Re: Pulley Wrap Factor
When considering a Chain & Bucket elevator with plain friction drive head wheels I once measured the coefficient of friction between chain and a smooth pulley. But I never repeated it for a rubber belt which was a pity as I had the motorised test rig, just needed a bit of belt and rubber lagged pulley.
Perhaps you'd like to have a go. You can always post the results. ■
Re: Pulley Wrap Factor
There has been work on this subject.
There are similar posts which may be of use:
https://forum.bulk-online.com/showth...riction+factor
https://forum.bulk-online.com/showth...riction+factor
https://forum.bulk-online.com/showth...riction+factor
https://forum.bulk-online.com/showth...riction+factor
https://forum.bulk-online.com/showth...riction+factor
https://forum.bulk-online.com/showth...riction+factor
https://forum.bulk-online.com/showth...riction+factor
A good start my be to look at ISO 5048 or DIN 22101.
Some sources imply the use of 0.2 to 0.45, depending on surface condition (wet, dry etc).
Maunfactures such as Belle Bane provide reccomendations in their product data.
Mr David Beckly, in his course "Practical Belt Conveying" provides reccomendations based on years of experience not only for power transmission, however also for belt life etc.
Regards,
Lyle ■
Re: Pulley Wrap Factor
There are loads of references to coefficients of friction, but I must admit that I've never seen the results of actual tests.
Refrences for actual tests anyone?? ■
Re: Pulley Wrap Factor
Mr David Beckly in his PBC notes references "Oehmen and Hohmann" work at Hannover regarding measurement of the firction values.
I suspect this is documented in a paper of some description.
He also references the work of his own company measuring the friction coefficients.
So yes it it exists and I would be suprised if others have not also attempted this measurement previously.
Regards,
Lyle ■
Re: Pulley Wrap Factor
Dear Mr. designer999,
The friction coefficient between rubber belt and rubber lagged pulley depends upon the application conditions. This is similar to friction grip between rubber tyre and road. This friction grip will depend upon the road surface contamination by water, soil etc. In case of belt conveyors, the DIN / ISO specifies following three conditions as a guideline and finally to consider the friction coefficient appropriate to the application:
For Rubber belt and herringbone pattern rubber lagging on pulley :
Friction coefficient : 0.4 to 0.45 for operation in dry condition
Friction coefficient : 0.35 for operation in clean and wet condition
Friction coefficient : 0.25 to 0.3 for operation in wet and dirty condition
In case of wet and clean condition, it is just wetting by water. In case of wet and dirty condition, the actual friction coefficient to be used will depend upon the pasty situation likely to be created by the material being handled, and it can be even lower than the specified value for abnormal situation.
Having chosen the appropriate friction coefficient, the calculation of factor to be used for multiplying to tractive pull, is by well used engineering formula.
Regards,
Ishwar G Mulani.
Author of Book : Engineering Science and Application Design for Belt Conveyors.
Author of Book : Belt Feeder Design and Hopper Bin Silo
Advisor / Consultant for Bulk Material Handling System & Issues.
Email : parimul@pn2.vsnl.net.in
Tel.: 0091 (0)20 25882916 ■
Pulley Wrap Factor
Hi everyone,
Today my question is regarding the Wrap factor Cw used for calculating T2 using eq. T2=Cw*Te
For 180deg wrap, rubber belt on lagged pulley with manual takeup, CEMA recommends Cw=0.8 . This is also derived from the equation
0.8 = Cw = 1 / (e^(uA) - 1)
Where
A = 180deg = 3.14 rad
u = 0.258 = friction factor for rubber to rubber
This friction factor seems extremely low and may be conservative to account for possible material build up between belt and pulley.
The likelyhood of this is low for our applications and I'd like use a more realistic friction factor.
Has anyone done any rubber backed belt to rubber lagged pulley friction tests? I can't seem to find any info on the net.
Thanks ■