Marland Clutch Backstops - Industrial and Bearing … Design Features Marland backstops are completely mechanical, automatic operating units, incorporating a time proven basic operating

Marland ClutchBackstops

WE7523 MCbckstpBroA4.qxp 8/8/07 3:49 PM Page 1

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The Company

MarlandSince 1931, Marland has beenproducing backstops, clutches andclutch couplings. Marland products are based on a one-way clutch design,utilizing the principle of cylindrical rollerson inclined cam planes.

Marland Clutch also brings to the NorthAmerican market a line of proven spragtype freewheel clutches. Marland utilizesthe knowledge of its sister divisions,Stieber ® of Germany and Formsprag® ofthe United States, to manufacture worldclass high performance sprag clutchesin the United States.

Marland ProductsThe Marland principle of rollers oninclined cam planes has proven itsdependability for over 60 years inworldwide installations ranging fromfood processing plants to equipmentused in steel mills and heavy miningindustries. Proving the inherently long-lifeMarland design, the first two Marlandclutch units installed in February, 1931,operated continuously for 31 yearswithout repairs or replacements of anykind until the system became obsolete in 1962. Cam, rollers and outer raceinspection showed them ready foradditional years of service.

The Need For AdequateBackstopsPositive protection against reversetorque runaways of inclined conveyor or elevated installations, and adequateprovision for the safety of operationpersonnel, can be assured byconsidering the following:

1. The causes of reverse torqueloading conditions.

2. The importance of installingbackstops on low speedheadshafts –where reversetorque loads originate.

3. Use of sound methods forselecting backstop sizes, basedon many years of successfulinstallations, rather thantheoretical reverse torquecalculations.

4. The basic design, operatingprinciple and uniformly hightorque capacity of Marland One-Way backstops.

5. The simple maintenance andlubrication requirement of theMarland design.

The cover photo and the photo below showsome of the thirteen size 240MA Backstopsinstalled on large conveyors at an Arizonamining operation.

Illustration 1

Alloy aluminum cage withprecisely phased rollerpocket spacing in radialand angular location.

Rollers, cam and outerrace, hardened rollerbearing steels.

Springs insure positiveengagement even for rapidindexing up to 240 strokesper minute.

Cam ground withsame precisely phasedcam lobe spacing asused for the cage.

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Operating Details

During freewheeling, (normal operation),the cam and roller assembly rotate withthe headshaft as shown by the arrows inIllustration 2. The outer race is securedto stationary coverplates and “I” BeamTorque arm. An oil film wedges andseparates the rollers from the outer race.This moves the rollers a few thousandthsof an inch imparting relative angularmotion between the roller cage andcam. This slight movement of the rollersinto the deeper cam zones, with a cleanlubricant film wedged between rollersand outer race, permits freewheelingwithout metal to metal contact.

When the conveyor decelerates and thecam subsequently comes to rest, thespring actuated roller cage, Illustration 1,has already positioned the rollers into the contact zone. All rollers have beenpositively guided to engage uniformlyand maintain their relative positionsaccurately to assure uniform loaddistribution. The rollers then engage in compression between the precisionground, hardened cam plane surfacesand the inside diameter of the outerrace. Relative motion between the camand outer race is not required to engagerollers. When the backstop is in the“engaged” or “backstopping” condition,the cam, rollers, and outer race arerelatively stationary and therefore, notsubject to wear if used within normaltabulated rating.

Mounting DetailsMarland backstops are furnished with a clearance fit in the bore for easy fieldinstallation. The key should be a “drivetight” fit on the sides only. This key fitmay be sufficient to prevent creeping of the backstop on the shaft, however, if desired, Marland can furnish shaftretaining collars as an option to insureaxial retention. (See Below)

RollersOuter Race

Roller CageCam

Illustration 2

Coverplate and roller cage end ring havebeen removed, exposing the rollers. Notethat while at rest, all rollers are strictly in-phase ready to share the load whentransmitting torque.

