TYRE TECHNOLOGY ▶▶▶
fitted with track tyres first and then with com- parable radial tyres. An extensive vibration test was also performed. The measurements show that the PneuTrac does not perform any better than a standard TM800 tyre. Remarka- bly the test drivers rated them higher despite that. They experience a comfortable rocking effect, and the PneuTrac absorbs the greatest impacts. To do this, however, requires rela- tively low pressure of 0.6 bar or less. In spite of that low pressure, the PneuTrac remains extremely stable, and the tread stays in line with the trim. Even so, something remarkable occurs in this vibration test. Comparing the test results of the PneuTrac and the radial tyre against previ- ous vibration measurements with narrow track tractors, we see a significant difference. The state-of-the-art TM800 and PneuTrac tyres absorb vibrations upwards and down- wards far more effectively than the smaller and firmer standard tyres of narrow track trac- tors. At high speed, vibration is reduced as much as 60%. According to the vibration test team, this significant difference determines whether or not the driver suffers back prob- lems in the longer term. This test shows that spending a little more money to ensure a good tyre not only benefits the soil, but also
provides significant benefits for the driver’s comfort and health.
Misconception load capacity The size of the air chamber in a standard tyre correlates directly with its load capacity. Which means that the higher the speed and the high- er the load, the higher the air pressure needs to be. The air in the tyre determines both the hori- zontal (lateral) and vertical (longitudinal) sta- bility, since the air exerts downward pressure on the tyre (from the trim outwards) while at the same time pressing the tyre into the edge of the trim. These facts do not hold true for (mechanical) tracks, because they have no air chamber. A track undercarriage gains its stability from the struc- ture of the undercarriage: the heavier and larger it is (such as supporting wheels, large drive wheels), the greater the load it can support. And then there’s the PneuTrac, which does have an air chamber half the size of that found in a standard tyre. It’s air pressure only affects the vertical (longitudinal) stability, not the hori- zontal (lateral) stability. Just like a track, the PneuTrac gains its stability entirely from the structure in the sidewall. The hinged sidewall could therefore be considered a hybrid tyre, or indeed a hybrid track.
PneuTrac beats steel track
In Montespertoli, Tuscany (It), a New Hol- land T4.110N narrow track tractor has been running on a set of PneuTracs since April 2018. The challenge in the vineyard there is to have traction in the slippery clay, particu- larly when the subsoiler penetrates the soil or when a 1000 litre-capacity sprayer needs to be pulled up the slippery hill slope. “We have noticed more grip and more stability in particular, and especially when turning on a steep slope on the headland,” says driver Salvini Lorenzo. “With standard tyres, we sometimes had to leave those areas alone, but with the PneuTracs on, you can carry on for longer. They really make you feel safe.” A demonstration of subsoiling between the rows of vines began with a tractor running on steel tracks. The 5.7 metric tonne-New Holland TK4050 had difficulty staying
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upright, and the tracks became caked with the heavy clay. When the driver steered to adjust, one track sometimes stayed com- pletely still, which is another factor limiting traction. Then the subsoiler moved to the conventional 4.1t narrow track tractor on PneuTracs. Three aspects struck us: firstly, the driver experiences far greater comfort and fewer jolts. Secondly, traction always re- mains intact, even when steering to adjust. And thirdly, the PneuTracs remain practically clean. “In the past, it was impossible to do this work using conventional tyres,” says Mr Salvini. “We had to work with the steel tracks. But this is far more convenient. What’s more, you don’t need an additional tractor with a trailer to transport the tracked tractor. I get on site more quickly and the work is finished sooner.”
▶ FUTURE FARMING | 22 February 2019
This is what posed the major challenge for the tyre manufacturer Trelleborg. The innovation lies in the tyre’s ‘hinge’: it must be stable, have a long service life, and provide as much stabili- ty as the mechanism in a track undercarriage. That’s why production began initially with the small 18 and 28-inch track tyres (2019), and quite some time later with the size 650/65 T38. Head of Development Piero Manchinelli ex- plains: “We intentionally started in the small segment with tyres that are sold to winegrow- ers. They require stable tyres that not only pro- vide traction on inclines, but are also less likely to damage tree roots.” Looking back at all the tests and experiences with the PneuTrac, we were surprised about the high level of traction, and we know that the track tyre does not need to have a larger footprint or a higher level of comfort. What was still striking, though, was that the test drivers in Italy and during the testing in the Netherlands perceived a much higher level of comfort. The PneuTrac is quite at home with low tyre pressure: that is where it excels. When pressure increases, the track tyre behaves in exactly the same way as a conventional tyre. That’s useful if you still have a few days of transporting work to do, but it’s not what the PneuTrac is intended for.
Left the 4.1 ton New Holland T4.110N on Pneutracs, right a 5.7 ton TK4050 on steel tracs.
Mr Salvini’s boss also mentions the diesel saving, and of course that a tractor on Pneu- Tracs is much cheaper to buy. On a full work- ing day (four sprayer tankfuls), the tractor on PneuTracs uses 29 litres of diesel, while an- other identical combination uses 40 litres. That equates to a saving of 33%. Mr Salvini puts it down to the fact that the PneuTracs have lower slippage.
PHOTO: BAS VAN HATTUM
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