Page 221 - The Tribology Handbook

Table 51.3 Tne effect of various factors on adhesion or traction [TI, skidding (S) and rolling resistance (RR)
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Load (W) Speed Elevated Temp. Water Wheel dta. (0) Wheel wtdth (0) Material Matinc surfaces Others
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Steel RR a w0.' Ta W Adhesion Little effect,
tyres as a first decreases except where Light rain has a RR a D-y where Little effect Little effect Adhesion can be Diesel- or
approximation slightly with very high local marked y = 0.5 to I increased by electric-driven
speed, see temperatures deleterious removing wheels have
Figure 11.6. are applied to effect on contaminants greater adhesion
Increased burn off adhesion. from the than steam
resistance with adhesion- Continuous surface of the because of the
speed results limiting heavy rain can rail or by smoother
mainly from surface improve sanding torque
the effect of rail contaminants adhesion by
joints and on wheel and cleaning the
suspension rail rail surface
characteris tics
OCI
A Pneumatic RR increases with See Figure 11.6 Rubber friction Large reduction Adhesion Rolling resistance Radial ply On wet roads Aquaplaning speed
in rubber load unless Adhesion coetficient in friction, see increases, decreases construction harshness is a (inflation
tyres inflation reduced by the decreases with Figure 1 1.6. while rolling slightly with gives more pressure) "'. Wear
pressure is also effect of temperature - Some rubbers resistance width with improvements important than down to 2 mm
increased. sideways forces about 10% per are less decreases with modern tyre in all three roughness tread depth has
Ta Was a first a (speed)'in 15°C change affected than increase in designs. coefficients. except at high little effect on
approximation cornering others diameter Traction Rubber speeds, see adhesion: smooth
increases with composition is Figure 11.6. treads give as little
width more Road surface is as half the
important than a more adhesion of
tread pattern important unworn patterned
factor than tyre treads on poor,
condition wet surfaces
Solid RR a @'3 Ta W Not suitable for Dependent on Affected in a RR a D-"' RR 0-* RR~E'I~ Solid tyres only
tyres as a first moderate high properties of similar manner (Eis Young's suitable for
approximation speeds (above tyre material to pneumatic modulus) smooth
40 km/h) tyres, but more surfaces
unless specially so
designed