Sealing and safety elements must all be checked during all replacement or repair works. We recommend replacing them. Complete sets of sealing material are available as spare parts. Flexibility fluid seals that are removed from joining surfaces must be applied and replaced again during assembly.
See the topic, General Torque for Metric Fasteners when the torques are not given in the text.
Schematic Drawing, Final Drive with HMV
Valve-plate Support of Variable-Displacement Motor HMV
VARIABLE-DISPLACEMENT MOTOR HMV
VARIABLE-DISPLACEMENT MOTOR HMV WITH BRAKE VALVE
Removal and Assembly of the Pressure Relief Valve
Pressure relief valve assembly removed (see items 21-30, page 92). For reassembly, respect order of assembling individual parts. Tighten the plug screw (see item 30, page 92) with torque 120 + 30 N·m.
Removing the ring (item 23, page 92).
Checking the Pilot Valve
(See item 7-9, page 92.)
Lock reduction adapter (item 9, page 92) with Loctite and tighten to a torque of 80 N·m.
Checking the Changeover Control
(See also item 5, page 92.)
Lock plug screw (item 6, page 92) with Loctite and tighten to a torque of 80 N·m.
Valve-Plate Support Of Variable-Displacement Motor HMV
Changing the Rotary Shaft Seal on Drive Shaft of Hydraulic Motor.
1. Remove the snap ring.
2. Remove the washer.
3. Carefully pick out defective rotary shaft seal with a pointed tool and remove it.
4. Slide the plastic sleeve over drive shaft. Install a new rotary shaft seal, using the mounting sleeve provided for this purpose (fig. 8). Then install the washer and install the snap ring.
Checking the Valve Plate and the Cylinder-barrel Running Surface
Loosen and unscrew mounting screws of valve-plate support (fig. 9).
Remove the valve-plate support (fig. 10) and do the following:
- - Visual check.
- - Cylinder barrel running surface.
- - Adjusting piston with sealing elements.
- - Insertion fits.
- - Cylinder barrel running surface.
Valve plate placed on valve-plate support (fig. 11).
Visual check of valve-plate running surface.
Antirotation lock by dowel pin.
Traces of wear of some depth in the valve-plate running surface, caused by contaminated hydraulic oil, cannot be removed by grinding off, because of the very hard but relatively thin hardening depth. In this case, a new valve plate must be installed.
When installing new sealing elements on adjusting piston (fig. 12)...
and on insertion fits (fig. 13), the correct mounting order for the sealing ring and back-up ring must be noted.
For reassembly, place valve plate on cylinder-barrel running surface in the correct order of assembly.
Install valve-plate support. Using a flat tool, successively insert:
- - the two adjusting pistons
- - the two insertion fits
- - the antirotation dowel pin
- - the two insertion fits
Screw in the mounting screws and tighten to a torque of 69 N·m.
Changing the Cylinder Barrel, Cradle and Bearing
In case of wear on the cylinder barrel running surface by contaminated hydraulic oil, the cylinder barrel must be replaced. To allow removal of the cylinder barrel, the tapered roller bearing must first be removed. This is only possible by means of a tapered roller bearing puller.
Close bearing puller's gripping claws after catching below the tapered rollers. (Do not apply gripping claws to bearing cage or bearing will be destroyed.)
Remove the bearing.
Removing the Cylinder Barrel
NOTE: The three needles (item 15) located in the cylinder-barrel teeth must not be lost during disassembly.
To allow reinstallation of the cylinder barrel (or possibly of a new one), the following items must be removed as well:
- - the 9 pistons together with the retraction plate
- - the retraction sphere
- - the cradle
- - the retraction sphere
The above indicated parts can be withdrawn together by pulling the two retraction pistons.
NOTE: At this stage of assembly, the running surface of bearing shell (item 9) must be checked as well. Due to the accurate manufacturing process, mating is not required for bearing shell (item 9) and cradle (item 11). Both parts can also be replaced separately.
In units having a relative long service time, both parts should be replaced together in case of wear.
