Coefficient of friction, Rolling resistance, Air resistance, Aerodynamics

Coefficient of friction, Rolling resistance and Aerodynamics

Coefficient of friction for many material combinations
Coefficient of friction in bearings
Coefficient of friction in screw joints
Rolling resistance
Air resistance, aerodynamics

Coefficient of friction for a range of material combinations
combination	Static		Dynamic
	dry	lubricated	dry	lubricated
steel-steel	0.5...0.6	0.15	0.4...0.6	0.15
copper-steel	-	-	0.5...0.8	0.15
steel-cast iron	0.2	0.1	0.2	0.05
cast iron - cast iron	0.25	0.15	0.2	0.15
friction material - steel	-	-	0.5-0.6	-
steel-ice	0.03	-	0.015	-
steel-wood	0.5-0.6	0.1	0.2-0.5	0.05
wood-wood	0.4-0.6	0.15...0.2	0.2...0.4	0.15
leather-metal	0.6	0.2	0.2...0.25	0.12
rubber-metal	1	-	0.5
plastic-metal	0.25...0.4	-	0.1...0.3	0.04...0.1
plastic-plastic	0.3-0.4	-	0.2...0.4	0.04...0.1

The coefficient of friction between two materials in relative sliding may depend on contact pressure, surface roughness of the relative harder contact surface, temperature, sliding velocity and the type of lubricant whether the level of contamination. It's the reason that the data found in the many reference tables available may show a large variation.

www.engineeringtoolbox.com/friction-coefficients-d_778.html
http://www.carbidedepot.com/formulas-frictioncoefficient.htm
http://www.engineershandbook.com/Tables/frictioncoefficients.htm
http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm
http://hypertextbook.com/facts/2005/steel.shtml
http://www.diracdelta.co.uk/science/source/f/r/friction/source.html
http://nl.wikibooks.org/wiki/Fysica/Dynamica
http://en.wikibooks.org/wiki/Physics_Study_Guide/Frictional_Coefficients
http://encarta.msn.com/media_461544499/Table_of_Friction_Coefficients.html

Coefficient of friction in bearings
	Coefficient of friction [-]
Slide bearing, hydrodynamic	0.003...0.04
Slide bearing, sinter bronze, oil lubricated	0.04...0.07
Slide bearings, solid bronze, grease lub	0.07...0.12
Polymer slide bearing, polyamide, dry	0.2...0.3
Polymer bearing, composite, dry	0.05...0.15
Ball bearings	0.001...0.0015
Roller bearings	0.0018
Needle bearings	0.0045
Air bearings, pressurized	0.0
Hydrostatic bearings	0.001...0.002, ref viscous shearing

Coefficient of friction in screw joints
lubricated	lubricated	dry	dry
oiled	MoS₂	Zn-plating	RVS
0.12...0.18	0.08...0.12	0.12...0.18	0.3...0.8
screw lubricants / friction >>

Rolling resistance
	C_r [-]
Steel wheel on rail	0.0002...0.0010
Car tire on road	0.010...0.035
Car tire energy safe	0.006...0.009
Tube 22mm, 8 bar	0.002
Race tyre 23 mm, 7 bar	0.003
Touring 32 mm, 5 bar	0.005
Tyre with leak protection 37 mm, 5 bar / 3 bar	0.007 / 0.01
Calculator rolling resistance >>

Air resistance
	C_w [-]	A_f [m²]	A_f嵩_w [m²]
Modern car	0.25...0.35	1.8	0.54
MPV	0.4...0.5	3	1.35
Truck	0.7	6	4.2
Formula 1	0.75	1.6	1.20
Nuna Solar Car	0.07	0.86	0.06
Sports plane	0.12	5	0.60
Card	0.8	1	0.80
Grand pa bike	1.1	0.6	0.66
Racing bike	0.9	0.35	0.31
Horizontal bicycle	0.8	0.25	0.20
aerodynamic bicycle	0.4...0.15	0.25	0.07
Ball	0.5	πR²	0.5πR²
Half sphere	0.4	πR²	0.4πR²
Half sphere	1.3	πR²	1.3πR²
Flat circular disc	1.1	πR²	1.1πR²
Calculator air resistance >>

Conversion of wind speed Beaufort to wind speed in m/s:
1: 1m/s	2: 2m/s	3: 4m/s	4: 7m/s	5: 10m/s	6: 13m/s
7: 16m/s	8: 19m/s	9: 23m/s	10: 27m/s	11: 31m/s	12: >36m/s

Conversion percentage of slope to slope angle

A 5% slope is a slope that rises 5 m for every 100 m horizontal distance, i.e. a slope of atan(5/100)=2.86 degrees. A 100% slope is one of 45 degrees.