Types of Mowers

Mower types include:

• Reciprocating finger-bar (sickle bar);
• Flail;
• Drum;
• Rotary disc; and
• Mower-conditioners (roller type, tyned or flail type).

Mowers and mower-conditioners are usually mounted to a tractor three-point linkage or trailed. The development of combination front- and rear-mounted mowers, trailed tandem-mounted and self-driven mowers have increased mowing rates.

Reciprocating finger-bar mowers

Lucerne growers often favour reciprocating finger-bar (also called sickle or cutterbar) mowers because they leave a ‘cleaner cut’ or reduced fragmentation of the stubble.

They have a relatively low power requirement, about 1.5 kW/m width of cut, but forward speed is restricted to 3-8 km/hr, giving a mowing capacity of about 0.6 ha/hr in good cutting conditions.

They have generally been superseded by rotary disc and drum type mowers that have a faster cutting speed, less chance of ‘blocking’ in wet or lodged material, and greater durability on stony ground.

Flail mowers

Flail mowers are modified flail harvesters, which leave the mown crop on the ground in a windrow. After wilting, the chute is changed to allow the material to be picked up and delivered to a cart.

Output ranges from 0.4 to 1.2 ha/hr for a 1.5 m width of cut, and up to 1.5 ha/hr with a 1.8 m width of cut, but requires at least 35 kW to operate at 8 km/hr.

They are no longer common, due to their inefficiency as mowers, lack of speed and high power requirement. The action of flail mowers can cause the forage to be contaminated with soil or manure.

Drum mowers

Drum mowers usually consist of one or more pairs of large drums, each fitted with several knives. The two drums in each pair rotate in opposite directions, forcing the mown material between them and leaving the swath in a windrow.

Drum mowers have a much greater capacity than fingerbar mowers but require 4-8 times the power, typically 7-15 kW at the PTO per metre width of crop cut. The swaths left behind these mowers tend to ‘sit higher’ than those left by rotary disc mowers.

Leaving the mown material in a windrow is a disadvantage. To increase wilting rate, the material should be tedded immediately after mowing.

Disc mowers

Multi-disc mowers are the most popular mowers due to their speed of operation and durability. Disc mowers consist of several pairs of small rotating discs, each usually fitted with two knives. The pairs of discs rotate in opposite directions, like drum mowers, but because the discs are much smaller in diameter, the material is essentially left where it is cut.

Disc mowers are fitted with swath plates, which allow the swath width to be adjusted, from a narrow windrow to one almost the width of cut.

Disc mowers have a similar throughput capacity to drum mowers. Cutting widths and work rates of individual mowers have increased substantially in recent years.

They (and drum mowers) can be operated at forward speeds of 10-13 km/hr, giving a cutting rate of 1.0-1.5 ha/hr/m width of cut, depending on crop and ground conditions, and operator skill.

There is some evidence that forage cut with a disc mower dries more quickly than that cut with a drum mower. In these studies, both in Australia and overseas, the principal advantage appears to be the wider swath width.

One disadvantage is that the forage drops to the ground with minimal disturbance, so the thickest and wettest parts of the crop remain at the base of the swath, on the ground. In very heavy crops, the base of the swath can be still very moist after several days unless the drying conditions are very good or the crop is tedded after mowing.