Prior to reassembly of the complete motor, the "lift off limitation S" (see illustration, WH 236) must be measured again, if only one of the following parts has been replaced:
- - Cylinder barrel (also in case of reworking the running surface)
- - Bearing shell
- - Drive shaft
- - Front tapered roller bearing
- - Bearing shell
- Remove compression spring (item 18) from cylinder barrel.
Using a small assembling press, compress the spring by means of washers (items 19, 21), and remove snap ring (item 20). Remove compression spring (item 18) and shim ring (item 21). Insert washer (item 19) and reinstall snap ring (item 21).
- Place cylinder barrel on the drive shaft until washer (item 19) sits close against the shaft collar.
Determine and note dimension (a) with a depth gauge.
Determine and note dimension (b) on valve-plate support with the valve plate installed.
Desired values: s = a - b = 0.2 - 0.4 mm
Any deviations are to be compensated by removing or adding shim rings (item 21, page 108). Then, reinstall all parts (items 17, 18 and 19, page 108) together with new determined shim rings (items 21, page 108) into the cylinder barrel and install snap ring (item 20, page 108) under the press.
Assemble Cylinder Barrel
If bearing shell (item 9) has been removed, place it back into the housing, together with two insertion fits (item 16). Check seal rings (items 14, 15) as before.
1. Place the three needles (item 15, WH 234, page 102) with some grease into the recesses of the cylinder-barrel teeth (fig. 19).
2. Assemble retraction plate with piston, retraction sphere (item 14, WH 234, page 102) and complete cylinder barrel assembly in the correct order.
Place this completely assembled subassembly on the cradle and install it as indicated in fig. 18. Make sure that the three needles (item 15, WH 234, page 102) remain within the grooves. For threading-in, slightly move the drive shaft if required (fig. 20).
Heat rear tapered roller bearing in hot oil to approximately 200°C and slide it completely against the shaft collar.
Assembly of valve plate and valve-plate support in accordance with fig. 9, topic, Checking the Valve Plate and Cylinder Barrel Running Surface.
Adjusting Minimum Intake Volume of Track Motor
Changing the minimum intake volume requires approval from Service Engineering.
If the known value of the minimum intake-volume setting of the track motor HMV is to be increased or reduced, the corresponding stop screw is to be turned in or out respectively. The position of the corresponding adjusting screw is indicated in fig. WH 241.
For adjusting, do the following:
1. Hold the adjusting screw with allen wrench (size 6 mm).
2. Loosen self-sealing lock nut (wrench size, 19 mm).
3. Turn adjusting screw by the calculated amount and hold it.
4. Tighten the lock nut.
Hydraulic Motor - HVM 55
According to thread pitch, 1 revolution corresponds to a travel s of:
One revolution (nv) of the adjustment screw corresponds to intake-volume difference of Delta v2
The angular scew displacement required for intake-volume change of 1 cm/rpm is:
NOTE: See the specifications for the Track motor. (1 gal. is equal to 3785 cm). The rpm for each machine is also shown.
To increase Vmin: screw to be turned in (CW rotation)
To decrease Vmin: Screw to be turned out (CCW rotation)
Example: HMV 55, set to Vmin = 26 cm3/rpm to be readjusted to Vmin = 29 cm3/rpm
Delta Dv = 29 - 26 = 3 cm3/rpm (Example: from 205 to 211)
Required number of revolutions nv:
adjusting screw to be screwed in.
NOTE: Fig. 21 shows the final drive and variable-displacement motor (track motor) in the normal mounting position within the excavator. The following pictures of individual repair operations have been taken in the workshop on the completely dismounted final drive.
Particularly in the case of checks, the following disassembly and assembly operations can be done on the final drive installed in the excavator.
Checking Transmission Stages I, II and III
Loosen allen-head screws (item 38, fig. WH 242) on gearbox cover and remove cover (item 37, fig. WH 242) with O-ring (item 36, fig. WH 242). Before doing so, drain off transmission oil through drain plug (item 39, fig. WH 242). If installed in the excavator, be sure the excavator is safely parked in such a way as to have the drain plug pointing downward.
Visual check of planetary-gear stage I.
NOTE: Check for damaged gears, snap rings, shafts, bearings, etc., on each of the three stages and the case.
