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Devineni Venkata Ramana & Dr. Hima Sekhar
MIC College of Technology KANCHIKACHERLA
MINI PROJECT ON
SLACK ADJUSTER BARREL BA RREL [SAB]
BHARAT MANDAVA www.micame.in
When brake is applied or released the clearance between brake shoe and wheel thread may increases or decreases. To avoid this slack adjuster barrel is used. Shortly SAB. Our project is about SLACK ADJUSTER BARREL (SAB). It is a device for automatic adjustment of clearance of 5mm between brake blocks and wheel thread. It is a double acting, clearance sensing, axial type and it comprising a barrel which rotate in either direction and Non rotatable Adjuster spindle comprising of pull rod and threaded spindle extending out of the barrel from one of it ends .
Basically, a SAB is divided into 4 sections known as µunits¶. They are Barrel Unit, Traction Unit, Leader Nut Unit and Adjustable Spindle Unit. Here we discuss about the dismantling and reassembly of each unit briefly. Several tests and inspections are followed to ensure the quality of the product. Testing is done to check the proper working of a SAB. The µA¶ dimension and µE¶ dimension plays an important role in checking the working of a SAB, hence the procedure for checking is discussed. Other external components like µEmpty/Load Device¶ is also attached to a SAB. Finally safety precautions, working of SAB and trouble-shooting t rouble-shooting are also included.
Introduction Functions Of SAB Principle Of Operation Components Of SAB Maintenance
Dismantling Cleaning And Inspection Wear Limits Procedure For Testing Springs Lubrication Reassembling Testing On Rack Testing In Brake Rigging Assembling Of Adjuster Spindle Assembling Of Control Rod Painting
µA¶ Dimension µE¶ Dimension Empty/Load Device Adjustment Of Empty Tie Rod Safety Precautions Safety P Working Of SAB Trouble Shooting Conclusion References
SLACK ADJUSTER Slack adjuster (also known as brake regulator DRV-2) is a device provided in the brake rigging for automatic adjustment of clearance/slack between brake blocks and wheel. It is fitted into the brake rigging as a part of mechanical pull rod. The slack adjuster is double acting and rapid working i.e. it quickly adjusts too large or too small clearance to a predetermined value known as µA¶ dimension. The slack adjuster maintains this `A¶ dimension throughout its operation. The slack adjuster, type IRSA-450 is used in passenger coaches, it is composed of the following parts :
Barrel Unit Traction Unit Leader Nut Unit Adjuster Spindle Unit
BENEFITS OF SLACK ADJUSTER Fully Automatic : Once initially set, no manual adjustment is further necessary at any time during its operation. Double-Acting : The brake shoe clearance is adjusted to its correct value both ways, either when it has become too large (owing to wear of the brake shoes and wheels) or when it has become too small (e.g. owing to renewal of µ worn out brake blocks¶). Rapid working : Correct brake shoe clearance is automatically restored after one or two applications of the brake. Verification : If resistance occurs early in the brake application, caused by heavy brake rigging, e.g. an ice coating on the brake shoes, etc., in such cases the slack adjuster does not pay out slack immediately, but indexes the amount of slack to be paid out. If the slack really is too small, the slack adjuster will pay out this indexed slack at the next brake application. Thus false payout will not occur. True Slack Adjuster : The slack adjuster adjusts incorrect slack only, thus giving the brake its best possible pre-adjusted limit of piston strokes, ensuring a smooth and efficient braking force at all times. Shock Resistant : Train shocks will not cause false take-up or payout of slack. When brakes are released, the moving parts of the slack adjuster are sec urely locked.
I PLE PL E O
he iti n dju te nut n dju te indl indlee dete dete mine the the len len th the l c dju te . he le de nut ll the m ement the b el nd it u e i t le d the dju te nut t it c ect iti n n the indle. nt l d i i ed t the the b e i in the the unde unde me th t hen hen the b ei lied, ied, b el m e t d the c nt l d he d ti n tel tely t the i t n t e. he di t nce nce bet bet een een the he d nd the the b el, hen hen the b e i ully ele ed i c lled led the the c nt l dimen dimen i n ' '. hi c e nd t the c ect l c . I the l c i c ect, ect, the c nt l d he d t uche the the end end the b el t the m ment hen the b e bl c t tt ly in t the heel nd n dju tment ill the then t e l ce. I the l c i t l e, the c nt l nut he d u he n t the b el inc e in the di t nce bet bet een een it nd the the u en i n e by n m unt c e ndin t the e ce l c be e the b e bl c ly. he le de nut ll t tin n dju te indle. hen hen the b e i ele ed, the le de nut i , h e e , l c ed in t the e t le de nut c in nd the b el in c u e dju te nut t t te n the indle t d the le de nut. hi d nce dju te nut n the indle h ten the l c dju te nd dju t the l c t the c ect lue. I the l c i t m ll the the i t b e lic ti n c u e the b el t c e t d the c nt l d he d unti untill t ed by it. he di t nce bet bet een the t nut i.e. le de nd dju te h been h tene tened d by n m unt c e ndin t the the de iciency l c . t the t t the ne t b e lic ti n le de nut i l c ed in it ne iti n n it dju te indle nd y ut in u he dju te nut t tin n the indl indlee unti untill the the n m l di t nce nce bet bet een een the the dju te nd le de nut h been e t ed. he l c dju te i in the the y len len thened thened by e m unt nd the the l c dju ted ted t n m l.
