 and 10a.9.3 Length calculations9.3.1 The approximate belt length for a two-pulley drive may becalculated using the formula:
Le52C11.57~De1de!1~De2de!2
4C(1)
where:
Le is effective length of belt;C is distance between centers of pulleys;De is effective diameter of large pulley;de is effective diameter of small pulley.
(See figure 11).
If pulley effective diameters (De and de) and belt effective length (Le) areknown, the approximate center distance between pulleys may becalculated as follows:
Figure 11 – Relation between center distance and belt length for drives withtwo pulleys
Figure 12 – Belt drive with more than two pulleys
1998 „R2008… 81
C5a1Aa22b (2)
where:
a 5 Le/420.393~De1de!;
b 5 0.125~De2de!2.
9.3.2 To determine belt length when more than two pulleys are used ona drive (figure 12), lay out the pulleys in terms of their effective diametersto scale in the position desired when a new belt is applied and firstbrought to driving tension. The length of belt shall be the sum of the
Table 10 – Minimum recommended diameters for idlers, in. 1)
Table 12 – Installation and take-up allowances for clas
Effective length range
Allowance
HAHAA
HAjoined
HBHBB
HBjoined
Up through 51.2 1.09 1.25 1.25 1.39Over 51.2 to & incl. 98.4 1.38 1.54 1.54 1.68Over 98.4 to & incl. 124.0 1.58 1.74 1.74 1.88Over 124.0 to & incl. 157.5 1.92 2.07 2.07 2.22Over 157.5 to & incl. 196.9 2.43 2.57Over 196.9 to & incl. 248.0 2.89 3.03Over 248.0 to & incl. 315.0 3.50 3.65Over 315.0 to & incl. 393.7
NOTE – Refer to table 14 for footnote key.
Table 12a – Installation and take-up allowances for clas
Effective length range
Allowance
13F13FD
13Fjoined
16F16FD
16Fjoined
Up through 1300 28 32 32 35Over 1300 to & incl. 2500 35 39 39 43Over 2500 to & incl. 3150 40 44 44 48Over 3150 to & incl. 4000 49 53 53 56Over 4000 to & incl. 5000 62 65Over 5000 to & incl. 6300 73 77Over 6300 to & incl. 8000 89 93Over 8000 to & incl. 10,000
NOTE – Refer to table 14a for footnote key.
Table 13 – Installation and take-up allowances
Effective length range
Allowance
3V3V
joined 5V
Up through 51.2 1.09 1.20 1.44Over 51.2 to & incl. 98.4 1.38 1.49 1.73Over 98.4 to & incl. 124.0 1.58 1.69 1.93
Over 124.0 to & incl. 157.5 2.26Over 157.5 to & incl. 196.9 2.62Over 196.9 to & incl. 248.0 3.08Over 248.0 to & incl. 315.0 3.69Over 315.0 to & incl. 393.7
Table 13a – Installation and take-up allowances for narrow and joined narrow belts, mm
Effective length range
Allowance for installation1)Allowance for
stretch and wear2)
9FN9FN
joined 15FN15FNjoined 25FN
25FNjoined
Normaltensile
modulus
Hightensile
modulus
Up through 1300 28 30 37 40 39 33Over 1300 to & incl. 2500 35 38 44 47 59 63 75 62Over 2500 to & incl. 3150 40 43 49 53 64 68 95 79Over 3150 to & incl. 4000 57 61 73 76 120 100Over 4000 to & incl. 5000 67 70 82 85 150 125Over 5000 to & incl. 6300 78 82 93 97 189 157Over 6300 to & incl. 8000 94 97 109 113 240 200Over 8000 to & incl. 10,000 127 131 300 250
NOTE – Refer to table 14a for footnote key.
Table 14 – Installation and take-up allowances for V-ribbed belts, in.
Effective length range
Allowance for installation1)Allowance for
stretch and wear2)
J L M
Normaltensile
modulus
Hightensile
modulus
Up through 51.2 0.86 1.20 1.54 1.28Over 51.2 to & incl. 98.4 1.15 1.49 1.93 2.95 2.46Over 98.4 to & incl. 124.0 1.69 2.13 3.72 3.10
Over 124.0 to & incl. 157.5 2.03 2.47 4.73 3.94Over 157.5 to & incl. 196.9 2.83 5.91 4.92Over 196.9 to & incl. 248.0 3.28 7.44 6.20Over 248.0 to & incl. 315.0 3.90 9.45 7.88Over 315.0 to & incl. 393.7 4.61 11.81 9.84
1)Allowance for installation includes the minus manufacturing length tolerance fromtable 3, the difference between the length of belt under no tension and the lengthunder installation tension, and an amount for installing the belts over the pulleyflanges without injury.
2)Allowance for stretch and wear includes the plus manufacturing tolerance fromtable 3 as well as an allowance for the stretch and wear of the belt resulting fromservice on the drive (see tables 12, 13, 14, and 15).Installation and take-up methods are shown in figure 13. In the first sketch, thecenter distance of the drive can be adjusted to furnish the necessary installationand take-up allowances. In the second sketch, the center distance is fixed, andthe allowance for installation and take-up is provided by the idler pulleys.Examples of the calculation of center distance, effective length, and installationand take-up allowances are shown in Annex A.
