ELGOTEX filament wound bushes, maintenance-free
Features
ELGOTEX filament wound bushes are maintenance-free, free from corrosion and have low wear and friction. Further advantages of the filament composite are low mass together with high load carrying capacity and resistance to shocks as well as suitability for applications involving vibrations.
ELGOTEX filament wound bushes are particularly suitable as an environmentally-friendly and maintenance-free bearing type for replacing steel or bronze bearings.
Maintenance-free plain bearing material
The radial dry plain bearings have a sliding layer made from ELGOTEX and a twin layer structure, ➤ Figure:
- The outer layer (the backing) ensures the strength of the bush. It comprises continuous glass fibres that are additionally stabilised by means of a specific winding angle, giving an increase in strength. The fibres are bound in epoxy resin.
- The inner layer (sliding layer) contains a polymer/PTFE yarn that is embedded together with fillers and solid lubricants in a resin matrix.
Due to the combination of filaments and resin matrix, the bushes are suited in preference for dry-running applications, see table.
Microsection
of a ELGOTEX filament wound bush
Resistance of the plain bearing material
The filament wound bushes are non-metallic and thus substantially resistant to media. For special environmental conditions, please consult the Schaeffler engineering service.
Technical data for ELGOTEX
Maintenance-free ELGOTEX filament wound bushes have the following mechanical and physical characteristics, see table.
ELGOTEX filament wound bushes are intended for dry running. They achieve their maximum operating life under these conditions.
Slight settling of the material occurs during running-in.
ACHTUNG
In underwater use, there is a considerable reduction in operating life. In this case, the coefficient of friction may increase significantly.
In the production of ELGOTEX filament wound bushes, defects (pores) and fraying may occur in the PTFE due to the production process. These cannot be prevented by technological measures and do not represent any impairment of the function.
Characteristics of ELGOTEX
Characteristic | Load | |||
|---|---|---|---|---|
Maximum pv value** | pv | 2,8 N/mm2 · m/s | ||
Permissible specific | Static | pmax | 200 N/mm2 | |
Rotary, oscillating | 140 N/mm2 | |||
Permissible sliding velocity | v | 0,18 m/s | ||
Permissible operating temperature | ϑ | –20 °C to +130 °C | ||
Coefficient of friction | μ | 0,03 – 0,2 | ||
Operating life behaviour with | ||||
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| dry running | +++ | ||
grease and oil lubrication | + | |||
media lubrication, water lubrication | + | |||
Definition of the symbols: | |
+++ | very good |
+ | adequate. |
**The maximum permissible bearing load as a function of velocity is determined by means of pv diagrams.
**For static loads of more than 180 N/mm2, the design of ELGOTEX filament wound bushes must be checked by the Schaeffler engineering service. For loads at or over this range, we alternatively recommend the use of ELGOGLIDE plain bushes.
Sealing
Standard plain bushes without a suffix are not sealed. These can, however, be combined with separate external seals in order to prevent the ingress of contamination and moisture.
Plain bushes ZWB are available by agreement with integrated seals 2RS on both sides or integrated seals RS on one side.
ACHTUNG
In the design of the sealing arrangement, it must be borne in mind that the bearing clearance will increase due to wear of the sliding layer.
Lubrication
During the running-in phase, PTFE particles are transferred from the sliding layer to the mating surface. As a result, the small roughness features of the shaft surface are filled in. It is only once this tribologically smooth surface is produced in conjunction with the detached PTFE particles that the bearings can achieve a long operating life.
ACHTUNG
Maintenance-free ELGOTEX filament wound bushes do not have relubrication facilities and must not be lubricated.
Any lubrication of maintenance-free ELGOTEX filament wound bushes after dry running-in will impair the smoothing effect necessary and will considerably reduce the operating life of the bearings.
Operating temperature
The permissible operating temperature for maintenance-free ELGOTEX filament wound bushes is between –20 °C and +130 °C.
Suffixes
Suffixes for available designs: see table.