t bu hin Se l rin Circli 9.45 x1. x1.75 R ubber ubber gask et et Spindle Spindle slee e/Pro e/Protecti tectio on Tube pin Dog pin Bearin aring g 45 45 TA 11 ( Com Complete) Leade ader nut casin asing g Circlip-9 clip-9..45 x 3 Sprin Spring g slee slee e/Spr e/Sprin ing g Cap Pa y -out -out sprin spring g Tracti Tractio on slee e Guid uide bus bushing hing Guid uide pin W ire ring ing Frictio iction washe washerr Ad jus juster te r tube soc sock et et Sprin Spring g dow el el slee e lig li ght ± 6 x 10 10 Clutch slee e Clutch ring in g Sprin Spring g Barrel Barrel Barrel Barr el Ad jus juster te r spin spind dle Saf ety c ety collar llar
Sprin Spring g dow el el slee e/Ro e/Roll ll Pin Cont Contro roll rod head he ad Loc Lock washe washerr Ad jus juster te r ear Ear bu Ear busshing hing Circlip clip - A 40 X 1. 1 . 75 Leade ader nut f lange Bearin aring g 45 45 TA 11 Loc Lock sc s cre w Ta b washe washerr Leade ader nut Ad jus juster te r nut Tak e ±up sprin spring g A ctua ctuating ting slee slee e Clutch sprin spring g Circlip clip - A 45 X 1. 1 . 75 Ad jus juster te r tube Barrel Barr el head he ad Seal ring ing Cont Contro roll rod Multi tooth oo th lock washe washerr B 28 Loc Lock nut k nut Name plate R i ets ets
DISMANTLING The process of disassembling every section from the SAB is known as µDismantling¶. It is done in a step-by-step manner. The order followed is :
Dismantling Of Control Rod.
Dismantling Of Adjuster Spindle.
Dismantling Of Traction Unit and Leader Nut Unit From Ba rrel.
Dismantling Of Traction Unit Assembly.
Dismantling Of Leader Nut Unit Assembly.
Dismantling Of Control Rod 1) Clamp Slack Adjuster barrel lightly, preferably in a pipe vic e, close to the barrel h head, ead, so as to avoid damage damage to the th e barrel. 2) Flatten lock washer. Hold adjuster tube firmly with a pipe wrench and unscrew
adjuster ear by rotating anti-clock wise. Remove R emove Control rod together with control rod head.
Dismantling Of Adjuster Spindle 1) Screw adjuster spindle into the slack adjuster until the end with the safety collar protrudes from the adjuster tube. 2) Remove spring dowel sleeve and unscrew unscre w safety collar. 3) Then screw adjuster spindle right back out of the slack adjuster. Note : It is possible that one, two or even three distinct clicks will be heard when the thread of the adjuster spindle leaves the adjuster nut. This is quite in order. Be careful in handling the adjuster, spindle after removal, to avoid damage to the threads. It is advisable to slip a piece of protective cardboard tubing over the threads t hreads or to wrap them in thick th ick paper.
T i Uni Uni and L ader Nut Uni Unit Di Di Mechani Mechanical cal Devi Device)
antli antling ng From Barrel Barrel Uni Unit (On
1) Pla Place the slack ad ju ad jusster te r on on mecha mech anica nic al de ice and cla clamp it tig tightly. 2) Tighten the coupler le r nut into into the ad jus juster te r tube. 3) Operate ra te the de ice w heel heel so tha th at the de ice le er is connected nnected to the coupler le r nut by nut by a a pin. 4) Now , ope operate rate the de ice w heel heel clo clock-w ise so tha that the ad jus juster ter tube is pulle pulled d out. out. 5) Now , open open the b the bo oth ends ends of the of the ta b washe washerr of the of the lock sc scre w an and un-s un-sccre w the w the lock scre w an and rem remov ov e it. 6)
nscre w the w the lead le adeer nut unit.
7) Send end the lead leadeer nut unit to the lead leadeer nut unit dismantling ntling ta ble. 8) Operate ra te the de v ice ice w heel heel antinti-clo clockw ise and rem remov ov e the coupler ler nut pin and rele releas asee le v er to norm ormal positi positio on by ro by rottating ting the w heel heel clo clockw ise. 9) Ext Extract ra ct out tracti ra ctio on unit and rem remov ov e the coupler ler nut f itted itted. Send en d the tracti ra ctio on unit to dism antling ntling ta ble.