Table 14a – Installation and take-up allowances for V-ribbed belts, mm
Effective length range
Allowance for installation1)Allowance for
stretch and wear2)
FPJ FPL FPM
Normaltensile
modulus
Hightensile
modulus
Up through 1300 22 30 39 33Over 1300 to & incl. 2500 29 38 49 75 62Over 2500 to & incl. 3150 43 54 95 79Over 3150 to & incl. 4000 52 63 120 100Over 4000 to & incl. 5000 72 150 125Over 5000 to & incl. 6300 83 189 157Over 6300 to & incl. 8000 99 240 200Over 8000 to & incl. 10,000 117 300 250
1)Allowance for installation includes the minus manufacturing length tolerance fromtable 3a, the difference between the length of belt under no tension and thelength under installation tension, and an amount for installing the belts over thepulley flanges without injury.
2)Allowance for stretch and wear includes the plus manufacturing tolerance fromtable 3a as well as an allowance for the stretch and wear of the belt resultingfrom service on the drive (see tables 12a, 13a, 14a, and 15a).Installation and take-up methods are shown in figure 13. In the first sketch, thecenter distance of the drive can be adjusted to furnish the necessary installationand take-up allowances. In the second sketch, the center distance is fixed, andthe allowance for installation and take-up is provided by the idler pulleys.
Table 15 – Installation and take-up allowances for adjustable speed belts, in.
Over 124.0 to & incl. 157.5 2.22 2.36 2.51 2.66 2.81 2.91 3.00 3.15 4.73 3.94Over 157.5 to & incl. 196.9 2.87 3.01 3.17 3.27 3.36 3.54 5.91 4.92
1)Installation allowance on a drive using two adjustable pulleys can be neglected.2)Allowance for stretch and wear includes the plus manufacturing tolerance from table 3 as well as an allowance for the stretch and wear of the belt resulting from service
on the drive (see tables 12, 13, 14, and 15).Installation and take-up methods are shown in figures 11 and 12. In the first sketch, the center distance of the drive can be adjusted to furnish the necessary installationand take-up allowances. In the second sketch, the center distance is fixed, and the allowance for installation and take-up is provided by the idler pulley.Examples of the calculation of center distance, effective length, and installation and take-up allowances are shown in Annex A.
1)Installation allowance on a drive using two adjustable pulleys can be neglected.2)Allowance for stretch and wear includes the plus manufacturing tolerance from table 3a as well as an allowance for the stretch and wear of the belt resulting from service
on the drive (see tables 12a, 13a, 14a, and 15a).Installation and take-up methods are shown in figures 11 and 12. In the first sketch, the center distance of the drive can be adjusted to furnish the necessary installationand take-up allowances. In the second sketch, the center distance is fixed, and the allowance for installation and take-up is provided by the idler pulley.
9.3.3 Belt manufacturers have computer programs for calculating beltlength and will provide assistance in solving complex drive geometries.9.4 Installation and take-up (see figure 13)9.4.1 The calculated belt length (clause 9.3) shall be the effective lengthof an ideal belt under operating tension. A belt drive shall be arranged sothat any belt within the length tolerances given in tables 3 and 3a can beplaced in the pulley groove without forcing. In addition, provision shall bemade to compensate for the change in effective length caused by theseating of the belt in the pulley groove and by the stretch and wear of thebelt during its life.
9.4.2 Installation and take-up allowance specified in tables 12, 12a, 13,13a, 14, 14a, 15, and 15a shall be provided on every belt drive to ensuresatisfactory operation.9.5 Clutching belt drives. Properly designed belt drive systems can beused as a clutching mechanism. The required belt effective length isdetermined by adding the clutching allowance to the calculateddeclutched length. The clutching allowance is calculated from the formula
Figure 14 – Typical two-pulley drive with one shaft movable for take-up
)
Clutching allowance (min.)53.14 hbS u
306 deg D +(minus belt length tol.
where
hb is belt thickness (see tables 1 and 1a);u is arc of contact on clutching pulley, deg.;Minus belt length tolerance5values from tables 3 and 3a.
9.5.1 The calculated clutching allowance should be equal to or exceedthe allowance for installation given in tables 12 through 15 and 12athrough 15a.9.5.2 The drive design should provide proper belt guide(s) to permit thebelt to disengage from the driving pulley.
9.6 Cross drives, mule drives, and other twisted-belt drives
ASAE S211.5 JUL86
9.6.1 The minimum tangent length for a 180 deg twist in a belt is shownin Tables 11 and 11a. The minimum tangent length for any amount oftwist other than 180 deg can be obtained by multiplying the minimumtangent length by the fraction
degrees of twist required
180.
Adjustable-speed belts are not recommended for these drives.9.6.2 Quarter-turn drives. On quarter-turn drives, the angle of entry ofthe belt into the plane of the pulley grooves should not exceed 5 deg. Acenter distance at least 5.5 times the diameter of the large pulley isnecessary to ensure this condition where one belt is used.9.7 Specification of belt drives. In submitting a drive design problem toengineering departments of the different belt manufacturers, it is stronglyrecommended that complete information be given. Annex A providesexamples of the data needed.
