Chances are you are considering buying one so let me explain the basic principles behind these versatile yard sprinklers and why they are so good.
There are a number of different brands of traveling lawn sprinkler. Some are full of plastic gears and cogs which soon break and others are of solid construction that will last for generations. My favorite is the National walking sprinkler. Needless to say it is in the last for generations category!
However whichever brand you buy they all operate in a very similar fashion. The sprinkler is on a small tractor. The tractor is placed upon its own hose (see the red tractor on the left) and the force of the water in the hose turns a series of gears which are connected to the axle and this slowly turns the sprinkler’s wheels. By this means the sprinkler creeps along the “hose track”.
Most brands are adjustable for both speed and water spray.
An important point for all brands of this type of yard sprinkler are to ensure you have the arms pointed in the right direction. If you have it set up wrong, the sprinkler either won’t move at all, or it will move backwards – not really what we want!
Each arm of the sprinkler needs to point in the opposite direction to the other. Stand above the sprinkler, facing in the direction it will travel and the arm on your left should point back towards you and the arm on your right point in the direction of travel. Study the diagram above and you’ll get the idea.
A traveling sprinkler has only five essential parts:
* Sprinkler arm assembly
* Worm gear
* Three wheels
* Hose connection
So water pressure is what drives this system. When you turn on your garden tap, the water pressure will typically be around 40 to 70 psi (pounds per square inch). The pressure forces water down the hose, through a pipe in the sprinkler and out through two sprinkler arms.
As the water pushes out, it exerts an equal and opposite force back on the two arms. You will have noticed in the pictures that these arms are bent at the end. This means that the force pushes on each arm at an angle and as the arms are bent to point in opposite directions, the force acting on both arms combines to produce torque. Torque is simply a rotational movement.
This rotational force is applied to the worm gear and if you buy a sturdy sprinkler it will be made from metal and last a lifetime and if you buy a crappy brand it will be made from plastic and will be stripped just as you try to ready the yard for your only daughter’s wedding and the grass will brown off and die and your wife and daughter will both stop talking to you and don’t come running to me saying I didn’t warn you!
To your left you can see an example of a worm drive or worm gear. Note the spiral bit which is the “worm” and how it drives the gear.
And you can see how cheap plastic gears will be stripped at the first challenge to your sprinkler. Let it run into a boggy patch, let the dog lie down in front of it, let the kids “zoom” it down the drive, and your plastic gears are history. Trust me on this latter point!
As the two arms spin they rotate the worm gear, which engages a gear in the transmission. This transmits the rotational force of the worm gear to the drive axle that turns the tractor’s back wheels. The drive comes from the back wheels which push the front wheels.
All the different brands work the same way. Differences in price come down to the construction. Cheap brands often don’t last the summer and rarely last more than a couple of years. Sturdy brands such as the National sprinkler – B3 is the original which all later brands tried to copy with varying degrees of success. The National will last a lifetime.
You work out the economics!