Technical
Nigel Church is a Product Trainer with Cutting Edge Training, an operating division of Ransomes Jacobsen. A well- known and highly respected figure within the industry for over 40 years, he began his career as an apprentice at Ransomes, Sims and Jefferies in 1970 and has worked in the UK and Europe. In this article, he looks at maintaining cut quality between regrinds
I
n the last article, we looked at “how to extend the life of machinery, by adopting correct maintenance procedures”. This month, we will be taking a look at how you can maintain a good quality of cut between
regrinds on your cutting units. Hopefully, your machinery is in peak
condition at the start of each season. It is either a new machine, or a machine that has been fully serviced; as a part of that process, the cutting cylinders will have been spun ground to ensure they have been returned to a true cylinder, and the bottom blades will have been reground or replaced with a new set. It is what you do now that will affect the
performance of your cutting units until the next regrind.
The Environment
Cylinder mowers work in a wide variety of environments, and this of course has a considerable effect upon the condition of the unit.
Commercial Mowers
Some heavy-duty mowers, like the popular Ransomes Highway and Parkway models, are designed to work on roadside verges and housing estates. These 8” and 10” diameter cutting units are a much heavier construction than the finer turf machines and can take a considerable number of hard knocks before being damaged. However, it is vital that the operator takes the time to clear the area of litter before cutting, and notes any large debris items before running the cutting unit. It is also much easier to pick up litter when it is in one piece, instead of hundreds of bits after passing through a Magna cylinder unit! As well as avoiding the worst of the debris on
the work site, the way that the cutting cylinder is adjusted is crucial to the number of hours the blades will last before they need to be replaced. The cylinder should be free turning, without drag from the bottom blade. If it is not, then precious hydraulic cutting power is being lost in forcing the cylinder to turn, and therefore there is less power left to cut grass with. In heavy growth conditions, very light contact is OK, as the lush grass will offer sufficient lubricant to keep the cylinder running without overheating. When the growth rate drops off, and the grass dries out, then the cylinder should run with a
Nigel Church
slight air gap between the cylinder and the bottom blade. This prevents friction and heat build-up, which will take the temper, or the hardness, out of the bottom blade and leave soft spots. Any blades which are damaged in this way will wear very quickly, and will need to be replaced frequently. How do you set it with a slight air gap? Well, use a piece of paper like a feeler gauge to accurately set the gap. Office copier paper is rolled to a very accurate thickness (to avoid jamming when it’s used in a printer or photocopier), so it’s a uniform 3 to 4 thou” (0.1mm) which just happens to be the average thickness of annual meadow grass, so it’s ideal for the job! You can also use the setting papers available from your manufacturer, as pictured. This sounds like a real fiddle but, if practised regularly, setting the cylinder correctly soon becomes second nature. The difference in the cutting quality is very noticeable, as is the increase in blade life, so it’s really worth getting it right at the start of the season.
Bottom Blades
So, how long should a bottom blade last? Well, if correctly adjusted, a genuine bottom blade should last 300+ hours, or you should use two sets of bottom blades per season (on average). If set too tightly, then six sets of blades per season is not unheard of, but it is very poor practice, not to mention expensive!
The Cylinder
Of course, if you are wearing out several sets of bottom blades per season, the cylinder will also be seeing excessive wear, and they are much more expensive to replace than bottom blades. A 6k Magna cylinder should last two full seasons. If you screw the blades down tight, then you will have to replace the cylinders every year as well!
Get those blades up!
Every turn of the height of cut adjuster will raise the bottom blade off of the ground slightly more. The higher the blades are, the less they will contact the ground (scalping), and the less debris will travel between the bottom blade and the cylinder. Unless it is a sports playing surface, it does not need a close cut. There is a common misconception that
shaving the grass will mean that there is less on PC JUNE/JULY 2017 I 131
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156
