As far as friction is concerned there is no difference.

Herringbone lagging is mainly used on drive pulleys and is used to displace water between the pulley face and the belt and therefore the direction of the grooves is very important. The center point always goes toward the direction of belt travel.

Diamond grooves are mainly used on reversing drive pulleys or for spare pulleys that can be used in different rotation applications.

The cost difference would be insignificant. ■

Not a trivial subject for those that get their jollies on the esoterics of mechanical behavior in the lagging grooves.

1. Herringbone grooves are more robust, but do not shed water as freely. To understand this phenomenon, you need to believe the 3-D spread of fluid at the lagging surface between grooves does not evacuate as freely as a diamond pattern. Water in the diamond pattern must only travel one-half the pattern width of one bounded lagging lug. Whereas, the herringbone pattern may have the water move from pulley center to half width of belt before exiting the wetted surface. Maybe not too likely but possible. The water spends a lot more time in travel to the groove with herringbone.

2. Diamond groove lagging failing is at the entry point of contact and the exit point of contact of each diamond lug. In both locations, the lagging can be stressed beyond its elastic limit or shear stress limit, thereby causing tearing of the rubber lagging lug as it enters into and exits out of the contact with the belt. In extreme cases, the lagging is decimated with large pieces being ripped from the lug leading and trailing diamond pattern geometry. This is a big problem with very high shear stress (high power or torque) values. Recently, Los Pelambres had such an event that was responsible for "white hair" disease. The conveyor took many minutes to come to rest. The pulley lagging had worn down beyond reasonable limits. It takes the right storm to bring out the extremes in behavior.

We can say the rubber exhibits more squirm with diamond than herringbone. My intuition tells me that the diamond pattern may offer more grip, but not significantly more. I would not bet the company on it without more study. ■

BTW-

I do not know of any large conveyor system that has opted for herringbone over diamond lagging. In the old days yes, but not today. Tell me I am wrong with these multi-thousand kW drives.

1. Los Pelambres

2. Collahuasi

3. El Abra

4. Kennecott

5. Channar

6. Curragh North

7. Palabora

8. Island Copper

9. Highland Vallley Copper

10. .............. and so on

The odd exception is Selby, now retired. The designer used a bare shell. They were afraid of lagging the 10,000 kW pulley due to the surface stresses involved. ■