Coeficients of friction for lumber 1

[toyguy]

I am developing a piece of lumber handling equipment which (among other things) must measure the length of the boards as they accelerate thru 4 pairs of steel pinch rolls. There is an encoder on the second pair of rolls, but to put together a program which compensates for the slippage of the rolls I need to know the friction values for Southern Yellow Pine, Spruce, Lodgepole Pine and Douglas Fir. I am looking for frozen or dry values, since I can interpolate one from the other.

 

[wroberts]

You might try earilier editions of Marks Handbook. I think the 2nd edition has the best values for wood. The 4th edition is good too. I don't have mine here at work, but I'll check at home. I think the older books are worth every penny, you should get yourself one. Try Ebay, they are always selling them. After all you never know what materials or equipment you may end up using.

Will

 

[wroberts]

According to the 2nd edition Marks Handbook.
The coeffecient of Sliding friction for dry materials at low velocity: Pine on pine is .294 @ 28-168 psi.

General coefficients of friction:
timber on timber: .7 to .3
timber on metals: .5 to .2

General coefficients of sliding friction are as follows:
wood on wood, dry: .25 to .5
wood on wood, soapy: .2
metals on oak, dry: .5 to .6
metals on oak, soapy: .24 to .26
metals on elm, dry: .2 to .25

Not exactly what you were looking for but a good starting point.
Will

 

[Clint]

'God made solids, but surfaces were made by the devil'

This is a quote from the tribologist Pauli. It basically demonstrates how complex friction is and how it really is difficult to deduce. The recommendation from most tribologists is to measure the friction yourself under conditions that are as close as possible to those you are interested in (Arnell, R.D. et al. "Tribology: Principles and Design Applications P29)

Regards

Clint