Shaft Retaining Collar


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Design FeaturesMarland backstops are completelymechanical, automatic operating units,incorporating a time proven basicoperating principle, to provide greatersafety and longer life with minimummaintenance requirements. Fifteenstandard sizes are available up to720,000 pound-feet of torque. Superiorperformance is assured by the followingdesign features:

SIMPLE INITIAL INSTALLATION.Backstop is symmetrical and can bemounted for desired free shaft rotation.Arrows on cam faces or inner labyrinthshow the direction of free rotation.

The torque arm is a single “I” beamsection which is attached to thebackstop with two precision groundtorque arm pins. This greatly simplifiesfield installation. The arm may be placedup, down, or at any angle, and providesuniform loading on both coverplates. Thepreferred position is horizontal to reducebearing loading for longer bearing life.

SEALED OIL CHAMBER. The Clutchelements and ball bearings arecontinuously self-oiled in a sealed oilchamber. The recommended lubricant isautomatic transmission fluid such as"Dexron", which is readily available andsuitable for a wide range of ambienttemperatures. A double-lip oil seal isprovided adjacent to the ball bearings to keep oil in and contaminants out. See Illustration 3.

POSITIVE TRIPLE SEALING. (See Illustration 4)

1. All metal labyrinth, greasepacked.

2. Full circle square packing againstground inner labyrinth whichmaintains grease seal and servesas an additional barrier to entry of dirt.

3. Double-lip oil seal to preventgrease from entering oil chamberand oil dilution of sealing grease.

MINIMUM MAINTENANCE. Greasefittings in each outer labyrinth areprovided for occasional renewal ofgrease seal which forces out dirt and oldgrease through relief fittings. A periodiccheck of oil level and purity can readilybe made through oil level indicator whilein operation or at rest. If inspectionreveals impurities in the oil, draining,flushing and refilling can be easilyaccomplished through the piping, tees,and drain plugs furnished.

Special RequirementsIn over 70 years as the recognizedleader in the design and manufacture of freewheeling clutches, the Marlandengineering staff has been given manyunusual and difficult requirements forclutches and backstops. This hasresulted in special designs to meet thoseexacting requirements. If your needscannot be filled by a standard item, give us the engineering details. It may be that we already have a solution toyour problem, and if not, we’ll go towork and find one.

Oil Breather

Oil Chamber

Grease pressure fittings

Grease packed all-metal labyrinth

Double-lip oil seal

Grease relief fittings

Grease Oil

Graphited grease seal

Oil level indicator filler- drain connection may be located on most convenient side of backstop.

Illustration 3

Shows the sealed oil chamber forcontinuous lubrication of clutchoperating parts and ball bearings.

Illustration 4

Positive triple sealing of the oilchamber by grease-packed all-metallabyrinth, graphited grease seal anddouble-lip oil seal. Illustration 3 Illustration 4

Design Features

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Advantages of Marland Cylindrical Rollers onFlat Inclined Cam Surfaces

Free RotationThe cylindrical rollers used in all Marlandclutch products are free to rotate in theirindividual pockets during freewheelingpermitting the load to be engaged andre-engaged on any part of the rollercircumference and cylinder surface asindicated by the arrows in Illustration 5.

Longer Service LifeEngagement of the roller under loaddoes not always fall on the same line,zone, or spot to result in spalling orcratering, as may occur with non-cylindrical, irregularly shaped wedges or sprags which are not free to rotate.This results in longer service life for thecontacting surfaces.

Accurate DimensionsCylindrical rollers are easy to produceand reproduce to precision dimensionlimits which are readily checked withmicrometers, go-no-go gauges, or ifnecessary, with the extreme closenessof light band inspection.

Full ContactPrecision-ground, flat cam areas furnishideal contacting surfaces for thecylindrical rollers and assure full contactwith the entire cylinder length of eachroller.

