Wheel flange lubrication


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Example Tram

Description

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Example: Tram
While older trams, model years 1950 to 80, which used FIXED supported wheel bodies on half-shafts ON BOTH SIDES, nowadays the most modern trams use independent wheels to SPECIFICALLY reduce wear off. An important advantage of idle gears against fixed wheel set axles is the unrolling of their ACTUAL path lengths.

The different independent wheel variations are shown on the animations below.

- unpowered independent wheels in a
steerable version (see following drawing)

                                           


- powered independent wheels in a steerable version with built in
hub driving motor (see following drawing)

                                           


- powered independent wheels in a steerable version combined with
a rpm differential, after the model of powered wheels
  in the automotive engineering. (see following drawing)

                                           


During curve travel the independent wheels
OF STEERABLE versions adjust themselves with their super imposements on the curve tracks centre. So that the gauge exactness sidewalls respectively the inside micrometre sidewalls approach angle contrary to the rails gauge exactness sidewalls respectively the inside micrometre sidewalls are theoretically always “Zero” (see following drawing)

                                           


It's a completely different situation with
fixed wheelset axles, where the approach angle is ONLY “Zero” in STRAIGHT track sections, but where the curve radii constantly get smaller (according to the spearway) they crucially rise over “Zero” and the wear off increases at the same time.(see drawing: short curve).
A
FIXED arrangement of the wheels on axles (vehicle travels in “spearway” going round a bend), lead, in curves to a repetitive JERKY overstepping of the static friction limit and a slipping of the not used wheels (the inside laying wheels) of a wheelset axle.
To reduce wear off it is recommendable to lubricate the RUNNING SURFACE of the INNER curve track.
There are no compensations of the shorter inside ways opposed to the longer outside ways on the wheelset axles.

These occurrences do not appear with independent wheels.

Travelling railbound vehicles generate:
- at slow travel speed ⇒ axial thrust forces
- at medium travel speed ⇒ from axial thrust- and centrifugal forces
- at high travel speed ⇒ centrifugal forces.

When rolling stocks travel from straight track sections into curve sections, transverse and horizontal axial thrust forces, depending on the travelling direction, develop. These are transferred from the vehicles body over the wheelset axles to the wheels flange and the gauge exactness sidewalls of the rails.

Factors for
axial thrust forces are:
- curve radii, “spearway”, angle
- vehicles speed.

Force reductions are possible through curve inclinations (meaning the lowering of the inner rail opposite the outer rail)
Dry friction between the wheels and rails can lead to wear offs which are not reasonable and also not wanted. Dry friction should be avoided, because it leads to high maintenance costs and lower railway operational safety.
PURE WATER FILMS lead to essential wear offs on wheel and rail.
During the
SEDIMENTATION PROCESSES of lubricator, lubricator fillings fill in the coarsenesses in the sliding and running surfaces of wheels and rails. Whereby very good sliding properties and in connection also good reduction of wear offs and noise pollution between wheel and rail are achieved.

NO or almost no operation of the lubrication system depending on:
- weather factors (high humidity, rain, snow- and ice-rain, snowfall, dry cold)
- seasonal demands (leaf foliage)
- curves where the longitudinal tilts are to high ( this means complicated travel conditions in general due to big gradient or
  slope on the route).

For example tram routes should be lubricated
several times a day, depending on traffic volume.

WITHOUT curve lubrication, the wear off of the gauge exactness sidewall or inside micrometre sidewall is so high, that the RISK OF DERAILMENT can occur after 15,000 kilometres.

Especially curve tracks at bending railway switch constructions have small curve radii and smaller running surfaces of the rails.



Usage of head rail/ grooved rail

Head rails (vignol rail), see following drawing


                         

are used for
open railway tracks (e.g. between two towns). The height of tram rail heads/tram rail heads height can be for example 149 mm.


Grooved rail, see following drawing

    

are used in areas, where trams and cars use the same roads. (e.g. in town centres)

Paving stones (and rail chamber filler blocks) are used as surface (which is also an advantage for cyclers). E.g. the height of a filler block element can be 180 mm. Grooved rails and paving stones are purposely higher, so that they don't bend or give in when travelled on.

Another possibility too prevent wear off is to lubricate curves with a graphite powder-water mixture. In this case water is used as a binding-, dosage- and
carrier medium for the graphite powder particles which swim in it. While the water dissolves quickly, the graphite particles sediment permanently into the coarsenesses of the running and sliding surfaces of the rails and wheels.

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