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Shavonne Francis
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48 DRUM BRAKE RIMS Periodic inspection of drum brake rims is necessary to determine indications of uneven or excessive wear. In general, brake rim failures other that regular wear are caused by brake linings being too soft or too hard. Soft woven linings usually cause deep circumferential growing. Very hard brake blocks cause the rims first to turn blue in spots and then crack. Frequent inspection of the brake rims and a complete change of lining might save a costly brake rim change. Two practiced methods for determining the amount of wear are: 1. The circumference of the worn rim may be measured with a steel tape. In using this method, care should be taken to wrap the tape around the rim at the point on maximum wear. 2. A gauge made of wood or metal may

49 BRAKE BANDS AND LINING Each lining block on the main drum is secured with six bolts. The lining bolts will loosen as the lining seats itself. They should be checked after putting new lining into service and retightened as required. Peening the end of the bolts will keep the nuts from coming off but it will not guarantee that the bolts will stay tight. They should be checked regularly. These bolts are made of brass and care should be taken not to break them by over torquing. The lining blocks are curved to the proper radius in manufacture, but in storage this radius may change slightly. Heat and pressure in service will eventually seat the lining against the band. Good practice prescribes a breaking in period before handling heavy loads at high speeds. Under load, the lining is kept in place on the band primarily by friction with the band. Therefore, the contact area between the lining and band should be free from oil, grease, mud, or soft paint so the block retainer bolts won t be sheared off as a result of reduced friction. The inside of the band should not have over one coat of protective paint. In fact, no paint at all is preferable. When replacing brake lining blocks the bands should be inspected for damage caused by corrosion, loose blocks, and rough handling. The band curvature should be a relatively true radius and free from kinks. New lining may never seat properly against a kinked band. The band should be checked for accuracy of curvature, and straightened if necessary and handled carefully. The clevis eyes should be kept tied together when the bands are not on the drawworks. The repetitive application of the main brake on a drawworks subjects the dead end (eye bolt end) of the band to a stress no stress condition. The magnitude of this stress range can lead to eventual metal fatigue. Therefore, whenever the bands are removed for relining, they should be magnafluxed to guard against fatigue cracks in the band and clevis on the dead end. The complete band should be replaced if there is any question at all about its quality.

50 PARTS FIT General Economic features enter into the normal overhaul job; no one wants to spend money needlessly; however, at the time the equipment is in the shop for repairs new parts may be installed at far less expense that when the equipment is in service. For example, it has become customary in our own shop, when making a major overhaul, to replace many roller bearings throughout the drawworks. Some of the bearings replaced may still have some life left in them, but should the repair shop fail to replace a bearing at the time of overhaul, and should this old bearing fail within the first few months of new service, the resultant costs from down time and emergency repairs will amount to many times the cost of replacement at regular overhaul time. When replacing parts on a shaft assembly, be sure that the new part fits within the tolerance shown. For assembly or removal of parts which fit from.000 to.004 tight, heat to approximately 400 F; for parts which fit from.005 to.010 tight, heat to approximately 650 F. Shafts Whenever possible, all shafting should be checked by magnaflux or other means to detect any cracks. Cracks are most likely to appear in the bottom of keyways. A cracked shaft should be discarded and replaced, as a crack is a danger signal for a bad failure. Shafts should also be checked for straightness. This is accomplished by supporting it by any anti friction means placed at the position of the main bearings and turning it. Straightness is then checked by means of a dial indicator placed at the extreme ends of the shaft. The total reading of the dial indicator should not exceed.010. If a shaft shows a greater run out than.010 a replacement should be considered. The lack of straightness in drawworks shafting caused vibration, whipping of chains and a generally poor running rig. To pull the bearing and/or the inner race, place a U puller behind bearing or inner race. Arrange balance of the pulling mechanism and tighten sufficiently to remove all slack. Apply heat evenly to the bearing or inner race, while at the same time increasing tension on the pulling mechanism. DO NOT OVERHEAT. Fits of the outer races to the bearing housings range from.002 to.004 loose. If the outer race is a tight fit it will be necessary to heat the housing in order to remove it. The bearing must be cool before it can be reassembled. When outer race is a tight fit, arrange the puller mechanism to apply pressure toward the open end of the housing. Apply heat to he housing and increase pressure on the puller mechanism at the same time. DO NOT OVERHEAT. Spacers Spacers used between bearings to maintain center lines of bearings, or between bearings and other parts, are usually.002 to.008 loose. Spacers which are used to hold a bearing in position which is not adjacent to another part securely fixed to the shaft are usually.001 to.003 tight. To remove a spacer which is shrunk on a shaft, proceed in accordance with instruction for removing a bearing. To replace, heat the spacer, make sure the shaft is cool, and proceed the same as for bearing replacement. Sprockets and Clutch Hubs The teeth of all but the largest sprockets are surface hardened. This hardening is effective to a depth of approximately 1/8. After several years usage the chain may wear into the sprocket teeth. When the sprocket teeth become worn to a depth near 1/8, the rate of wear will accelerate. The amount of wear may be ascertained by visual inspection. Bearings Roller bearings should always be discarded if they show pitting, rust or corrosion, chipping or spalling off of small particles, excessive internal looseness which indicates extreme wear, or cracks in rollers or races. In most cases it will be necessary to heat the bearing inner race, in order to remove it from the shaft. It will be necessary to heat the inner race and cool the shaft for reassembly. PAGE: 50