Tracti raction Uni Unit and Leader Nut Uni Unit Di Di mantli mantling ng From Barrel Barrel Uni Unit (On Pneumati Pneumatic Devi Device)
1) Cou Couple the coupler ler nut to the ad jus juster te r tube of the of the slack ad ju ad jusster te r. 2) Pla Place the slack ad ju ad jusster te r on on the b the bo otto ttom half porti portio on of the of the cla clamp s y stem and clos closee the top porti portio on cla clamp. 3) Operate ra te pneuma neumatic air cock n k no.1 so tha that the piston no.1 w ill ill hold the slack ad jus juster ter in the cla cl amp s y stem f ully ti ully tig ght. 4) ns ert the pin connecting nnecting the coupler ler nut and pneum pneuma atic de v ice ice le v ers. rs. 5) Operate ra te air cock n k no.2 so tha th at the le v er w ill ill pull out the tracti ra ctio on unit from from the b the barr arrel. el. 6) Now , open open the b the bo oth ends ends of the of the washe washers rs of the of the lock sc s cre w an and un-s un-sccre w the w the lock scre w an and rem remov ov e it. 7) Now , uns unscre w the w the lead leadeer nut unit from from the b the barr arrel el and sen send d it to lead leadeer nut unit dism antling ntling ta ble. 8) R eleas ele asee air cock n k no.2 so tha that the tracti ra ctio on unit w ill be ill be pushed he d into into the b the barr arrel el by by le le v ers. rs. 9) R emov rs. emov e the pin connecting nnecting the coupler le r nut a nd le v ers. 10)N 0) Now , extract ra ct tracti ractio on unit and sen send d it to di d ism antling ntling unit. 11) 11 ) Now , releas ele asee air cock n k no.1 so tha that the b the barr arrel el is rele r eleas aseed in the cla cl amp s y stem. Send en d the barr barrel el and barr barrel el sprin spr ing g to the clea cleaning ning an and insp inspecti ectio on ta ble.
Tracti raction Uni Unit Di Di mantli mantling ng
1) Clamp tracti ractio on unit lig lightly in htly in a v ice ice (ad jus juster te r tube pointin pointing g upwards). pwards). 2) R eemov mov e cir circlip clip w ith ith pliers liers.. 3) R emov emov e Bering ing dow el el slee v e by dr by drii v v ing ing it in wards thro throu ugh tracti ractio on slee v e and clutch slee v e. e. 4) nscre w clutch w clutch slee v e w ith ith spanne spannerr B. B. 5) Separate parate the tracti ra ctio on unit part parts from fro m each other ther. No
It is not necessar necessar y t y to se separate parate ad jus juster ter tube soc sock et et from from ad jus juster ter tube 41 for clea cleaning ning purpose. rpose.
Leader Nut Uni Unit Di Di mantli mantling ng
1) 2) 3) 4)
Clamp lead le adeer nut unit lig lightly in htly in a v ice. ice. R emov emov e cir circlip clip w ith ith pliers liers.. R emov emov e sprin spring g cap an and tak e out the sprin spr ing g, ba ball race ra ce , ba ball cage age and lead le adeer nut. Separate parate the lead le adeer nut unit part parts from from each other ther.
fter dismantling every unit separately the th e next steps to be followed are : A fter
Cleaning of Parts W ash ash all parts thoroughly in suitable cleaning fluid, preferably by dipping, and with the aid of brush. Remove all visible foreign particles such as dirt and grit and check worn parts according to the wear Units specified. The threads of adjuster nut, leader nut and adjuster spindle should be given special attention. Test the thread of the adjuster spindle with one of the nuts, the nut lust run freely over the entire length of the thread. Should any damage have occurred, such as for insta nce a burr or nick, smooth the area with a fine file and wash clean, making sure that all filings are removed.
Inspection Inspection of Parts Give all other parts a thorough visual inspection to detect apparent defects.
1) Ball Bearing
a) Mold the upper and lower races with the ball cage between them and with normal hand pressure the ball cage should not rub against either ball race at any peripheral point. b) Ensure that the balls are securely se curely housed in the cage and would not fall out. 2) Adjuster Tube Socket
a) Ensure the radius is free of any burrs. Burrs, if any, must be carefully removed by abrasive paste or paper. b) Replace socket, if its radius edge has worn out flat.
3) Adjuster Tube Assembly
a) Ensure that guide bushing and socket are properly tight. b) In case of any movement of socket or guide bush, the assembly should be dismantled and reassembled. c) The guide bushing must be locked by the socket screwed on to the adjuster tube and
finally secured by spring dowel sleeve. The 6 mm dia. hole for spring dowel sleeve should be drilled on assembly through marked hole on socket. 4) Friction Washer
a) Ensure that the corners of ear of the friction washer are sharp, washer with worn out ears should be replaced. 5) Wire Ring Part
a) Ensure that the wire ring securing the friction washer is snap fitted properly into the recess provided for it.
6) Actuating Sleeve
a) Ensure the chamfer as shown in the fig is free from any burrs. Burrs if noted, must be dressed smooth with abrasive paste or paper. b) If the chamfer is badly b adly scored, the sleeve should be replaced.
