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Rotor angle vs precipitation rate
If I understand correctly, rotors put out the same gpm regardless of the operating angle, and thus the precipitation rate depends on the angle. Why is this not a problem?! Won't the corners (with 90 degree rotors) be getting 4x the water compared to out in the middle of the turf where you've only got full circle rotors?
Note: this is completely different behavior than sprays which have a precipitation rate that's independent of angle (a 1/4 circle puts out 1/4 the water as a full circle as you'd expect).
I think I found the answer on the irrigationtutorials.com. The solution is to use different nozzles to match the gpm based on the angle coverage. E.g. use a 1gpm for the 1/4 circle, 2gpm for the 1/2, 4gpm for the full circle.
But this raises a second question. When you use different nozzles, you also change the radius. If I'm using a nozzle 4 times larger than the radius I need for the full heads, it would seem I need to cut the radius by nearly half. Does that cause any problems? Doesn't that significantly affect the distribution profile? Also, I'm looking at the Hunter PGJ and their brochure says that the radius adjustment screw can reduce the radius by up to 25% which isn't enough to get the 4gpm nozzle down to the radius of the 1gpm. So is it just impossible to mix 1/4 and full head rotors with the PGJ? Are there other small-radius rotors that don't have this problem?
Again, MPRotators sound like they can solve your issues. As I understand the way they have been designed, they all ways have a matched (or close enough) percipitation rate no mater how you mix and match them.
http://www.mprotator.com/
Basically, you install something like Rainbird 1800 series Pop-up Spray Heads, and replace the nozzles with the MPRotators.
Burley - you are right about mixing 1/4 rotor heads with full circles- the radius can be difficult to match and more than likely you'll exceed the recommended 25% reduction radius or distort the nozzle stream so bad that the stream will not cover properly.
The way to prevent this is the have 1/4's and 1/2's on the same valve with full circle heads on a seperate valve/zone. The full circle heads would use the 1/2 nozzles and the zone would have to run for twice as long to achieve the same precip rate.
Rainbird has come up with a good solution for this in their 5000 series rotors. They have matched precipatation nozzles (that are color coded) for these heads that are available in 25', 30' and 35' distances so that 1/4's, 1/2's and full circles can all be on the same zone
Burley - you are right about mixing 1/4 rotor heads with full circles- the radius can be difficult to match and more than likely you'll exceed the recommended 25% reduction radius or distort the nozzle stream so bad that the stream will not cover properly.
The way to prevent this is the have 1/4's and 1/2's on the same valve with full circle heads on a seperate valve/zone. The full circle heads would use the 1/2 nozzles and the zone would have to run for twice as long to achieve the same precip rate.
Rainbird has come up with a good solution for this in their 5000 series rotors. They have matched precipatation nozzles (that are color coded) for these heads that are available in 25', 30' and 35' distances so that 1/4's, 1/2's and full circles can all be on the same zone
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