Lower StressWhen roller and cam are engaged undercompressive loading, (Illustration 5), theload is uniformly distributed over a largezone of contact with consequently lowerstresses to result in more durable,efficient operation.

The Limitation of Non-CylindricalClutch Wedges or SpragsNon-cylindrical, irregularly shapedwedges or sprags have been resorted to by some designers whose primaryaim was to lower clutch productioncosts. This design uses a cheapercylindrical inner race, in place of theprecision ground cam used in theMarland design.

Odd-shaped sprag elements withcompound curves are difficult toproduce, and reproduce, to the samehigh degree of accuracy consistentlymaintained in the production ofcylindrical rollers. Many non-cylindricalsprags, produced by cold die drawing,may be subject to dimensional variationswhich can occur between spragsproduced when the die is new and thosedrawn after the die becomes worn andenlarged with use.

When an assembly of such odd-shapedsprag elements is engaged incompressive loading between the innerand outer races, dimensional variationssuch as a slightly oversized curve radius,will subject such individual elements tohigher stresses and may cause failuredue to spalling or cratering of therelatively higher stressed surfaces.

Sprags with compound curves are notfree-to-rotate when confined within theannular space between cylindrical innerand outer races, but must be retained inposition to engage. This causes arubbing of the sprags on the racesduring freewheeling and consequentwear, since a backstop is in thefreewheeling condition most of itsoperating time. In addition, spragcontact surface for engaging is limited tothe small zone indicted by the arrows inIllustration 6. This reduced available zoneof contact can result in shorter life ofwedges or sprags.

Note in Illustrations 5 and 6, the availableload-bearing surface of a Marland rollerincludes the entire roller circumferenceand full cylinder length, compared to therelatively limited load-bearing zone of theretained sprag.

Illustration 5

Marland cylindrical rollers are free to rotateduring freewheeling and provide broadcontact over the entire length of the rollersunder compressive loading.

Illustration 6

Non-cylindrical clutch wedges are not free to rotate. Any dimensional variations areaccentuated by repeated contact in the samereduced areas during compressive loading.

Illustration 5

Illustration 6


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Locate Backstops Where ReverseTorque Loads Originate

Where Reverse Torque LoadsOriginateThe ideal time to prevent reversal of aloaded inclined conveyor or elevator is atthe very instant when forward rotation ofthe headshaft ceases. Even a small timelag before arresting the backward travelresults in a greater effort needed to bringthe inclined conveyor to rest and to holdthe load.

When high speed shaft backstops areused the amount of time and thedistance of reverse motion of theinclined conveyor or elevator before the backstop can become effective, is determined by the accumulatedbacklash of any gears, couplings, keys,chains, sprockets and shafts in the drivesystem.

It is obvious that a reversed torque load,further reinforced by any accumulatedbacklash in the drive system, couldresult in the failure of any one of theseconnecting drive components when thereverse torque load is permitted to travelbeyond the headshaft where itoriginated, to reach a backstop installedat some higher speed location in thedrive system.

Locating Backstops on Low-Speed Drive Pulley(s)Failure of any part of the drive betweenthe head (or drive pulley) shaft, and ahigh speed shaft backstop can cause areversed runaway condition. Maximumprotection against such reversedrunaways can be obtained only whenbackstops are installed on low speeddrive pulley shafts where the reversetorque originates and where suchbackstops can function instantly, beforebacklash and reverse motion can occur.

In some installations it may be physicallyimpossible to locate the backstop on the pulley shaft. In these cases, thealternate location could be on thedouble extended low speed reducershaft. (See Illustration 7)

Where the design and speed of theequipment will not permit the use of a low speed backstop, refer to Ceconbackstop units.

A Marland automatic backstop located at this end of the headshaft will provide a maximum of safety against reversal.