Note : When : When the actuating sleeve is rejected the corresponding socket should also be replaced to ensure formation of correct matching of re-dressed lap of socket and chamfer on actuating sleeve in assembly which is essential essential for the function of Slack Adjuster. c) If the chamfer is slightly scored, the face may be ground and matched with the socket radius to ensure free movement between the two contact area, falling which the same are to be rejected. d) Insure that the taper face is free from any step formation or recess created by wear and tear. If any such thing is observed as shown in fig the actuating sleeve must be rejected. 7) Clutch Sleeve
a) After assembly of the traction unit, it is necessary to check that the short cone of clutch ring can contact clutch sleeve without being topped by the ball bearing. If the clutch ring abuts on the ball bearing before it can touch the clutch sleeve, the clutch ring must be replaced. 8) Barrel With Barrel Head
a) The assembly must be rejected reje cted when the barrel head he ad has worked loose. Tack welding is not recommended.
9) Leader Nut With Dog Pin
a) Ensure that the dog pin is press fit. If loose the pin should be replaced. A hole of size 5±0.1 5±0.1 mm should be drilled at a different location on the same periphery and a new standard dog pin should be pressed inside.
Leader Nut Flange
a) Ball cage with race under hand pressure should not contact any point of flange due to the groove developed on working. If so, the flange may be reversed and used in assembly. 11)
Spindle Sleeve With B ushing
a) Spindle sleeve assembly must be free to move on the adjuster spindle. If the free movement is restricted due to any external damage on the protection tube the same is to be replaced. 12) Adjuster Spindle Part
a) Spindle bend within the space should not be used and must be replaced . b) Hold the spindle upright with threaded portion above and just engage and leave a good adjuster nut on to it. If the adjuster spindle is good, the nut should move freely down to the bottom of the thread of spindle without any interference. If not, the spindle should be replaced. 13) Adjuster Ear With Adjuster Tube
a) The adjuster ear should be secured on to adjuster tube and locked by lock. b) In case of thread damage either in adjuster tube or on adjuster ear, the defective part should be replaced. 14)
a) When the height as shown in fig.27 is increased i ncreased to 67 mm. this should be replaced. b) Any external damage/crack damage/cr ack to this item should be replaced. 15)
Leader Nut Casing
a) Ensure the chamfer as shown in the fig.28 is free from any burrs. Burrs if noted, must be dressed smooth with abrasive paste or paper. b adly scored, the leader nut casing should be replaced. b) If the chamfer is badly
Wear Limits The item given below shall be condemned when it reaches the condemning limit indicated against each. Adjuster spindle a) Plank abrasion should not exceed 0.3 0. 3 mm to be checked with gauge. b) When replacing a spindle, the corresponding adjuster nut and leader nut also be replaced. Adjuster nut and leader nut a) Axial play of worn nuts and new spindle must not exceed 2 mm. Check the threads of the nuts with gauge.
Dimensions of Different Parts Leader Nut a) Inside diameter of non-threaded end maximum -- 30.50mm b) Outside diameter of non-threaded end minimum -- 3 .00 mm Adjuster Tube a) Outside diameter must not at any point be less than -- 43 4 3.50 mm Guide Bushing
a) Inside diameter maximum -- 29.50 mm. Barrel Head Part a) Hole diameter maximum -- 46.5mm Leader Nut Casing a) Diameter of guide guide recess maximum -- 40.50mm [Housing for non threaded portion portion of the leader nut] nut ] Guide Pin
a) Width of hexagonal guide pin maximum m aximum -- 8.50 mm Actuating Sleeve a) Width of slot for guide pin maximum -- 11.50 11.50 mm Spring Sleeve a) Thickness of the plate of the flange minimum -- 0.80mm b) Height as shown in figure, maximum -- 67 mm
re for for
estin est in
a) Firs Firstt w e hav e to check check free fr ee heig hei ght of the of the sprin springs gs if it f it is correct orr ect accord ccordin ing g a bov bov e ta ble then w e hav e to procee proceed d the nex next step te p. b)
ere all sprin spr ings gs are are tes tested ted on pneuma neumatic de v ices ices.
c) For any any spr sprin ing g w e hav e to pl place sprin spr ing g below below pi p iston and apply apply the the pre pressu ssure gi v v en en on the ta ble. d) Then w e hav e to see s ee tha that the compre presse ss ed heig hei ght should uld be compre presse ssed a bov bov e or below below the the red mark .
Springs with following characteristics charact eristics are suitable for satisfactory s atisfactory working of of the Slack Adjuster.
Compressed Correspond Height Minimum 475 143
Take up Spring 37
1) Any spring which does not not conform to the above characteristic should not be used. 2) In addition any spring badly rusted, or having compressed coil turns should not be used.
Replacement of B of Basic Items The following items shall be replaced irrespective of the condition at the time of P of POH of Slack Adjuster.
Spring Dowel Sleeve
Spring Dowel Sleeve
Seal Ring 1
Seal Ring 2
Lubrication A fter fter completing the cleaning and inspection of all parts and before reassembling the Slack adjuster, coat all parts liberally with Lithium base MP-2 MP -2 grease or equivalent. Approximate requirement of lubricant is 1.2 kg excess grease should not be used.
