Counter knives in a feed mixer wagon – how do they work and when should you use them?
Counter knives in a feed mixer wagon – how do they work and when should you use them?
Counter knives in a feed mixer wagon help to chop long, fibrous materials such as straw, hay and haylage more effectively. They work together with the knives mounted on the mixing auger, increasing the resistance applied to the moving feed. As a result, the material does not simply rotate with the auger but can be cut more efficiently.
Correct adjustment of the counter knives affects more than just the time required to break up a bale. It also influences the physical structure of the TMR, mixing time, tractor load and fuel consumption. However, this does not mean that the counter knives should always be fully extended into the mixing chamber. Their position should be adjusted to the type of feed and the current stage of the mixing cycle.
What are counter knives in a feed mixer wagon?
Counter knives are stationary components installed in the wall of the feed mixer’s tub. Their working sections can be extended into the mixing chamber or retracted from it.
During operation, the auger moves the feed vertically and around the inside of the tub. When the chamber contains long straw, hay or compacted haylage, some of the material may rotate together with the auger without being shortened effectively. Extended counter knives restrict this movement and create an additional point of resistance. This allows the knives mounted on the rotating auger to chop fibrous ingredients more efficiently.
Counter knives do not replace the knives on the auger. The two components have different functions, but they work together during the chopping process.
How do counter knives work?
The operation of counter knives can be explained in several stages:
- The mixing auger lifts the feed from the bottom of the tub.
- The material moves vertically and along the walls of the mixing chamber.
- Long fibres come into contact with the extended counter knives, which restrict their free movement.
- The rotating auger knives pass through the restrained material and can chop it more effectively.
- The shortened material returns to the circulation inside the tub and is mixed with the remaining TMR ingredients.
The system does not work exactly like a pair of scissors because there is a specific amount of clearance between the auger knives and the counter knives. The main purpose of a counter knife is to increase resistance and prevent long material from rotating freely with the entire feed mass.
The further a counter knife extends into the tub, the greater its effect on the movement of the material. This can accelerate chopping, but it also increases the resistance acting against the auger.
Counter knives and auger knives – what is the difference?
Auger knives and counter knives perform different functions:
| Component | Main function | How it works |
|---|---|---|
| Auger knives | Directly cut and chop the feed | Rotate together with the mixing auger |
| Counter knives | Increase resistance and restrict the movement of long material | Remain stationary in the wall of the tub |
| Mixing auger | Lifts, moves and combines the ingredients | Circulates the entire feed mass inside the tub |
Even correctly adjusted counter knives will not produce good results if the auger knives are blunt, damaged or incorrectly installed. Chopping quality depends on the entire system: the auger, knives, counter knives, operating speed, type of material and the amount of feed loaded into the tub.
When should counter knives be used?
Counter knives are most useful when the ration contains long, fibrous or tightly compacted ingredients. However, they do not always need to be extended to the same position.
Chopping straw bales
Dry straw is light and springy and may move together with the auger without being shortened effectively. Extending the counter knives increases resistance, making it easier for the auger knives to cut long stalks.
Counter knives are particularly useful when chopping whole bales and straw with a long, tough structure. Once the required fibre length has been achieved, the counter knives can be partially or fully retracted.
Chopping hay
Long, dry hay can form a compact mass inside the mixing chamber. Depending on its moisture content, compaction and fibre length, extended counter knives can help break up the bale more quickly and prevent the material from simply rotating with the auger.
Chopping haylage
Tightly compacted haylage bales may also require more intensive cutting. This is particularly true for crops that were not chopped before baling or contain long fibres.
Moist haylage behaves differently from dry straw. The counter knives should therefore be extended gradually while the operator monitors the machine’s performance and the resulting feed structure.
Preparing rations containing long fibres
If excessively long pieces remain in the TMR after the normal mixing time, extending the counter knives may improve the cutting process. However, the condition of the auger knives and the loading order should also be checked.
Simply extending the mixing time does not always produce a better result. It may increase fuel consumption, accelerate wear on working components and cause other ingredients in the ration to become excessively processed.
When should the counter knives be retracted?
Counter knives should not remain fully extended throughout the entire mixing cycle simply because this position provides the most intensive chopping action. Once the material has reached the required fibre length, the additional resistance may no longer be necessary.
