The Picking Head Shaker Bars


The main feature of the picking head is the stacked shaker picking rods inside. I call them rods or bars, but technically they are shaped with a taper at the front and a full return curve at the rear, and are better described as arms.

These arms have the greatest effect on the vines and the resulting quality of the fruit sample. With an inexperienced driver, they can be partly responsible for the breaking of posts, tearing out strainer posts, ripping out vines, and damaging the machine itself.

A picking arm axle can break lose, resulting in the arm swinging around and beating the lower fan casing so hard that it will compress it to the point where the fan will jam solid in its housing.

If it can do that amount of damage to itself, spare a thought for your vines.

The preference is for only 3 to 4 picking arms per side, but the height and position of the fruiting zone will determine this. Using a lower number of picking arms pairs results in the shaking force applied over a smaller area, and increasing them in this force being applied over a greater area. Pellenc recommend the arms centered at 130mm, but this can vary if required. Difficult early season crops would require arms centred from as low as 90mm to 110mm, whereas later in the season could see an increase from 120mm to 150mm.

activ_head_shakers

Shaker system & picking arms.
Courtesy: http://www.pellenc.com

The shaker arms are mounted via rubber-isolated axles to a pair of shaker poles. If the shaker axles are not of a similar age or condition, then the newer one will not only wear out faster, but the effectiveness of the whole arm is somewhat compromised. If there is one or more arms that have loose axles, the picking process is compromised further and this may result in the driver needlessly increasing his settings to offset this.

Not only does low picking arm centres significantly increase the pressure on the vine (used on early or difficult crops), it may also allow lower shaking parameters. An aside, an increase in the height of the lower arms to the bottom tray reduces fruit loses through the collector plates. It is not generally advisable to alter these heights for every individual vineyard, but an awareness of this increase your knowledge of everything that can be altered of adjusted here.

The action of the picking arms are controlled in-cab by 5 settings. These are as follows:

  • Pinch, controls the ‘press’ or ‘squeeze’ on the canopy.
  • Amplitude, controls the stroke or distance of the shaker bars.
  • Acceleration, controls the speed² or the acceleration of the shakers towards the canopy.
  • Frequency, controls the cycles per minute.

To begin, setting the pinch is the easy part. It’s an estimate and usually only requires altering one way or the other depending on the width of the canopy. It is measured in millimetres, and essentially is the space allowed for the vine to pass through. I usually have it set somewhere between 20-40 (for young vines) and 60-80 (for more mature vines).  This setting can go up to a maximum of 240, although for heavy mature Scott Henry vines I’ve harvested, this has not needed to be higher than 120. If the pinch is too wide, the picking arms will slap the vines causing significant damage. If it is too narrow, you will notice the canes being dragged forward, in the direction of the harvester. Rookies would frequently set this to the canopy width, instead of the width of the fruit zone – which can include the cordon area.

Amplitude is the nasty one. In hydraulic ram terminology it is the stroke. An operator on a setting higher than 100% could very well be out of control and if inexperienced, could be causing damage to machine and vines. I usually prefer a setting anywhere from 65% to 95%, although this depends on the variety and time of the season. For example, pinot at the beginning of the season is difficult to get off at times, and may require a setting close to 100% (I usually never go over 100%). Mid-season, amplitude can drop to 75-80%. Sauvignon and chardonnay should be set at about 80-95%, dropping to 55-75% later in the season. Late harvest varieties can be picked with settings as low as 45%. For reference, 100% amplitude results in a 150mm movement of the arms.

Acceleration controls the speed at which the arms come in to the vines. It is used to change the dynamic shape of the shaking rhythm, and only should be used when an operator understands the full implications of the amplitude versus the frequency (or cycles, discussed later). A mechanically driven picking arm / shaker mechanism that relies on an offset pulley and chain drive has a built-in acceleration of 15, corresponding to the Pellenc SMART System as 100%. It is therefore assumed that using this feature within the 0-15 range only has a minute discernible effect on the picking result. Settings above 15 begin to have a more significant effect. The more accurate description of acceleration would be ‘the punch’.

The frequency setting controls the number of cycles per minute the picking arms move from their start position to the full stroke of their amplitude and return. Early season settings may be around 500-510, but after a few weeks and depending on the variety, these values can be lowered to 475-490 and sometimes even lower.

Shaker_arms_2

Shaker picking arms.
Courtesy: http://www.pellenc.com

Those are the four main picking arm settings that are used to control the picking head via the controller.

The fifth setting I referred to earlier, is actually the ground speed. This has a direct influence on the frequency setting, and a skilled operator can often use speed as a method to control the frequency setting, in addition to altering the SMART controller. Many times I increase or decrease my speed to influence the frequency setting. Combined with the effect of the ambient temperatures, speed and frequency will and can vary throughout the day.

In addition to these, post detection is another feature whereby the operator can make adjustments to the picking arm settings, such as when a post is detected. There are various settings to achieve this, including altering  the aforementioned four main settings, to a range of sensitivity and the zone or range whereby the changes are made – from 50% of the picking rod area to 150% of the same.

It should be pointed out here that the shaker arms very rarely break posts. There are some specific conditions where this can happen, but in most cases – post breakages are generally the fault of the driver. Old posts can become both brittle and rotten (dry or wet), can be from inferior timber quality, or the remains of forest fires – common in Australia. The operator needs to be aware of this.

This introduces the discussion of the SMART controller, and typical settings.

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One response to “The Picking Head Shaker Bars

  1. Pingback: The Rear Visual Effects | Musings of a Know-It-All

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