You can either go to the Rothe Erde website (manufacturer of a wide variety of ball and roller bearing slewing rings, turntables as well as seamless rolled steel and non-ferrous metal rings)
here and read all about it or you can read this...
Komatsu, Terex O&K, Hitachi and Liebherr all use Roth Erde slew bearings.
Here’s a brief summary from Komatsu’s P.O.V:-
The large Komatsu’s (KMG range) use what is known as a triple bearing slew ring (three-row bearing with axial-roller bearing) with an external gear or as Roth call them the Standard Series RD90. Like all bearings, it has an internal clearance between the roller’s and the race
The clearance on these bearings is particularly fine especially considering the size of the bearing (3.5 tonne for the old H185 and 16.3 tonne for a PC8000-6). In order to maintain the clearance constant and at its specification it is crucial that both the upper and lower mounting surfaces (carbody (as seen being machined your video and my photos) and superstructure) remain true, because if the internal clearance is reduced then the bearing WILL fail prematurely and in a very short period of time (and no warranty from the manufacturer).
Firstly, the mounting surface where the bearing will sit on the machine must be measured using a laser device. This is ascertain that the surface is true and has not been blemished in any way from, for example, welding beads, burrs and strong paint residues and other uneven surfaces caused by fretting etc. To prevent incorrect measurements caused by radiation from the sun projected onto the pedestal/carbody, it is recommended that the entire area is to be protected from direct sunlight.
Example: P = Maximum permissible deviation (deflection)
Inside diameter = 4000mm
Outside diameter = 3600mm
P = (4000 – 3600) ÷ 1000
P = 400mm ÷ 1000
P = 0.4mm
If the measured value exceeds the calculated value P, then the surface has to be remachined.
Once the machining is complete and all the surfaces are clean, the bearing can be sat down.
The next step is to determine the tightening torque of the mounting bolts (yes, you have to calculate it yourself) this is because each batch and each bolt has their own individual strength characteristic, and for such a crucial component which is exposed to load and torque stress it is imperative that you get it as accurate as possible. Each slew bearing is supplied with fastening bolts, measuring bolts, a measuring device and mounting compound. You are supplied with 8 measuring bolts (which are strictly for test only (marked with a z on the head)) to determine the torque, the eight bolts have to be mounted one by one to the measuring device. Then the bolt has to be tightened in steps to the prescribed elongation (for example PC8000-6 M36 x 295, 10.9 grade, and 55 mm width across flats at 0.71 ±0.020mm elongation). The needed tightening torque will be determined as a result of an average of eight tightening torques. When determining the tightening toques of the bolts, it is essential that the measurements are carried out in conditions (e.g. temperature) that are equal to those at the place of mounting.
To achieve the most accurate results, you should use a smaller Hytorc head as this allows the pressure of the Hytorc power pack to operate in its mid range. Slight deviations of the pressure have a lesser effect on the bolt elongation and torque. For example, 200 psi increment with a 10MXT head equates to 296 Nm whereas a 5MXT head equates to 149 Nm. This would allow a more precise bolt torque when using a 10,000psi gauge.
As an example, the last one I did averaged 1431.25 psi, 0.65mm elongation at 2277.38 Nm.
You then have to set the tooth and pinion backlash but that’s going off topic a bit.
In addition to ensuring these standards are met, constant condition monitoring of the bearing are crucial – for example, checking the slew ring bolts after 1000 hours of fitment of a new bearing, regular slew deflection inspections, grease sampling, tooth and bolt condition etc.
Hope this answers your question