For checking planetary-gear stage II, stage I must be removed. To do so, remove snap ring (item 35, fig. WH 242) from sun gear and remove sun gear I (item 34, fig. WH 242). Remove planetary gear stage I (with attached sun gear of stage II).
Visual check of planetary-gear stage II
For checking planetary gear stage III, stage II must be removed. Removal of stage II with attached sun gear of stage III (Fig. 26). Visual check of planetary gears of stage III and teeth of the ring gear (item 18 Fig. WH 242).
NOTE: Removal of the ring gear (item 18, fig. WH 242) and of the stationary planetary gears of stage III is possible only with the final drive having been removed from the excavator.
Do not install the old snap rings or O-rings. Replace with new ones. There is a possibility of damage or stress when the old snap rings or O-rings were removed. Machine damage can result with using one that has damage.
After visual check, assembly of individual stages in the reverse order; close cover (item 37, WH 242), after having checked O-ring (item 36, fig. WH 242). Tighten screws of cover (item 38, fig. WH 242) to a torque of 46 N·m. Fill in the prescribed quantity of transmission oil and check oil level on the sight gauge. See the Operation and Maintenance Guide.
Removing and Installing the Hydraulic Motor
(Possible with final drive on the excavator.)
Remove the allen-head screws (item 16 fig. WH 242).
Remove the motor (fig. 29). Prior to reinstallation or installation of a new motor, check and install O-ring (item 59, fig. WH 242). Install motor and tighten allen-head screws (item 60, fig. WH 242) to a torque of 80 N·m.
Checking or Replacing Brake Discs
Remove hydraulic motor in accordance with previous step. To have access to brake discs 44 and 45, the complete brake unit (46-45) must be dismounted.
Prior to removal of the brake unit:
- 1. A hydraulic hand pump (P/max = 40 bar, 4000 kPa) must be available. This is required for reinstallation (brake lifting).
- 2. Dimension "x" (with built-in final drive) or dimension "y" (with final drive removed) must be determined and noted down. The brake unit is held together with four allen-head screws (55) (see fig. WH 245).
These four screws must not be loosened.
Release the brake with the hydraulic hand pump. [Maintain minimum pressure of 22 bar (2200 kPa), maximum pressure of 40 bar (4000 kPa)]. Now, remove the remaining eight allen-head screws (item 57, fig. WH 242).
Remove the brake assembly. (If excessively tight, use mounting lever.) Withdraw and check brake discs (2 x outer disc, item 44, fig. WH 243 and 1 x inner disc, item 45.
For assembly, release the brake with hydraulic hand pump (as in fig. 30). Place discs on the brake unit in the correct order (see WH 243 items 44 and 45). Use grease to facilitate assembly. External teeth of discs (item 44, fig. WH 243) must be in perfect mesh with the teeth of cylinder housing (item 46, fig. WH 243).
With caution, install hydraulically lifted brake unit with inserted discs.
a. Brake lifting connection pointing upward.
b. Insert the teeth of inner disc (item 45, fig. 9, WH 243) with the brake being lifted into the teeth of the floating shaft. Install the eight allen-head screws (item 57, fig. WH 243) with new sealing rings (item 56, fig. WH 243) and tighten to a torque of 23 N·m.
After brake removal and tightening the screws, check dimensions (x) or (y) respectively. See fig. WH 244.
- a. If this dimension is the same as prior to removal, assembly has been okay.
- b. If this dimension is smaller then prior to removal, the foremost disc (item 44, fig. WH 243) has gotten out of place during assembly and has been wedged. In this case, removal and assembly must be repeated, since otherwise the brake will not operate or may be damaged.
After having installed the brake correctly, install hydraulic motor in accordance with topic, Removing and Installing the Hydraulic Motor.
Changing the Planetary Gears
Replacement of planetary gears should normally not be effected, but the complete stage should be changed (in accordance with topic, Checking Transmission Stages I, II and III.
If for any reasons planetary gears of stage I or stage II have been extracted after removing snap rings (items 32, 25, fig. WH 24) complete with bearings (items 30, 23, fig. WH 242) (in accordance with fig. 34), the following must be noted.
Prior to reinstallation, new snap rings (items 22 and 29, fig. WH 242) must be inserted. Check also for perfect fit of the snap rings in their grooves. Machine damage can result if new ones are not installed.