51 If inspection shows the amount of wear to be near 1/8, the sprocket should be replaced at the time of overhaul. Four methods are used for mounting clutch hubs, bearing inner races and sprockets on shaft assemblies. (1) Press fit without key. (2) Press fit with key. (3) Shrink fit without key. (4) Tapered shaft with key. When removing and replacing parts mounted according to arrangement (1) above, refer to instructions for removing bearings. When removing and replacing parts mounted according to arrangement (2) above, use the following method. Insert puller studs through openings between sprocket spokes 180 degrees apart. Place steel plates and nuts on stud ends extending through the openings. Arrange balance of pulling mechanism and tighten only enough to remove any slack. Apply heat evenly and as near to the hub as possible while increasing tension with the puller at the same time. DO NOT OVERHEAT. In some cases the hubs will have two tapped holes in the end so that puller studs may be screwed in. In other cases where neither spokes or tapped holes are available for utilization of puller studs it will be necessary to use a strongback or U plate behind the sprocket and secure the puller studs to it. Proceed to remove the sprocket as described in the foregoing paragraph. To replace the sprocket, first be sure that the shaft is cool. Heat the sprocket to approximately 400 F. Be sure that the keyways in the shaft and sprocket are aligned before the sprocket tightens on the shaft. Insert key after sprocket has been installed. sprocket to remove it. Let the shaft cool, heat the new sprocket to 650 F and assemble on the shaft. Important When a shaft assembly is disassembled for any reason, be sure that passages for admission of air or grease are thoroughly cleaned. Hub and Shaft Fits The temperature required to expand a hub enough to be assembled easily over an interference fit can be determined by the following equation: Required T = E + Tr x B Where T = Heated Temperature, F E = Expansion of bore Diameter B = Bore Diameter (inches) Tr = Room Temperature, F = Approximate Coefficient of Expansion of steel per degree Fahrenheit per inch of length (or diameter). For example, if we have a diameter bore hub which has an.008 interference fit with the shaft and we wish to have.010 clearance while assembling the hub over the shaft the total bore expansion needed will be.018, Caution Excess heat at the hub and attempting to pull the sprocket with a chain attached to the outer rim, powered by a jack on the end of the shaft will bend the sprocket. Sprockets with shrink fits are very difficult to remove. This should only be attempted on a shop where a hydraulic press is available. If the sprocket is being removed for salvaging and installing on a new shaft, cut the shaft near the sprocket and machine part of the metal from the shaft under the sprocket. Heat the sprocket and press out Dutchman. If purpose of removal is to replace the sprocket with a new one it is advisable to machine or torch cut the old PAGE: 51