Reassembling E very unit is individually assembled and then joined together. Various parts are used in assembling of a SAB. Finally adjuster spindle and control rod are attached to the tested SAB.
nit ni t A ssembly ssembly
1) Apply Apply gr greease ase to the inter interior porti portio on of t of tracti ra ctio on slee v lee v e. e. 2) Apply Apply gre grease as e to ad jus juster te r nut, ba ball race, ra ce, baa baa cage age and baa baa race race no2 and place them ins inside the tracti ra ctio on slee v e . place tak e up sprin spr ing g an and ba ball race ra ce ins inside slee v e. e. 3) Insert ad jus juster te r tube into into the actua ctuating ting slee v e so tha that it s eats on the ad jus juster te r tube soc sock et. et. 4) Insert this this assembly assembly int into o tracti ra ctio on slee v e. e. 5) Apply Apply gr greease as e to clutch sprin spring g and clutch slee v lee v e and f it it them on to the tracti ractio on slee v lee v e to se s eat on the actua ctuating ting slee s lee v e. e. 6) Now cl ow cla amp the assemble assembled d tracti ra ctio on unit on the bench the bench v ice ice and tig tighten the v ice ice f ully. ully. 7) Tighten the clutch slee v e w ith ith speci specia al spanne spannerr till the holes les of tracti ra ctio on slee v e and clutch s lee v e coincid incides. 8) Ins ert sprin spring g dow el el slee v lee v e 6x10mm 6x1 0mm in to the coincid incided holes le s. 9) Ins ert cir circlip clip 45 45 x2.5mm x2.5mm si e into into the ad jus juster te r tube groov e. e. 10)N 0) Now f it it on ba ballra llrace, ce, b ba allcag llcagee and clutch ring ing on on clutch slee v e. e. 11) 11 ) Now t ow tracti ra ctio on unit assembly assembly iis re r ead y.
Leader Nu t
nit ni t A ssembly ssembly
1) Apply Apply gr greease ase to inter interior porti portio on of the of the lead leadeer nut casin as ing g. 2) Ins ert dog pin pin into into lead le adeer nut and place lead leadeer nut f lange on the bo botto ttom porti portio on of lead leadeer nut. 3) Fit lead le adeer nut cir circlip clip si si e 40*2 0*2.5mm into into lead leadeer nut groov e. e. 4) Apply Apply gre gr ease as e to the lead leadeer nut and lead leadeer nut f lange, b e, ba all cage age , ba ball race. ra ce. Pla Place ba ball cage. age. 5) and ba ball race ra ce on the lead le adeer nut f lange. Pla Place this this assembly assembly int into o lead le adeer nut casin asing g. 6) Apply Apply gre grease as e to pa y out sprin spring g and pl p lace it on the lead leadeer nut assembly. assembly. Apply Apply gre gr ease ase to the sprin spr ing g slee s lee v e inter inte rior porti portio on and pl place it on the pa y out sprin spr ing g. Pla Place cir circlip clip of si e 85*4 5* 4mm on sprin spr ing g slee slee v v e. e. 7) Now place the lead leadeer nut assembly assembly o on the machine be chine bed d so tha that the lead leadeer nut casin asing g is se s eated ted on on the machine be chine bed d bus bush. 8) Pla Place the 20mm ms pac pack ing ing piece piece prov ide on to the lead leadeer nut unit. 9) Open air cock no1 so tha that piston of de v ice ice trav el el dow n and pre press again againsst the 20mm pac pack ing ing piece, piece, ther there by the by the sprin spring g slee slee v e slid lides dow n. n. 10) Insert prope properly the of the lead asing g w ith plierr. ly the cir circlip clip into into the groov e of the leadeer nut casin ith help hel p of plie 11) 11 ) Now ope operate ra te air cock n k no2 so tha that the piston trav els els up f ully. ully. 12) 12) Now the ow the lead leadeer nut assembly assembly iis re read y.
A ssembled ssembled Leader Nu t
nit ni t
R eassemblin eassembl in of Traction raction nit ni t and Leader Nu t u nit nit nit nit on Pn eumat ma tic e vice vi ce
1) Pla Place the b the barr arrel el on the b the bo otto ttom half of cl of cla amp s y stem and clos closee the top porti portio on cla clamp. 2) Operate ra te air cock n k no1 so tha that the piston no1 w ill ill hold the b the barr arrel el in cla cl amp s y s y stem f ully ully tig tight. 3) Apply Apply gr greease ase on the b the barr arrel el sprin spr ing g an a nd ins insert barr barrel el sprin spr ing g into into barr barrel. el. 4) Scre w the w the coupler le r nut on to the tracti ractio on and ins insert the tracti ra ctio on unit into into barr barrel. el. 5) Connect Connect the coupler ler nut and pneum pneuma atic de v ice ice le v ers by rs by the the pin. 6) Operate ra te air cock n k no2 so tha that tracti ra ctio on unit w ill be ill be pulled ulle d out. out. 7) Scre w the w the lead leadeer nut unit to barr barrel el at other the r end end. 8) Pla Place the ta b washe washerr on on the b the barr arrel el hole and ins insert the lock sc s cre w an and tig tighten it. 9) Bend end the t wo ends ends of the of the ta b washe washerr on on the lock sc s cre w he w head ad.. 10)R 0) R eleas ele asee the air cock n k no2 so tha that the tracti ra ctio on unit w ill be ill be pushed he d ba back in k in to the b the barr arrel el and tracti ra ctio on slee v lee v e touches uches sprin spring g slee slee v e. e. 11) 11 ) R emov emov e the coupler le r nut pin and un-s un -sccre w the w the coupler ler nut from from tracti ra ctio on tube. 12) 12) Now rele r eleas asee the air cock n k no1 so tha that the b the barr arrel el is rele r eleas aseed freely freely in in the cla clamp s y stem. 13) 13) Lif t the cla clamp s y stem top porti portio on and send end the f ully ully assemble assembled d slack ad jus juster ter for f ina inal tes te st on rac ra ck .