Conveyor Belt

Speed Reducer

Possible Alternate Backstop Location

Motor

Illustration 7

Failure may occur at any of these driving parts circled,their keys, the speed reducer, couplings, motor or ofelectric current, while the inclined conveyor or elevator isheavily loaded. Any motor brake or backstop, locatedbetween the motor and the heavily loaded headshaft wouldbe of no value in preventing a reversed runaway.

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Recommended Backstop Locationsfor Typical Conveyor Arrangements

Single Drive PulleyFor head pulley driven inclinedconveyors or elevators, the backstopshould be located on the head pulleydrive shaft. With the drive at one end ofthe head pulley shaft, the backstopshould be located at the opposite end,away from the speed reducer andcoupling. (See Illustration 8)

For a single drive pulley other than thehead pulley, the backstop should belocated on the drive pulley shaft, ratherthan on the head pulley shaft. The headpulley may not have sufficient belt wrapto keep the loaded belt from slippingbackward when the backstop preventsreversal of the pulley and its shaft. Withthe drive at one end of the drive pulleyshaft, the backstop should be located atthe opposite end, away from the speedreducer and coupling. See Illustration 9.

When dual drives to a single pulley shaftare used as in Illustration 10, thebackstops should be located on theshaft between the low speed couplingsand adjacent pulley shaft bearings.

Tandem Drive PulleysBackstops should be located on bothprimary and secondary drive pulleyshafts. Thus the secondary pulleybackstop(s) will insure tractive friction on both pulleys. (See Illustration 11)

Primary drive pulley shaft backstopsshould have capacity equal to the totalprimary and secondary motor (ormotors) normal rating. Secondary drivepulley shaft backstops should havecapacity equal to the secondary motors normal rating.

Illustration 8

Illustration 9

Illustration 10

Illustration 11


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Principles of Backstop SizeSelection for Low Speed Shafts

In the past, the usual basis fordetermining the size of a backstopincluded only consideration of calculatedlift and frictional loads. In some casesselection was made based onsubtraction of all of the frictional loadfrom the lift load to arrive at the netbackstop capacity required. Backstopsso selected could prove to be ofinadequate capacity and could result invery serious and costly damage. Moreconservative selection was based onsubtracting only one-half the frictionalload from the lift load. Lift loads werealso calculated at the maximum depth"spill load", rather than at normal orrecommended conveyor or elevatorvalues, in an attempt to guard againsteither an expected or intentionaloverloading of conveyors and theirrespective backstops. This methoddictated the use of larger backstopswhich reduced the danger fromoverloads and resulted in fewerrunaways. The more conservativeselection procedure could bedangerously misleading where a heavily overloaded or completely stalled motor could develop.

Improper Feed AdjustmentWhere a conveyor or elevator feed isimproperly adjusted during initialinstallation or later regular operation ofthe equipment, a stalled condition maydevelop resulting from flooding of thebelt or choking of the elevator. Duringsuch overloads, electric motors maydevelop 200 to 250 percent of normaltorque rating before they “cut out” byautomatic or manual control in order toprevent damage to the motor windings.Such high torque is transmitted from themotor to the drive pulley shaft where itinduces a high tension or “rubber bandstretch” in the belt. When the motor “cutout” occurs, the “stretched rubber band”effect of the overloaded or stalled beltreacts on the drive pulley to rotate it inreverse. This condition overloads thebackstop to the fully stalled motortorque rating, less only the frictional lossof the driving unit between the stalledmotor and the headshaft.

Momentary Starting Under LoadMomentary starting of the drive motor at a time when the stationary belt wasalready fully loaded to its normalcapacity, developed into an overloadedbackstop condition. We found that whenthe motor was so started, stretching thebelt so that conveyor motion was justbeginning, and at that instant the motorwas intentionally cut out, the storedenergy in the “rubber band stretch”reacted on the backstop with muchgreater force than occurs after a fullyloaded conveyor comes to a normal stop.

