Nelson Big Gun Troubleshooting


Welcome back to Walla Walla Washington.
My name is Chad Leinweber, and I am the Project Engineer at Nelson Irrigation
for the Big Gun® Family of Sprinklers. Today, I’d like to talk for a few minutes
about some of the common troubleshooting issues that we run into and to give you
some hints that could help you in the field without having to take
a sprinkler into a dealer. I’m going to be working on the SR100 today, and I
will use it as an example. But anything we talk about here with the SR100 is
applicable to the SR75, the SR150, and the SR200 as well. The first issue that
I think needs to be addressed is slow drive. When I say slow drive, I’m speaking
about the actual rotation speed of the sprinkler around its center axis.
For some reason after years of operation, we have a gun that is moving very
sluggishly or very slow. This what I’m calling slow drive. When you encounter
this situation, the first thing that you need to do to check it is to ensure that
you have adequate pressure at the sprinkler. If you have access to a
pressure gauge (specifically a pitot tube would be nice) or a gauge
somewhere near the base, it could give you a pressure reading. It’s always
helpful to verify it. Many times people will call us and tell us they’re
having problems with the sprinkler driving. I’ll ask them what pressure they
have, and they’ll they’ll tell us it’s 40 or 50 psi or whatever. It turns out that
40 or 50 psi is backed by the pump, maybe several hundred feet away. At 40 or 50
psi, several hundred feet away is much less at the gun. It’s very important to
find out what that nozzle pressure is. If that nozzle pressure is low, that doesn’t
mean it’s hopeless. You don’t have to go necessarily buy a new pump. I have
a couple of tricks that we can use to help you in those situations. The first
one is that this drive spoon or drive vane here is a black color. That’s the
standard drive vane on the SR100, and also for smaller or the larger nozzles on the
SR75. If you find that you’re in a low pressure situation, say you’re
lower than 40 psi or somewhere down there, and you have sluggish driving, you can use
this gray drive spoon. It’s our low pressure drive spoon. Its part number is 10612. You can order it from us and
it’s very easy to replace these out. The two bolts essentially require a 7/16″ box
wrench. You can pop this one off and drop this one. This will give you a
lot more drive around this direction, and it will also kick the arm out of the stream
much further as well. This is one solution for a low pressure situation.
Another solution, which is just as viable but probably not as preferable, is to
remove some of the brake springs out of the lower unit. This section of the
sprinkler is the lower unit, which houses the main bearings and the main
pressure seal. There’s a brown ring right here that is a brake.
Underneath this elbow are eight springs, which press this brake against this brass piece here called the cover. This is what gives us a braking
force that prevents the sprinkle from operating too fast, and it also keeps the
sprinkler level. If we were on a bit of an incline, then the sprinkler would want to
slide back after it drives with each stroke, if it wasn’t for the brake. As
long as you’re not on an incline, you you can take some of those brake springs
out. The way to do that is just by using a wrench, you will remove these four
bolts that hold the elbow to the lower unit. The brake spring will extend and
kind of pull this up, so you’re going to want to hold it — probably by the range tube —
and then I would recommend removing every other spring and giving
that a try. Again, it’s preferable probably to go with the low-pressure
drive spoon but that removal of the brake springs is another option. One other
method you can use to increase the drive speed is the moving of this arm
weight. On each of the driver arms, there are actually going to be arrows with the words “fast” and “slow” giving you directions for which way to move the arm
way to increase the drive speed. One thing to remember is even
though I can increase the drive speed going around this way by moving the arm
weight, that also shortens up the arm stroke as well. The more you shorten up
the arm stroke, you will have a tendency to bring the radius of the water in a
little bit as the sprinkler moves faster. Again, that’s why I point to this
as being probably the best solution because what this does is it gives you more
drive and also kicks the arm out of the stream for a long period of time. It gives you a dwelling period when the gun is stationary, and it allows the water to travel its furthest distance If you have adequate pressure and you’re
still having a slow drive problem, the next thing we’re going to want to check
is we’re going to take a look at the drive spoon itself. On this drive spoon
— and again, this is very similar to this one — if any of these vanes get broken or chipped, sometimes that can have an effect on how how it drives. A
lot of times if that’s the case, it would be driving fast in one direction and
slow in the other direction. So that’s a quick and easy thing to check out and to
make sure that it’s fine. After that I would reach up, and I would grab the
sprinkler nozzle to make sure that the lower unit is not binding up and that it rotates freely. Now, it’s very possible through time that you may have a
problem with the bearings of the seal down here. You’ll be able to detect that
because this would be very hard to turn. If that’s the case, your best bet at that
point is to contact a dealer or contact the factory, and we can get you
instructions on either how to further diagnose that or to repair it.
Another failure that leads to drive problems is, in this drive, often these will get
bent. If you have a gun on a pivot, then this is probably very rare. But
if you have a gun that is on a traveler or some sort of a mobile
irrigation device and it gets tipped over, these arms can get bent. If
this arm is bent and twisted in a direction like this, what will
