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
 

Cr [-]

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

 

Cw [-]

Af [m2]

AfĚCw [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.

 

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