Where an electronic tramp iron detectorresulted in such momentary but veryfrequent stopping and starting condition,the backstop was severely overloadedfar beyond the normal motor rating.

Stalled ConveyorsEven though the conveyor equipmenthas been in satisfactory operation forsome time without overloading, the entryof oversize pieces, timbers or structuralscrap, jammed between the bin gateand the belt, could cause the conveyorto stall and overload the motor as notedunder improper feed adjustment. Underthese conditions the backstops could beoverloaded much beyond what wouldordinarily be the calculated lift or reversetorque loads.

Other Motor OverloadingStudies further showed that conveyorbelts also can be stalled due toimproper setting of skirt boards,misaligned pulley and idlers. To properlyhandle such conditions, selection of thebackstop should be based on themaximum possible motor overloadrather than on the normal belt loadingtheoretical calculations.

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How to Select a Marland Backstop

GeneralBackstop selection is based on stalledtorque rating of the driving motor toprovide for the conditions whenoverloaded motor “cut out” may occurand the “stretched rubber band” effectof the stalled belt would react on thepulley to rotate it in reverse against thenon-reversing backstop.

The preferred mounting of backstops is directly onto the drive pulley shaftwhether headshaft or intermediate shaft.For some typical arrangements andrecommended backstop locations, see Page 7.

Backstop Size Selection Basedon Breakdown or Stalled TorqueRating of Driving Motor

Step 1 — Calculate torque

Multiply the nameplate motorhorsepower(kw) rating by 5250 (9550metric), then divide the result by theRPM of the low speed drive pulley shafton which the backstop should bemounted. This determines the pound-feet (N-m) torque which is the basis ofbackstop ratings.

Step 2 — Service factor to be used

Multiply the value obtained in Step 1 bythe proper factor for the driving motorshown in Table B (factors are based onthe maximum stalled torque percent ofthe normal motor rating). The result willbe the minimum required torquecapacity which is to be used whenreferring to the rating table.

Step 3 — Select the MarlandBackstop

Refer to Page 11 and select the size of Backstop with a rated torque equal to or greater than the calculated torque.

Check backstop RPM to see whether it is within the listed catalog maximumRPM. If greater, consult Home Office.

Check shaft diameter to see whether it is within the backstop bore limits. If the shafts are too large, a larger sizebackstop may be selected, or ifpreferred, shafts may be turned down to accommodate maximum bore forselected backstop.

In all cases, calculate the resulting stressand check conformance of shafting withthe applicable design codes.

Ordering InformationWhen ordering or requesting sizeselection from Home Office, the followinginformation should be included:

1. Horsepower (kw) of drivingmotor(s) and maximum stalledtorque percent of normal motorrating.

2. RPM of shaft on which backstop is to be mounted.

3. Shaft diameter and keyway sizeat backstop location.

4. Profile drawing of system and/orgeneral arrangement drawing (ifavailable).

Table "B"Maximum Breakdown or

Stalled Torque

% ofNormal Motor Service

Rating Factor

175% 1.00

200% 1.15

225% 1.30

250% 1.50

Note: Consult factory for Size Selection for Dual Drive or Tandem Pulley Drives.

English

Example of Selection ProcedureRequired backstop for mounting ondrive pulley shaft rotating at 55 RPM,driven by a 150 HP motor having amaximum stalled torque rating at 200%of normal:

Step 1

150 x 5,250 = 14,318 lb.ft.55

Step 2

14,318 x 1.15 (service factor)equals 16,466 lb.ft.

Step 3

From tabulated rating on Page 11,proper backstop selection is the BC-18MA, rated 18,000 lb.ft., withmaximum bore 5-7/16". If drive pulleyshaft exceeds this maximum, it will benecessary that shaft be turned to suit, orthat the next larger backstop be used.