Figure 16 – Double-V belt drive with four pulleys on fixed centers
Annex A(informative)
Examples of the calculation of beltlength, center distance, installation and
take-up allowances, and inspection requirements
EXAMPLE 1 (Refer to figure 14)The drive consists of two pulleys; one of the shafts may be moved forinstallation and take-up. Effective diameters have been determined. Thepreferred center distance is about 20 in.
Belt length and center distance1. Substitute the effective diameters and preferred center distance in
formula [1]. The effective belt length required is 79.02 in.2. Round to the nearest tenth of an inch, or 79.0 in.3. This length substituted in formula [2] will give a center distance of
19.97 in.
Installation allowance1. From table 12 the installation allowance will be 1.54 in.2. Subtract this amount from the effective belt length of 79.0 in. to get
a length of 77.46 in.
3. This length substituted in formula [2] will give a center distance of19.16 in., the minimum center distance needed for installation ofthe belt.
Take-up allowance1. From table 12 the allowance needed for take-up is 2.95 in.2. Add this amount to the effective belt length of 79.0 in. to get a
maximum length of 81.95 in.3. This length substituted in formula [2] will give the maximum
required center distance of 21.51 in.Inspection requirementFill in the inspection requirements for the belt required in Example 1.
1. Fill in values from table 5 as follows:Tension5100 lbhg50.580 in.bg50.630 in.a532 deg.OD54.775 in.Maximum ride position of belt with respect to top of groove is 0.09in. (Note: From table 5, the effective circumference of themeasuring pulley is 15.000 in.)
2. From the effective length of 79.0 in., subtract 15.000 in. and dividethe remainder by 2 to find Y, orY5~79.0215.000!/2532.0 in.
3. From table 3, the length tolerance is 60.50 in. The tolerance ondimension Y will be equal to these length tolerances divided by 2,orTolerance on Y560.25 in.
EXAMPLE 2 (Refer to figure 15)The effective diameters have been determined. Both shafts arefixed in position and the center distance is 26.66 in. An 8.5 in.outside diameter flat idler will be used for take-up on the drive.
Belt length1. Substitute the effective outside diameters of the pulleys and the
fixed center distance of 26.66 in. in formula [1]. The resulting beltlength is 80.01 in.
2. Since the centers cannot be moved for installation, the shortestpossible belt must go on the drive with the idler out of the way.Consequently, the installation allowance must be added to the beltlength obtained above. The installation allowance from table 12 is1.73 in. This added to the length of 80.01 in. gives a requiredeffective belt length of 81.74 in.
Take-up allowancesFrom table 12, the take-up allowance needed for this belt is 2.95 in. Thisamount added to the effective belt length of 81.74 in. gives a maximumlength of 84.69 in. By one of the methods outlined above for determiningbelt length when more than two pulleys are used on a drive, locate theposition of the idler so that it will provide take-up for this length of belt.
Inspection requirements
Fill in the inspection requirements for the belt required in example 2.
1. Fill in values from table 5 as follows:Tension5190 lbhg50.780 in.bg50.879 in.a534 degOD57.958 in.Maximum ride position of belt with respect to top of groove is 0.09in. (Note: From table 5, the effective circumference of themeasuring pulley is 25.000 in.)
2. From the effective length of 81.74 in. subtract 25.000 in. and divide
ASAE S211.5 JUL88
the remainder by 2 to find Y, orY5(81.74225.000)/2528.37 in.
1. From table 3, the length tolerance is 60.50 in. The tolerance ondimension Y will be equal to these length tolerances divided by 2,orTolerance on Y560.25 in.
EXAMPLE 3 (Refer to figure 16)2. The effective diameters have been selected and shaft centers have
been located approximately. All shafts will be fixed in position andbelt take-up will be accomplished by means of a grooved idlerpulley.
Belt length1. With the idler in its ‘‘installation position,’’ use one of the methods
outlined above for determining belt length when more than twopulleys are used on a drive.
2. To find the length of belt for the drive, add to the length obtainedin step 1 the allowance for installation from table 12.
Take-up allowanceTo the length of belt for the drive, add the allowance for take-up fromtable 12. Check the drive with the idler in its maximum take-up positionto see that this length of belt can be accommodated.Inspection requirementsFill in the inspection requirements for the belt required in example 3.
1. Fill in values from table 5 as follows:Tension5190 lbhg50.780 in.bg50.630 in.a534 degOD57.958 in.Maximum ride position of belt with respect to top of groove is 0.03in. (Note: From table 5, the effective circumference of themeasuring pulley is 25.000 in.)
2. From the effective length of 176.7 in., subtract 25.000 in. anddivide the remainder by 2 to find Y, orY5~176.7225.000!/2575.85 in.
3. From table 3, the length tolerance is 61.00 in. The tolerance ondimension Y will be equal to these length tolerances divided by 2,orTolerance on Y560.50 in.