Sa f ety ety Precau tions ion s The foll follow ow ing ing saf ety pr ety prec eca autio utions sh should uld be o bs bserv ed du during ing ov erhauling uling of sl slack ad ju ad jusster te r. 1) The place of ov erhauling uling mus must be clea clean and free free from from dust. 2) Ensure tha that no forei foreig gn particle particle rem ema ain ins inside the sub-ass ub-assemblie embliess du during ing re re-assembly. -assembly. 3) A ll ll rubber ubber gask et, et, s eal ring ing, washe washers rs mus must be replaced ced du during ing ov erhaul. 4) Speci Specif f ied ied tool oo ls an and f ixtur tures are ar e used for di disassembly sassembly a and assembly assembly op opeerati ra tio o ns.
Testin est in
of Slack A lack A d juster
Af ter te r ov erhauling uling, tes te sting ting of sl slack ad jus juster ter in carrie arried d out out in a tes te st rac rack for :
Pa y -in Test Pa y -out -out Test
a) A tta ttach the ad jus juster ter ear to the free fr ee end end of the of the cylind cylinder le v er of the of the tes test rac ra ck . b) Scre w the tes test rac ra ck spin sp ind dle into into the Slack Ad jus juster ter until the entir entire leng len gth of thr thread is cov ered by sp by spin ind dle slee v e and att atta ach the free free end end of the of the spin spind dle to the tes test rac rack .
Pay-in test 1) Let down the control rod, so that the fork of the rod clasps the adjuster tube of the Slack Adjuster. 2) Apply and release the brake a few times letting the slack Adjuster take up until the correct piston stroke is obtained (until the indicator is within + 5 mm tolerance field of the scale).
Pay-out test 1) Turn up control rod and make two brake applications letting the slack adjuster pay out. 2) Repeat the above pay in and pay-out tests a couple of times. 3) Satisfactorily, dismantle it and check that the parts are placed correctly. 4) The slack adjuster must then be tested once more in the test rack in accordance with the above instruction. 5) After the test is finish finished, ed, remove the spindle from the slack adjuster. 6) Remove the slack adjuster from the test rack and unscrew adjuster ear.
If test rack is not available Testing of slack adjuster in brake rigging with hand brake In case a test rack is not available in the work shop, a test of function of the slack adjuster ought to be carried out after the slack adjuster is installed in the brake rigging and the correct piston stroke is i s obtained as follows : 1) Place an iron object e.g. a hammer between the brake block and the wheel tread. Make two brake applications after the second application the correct piston stroke should be obtained. 2) Remove the iron object. Make two brake applications. After the first application the
piston stroke is too long, but after the second application the correct piston stroke is recorded by the slack adjuster.
of Pull-rod with Adjuster Spindle
1) Arrange for eye ended pull rod of correct length as par th e Installation drawing. 2) Join them preferably by electric flash butt welding. If this is not possible, prepare both the ends by tapering to an angle of 30 degree, 25mm.length of both rods and weld the prepared faces by electric arc welding. While welding the following precautions to be taken: a) Centre lines of both pull rods must lie on one common centre line . b) Provide protective cover over threaded portion of Adjuster spindle to prevent molten metal falling on threads. 3) Give adjuster spindle a final thorough inspection making sure that the threads are liberally greased.
Assembling of Adjuster Spindle to Barrel Unit 1) Unlock the washer and screw out the adjuster ear. e ar. 2) Taka Out the spring dowel sleeve and screw out safety collar. 3) Insert the Adjuster spindle through spindle sleeve, then rotate it clockwise until the spindle comes out through adjuster tube. 4) Assemble the safety collar and spring dowel sleeve. Rotate the spindle anticlockwise until the spindle has come out equal to dimension µE¶. 5) Slide control rod head with control rod assembly over the adjuster tube. 6) Screw in the adjuster ear with lock washer and tighten up. Lock the adjuster tube by lock washer.
Assembling Of Control Rod Slide control rod head with control rod on to adjuster tube. Place lock washer on threaded portion of adjuster ear and screw ear into threaded end of adjus ter tube.
