Rotors

Rotors are gear-drive movements best used for 18- to 55-foot spacing (5.5 m to 16.8 m), with options for larger diameters that are mainly used for golf courses or special circumstances. They usually come with a number of nozzle sizes and offer some flexibility in upsizing or downsizing nozzles in case you find a deficiency in coverage.

For information on using rotor heads with our software, see our documentation sections on Adding Rotor Heads to a Land F/X Project and Placing Rotor Heads in a Drawing.

Design Pressure

As a general rule, assume at least 1 psi of design pressure for each foot of radius (0,232 bars per meter of radius). Thus, a 50-foot (15.2 m) radius should result in a head requiring a design pressure of 50 psi (3,53 bars). Because design pressure is the pressure at the last head, you should add on to that loss for the system. Be careful of the smaller nozzle sizes available for a given rotor, as they may have smaller droplets of water that can easily be disrupted by wind. You may want larger nozzle sizes for heavier, more wind-tolerant droplets.

General Recommendations

We recommend using rotors with rubber caps in play areas. Stainless-steel risers are often an option – and are necessary in sandy soil situations to prevent scarring and damage to the riser from sand.

Rotor heads have a radius reduction screw, but we recommend not adjusting this screw unless you really have to, as it breaks up the spray pattern.

Using rotors in turf can often result in “donuts” of dry grass areas, with typical reasons being:

• If your system has a low-pressure problem, the sprinkler will create a donut-shaped water pattern with green right around the sprinkler, then a dry area for several feet, with wet areas farther out. If you run into this condition, try turning the adjustment screw to allow some water to enter the dry area.

• If you notice dry patches located midway between two rotors, but no donut pattern, the rotors are likely spaced too far apart, or the radius adjustment screw is too far into the stream. Either make sure the adjustment screw is all the way out, or change to a larger nozzle size for more water and a larger radius.

Bad design is bad design, however. Rotors placed too far apart may not be able to be fixed with a change in nozzles, as the pressure may also change. You may even need to add a booster pump to the system

Nozzles

Unlike other spray heads, rotors have a set nozzle, and their flow never changes no matter how the arc is positioned.

The precipitation rate is what changes, which is why you'll need to hydrozone properly when placing or piping rotors. In basic terms, the quarter head will emit twice as much water as the half, and four times more than the full. Therefore, the best practice with rotors is to either:

• Keep the quarter (Q), half (H), and full (F) heads on different zones, or
• Match precip rates by adjusting which nozzles are assigned to the Q, H, F rotors (4 for the Q, 8 for the H, 16 for the F, etc).

Spacing

For rotors, head-to-head coverage may be inadequate. Different designers will have different ideas of the overspray, but consider a spacing of 90% or 85% of the radius for the head-to-head spacing.