Plain talk on surface planers

Basic understanding of flail configurations makes renting easier

The four flail configurations, which are named for the type of tooth on each, come in various industry standard diameters and thicknesses to meet the needs of virtually any application.

After being introduced 35 years ago, the popularity of small surface planers continues to grow as more and more rental companies find markets for the machine. Planers, which also are called scarifiers, work well on everyday municipal maintenance projects, trip-and-fall sidewalk projects, traffic line removal and any other task requiring the removal of excess concrete.

The planing process itself is considered rather destructive and unrefined in contrast to more controlled grinding with diamond discs or blades. How much material is actually removed with flails is dependent upon a number of factors, including drum/flail configuration, tensile strength of the material being removed, and the machine’s travel speed. Understanding these factors allows a rental centre to make the best recommendation to a customer for any specific application.

As surface planers became more commonplace over the past few decades, the technology changed little. All surface planers share the same basic platform configuration. A variety of sources power the machines, from gas and diesel engines to electric and even pneumatic motors. Some planers are manually propelled, while others incorporate self-propelled drive systems. A belt reduction connected to a high-speed, rotating drum typically transfers the power since the belt can minimize the amount of destructive resonance transferred back to the power source. Manufacturers supply drums in a variety of diameters and widths, and planers are classified by the drum width, such as 8, 10 or 12 inches.

Planers, which also are called scarifiers, work well on everyday municipal maintenance projects such as removing traffic lines or grinding down misaligned sidewalks.

Regardless of the manufacturer, drive configuration or drum width, all surface planers utilize a rotating drum loaded with rows of flails that impact directly against a target surface. This flailing action transfers a large amount of kinetic energy to strike against and subsequently remove material.

As job applications have increased over the years, so have the kinds of flails available. This made things pretty complicated and expensive for rental centres that needed to maintain an expansive inventory for customers. Manufacturers have responded to this frustration by consolidating some configurations and eliminating others.

Flailing for a solution
Today, it’s only necessary to stock four flail configurations, which are named for the type of tooth on each: star flail, beam flail, tungsten carbide tipped flail and milling flail. The four configurations come in various industry standard diameters and thicknesses to meet the needs of virtually any application.

Star flails work best in removing coatings and encrusted material, cleaning concrete and asphalt surfaces, de-scaling steel ship decks or performing light scarification prior to applying a new surface coating. The flails are stamped from high-manganese-content alloy steel and are through hardened for additional service life. While every application is different, star flails generally last one to three hours.

Like star flails, beam flails are stamped from a high-manganese-content steel and are through hardened for added durability. Beam flails’ finish texture is between medium course and course, and they also last about one to three hours, depending upon the application. Most often, this type is used to remove medium-duty asphalt and concrete, traffic lines, thicker coatings and encrusted materials.

Understanding factors such as drum/flail configuration, tensile strength of the material being removed and the machine’s travel speed allows a rental centre to make the best recommendation to a customer for any specific application.

Tungsten carbide tipped flails can be five or six sided and will produce a medium to course surface texture. The flails will last as long as 250 hours on typical applications, such as removing trip-and-fall hazards on sidewalks, grooving concrete and asphalt or removing heavy-duty concrete and asphalt. The flails’ durability comes through the tungsten carbide inserts brazed in a perimeter configuration around an alloy steel body. This higher quality construction delivers maximum performance and the best return on investment on most material removal projects.

Milling flails incorporate rectangular tungsten carbide inserts, which also are brazed around the perimeter of an alloy steel body. The configuration is very similar to that of standard machine tool cutters, making milling flails directional in nature. This requires them to be operated in an “upcut” or “climb cut” mode. This means that a manually propelled planer will need to be pulled toward the operator. If the planer is pushed forward, the flails will “down cut,” causing wear on the back side of the inserts and significantly decreasing the service life of the flails. When used correctly, milling flails should last as long as 30 hours, depending on the specific application. Typically, milling flails are used to remove traffic lines from concrete and asphalt surfaces, as well as to remove membrane-type materials from concrete surfaces.

Watch where it wears
No matter what flail style is most frequently rented, one may find that some will begin to wear excessively on one side rather than evenly around the perimeter. There are two possible causes to consider.

A worn tungsten flail occurs if flails are loaded too tightly on the planer drum or if the user is raising the planer’s guiding wheels off the application surface and putting unnecessary pressure on the flails.

First, the flails may be loaded too tightly on the drum shafts. This will not allow them to spin freely as intended. The spinning action allows the wear to be distributed evenly about the flail’s perimeter. If the flails are tight and cannot spin properly, wear will occur predominately to one side. Even if manufacturer’s guidelines are followed and the correct number of flails and spacer washers are loaded, variances in manufacturing tolerances and material thickness may require that slight adjustments be made.

To prevent this, adjust the number of flails and spacer washers to allow them to spin freely so they can properly “flail” against the surface.

The other possible cause for uneven wear could be attributed to the customer. If the operator raises the planer’s forward wheels off of the surface, the rotating drum will incorrectly support the machine’s weight. This also does not allow the flails to properly spin and will create excessive wear to one side.

Despite some beliefs to the contrary, raising the machine off its front wheels does not increase but, instead, decreases the material removal rate. This is because the resulting increase in recoil forces makes the surface planer unstable. The more a machine hops or jumps, the less kinetic energy it can effectively transfer to the surface.

To prevent this, instruct customers that the proper and most effective operation will involve keeping all wheels in contact with the surface.

Flails are the heart and soul of the material removal process. The quality and style define how fast the material is removed and the corresponding surface finish. In the end, understanding the customers’ application, making the appropriate flail recommendation and sharing a bit of advice on planer usage will help ensure proper handling and thus more productive, happier customers. Together, these will bring an optimum return on investment for rental centres. ■

*Dennis Von Ruden is the president of General Equipment Company.