Available designs
Suffix | Description | Design |
|---|---|---|
RS | Standard lip seals on one side | Special design, |
2RS | Standard lip seals on both sides |
Design and safety guidelines
In addition to the design and safety guidelines described here, the following guidelines in the Technical principles must also be observed:
- theoretical bearing clearance of ELGOTEX filament wound bushes
- design of bearing arrangements
- recommended mounting tolerances
- misalignment of plain bushes
- pressing in of bushes.
ACHTUNG
Plain bushes should not be used for movement involving spatial motion. Any skewing of the shaft will reduce the operating life.
Friction
The characteristic coefficients of friction, calculation of the bearing frictional torque and the typical wear characteristics are given in the chapter Technical principles.
Dimensioning and rating life
The dimensioning of plain bushes is summarised in the chapter Technical principles.
Depending on whether the bearing is subjected to dynamic or static load, the following must be checked:
- static load safety factor S0
- maximum permissible specific bearing load p
- maximum permissible sliding velocity v
- maximum specific frictional energy pv.
ACHTUNG
The rating life can be calculated if the range of validity is observed.
Calculation example for bush ZWB607060
The rating life of the bush is calculated on the basis of the sliding layer ELGOTEX.
Given data
The given data for calculation of the rating life are as follows:
- highly loaded pivots on an angled lever
- steel shaft (hard chromium coating, roughness depth Rz 1,6)
- point load (rotating shaft, stationary bush).
Operating parameters
Bearing load | Fr | = | 120 000 N |
Swivel angle | β | = | 30° |
Swivel frequency | f | = | 6 min–1 |
Operating temperature | ϑmin | = | 0 °C |
ϑmax | = | +30 °C |
Bearing data
ELGOTEX bush | = | ZWB607060 | ||
| Basic dynamic load rating | Cr | = | 504 000 N |
Inside diameter | Di | = | 60 mm | |
Width of bush | B | = | 60 mm | |
Sliding material | ELGOTEX | |||
Required
- Bearing with the required rating life Lh ≧ 15 000 h.
Checking of permissible loads
ACHTUNG
The validity of the permissible loads and sliding velocities must be checked, since useful rating life calculation is only possible within this range.
Specific bearing load
The specific bearing load must be calculated with the aid of the specific load parameter K and checked for validity:
Sliding velocity in swivel motion
The sliding velocity must be calculated with the aid of the inside diameter Di and the swivel angle β and checked for validity:
Specific frictional energy pv
The specific frictional energy pv must be checked for validity.
Determining the rating life equation
For calculation of the rating life, the valid rating life equation must be selected and then subjected to correction.
Selection of the valid rating life equation
For maintenance-free plain bearings, the following applies:
Correction factors, as a function of bearing type
The correction factors necessary for the plain bearing material ELGOTEX must be selected from the matrix and used to correct the rating life equation appropriately.
Series | Sliding layer | Motion | Correction factors | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
fp | fv | fpv | fpv* | fϑ | fR | fW | fA | fB | fL | fα | fβ | fHz | |||
ZWB | ELGOTEX | Rotary | ■ | ‒ | ‒ | ■ | ■ | ■ | ■ | ■ | ■ | ‒ | ‒ | ■ | ‒ |
Rating life equation following correction
Calculation of rating life
The values for the correction factors in the corrected rating life equation must be taken from the diagrams. The specific plain bearing factor KL = 7 000.
Correction factors
Correction factor | Value |
|---|---|
Load fp | 0,99 |
Frictional energy fpv* | 0,9 |
| |
| |
Temperature fϑ | 1 |
Roughness depth fR | 0,82 |
Material fW | 1 |
Condition of rotation fA | 1 |
Width ratio fB | 0,7 |
B/d = 1 | |
Swivel angle fβ | 0,75 |
Rating life Lh
The rating life is calculated as follows:
Result
The selected ELGOTEX plain bush ZWB607060 fulfils the required rating life Lh ≧ 15 000 h.