The counter knives can be partially or fully retracted:
- after the entire bale has been broken up,
- once the material has reached the required length,
- when mixing short or loose ingredients,
- when further chopping could damage the required TMR structure,
- if the drive system is under excessive load,
- during the final mixing stage, when the priority is to combine the ingredients evenly.
Retracting the counter knives allows the feed to circulate more freely inside the tub. It may also reduce the resistance acting against the auger and therefore lower the tractor’s power requirement.
How should counter knives be adjusted?
There is no single universal position suitable for every farm and every ration. The correct setting depends on factors such as:
- type of feed,
- fibre length,
- moisture content,
- bale density,
- amount of feed inside the tub,
- required TMR structure,
- tractor power,
- condition of the auger knives.
It is usually best to start with the counter knives partially extended and observe how the material behaves. If the bale is breaking up too slowly and long fibres remain in the mixture, the counter knives can be extended gradually.
Once the material has been chopped to the required length, the counter knives should be retracted. Continuing to operate with maximum resistance may not improve the quality of the mixture and can unnecessarily increase the load on the tractor.
The size of the prepared batch is also important. Both overfilling the tub and operating with too little material can change the way the feed circulates around the auger. The performance of the counter knives should therefore be assessed together with the correct filling level of the feed mixer.
Manually or hydraulically operated counter knives?
The method used to adjust the counter knives depends on the design and equipment of the feed mixer wagon.
Manually adjusted counter knives
In simpler systems, the position of the counter knives is changed directly at the machine. This uncomplicated solution can be sufficient on farms where similar rations are prepared every day and the type of material rarely changes.
Changing the position requires the machine to be stopped and the adjustment mechanism to be approached safely.
Hydraulically operated counter knives
Hydraulic adjustment allows the position of the counter knives to be changed from the tractor. The operator can extend them while breaking up a bale and then retract them once the feed has reached the required structure.
This solution is particularly convenient when:
- the ration contains materials of different lengths,
- the composition of the TMR changes frequently,
- the feed mixer operates several times a day,
- the operator wants to adjust the chopping intensity during operation,
- whole bales of straw, hay or haylage are loaded into the tub.
Hydraulic adjustment does not change the basic operating principle of the counter knives, but it makes their position much easier to adapt to each stage of the mixing process.
How do counter knives affect mixing time?
When used correctly, counter knives can reduce the time required to chop long material. The bale loses its compact form more quickly, and its individual sections are incorporated more efficiently into the circulation inside the tub.
However, this does not mean that fully extending the counter knives will always provide the shortest mixing time. Excessive resistance can restrict the smooth movement of the feed, particularly when the tub is full or contains very heavy and moist material.
The best results are achieved when the counter knives are used intensively during the chopping stage and then retracted to allow the complete ration to mix more freely.
Do counter knives increase fuel consumption?
Extended counter knives increase the resistance of the moving feed. As a result, the auger may require more power, especially when working with heavy, moist or tightly compacted silage.
Fuel consumption should not, however, be assessed solely on the basis of the temporary load. If the counter knives significantly reduce the time required to break up a bale, the complete TMR preparation cycle may be shorter.
The least efficient approach is to keep the counter knives fully extended after the chopping process has finished. In this situation, the additional resistance may not provide any further improvement in the quality of the mixture.
Do counter knives improve TMR quality?
Counter knives help to produce a more consistent fibre length, allowing the ingredients to be combined more evenly. A properly prepared TMR should reduce the opportunity for animals to sort the ration and select only its most attractive components.
However, more intensive chopping does not always mean better feed. If the fibres become too short, the resulting physical structure may not meet the nutritional requirements of the herd. The target fibre length should be adjusted to the TMR recipe, type of livestock and recommendations of the farm’s nutrition adviser.
The purpose of counter knives is to help achieve the required structure, not to chop every ingredient as finely as possible.
Common mistakes when using counter knives
Keeping the counter knives fully extended throughout the cycle
One of the most common mistakes is leaving the counter knives fully extended for the entire mixing process. This position may be useful at the beginning, but it is often unnecessary once the material has been shortened.
Failing to adjust them to the type of feed
Dry straw, hay and moist haylage produce different levels of resistance. A setting that works well for one material may be unsuitable for another.
Extending mixing time instead of checking the knives
If the feed is not being chopped correctly, the auger knives may be blunt or damaged. Counter knives cannot fully compensate for worn cutting components.