happen is that your water will miss most of your drive spoon. When that
happens you can also get a very short drive stroke. If you see that
type of thing, you will want to take a look at your arm. You can run a ruler across it
to see if it’s flat or not. If it is bent, then it will need to be replaced.
In the meantime, if you’re waiting to replace it, you might be able to
straighten it a little bit. I would only recommend that for a temporary fix if
you’re in dire need for water while you’re waiting for your new arm to come.
Another common problem is tripping. By tripping I mean that’s the reversing of
directions. This here is the trip lever; it’s connected to an over-center mechanism,
which changes the direction of the drive arm and which switches the
sides of the drive spoon where the water hits and drives the sprinkler. If
you’re finding that this won’t reverse direction, or if it’s hanging up
on one side and just staying there, there’s a couple of things to look for.
The first thing is you want to verify that each of these
stops here has an arrow. These arrows should be pointing in towards the
trip lever. This tail on the elbow and the trip lever should always be between
the arrows. You’ll also want to make sure that you can see the arrows on the top.
If you put these upside down so that the stops on the bottom and this clamp part
down here is on the top or if the arrows are switched backwards, the sprinkler
won’t reverse. The reason for that is before this over-center mechanism of the
trip lever can toggle and change directions, this tab here — this boss on the
elbow — will strike this boss right here and prevent it from going over center.
Essentially, you would drive around, your sprinkler would stay right here, and it
would never change directions. It would just keep operating in one spot
like that. Those would be the first two things that I would check
and verify if I was having a trip lever problem. The next thing I would
look at is again, if it could be a bending problem. This does not
happen very often on a pivot but again if you have a Solid Set situation
or if you have a gun on a QC that’s being moved around or on a
traveler. As those things travel, sometimes they get spilled, and
you could bend the trip lever pin. If you bend that trip lever pin,
oftentimes that can cause a problem with reversing. If you bend the drive arm
severely enough as well, as I was alluding to before, that would give you
problems reversing. Most likely, you would also notice drive problems in that case.
There’s one other thing to check. If you look right down the center tube of
the nozzle here and you look right above it, there’s a post that the
shift lever sits on. There’s two bearings from the shift lever, and they’re pressed
down around this post. That’s what rotates
the trip mechanism. Those should be roughly even on each side. Occasionally,
these will bend if a gun and cart is tipped over or something like
that. When that’s bent, it rotates the shift lever, the drive arm, and
everything. This can cause a problem with with tripping as well. Especially during the spring, we’ll hear people talking about problems
with short stroking. By short stroking, I mean this arm is moving very quickly, you’re not getting a whole lot of bite into the stream, and you’re not getting a
whole lot of drive. One thing to keep in mind depending on where you are in the
world — certainly up here in Washington in our area where they start irrigating
in early March and it’s quite cold — often what will happen is the lubricating
grease and the bearing cavities get very viscous. We often get calls around mid-March about, “hey my gun’s having difficulty driving” and then in a week or
two those calls go away as the temperature warms up. Be aware that
if you have a short stroking and you know you’ve had cold nights (say it’s
getting down in the mid 30s at night), that may be the cause of that. You
may not have any more to worry about other than that. Again, give that a little
time and if that goes away, then you can be rest assured that it probably
was the grease. The other thing is if you are having short stroking problems,
and it is not the temperature, you’re probably going to want to take a look at
your drive arm. You’re going to want to get up there, and you’re actually
going to want to feel this and wiggle this around. If I hold the shift lever
with my left hand right here, there shouldn’t be any slop
in the arm bearings. If there is slop in the arm bearings that means we’ve
probably had a seal failure at some point in time, which has led to water
getting in the bearings and most likely a bearing failure as well. Again,
that’s easily diagnosed because if there’s slop or movement in here, that’s
usually the case. Same thing if you find any binding. If there’s any grabbing,
these should be very easy to move and completely free to move. If you run
into any one of those cases, I’d recommend you go online and
take a look at our 9822 arm bearing replacement kit literature. It will walk you through how to replace those and give you instructions on replacing them, as well as ordering them. The other
thing to keep in mind if you have a short stroke as I said before, this arm
weight position can be adjusted. It’s possible that maybe somebody adjusted
the arm weight and you weren’t aware of it. Maybe it was moved it back into the fast position
here and that give you, again, a very short stroking situation there as
well. These are some of the typical troubleshooting problems
we run into out in the field. If you run anything beyond that at any point in time,
you can call your dealer or give the factory here a call. We’re more than
happy to help you out troubleshoot your gun.

One comment

  • Gosselin Farms Ed Gosselin

    Very good informative video!!!
    Only one problem, the captioning ends up covering part of what is being shown…. But, I know what the guns look like, so I've got a good idea of what was being discussed.
    Thank you!!!!

    Reply

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