Metric

Example of Selection ProcedureRequired backstop for mounting ondrive pulley shaft rotating at 55 RPM,driven by a 150 KW motor having amaximum stalled torque rating at 200%of normal:

Step 1

150 x 9,550 = 26,045 N-m55

Step 2

26,045 x 1.15 (service factor)equals 29,952 N-m

Step 3

From tabulated rating on Page 11,proper backstop selection is the BC-27MA, rated 36,607 N-m, withmaximum bore 165 mm. If drive pulleyshaft exceeds this maximum, it will benecessary that shaft be turned to suit, orthat the next larger backstop be used.


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Marland Backstops Type BC Series MA

Breather Filter

Oil Fill Fitting

Grease Relief Fittings J B

See note M page 11

See note P page 11

G

Oil Level Indicator

A

E

1/4" (6.35 mm)

Min. clearance to permit backstop To center itself when freewheeling

Stirrup for end of torque arm by customer. Make brackets above and below torque arm sufficient for "L" loads.

8

11

4

3

7

910

6

5

2

1

12

13

14K

H C D

Clearance Dia.

Bore

Pull-Off Holes

Grease pressure fittings See note N page 11

1" (25.4 mm) Clearance on all units

1-1/2" to 2-1/2" (38.1 mm-63.5 mm) clearance on all units

1-1/2" (38.1 mm)

1-1/2" (38.1 mm)

Clearance for axial positioning

F

1 Coverplate

2 Gasket

3 Ball Bearing

4 Oil Seal

5 Outer Race

6 Roller Assembly

7 Cam

8 Spring

9 Pin and Cotter Keys

10 Torque Arm

11 Stop Lug

12 Inner Labyrinth

13 Outer Labyrinth

14 Grease Seal

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Dimensions and Data

The torque arm end must not be rigidlyattached to steel framework. Thebracket or stirrup for the end of thetorque arm must provide clearance topermit the backstop to center itself inaxial and angular positions to preventpinching of bearings and damage orfailure of unit, and must be sufficient for"L" loads above and below torque armfor backstop size selected. The preferredposition is horizontal to reduce bearingloading for longer bearing life. Refer tocertified drawings and instructionbulletins furnished with each order.

Note: M - Backstop is symmetrical andcan be mounted for desired rotation.Arrow on cam face or inner labyrinthindicates direction of free shaft rotation.Before mounting on shaft, be sure tocheck direction of free rotation.

Note: N - Labyrinth seals only arefactory packed with grease. Beforeplacing in operation, backstop must befilled internally with recommended oil.

Note: P - When installed, backstopmust be restrained from the possibility of axial movement on the shaft by one of the following:

1. Retention collar2. Retention key3. Keeper plate4. Drive tight cam key

*Keys are furnished for all units suppliedwith maximum bores. Other bore andkey sizes are available meeting metric,AGMA and USA standards as well ascustom design requirements. Marlandhas, on the shelf, many of the popularUSA standard sizes for customerconvenience.

Engineering DataRated Load Load Max.* Max.* Max.* Bore Max.* Bore Ship Ship

Backstop Torque Torque Max "L" "L" Bore Bore Keyway Keyway Weight WeightSize N-m lb. ft. RPM Kgs lbs. mm in. mm in. Kgs. lbs.

