They twist, grab and tie twine like nothing else, but the humble knotter still has the potential to tie many operators in knots.
Geoff Ashcroft sought a few pre-season tips from John Deere harvesting territory manager Mike Baker...
Few machines have the ability to strike fear into the hearts of operators like a conventional or large square baler.
Whether it has two, four or six knotters, waiting for the inevitable mis-tied bale and the hair-pulling which often follows is all part of the operating process, right? Not so, says John Deere’s baler specialist Mike Baker.
He says: “A bit of effort spent checking and examining the knotter bank and its components can save you a lot of hassle in the middle of harvest. Often the problems are simpler to resolve than you might think, though it is easy to jump to the wrong conclusion, instead of starting with the basics.”
While all knotter types operate in the same mechanical way, there are balers which tie one knot, and models which tie two. Many large square balers have moved to a double knotting system, simply to handle higher bale densities.
It is a process which sees twine presented to the knotter from above and below the bale, with a knot tied at either end of the bale, on the top face. This technique reduces twine and knotter load, simply because the twine is not kept under constant tension during bale formation.
Conventional two-string balers operate with a single knot, which requires twine tension to be maintained throughout bale formation, putting additional load on the knotting process.
Knotting string is a simple mechanical process. A needle presents twine to a retainer which holds it firmly while a rotating billhook collects and twists the twine to form a loop.
As the billhook rotates, its jaws are opened, allowing the twine to be drawn through the loop, creating the knot as the loop slides off the billhook.
The billhook rests on a swiper arm, which moves laterally to position twine and also to provide a cutting function as it sweeps past the retaining discs which are used to anchor the twine.
Knotter movement is provided by cams and gears to carry out the correct amount of movement to create a knot and cut twine.
Mr Baker says: “The system is surprisingly reliable, but when an intermittent fault does occur, it can test the patience of a saint.”
Key components include this swiper arm, which carries a stationary blade, and it works in conjunction with the billhook. Do not be tempted to remove and sharpen the knife to save money, suggests Mr Baker.
“Knife sharpening will remove material and create a gap which will affect twine cutting durability,” he says.
“Before you remove a knife, look at how it sits on the swiper arm with its shim – it will not be mounted square to the edge. And this is deliberate positioning so it cuts neatly and cleanly.”
The billhook sits against the swiper arm when knotting is complete.
“If you can move the jaws, either the roll pin or roller bearing could be worn and this is unwanted movement which will affect twine tying reliability.”
Multi-knotter systems provide an opportunity to compare and contrast.
“If you get one knotter playing up, take the time to study them to see what is different,” says Mr Baker.
“Measure any gaps and look for mis-alignment or broken parts. If they all play up at once, it is likely there is a huge failure – perhaps from debris, a foreign object or needle timing – or it is a twine problem.”
Individual knotter faults can take some time to fathom, he says.
“Pull the securing pins and lift the troublesome knotter assembly so you can take a good look around and under it. If you think a component is suspect, swap it to another knotter and see if the problem persists. But remember to refit the securing pins.”
If a problem persists, Mr Baker suggests it can be worth fitting an action camera to film the knotting process and review the operation in slow motion.
“It might hold the clue to what is causing the issue. Usually, the only time you ever get to study knotters is when they go wrong.”
Mr Baker advises operators of big square balers to pay particular attention to the lollipops which sit above the knotters, or in Deere’s case, to the in-cab terminal which displays virtual lollipops.
“When you become used to a pattern of movement from the lollipops – which can bounce during operation – you will soon spot one which shoots upwards or downwards. You then need to stop and look for what is not going on.”
He says the tendency is to keep driving in the belief it was just a glitch, and it will correct itself on the next knot.
“If a lollipop goes up, the knot has not tied and the top twine is not being pulled through,” he says. “If a lollipop goes down, the twine is likely to be wrapped around the billhook and something will break if you continue,” he says.
“If you have to adjustments the spring tensioners then make small adjustments – one flat at a time with a nut can be plenty. It is easy to reintroduce a problem than it is to fix.”
String has a huge influence in the way knotters operate. And mixing different string types is a recipe for disaster.
Mr Baker says: “Twine should pull freely from the twine box, but the top and bottom twines will then pass through a holder to create tension as it is pulled into the knotting mechanism.
“There are different thicknesses of twine and the twine on a double knotting system needs to be tensioned correctly. If too loose, string can tangle around the billhook resulting in either the string or the billhook jaw being snapped.
“If you change twine type, you may need to adjust twine tensioners to maintain consistent reliable knot production.”
Debris and dust are the enemy, so fan operation is essential to blowing the area clean during operation.
“Too much grease can be problematic too,” says Mr Baker. “Use an airline to remove unwanted chaff or trash from the area. And remove excess grease too as you do not want to contaminate the twine retainers.”
He suggests not reaching for the pressure washer.
“This can push water into bearings and bushes, leading to corrosion and seized parts,” he says.
“And when rust is worn away, this creates free-play in areas where you need a snug fit.”
He also suggests storing balers under cover when not in use.