Pai Painti nting Gi v v e the slack ad ju ad jusster ter a coat oat of antic anticorros orrosii v v e paint, paint, exclud cluding in g the ad jus juster te r tube ( v isible). Note : The The unthr unthreade aded porti portio on of the of the ad jus juster te r spin spind dle should uld not hav e a thick thick ccoatin oating g.
Fitment on wagon for check ing Genera enerall arran arrangement show ing ing the f itment itment of sl s lack Ad ju Ad jusster te r prov ided w ith ith vacuum va cuum
brak brak e and A ir brak brak e .For .For the prope proper work ing ing of sl slack ad jus juster ter. It Is essenti ss entia al to ens ensure tha that the brak brak e riggin gging g is work ing ing prope properly and µE¶ dimen dimenssions are ar e correct orr ect and also w e hav e to check check the the em emp pty l ty load de de v ice. ice.
µA¶ dimension is measured between barr el head and control rod head and it is 92mm for manual A Dimension. For
µA¶ dimension (16 +2/-0 mm for 13t bogie and 22 +2/-0 mm for 16.25t bogie)
a) Ensure the air brake is in fully released re leased condition and all the brake rigging gears are in proper condition. b) Apply brake three to four times to ease the rigging, by dropping and re -charging the air pressure in the brake pipe c) Ensure once again that brake rigging is in fully released condition.
If µA¶ dimension is not correct a) Remove pin securing the control rod in U bracket. b) Detach control rod and rotate it to adjust the gap between barrel end face f ace & control rod head as specified in note above. Secure the control rod in U bracket. c) Apply brakes two to three times. d) Check the µA¶ dimension using the gauge. e) Recheck dimension µA¶ with brakes fully released after every brake release. f) Lock the control rod head firmly with check che ck nut and tooth tooth lock washer. g) Secure pin with split pin. Check
µA¶ dimension. This should be as follows for different wagons.
1) 50 ± 2 mm for BOX,BCX,BCXC III, BTP BTPGL ,M ,MBTP BTPS type of wagon. 2) 70 ±.2 mm
for BOXN,BCN,BRN,BOY, BTP BTPN type Of wagons.
3) 60 ±.2 mm
for BFKI wagons.
4) 20 ±2 mm
for B0BRN wagons.
a) If slack is in excess beyond the capacity of slack adjuster (µE¶ dimension 375+25mm) mm) there won't be any slack take up provision in the slack adjuster and slack adjuster will only act as strut/pull rod. This is because of brake shoes and wheel wear reaching their condemning limit/near condemning limit. In such cases the `e' dimension can be restored re stored by adjusting link provided on the bogie frame h ead stock. b) Measure µe¶ dimension i.e. distance between betwe en protection tube end and mark on adjuster spindle using measuring stick after t wo or three brake application. It should be set to nearly to its maximum limit i.e. 575±25mm. mm.
Empty/Load Device : Traction between the wheels wh eels and the rail is directly proportional to the weight on the wheels. The amount of traction determines the amount of braking that can be applied without sliding the wheels. Sliding wheels develop flat spots within a few feet. Train cars have a large weight difference between betwe en the loaded condition and the empty condition, especially modern coal hoppers and grain cars. The maximum braking effort of a car must be designed so that when in emergency (when the highest brake br ake cylinder pressure is obtained) the EMP EMPTY TY car will not slide its wheels. Unfortunately this means a heavily loaded car c ar is under braked even in emergency. emergenc y. A way was needed to allow higher brake cylinder c ylinder pressures on loaded cars than on empty cars. The first step was to put larger reservoirs rese rvoirs on the cars c ars so that the traditional 2.5 to1 to1 ratio of reservoir volume to brake cylinder volume was greater. This will result in higher brake cylinder pressures for any given brake pipe reduction. r eduction. The problem is that higher pressure will slide the wheels whe els of an empty car. So a pressure pres sure limiting valve is attached to the brake cylinder which will vent any excessive exce ssive pressure to the atmosphere thus limiting braking effort. The exhaust of this limiting valve is op en to atmosphere on an empty car allowing it to vent excess pressure. pressur e. On a loaded car it is closed off so it cannot vent any pressure from the brake cylinder thus taking advantage of the higher pressure wh ich results in higher braking effort. The closing or opening of the limiting valve exhaust is controlled by a load/empty sensing arm. The pressure pressur e limiting exhaust close off valve is mounted on the car frame just above the truck frame. One end of an arm is attached to the close off valve an d the other end rests on the truck frame. If the car is EMP EMPTY TY the car body rides high on the springs and the arm moves the close off valve to the open position allowing the limiting valve to vent excess pressure. A LOADED car rides ri des low on the springs and the arm is i s pushed up, moving the close off valve to the closed position, thus preventing the limiting valve from venting the higher brake cylinder pressure.
