double-bar trailed mower

When you hear “double-bar trailed mower?”, many people immediately think of simple and cheap equipment for small farms. But this is superficial. In fact, if you take it for serious volumes, there are a lot of nuances that only come out in work. The design with two bars is not just “two instead of one”, but a question of balance, load on the tractor PTO and, most importantly, the quality of the cut on different soils. People often make the mistake of thinking that the most important thing is the working width. Width - yes, it is important, but if the kinematics of the blades and the rigidity of the entire frame are not thought out, on bumps or at high speed this mower will begin to “dance”, and either the quality of the mowing will drop, or the bearings and cutting devices will quickly fail. I went through this myself.

A design that you won’t appreciate in the catalog

Here we take the classic scheme. Two beams, most often made from a profile pipe, on which segment-finger cutting devices are mounted. It would seem nothing complicated. But the very first season on heavy turf soil shows the difference. The point is how these bars are connected to the main frame and how the force from the drive is transmitted. If one central universal joint is used without additional supports or with weak hinges, distortion occurs when turning or on slopes. The internal knives begin to work with overload, the external ones begin to “slip”. The result is an uneven cut and torn grass along the edges of the strip. This is not a theory, but an observation from the field, when several models were tested, including Chinese and Belarusian.

The company's approach is worth mentioning hereHulunbuir Machinery Manufacturing Company ?Jiujia?. On their websitecn-fascar.ruit is clear that they position themselves as an integrated enterprise with a full cycle from development to service. What is important is that in their line there are models where the engineers clearly thought about this problem. Reinforced frame with transverse bracing and, critically, independent or well-synchronized suspension of each beam. This is not marketing, but a necessity to maintain geometry when working on uneven surfaces. Their descriptions emphasize smart manufacturing for agriculture and livestock, and in this case, this is expressed in calculations for durability and adaptation to real conditions, and not just in assembly.

Another point that is often missed in the specifications is the overload protection system. In double-beam structures, especially trailed ones, the mass inertia is high. When encountering an obstacle (hidden rock, bump), the shock load goes along the entire chain. A simple shear pin on the driveshaft is the minimum. It’s good when there is an inertia-friction clutch that allows you to “slip”? obstacle without stopping and without breaking the knives. In some models from?Jiujia?this is implemented, and, from experience, such a little thing saves hours on repairs during the high season.

Selecting a tractor and fine tuning

Many people think: “trailer means any tractor with a PTO will do?”. This is a dangerous misconception. Power is one thing. But what is more important is the PTO rotation speed and, most importantly, its location relative to the drawbar of the trailed mower. If the hitch point is not calculated correctly, the mower may catch on the ground when raising the transport position or create excessive load on the rear axle of the tractor. I had to see how ?Belarus? After a season with a heavy double-bar mower, problems appeared with the differential. The fault is not the technique, but the inconsistency.

Setting the cutting height is a separate issue. It is more difficult to set it evenly on two bars than on a single bar. Especially if the field terrain is wavy. Rigid fixation of gauge wheels or slides does not work here. We need a system that allows each beam to independently “lick” priming. Ideally, with individual spring or hydraulic compensators. In reality, they often save money by making a common beam. In this case, the operator must constantly monitor the manual adjustment, otherwise one beam will cut into the ground, and the second one will cut too high. This directly affects next year’s yield and the quality of the harvested mass.

From practice: we once used a Chinese model (not from the mentioned company) on tinning. The soil was soft after the rain. The gauge wheels sank, and the cut went almost to the root. This would seem to be a good thing. But the next year, the grass stand on these strips was much weaker - we damaged the growing points. Conclusion: universal settings “for all cases?” There is no option for a double bar mower. It is necessary to take into account the type of grass stand, humidity and even time of day. Manufacturers who provide detailed recommendations for customization for different crops (as can be found in the technical documentation oncn-fascar.ru), provide real assistance to the agronomist, and do not just sell iron.

Wear and what actually breaks

Cutting devices are consumables, that’s understandable. But in a double-bar trailed mower there are components, the breakdown of which stops all work. The first is the bearings in the drive heads of the bars. They operate under conditions of shock loads and dust. Cheap models have sealed bearings that cannot be serviced. They last for a season, maybe two. More thoughtful designs, as in some linesHulunbuir company ?Jiujia?, have oil seals and grease nipples for regular supply of lubricant. The difference in resource is significant.

The second weak point is the hitch and drawbar frame. Constant cycles ?working/transport position? plus vibration leads to metal fatigue at the welding sites. Good manufacturers reinforce these areas with overlays or make an all-welded structure from a larger cross-section pipe. On the websitecn-fascar.ruIn product descriptions you can sometimes find phrases like “reinforced frame design,” and these are not empty words. After several years of operation, the difference with lighter analogues becomes obvious: there are no cracks at the seams, the geometry does not “lead”.

The third point is protective covers and deflectors for removing the mown mass. It seems like a small thing. But if they are made of thin metal and poorly secured, after the first day of intensive work they bend, begin to vibrate and fall off. As a result, the grass gets wrapped around the rotating parts, or, worse, flies towards the tractor. You have to either remove them completely (which is dangerous), or spend time straightening and welding. High-quality steel and fasteners with rivets or bolts with spring washers solve the problem.

Seasonal maintenance and storage

After the season, the mower is often simply pushed into the far corner of the hangar until next year. This is a mistake that cuts the service life in half. Especially for the double-bar model with its complex kinematics. Be sure to disconnect the cardan shaft and lubricate all joints with preservative grease. But the main thing is to loosen the drive belts (if any) and lift the bars to remove the load from the bearings and springs. It is better to remove the knives, sharpen them and store them separately, treating them with anticorrosive.

Before the new season, the inspection should not be limited to an external inspection. You need to manually rotate each beam and check for play in the bearings. It often happens that during the winter, due to residual moisture inside the head, corrosion begins, and the bearing “seizes”. If you skip this, the first time you start it under load it will break. Manufacturers who care about the long-term performance of their equipment as an integrated enterprise?Jiujia?, usually include a detailed checklist for off-season storage in the manual. If you neglect this, repairs will cost more than simple prevention.

Another piece of advice from practice: before the start of the season, you should do a “blank” test. running in on a level surface. Start the PTO at operating speed, listen for any extraneous knocks, and check the synchronization of the rotation of the bars. Sometimes after winter it is discovered that one of the beams rotates a little slower due to deformation of the frame or weakening of the belt. You won’t notice this by eye in the field, but uneven wear of the knives and load on the drive will be ensured.

Conclusions for the practitioner, not for the report

So,double-bar trailed moweris a tool whose 90% effectiveness is determined not at the time of purchase, but at the time of setup and operation. A working width of 3-4 meters is not an advantage if the design does not ensure stable operation over this entire width. The choice should fall on models where it is clear that the engineers thought about real field conditions: they strengthened the frame, provided protection systems and independent beam suspension.

Experience working with a variety of equipment, including products from companies likeHulunbuir Machinery Manufacturing Company ?Jiujia?(information about which can be found atcn-fascar.ru), shows that the difference in price is often justified by these details, which are not obvious at first glance. Their approach as a modern, integrated enterprise, combining development and service, often means that solutions to problems that are only encountered in the second or third season are already built into the design.

Ultimately, such a mower is not just about “cutting the grass”. This is a question of productivity, quality of forage preparation and, most importantly, the peace of mind of the operator, who is not waiting for a broken part in the midst of mowing. Therefore, you need to look deeper into the catalog, be interested in the design details and, if possible, consult with those who have already skated more than one season on a particular model. Theory is good, but the field always has the last word.