52 Therefore, E =.018 B = Let Tr = 70 F Then T = = 420 F x Caution: Hardened parts such as bearing races should not be heated to over F, since their hardness might be affected. Heat should be applied carefully and evenly to prevent distortion. The general rule for the average interference used in cylindrical fits is as follows: Press fit:.0005 x Shaft Diameter Shrink fit:.001 x Shaft Diameter The actual fit will have a plus or minus tolerance depending on the shaft and bore tolerances used. Overhung sprockets, clutch hubs, etc., are often made with tapered shaft fits for convenience of assembly and disassembly. In some cases the hub must be shimmed against as adjacent bearing spacer. Care must be taken to be certain that the shims do not interfere with drawing the hub up tight on the taper. A recommended method of assembling hubs requiring shimming is to assemble the hub firmly on the shaft without shims and without heat. Measure the shim gap behind the hub. The thickness of the shim pack require will be this measurement minus the draw allowance to be provided for tightening the hub up on the shaft. For each.001 of diametral interference on a per ft. taper the hub will advance approximately.010. Therefore, for example, if a.003 interference is desired on the taper fit, the shim gap must allow for a.030 advance of the hub on the shaft. The hub may be lightly heated to facilitate the draw. PAGE: 52

53 ADJUSTMENTS MAIN DRUM BRAKES The K brake mechanisms on OIL WORKS drawworks requires little inspection; however, a common mistake is to adjust the brake bands so that the equalizer bar is down solid on one end. This prevents it from performing its function properly. Check the K brake equalizer mechanism during operation to be sure the equalizer bar is free to equalize. All of the link connections and shaft bearings are grease lubricated from two central lubrication terminals located inside the brake adjustment access door. Adjustment of the brakes can be accomplished quickly and easily. Brake adjusting wrenches for each band are held in place on the adjusting nuts by lugs on the equalizer beam for immediate use. The following illustration shows the brake adjusting eye bolt connection to the equalizer beam. The spherical shoulder on the adjusting nut is held against a spherical seat on the equalizer beam by a coil spring. The spherical seat connection allows the eye bolt to align with the brake band pull as the brake lining wears and as the equalizer beam actuates. This arrangement prevents application of bending stresses to the adjusting eye bolt. The spring keeps the spherical surfaces in contact to eliminate slack and prevent impact loads when the brake is applied. Correct brake adjusting procedure is as follows: 1. Loosen eye bolt lock nuts C and D with wrench E and adjust eye bolts to set the brake lever hand pad approximately 32 above the floor level. 2. Be sure eye bolt adjustments are made so that the equalizer beam remains level when brakes are applied. There should be equal clearance (approx. ¼ ) between the bottom of the adjusting nut and the spring retainer (welded to frame) A and B. 3. Be sure the eye bolts are not bent, and after adjustment, retighten the eye bolt lock nuts C and D. 4. Check the position of the support roller assembly at the rear of each brake band. The roller should be set ¼ maximum clearance with the band, with brakes on. This should prevent the brake lining from dragging on the rims at the top and front when brakes are released. Dragging can cause unnecessary heating, and possibly, brake lever kickback. 5. Check the bands for roundness and uneven lining clearance when brakes are released. If bands are bent to an unsymmetrical curvature or have flattened areas which cause dragging, they can be reshaped by a beating treatment with a heavy lead hammer. 6. Check nuts on brake lining bolts to be sure they are tight. 7. Lubricate brake mechanism at regular periods. Use oil for brake band rollers and eye bolt hinge pins. 8. Do not allow band wear to cause very low operating positions of the brake lever. Keep bands adjusted so the lever hand pad is approximately 32 above the floor. Very low lever position will give a spring like or spongy feel. Also, extreme low positions may allow the brake mechanism to come against its end stops. Further, with new brake lining, low lever positions may allow the heads of the eye bolts to drag on the brake rims.

Maintenance Instructions

Maintenance Instructions General Note These instructions contain information common to more than one model of Bevel Gear Drive. To simplify reading, similar models have been grouped as follows: GROUP 1 Models 11, 0, 1,, (illustrated),,