Overprocessing the TMR
Operating with extended counter knives for too long can produce fibres that are shorter than required. The operator should assess the resulting TMR structure and adjust the settings during subsequent mixing cycles.
Ignoring the load on the tractor
A noticeable reduction in engine speed, uneven operation or excessive load on the drive system may indicate that the counter knives are extended too far, the tub is overloaded or the material is exceptionally heavy.
Inspection and wear of counter knives
Counter knives are constantly exposed to large quantities of feed and will gradually wear. The following components and areas should be inspected regularly:
- condition of the working edges,
- wear of the surface,
- mountings and bolted connections,
- free movement of the adjustment mechanism,
- hydraulic system for leaks,
- cracks, deformation and other damage.
Worn counter knives may have less effect on the material even when fully extended into the tub. In this situation, the operator may unnecessarily increase mixing time without achieving the expected result.
Inspection, cleaning and adjustment must only be performed after the machine has been stopped, the PTO has been disengaged, the tractor engine has been switched off and the entire combination has been secured against accidental starting. Never enter the tub or approach the working components if there is any possibility that the auger could be started.
Example of using counter knives when preparing TMR
When preparing a ration containing long straw or a whole bale of haylage, the process may look as follows:
- The counter knives are partially extended before intensive chopping begins.
- The operator observes how the bale breaks up and monitors the load on the machine.
- If the material remains too long, the counter knives can be extended further.
- Once the required fibre length has been achieved, the counter knives are retracted.
- The remaining ingredients are mixed until an even TMR is obtained.
This is only a general operating principle. The loading order and mixing time should take account of the ration recipe, the characteristics of the specific machine and the applicable feeding recommendations.
Counter knives in ZAMET feed mixer wagons
ZAMET feed mixer wagons can be equipped with two hydraulically operated counter knives. The operator can adjust their position from the tractor and adapt the chopping intensity to the type of material loaded into the tub.
This solution is particularly useful on farms that process whole bales or frequently change the composition of the ration. Hydraulic control allows the counter knives to be extended while long fibres are being chopped and then quickly retracted during the next stage of the mixing process.
Hydraulic counter knives can be selected for suitably configured feed mixer wagons from the following product ranges:
- FIDER-i MINI,
- FIDER-i EKO,
- FIDER-i MAXI,
- FIDER-i 2S EKO,
- FIDER-i 2S MAXI.
The equipment configuration should take account of the mixer’s capacity, the type of feed being prepared, the tractor’s available hydraulic connections and any other functions that require hydraulic control.
Summary – how should counter knives be used?
Counter knives are most useful when chopping long, fibrous and tightly compacted material. They increase the resistance applied to the feed, allowing the knives mounted on the auger to cut it more effectively.
Once the required fibre length has been achieved, the counter knives should be partially or fully retracted. This improves the circulation of the feed, reduces the load on the drive system and limits the risk of overprocessing the TMR.
The most important rule is: adjust the position of the counter knives to the type of feed and the current stage of the mixing process instead of leaving them in the same position throughout the entire cycle.
Frequently asked questions
Should counter knives always be extended?
No. Maximum extension is useful during intensive chopping of long material. Once the required structure has been achieved, the counter knives can be retracted to reduce resistance and allow the ration to mix more freely.
Do counter knives reduce the time required to break up a bale?
In many cases, yes. They restrict the movement of long fibres with the auger, allowing the knives to cut the material more effectively. The actual processing time also depends on the type of bale, moisture content, sharpness of the knives and filling level of the tub.
Can the feed mixer operate with only one counter knife extended?
If the machine’s design allows independent adjustment, one counter knife may be used to provide a lower level of resistance. The setting should always comply with the operating instructions for the specific model.
Does fully extending the counter knives increase the power requirement?
It can increase the power requirement because the material creates greater resistance against the rotating auger. For this reason, the counter knives should be retracted once the chopping stage has been completed.
How can worn counter knives be identified?
Signs of wear may include rounded or uneven edges, visible material loss, deformation, cracks and reduced chopping performance despite correct adjustment.
Are hydraulic counter knives better than manually adjusted ones?
Both systems perform the same basic function. Hydraulic counter knives provide greater convenience because their position can be changed from the tractor during the different stages of TMR preparation.
Can counter knives chop the feed too finely?
Yes, if they remain fully extended for too long. The operator should monitor the TMR structure and retract the counter knives once the material has reached the required fibre length.