3MA 4067 3,000 300 510 1,120 75 2-15/16 20 x 4.9 3/4 x 1/4 46 100

6MA 8135 6,000 250 920 2,000 95 3-11/16 25 x 5.4 7/8 x 5/16 69 150

12MA 16270 12,000 210 1325 2,880 115 4-1/2 32 x 7.4 1 x 3/8 100 220

18MA 24405 18,000 180 1776 3,860 140 5-7/16 36 x 8.4 1-1/4 x 7/16 152 330

27MA 36607 27,000 150 2259 4,910 165 6-1/2 40 x 9.4 1-1/2 x 1/2 207 450

45MA 61012 45,000 135 3450 7,500 180 7 45 x 10.4 1-3/4 x 9/16 276 600

63MA 85417 63,000 120 4462 9,700 205 8 50 x 11.4 2 x 11/16 381 830

90MA 122024 90,000 105 6072 13,200 235 9 56 x 12.4 2-1/2 x 3/4 520 1,130

135MA 183035 135,000 90 8464 18,400 265 10 63 x 12.4 2-1/2 x 7/8 690 1,500

180MA 244047 180,000 80 10580 23,000 300 11-3/4 70 x 14.4 3 x 1 966 2,100

240MA 325396 240,000 70 13248 28,800 360 14 80 x 15.4 3-1/2 x 1 1242 2,700

300MA 406745 300,000 70 15180 33,400 360 14 80 x 15.4 3-1/2 x 1 1720 3800

375MA 508432 375,000 60 17250 37,500 460 18 100 x 19.4 4 x 1-1/2 2760 6,000

540MA 732142 540,000 60 20460 45,000 540 21 100 x 21.4 5 x 1-3/4 4140 9,000

720MA 976271 720,000 60 27280 60,000 540 21 100 x 21.4 5 x 1-3/4 4545 10,000

Dimensions

BackstopSize mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in.

3MA 210 8-1/4 143 5-5/8 105 4-1/8 64 2-1/2 76 3 133 5-1/4 813 32 119 4-11/16 105 4-1/8 86 3-3/8

6MA 248 9-3/4 165 6-1/2 127 5 70 2-3/4 102 4 159 6-1/4 914 36 143 5-5/8 124 4-7/8 108 4-1/412MA 292 11-1/2 203 8 133 5-1/4 83 3-1/4 127 6 165 6-1/2 1270 50 149 5-7/8 146 5-3/4 133 5-1/4

18MA 343 13-1/2 235 9-1/4 148 5-13/16 92 3-5/8 152 6 179 7-1/16 1422 56 164 6-7/16 168 6-5/8 162 6-3/8

27MA 384 15-1/8 254 10 178 7 98 3-7/8 178 7 213 8-3/8 1676 66 195 7-11/16 191 7-1/2 181 7-1/8

45MA 445 17-1/2 289 11-3/8 191 7-1/2 105 4-1/8 203 8 225 8-7/8 1829 72 208 8-3/16 216 8-1/2 206 8-1/8

63MA 498 19-5/8 311 12-1/4 203 8 127 5 254 10 238 9-3/8 1981 78 221 8-11/16 244 9-5/8 241 9-1/290MA 584 23 362 14-1/4 229 9 140 5-1/2 305 12 267 10-1/2 2083 82 248 9-3/4 270 10-5/8 270 10-5/8

135MA 654 25-3/4 406 16 254 10 143 5-5/8 381 15 298 11-3/4 2235 88 276 10-7/8 308 12-1/8 324 12-3/4

180MA 772 30-3/8 419 16-1/2 273 10-3/4 159 6-1/4 457 18 321 12-5/8 2388 94 297 11-11/16 349 13-3/4 362 14-1/4

240MA 876 34-1/2 457 18 387 15-1/4 162 6-3/8 508 20 406 16 2540 100 – – 413 16-1/4 – –

300MA 876 34-1/2 457 18 413 16-1/4 162 6-3/8 508 20 432 17 2745 108 – – 413 16-1/4 – –

375MA 1041 41 584 23 445 17-1/2 203 8 622 24-1/4 476 18-3/4 3048 120 – – 495 19-1/2 – –

540MA 1194 47 673 26-1/2 527 20-3/4 257 10-1/8 692 27-1/4 572 22-1/2 3658 144 – – 578 22-3/4 – –

720MA 1194 47 673 26-1/2 552 21-3/4 257 10-1/8 692 27-1/4 597 23-1/2 3658 144 – – 578 22-3/4 – –

A B C D E F G H J K


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Marland Clutch Backstops - Industrial and Bearing … Design Features Marland backstops are completely mechanical, automatic operating units, incorporating a time proven basic operating