Changing the Duo-Cone Seal
NOTE: These operations can only be done with the final drive removed from the excavator.
Design Layout and Operation
This type of Duo-Cone seal comprises two metallic sealing rings of identical geometric contours, elastically supported in O-seals. These O-seals, acting as springs, adopt the function of axial compression sealing, of static sealing between sealing ring and location hole, as well as frictional torque transmission. The sealing is arranged in such a way that one of the two sealing rings is rotating while the other is stationary. The axial force required for tight sealing is achieved by upsetting the elastomer parts between the clamping cones of sealing ring and location hole when compressing the sealing axially into fitting dimension. The contact surfaces of the sealing rings are lapped over a width of approximately 2.5 mm. Starting from these contact surfaces, the sealing rings are conical under a definite angle so that a conical gap opening toward the shaft is formed by the sealing rings leaning against each other. This facilitates access of lubricant to the mating surfaces. In addition, this configuration results in the possiblity for the mating surfaces to shift toward the inner diameter while wearing off, which provides extensive wear take-up. The limit of useful life has been reached when the sliding surface has been transferred up to the inner diameter of the sealing rings.
Do not open the Duo-Cone seal arbitrarily for visual check. Whenever the run-in and still intact sealing ring has been opened, a new sealing-ring set (item 6) is required. The sealing-ring set, as a complete spare part assembly, comprises the two metallic sealing rings and two O-seals. These parts are symmetrical, the mounting position is therefore arbitrary.
Removing the Duo-Cone Seals
For removing the sealing set, first remove three set screws (item 5), using an allen wrench. (Absolutely, remove dirt from threaded hole first.) Remove seal retainer (item 4). If required, install three screws into the holes provided for set screws to facilitate handling. Remove sealing ring (item 6a) and O-seal (item 6c) from seal retainer (item 4). Loosen the allen-head screws (item 7) and remove seal retainer (item 8). Remove second seal half from seal retainer. Clean the mating surface on cross roll bearing (item 16) from sealing compound, as well as the two seal retainers (items 4 and 8) particularly the contact surfaces toward the O-seals (items 6c and 6d).
Installing the New Duo-Cone Seal
Carefully coat mating surface (toward cross roll bearing (item 16) on seal retainer (item 8) with Loctite No. 572. Insert seal half (items 6b, 6d) into seal retainer (item 8). Install seal retainer (item 8) with sealing-set half, and tighten the allen-head screws (item 7) to a torque of 80 N·m.
Insert sealing-set half (items 6a and 6c, figure WH 248) into the seal retainer (item 4).
Install the complete seal-retainer assembly (item 4, figure WH 248) and preload the sealing set with an auxiliary device (in accordance with fig. 37).
Install three set screws (item 5, fig. WH 248) with Loctice No. 265.
Tighten the set screws to a torque of 8-10 N·m.
Brake Valve On Both Sides Effective
Dual Track Brake Valve
The dual track brake valve in use is a flanged special-design slide valve intended to prevent the machine from leading in downgrade travel.
In normal travel conditions, the oil flow enters the hydraulic motor, i.e., through connection (B). Oil flows through the check valve to the hydraulic-motor connection (B'). Since the connection (A') on the discharge side is connected to connection (A) only through small orifices, pressure will build up on connection (B) until the oil flowing through the diagonal bore on connection (B) to the piston face will shift the piston to the left, opening an increasing cross-section passage from (A') to (A). If the machine is travelling downgrade, the mass of the machine will try to accelerate it, whereby the pressure applied to connection (B) will decrease. As soon as the pressure applied to connection (B) drops below the spring control pressure, the passage cross-section from (A') to (A) will be closed until the desired control pressure has built up again at (B). By closing the discharge side, the machine will be prevented from running into overspeed.
To eliminate the well-known critical "hunting" behavior, particular importance was attached to design of the damping system.
During initial operation, be sure to carry out some travel in the reversing range to allow air to bleed out from the cup sides.
The unit is fastened on the respective hydraulic motor by means of an adaptor plate. In case of trouble, check whether the main plunger can move inside its bore. For this purpose, the spring cup can be removed to check manually whether the piston has freedom of action.