Drum mowers, though widely used in Europe for 40 years or more, are just recently becoming a popular choice in the US. Drum mowers have a significantly different design from the other two types of mowers. Instead of powering the cutting blades from the cutter bar, the “drums” of a drum mower are powered from a gearbox above. The standard drum mower has two counter-rotating drums. Each drum is essentially a cylinder of 10-14 inches in diameter and length of 15-24 inches, with a large disc attached to the bottom. Depending on the model, either 3 or 4 free-swinging blades are attached to each of these discs. When in operation, the entire drum/disc/blade assembly rotates. This heavy rotating mass creates a great deal of momentum, which helps to power the mower through thick spots in the field. On the bottom of this assembly is a dish which is mounted on ball bearings. This dish does not rotate with the rest of the drum assembly, but rather slides along the ground and can rotate freely in either direction depending on the surface it slides over.
As a drum mower moves through the field, the drums are rotating toward each other, which causes the cut crop to pass between the drums and be dropped in a windrow behind the mower. This windrowing effect eventually must be spread back out with a tedder or rake in order for the hay to dry properly. This has been the major drawback of drum mowers up to this point. Galfre, however, has solved this problem with the patent-pending Black Hole conditioning system. This system ejects the cut hay out the rear of the mower in a spread-out and fluffed manner, allowing the hay to dry where it sits. This potentially saves an additional trip through the field with a rake or tedder and can shorten drying time by up to a day. Amazingly, Galfre’s design accomplishes this feat with absolutely no additional moving parts.
Drum mowers are designed to be very robust, simple machines. They have only a fraction of the parts that either sickle bars or disc mowers require. They also can be run with modest horsepower. Once the drums are up to speed, they do not draw a lot of power from the tractor to keep spinning.
Drum mower advantages are:
• No hydraulic requirement. You do not have to have hydraulics on your tractor. For transport, the drums swing to the rear of the tractor manually.
• Durability. Drum mowers are easily the most rugged of the hay mower types. They rarely sustain damage even from striking an unmovable object. This makes them a great choice for contract cutting in unfamiliar fields or for mowing unruly pastures.
• High ground speeds. A drum mower can be run at even higher speeds than a disc mower, and double the speed of a sickle bar.
• Low power consumption. This feature is important particularly with older utility tractors of modest horsepower.
Drum mower disadvantages are:
• Contour mowing. Because the drums are very heavy, it is not recommended to hang the mower out over a downward slope. Drum mowers also do not pivot enough to effectively follow extreme contours like a sickle bar will.
• Weight. The drum mower’s heavy weight can be detrimental for tractors with light front ends. Drum mowers are very heavy in relation to other mower types of the same width. This can make maneuverability and transport difficult if there is not sufficient weight holding the front wheels of the tractor down.
• Windrowing. Since most drum mowers windrow the cut crop, it will not dry in the field without being spread out or double-raked. However, Galfre drum mowers are the exception to this rule. Their Black Hole conditioning system fluffs and spreads the cut crop for faster drying time.