Empty Load Devi Device and Empty Load Tie Tie Rods :
1) Put the le v er arm arm in em emp pty pos ty positi itio on as sh s how n in f ig. 4 an and hear he ar the clear cle ar click click soun so und d. 2) Apply Apply the the b brak rak e. e. If vacuum vacuum / air pre pressu ss ure is not avail ava ila a ble apply apply ba band brak brak e f ully. ully. 3) Tap em emp pty tie ty tie rod pin pinss. Thes hes e should uld be tig tight, if so the ad jus justment is correct. orr ect. 4) If l If load tie rod pin pinss are are foun found d tig ti ght the ad jus ju stment is wron wro ng as the slee v e nut has been as been
temp tempered w ith. ith.
Of E Of Empty Tie Tie Rod :
1) Ensure brake rigging is fully released (Hand (Hand brake also). also). 2) Insure horizontal levers can move freely. 3) Inspect tie rods and aleeve nut for Mechanical damage. 4) Put lever arm in loaded position. 5) Shift lock nuts and washer as far away fron aleeva nut as is is possible. 6) Rotate sleeve nut in direction. This will shorten empty tie rod fully. 7) Rotate sleeve nut in direction. This will lengthen the empty tie rod. 8) Stop rotating the sleeve nut when the end of the µLIVE LEVER¶starts LEVER¶starts moving. moving. 9) Then carry out out test as mentioned above. 10)Tighten 0) Tighten lock nuts with washers. This should be done with brake still on. 11) 11) Bend over lock nut washer ( Z shape). sh ape). Note : If test fails and load tie rod pins are still found tight, empty load davice operating pawl (catch) may be broken. Replace empty load device.
Safety Precautions 1) Always use wedge between wheel and rail before application and release rele ase operations for setting and measuring A and e dimension to prevent rolling of coach. 2) Ensure no part of the worker¶s body is in touch with moving brake rigging gears during application and releasing of brakes. 3) Do not touch or hold slack adjuster adjuster ba rrel while it is in motion. 4) Before setting any dimension ensure ensur e wear of brake shoe does not exceed to its minimum permissible worn limit (i.e. thickness of the shoe should not be less than 20 mm). 5) There won't be any slack take up provision in the slack a djuster and slack adjuster will only act as strut/pull rod. This is because of brake shoes and wheel wear reaching their condemning limit/near condemning limit. In s uch cases the `e' dimension can be restored by adjusting link provided on the bogie frame h ead stock.
The Sl Slack Adjuster Operates
dist ance µA¶ me meas asu ured bet w een een contro ntroll rod head head 26 an and barr barrel el 22 w hen hen the b the brak rak e is f ully r ully releas ele aseed corre orr espon sponds to the correct orr ect slack . If the If the slack i k is correct, orrect, as the brak brak e is applie applied d, head head 26 touches uches barr barrel el 22 at at the moment w hen hen the b the brak rak e shoes st start art to apply apply aga again insst the w heels heel s an and no ad ju ad jusstment w ill ill then tak e place.
If the f the slack beco become mess too large, arg e, as the b the brak rak e is applie applied d, head head 26 pu pushes he s the b the barr arrel el 22 an and at at the moment w hen hen the b the brak rak e shoes apply, apply, the distance bet nce bet w een b een barr arrel el 22 an and ad jus juster te r ear 28 is incr increase ased by a by an amount corre orr espon sponding in g to the excess ce ss of sl s lack . Clutch B is releas eleaseed an and lead le adeer nut 35 foll follows ows the positi positio on of barr barrel el 22 , rot rotating ting on on spin spind dle 23 to rem ema ain in co nta ntact w ith ith the lef lef t hand end end of the of the b barr arrel. el. W hen hen the b the brak rak e is rele r eleas aseed, nut 35 is lock ed again againsst the lef lef t-hand end end of barr barrel el 22 an a nd sprin spring g 21 causes ad jus juster te r nut 36 to rot ro tate on spin spind dle 23 towards nut 35. This his mov ement ement of nut of nut 36 on on spin spind dle 23 sh s horten ortenss the Slack Ad jus juster te r an and thus thus ad jus justs the slack t k to its its correct orr ect value. value.
If the f the s lack beco become mess too small, the f irst rs t subs ubsequent b equent brak rak e applic applica atio tion releas eleasees clutch C an a nd causes nut 35 and barr barrel el 22 to rot ro tate towards head he ad 26 until stoppe opp ed by it. by it. The distance bet nce bet w een een nuts nuts 36 an and 35 35 has been as been shortene ortened d by a by an amount corre orr espon sponding ing to the def iciency of iciency of sl s lack . A t the start art of ne of nex xt brak brak e applic applica atio tion, nut 35 is lock ed in its its ne w positi positio on on spin spind dle 23, 23 , and pa y -out -out sprin spring g 11 pu pushes he s nut 36, 36, rot rot ating ting on on the spin spind dle until norm ormal distance bet nce bet w een een the t wo nuts nuts hav e been restore or ed. The slack Ad ju Ad jusster te r is in this this wa y leng lengthened thened an and the slack ad ju ad jussted te d to its its correct orr ect value. va lue.
Conclusion Though the SAB section is small in wagon assembly sections but due its parts, its function and its working make this to compete with other sections (wheels, bogie). It is one of major function in brake application. The most interesting features in this SAB is it consists of 49 parts and the whole over- hauling process is done manually.