Noel Mackenzie: The science behind course machinery

Seamus Rotherick
By Seamus Rotherick October 17, 2011 15:30

This article takes us to a slightly different perspective at a level we seldom look at on the course – right down to a few millimetres off the soil surface. But for a change we are looking at the ‘doing’ bit rather than the ‘end result’ bit of mowing and other mechanical operations. Those expecting an intricate article on the benefits or otherwise of close cutting on grasses should look away now … unless you find your appetite whetted by something less than expected?

The business of managing fine turf for good putting green speeds is demanding and at nearly all courses these days it is a 365 day-a-year operation with around 2.5 hours of triple mowing undertaken per day as an average for 18 holes. Treble that figure for hand cutting! Beyond the mowing the other fine turf mechanical treatments undertaken to condition turf and maintain or improve green speeds include: grooming, brushing and rolling. For this piece the focus is on what happens to the mechanical tools we use and why we should be concerned about events so small we cannot see them.

Mowing is carried out more than any other maintenance operation and, perhaps because of this, it is the most frequently taken for granted operation. Both agronomists and greenkeepers can easily overlook its significance in the overall scheme of things and players and club managers seldom give it a second thought. Day in, day out, on the putting surfaces the mowers whirr away trimming and taking away the cut leaves. So much of greenkeeping revolves around this work and its implications for the rest of the maintenance programme, for example, if clippings were not taken there would be no need to fertilise; how cutting height affects species composition and so on.

One very significant implication is the effect that cutting has on the grass. The closer the cut the more the grass has a tendency to spread its growth laterally over the surface to ensure sufficient leaf area for optimum growth. The downside to this situation is that this tends to slow the putting surface. The laterally growing leaves slow the passage of the ball by increasing friction on its surface. To maintain speed in the greens and to reduce the chance of dead leaves being trapped in the soil to form thatch, routine grooming and verti-cutting work are completed to help stand the leaf blades up and achieve better cutting.

The greens mowing, aside from less frequently used pedestrian units, is most commonly undertaken using a triple machine, meaning it has three ‘floating’ heads that follow the contours of the ground closely. Each head contains a cylinder mower unit that cuts in the region of 160-200+ cuts per metre that the machine travels forward. The cutting system is therefore subject to enormous wear and tear. Beyond the cutting system the engine and hydraulic drives that work the cutting heads also see a lot of wear and tear but this tends to be an area covered by routine maintenance schedules and servicing. All this wear and tear means that many machines only remain on front line (and by that we mean daily mowing duties) for a period of three years before being shifted to the position of second mower carrying verti-cut heads, rollers or similar attachments for a few more years before eventually being traded in or sold off. Wealthier clubs may just have a new fleet of machines rather than semi-retiring these three year-olds to less onerous duties.

STIRLING, UK – November 2018: A fleet of Toro specialist landscaping machinery has been used at Stirling Golf Club to keep the course prepared during its 150th Anniversary year. Pictured Greenkeeping staff with the Toro equipment. (Photograph: MAVERICK PHOTO AGENCY)

At the cutting end of things it pays to understand how the machinery works. In order to cut, the cylinder and the bottom blade have to be close so that as the cylinder blade passes over the bottom plate a ‘scissor cut’ is created. The tolerances are therefore very fine when adjusting the blades and if they pass too close then the surfaces will wear rapidly. Too far apart and the grass may not cut at all or be ‘stripped’ to leave a white and straggly finish that is very unattractive and renders disease attack more likely.

The material being cut is just grass so that is the easy bit right? After all, grass is not very hard to cut is it? Surprisingly grass leaves are actually quite tough and there are millions upon millions of them going through the cutting unit every time the machine goes out for its 2.5 hours or so of cutting each day. The leaf has a tough and sometimes abrasive surface and even good quality hardened steel will wear under constant contact with the grass alone. But there are more abrasive materials going though than just the grass.

Topdressing is a key element of keeping greens surfaces smooth and consistent which, in turn, aids the maintenance of speed on a putting green. However, the majority of topdressing material is sand, usually not particularly fine particle sizes either with many surfaces receiving material that is dominated by medium and coarse particles of 0.25-0.5mm and 0.5-1mm diameter respectively. After topdressing operations or any activity such as verticutting, scarifying, aeration and so on, sand particles can be more commonly found on the greens surface and even with careful brushing or using vibrating rollers some of that sand is going to go through the cutting interface of the cylinder blade and bottom plate. The silica particles are hard and scratch and score the metal surfaces reducing their sharpness. The sand also gets into bearings and other moving parts and causes significant wear in these areas too.

To combat this, greenkeepers try firstly to minimise the presence of sand on the surface of the greens. Of course, this is not solely for the admirable purpose of protecting their beloved mowers, it is also necessary to ensure that the members don’t lynch him / her because the greens are covered in topdressing when they are trying to putt. Brushing and using the new generation of vibrating rollers to bed the sand into the base of the sward is a key element of this. Even the way the topdressing is applied is important and the newer topdressers that ‘fire’ the topdressing down and into the sward help in this area too.

Despite all these efforts there is no escaping the fact that a machine that is cutting grass at between say 3mm and 6mm is working very close to the soil surface and it is therefore impossible to avoid the sand getting into the blades and cutting cycle. To combat this greenkeepers have, for many years, ‘backlapped’ cylinders (applying a carborundum paste whilst reversing the action of the blades) to smooth the cutting faces and improve cutting quality. A significant number of clubs, especially those hosting important playing events, will own a grinder and the blades will be mechanically sharpened on site. Such work may seem excessive and certainly not all clubs could or should be expecting to afford such an investment but where events or standards of expectation demand, grinding is a very useful way of improving cutting quality and therefore helping to keep green speeds high. This is particularly so with ‘relief grinding’ which sharpens the blades so as to produce a clearance angle behind the leading edge of the blade (as ‘backlapping’ would), thus ensuring less wear and tear on the equipment but also a better finish and is widely used at top courses such as Muirfield, Carnoustie and Royal Lytham & St. Annes to name a few. High class facilities will use the grinders to ensure that cutting is as near to perfection as can be achieved.

Machinery issues are so often seen in terms of budget prices for approval by committee or in terms of replacement cycles but looking beyond this it is possible to see the need for ‘joined-up-thinking’. Key items are:

• The quality of metal used in the blades of the machine you are using / buying.

• The effectiveness of other machines, for example firing in topdressing below the sward canopy.

• Timing operations to minimise sand presence on the playing surface, for example the use of brushing after verticutting, vibrating rollers after topdressing, and so on.

• Maintaining blades and other equipment in a manner to optimise its operational efficiency through routine servicing.

Thus, the case for ‘joined-up-thinking’ is strong and demands not only that a course manager or greenkeeper knows his machines but also how to extend their life, to fit their capabilities into the way the course responds to the environmental conditions and to manage their maintenance effectively by scheduling in servicing and so on.

This is not always an exact science but one that is usually achieved with experience and resources.

Seamus Rotherick
By Seamus Rotherick October 17, 2011 15:30
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