Self Propelled Sprayers in the UK
Farming News Update for 2012:
We have noticed a shift in interest towards smaller self propelled sprayers throughout 2012. Such a wet year has meant that real questions have been asked regarding the performance of hydrostatic wheel motors. Many manufacturers seem to favour small wheels and when they are fitted to a hydrostatic wheel motor, this can mean trouble, particularly when the ground conditions are wet. To counter this, some manufacturers have used a mechanical axle to enable a large wheel to be fitted. This has three benefits and one perceived negative. The first benefit is having a positive displacement of power - four driving wheels connected by shafts. The second is the ability to run the machine in the field at low rpm, therefore saving fuel and decreasing wear and tear on the engine. The third is the ability to fit a wheel with a huge diameter, which allows massive traction. A longer footprint reduces the ground pressure and when the going gets tricky, this means the machine can handle the worst conditions. The perceived negative is the clearance. For example, on a 3000 or 4000lt Bargam self propelled sprayer fitted with a 340 85 R48 wheel, the clearance is 800mm. On a hydrostatic machine, the average seems to be around 1000mm. If a sprayer drives through a crop of oil seed rape and the clearance is 800mm or 1000mm, when the crop is 2000mm it really makes no difference to crop damage. The machine with 1000mm of clearance will do the same amount of damage.
All forward mounted cab machines in the UK seem to hold a simlar value when it comes to the used sprayer market. However, mechanically driven machines exceed the norm. This general perception is that this is because the farmer is buying a machine without the worry of a wheel motor issues. This now appears to be swaying the interest towards the mechanical drive market. However, despite me believing that the 800mm axle clearance is perfectly workable, European manufacturer 'Bargam', now seem to have another option. A mechanically driven machine with 1m under axle clearance! This is achieved by portal drop axles. A simple geared axle which benefits from high clearance without the worries of seriously expensive wheel motor repairs. This does add cost to a machine, but the farmer has to weigh up whether the extra cost out weighs the 800mm clearance.
There is also a lot of confusion in the market as to ground pressure vs machine weights! It is fairly simple, although some manufacturers make a meal of it! Take a Bargam 4000lt mechanically driven self propelled with a 24m steel boom. The machine weighs around 7650kgs unladen. Then take a 3000lt hydrostatic machine with a steel 24m boom, this machine weighs around 7250kgs unladen. The hydrostatic would normally be fitted with a 320 85 R32 wheel and tyre. This wheel & tyre combination has an overall height of 1360mm (4' 4"). The mechanical drive machine (which can carry an extra 1000lt) if required would normally have a 340 85 R48 wheel & tyre combination. This actually stands with a diamteter of 1835mm (6' 1"). Therefore the weight is spread over 30% more contact area which, in turn equals a far lower ground pressure. When we look at LGP wheels and tyres, the story is the same. Average 4000lt hydrostatic LGP wheel & tyre: 600 65 R28. Average 4000lt mechanical drive LGP wheel & tyre unit: 600 65 R34 with the ability to fit a 650 60 R38 if the budget stretches that far. The other questions that must be asked when purchasing a larger self propelled like a 4000lt 30 or 36m machine is: when loaded, what is the total weight, and are the rowcrop wheels legally allowed to carry that weight on the road? Most 32" row crop tyres are not and some manufacturers seem to be turning a blind eye to this! Interesting times are ahead with saturated ground and new concepts for self propelled sprayers for 2013.
Below is an image of a high clearance Bargam 2500lt 'High Clear' machine with mechanical axles.
Posted on 11/12/2012
by the sprayer specialist