Review: Alpego DK 400 power harrow
Brent Lilley believes that using the right equipment for the job (like an Alpego DK 400 power harrow) is essential.
As the days get longer and soil temperatures get warmer, I'm sure there are a few of you out there who have already started cultivating ground for summer crops. Whether it's maize, turnips, grass or something else, you can't afford to cut corners when preparing the soil for planting. If you don't put the effort in at the beginning, it will certainly show up in your crop yields at the end.
Nearly every farmer or contractor harbours their own opinion on the best practice for establishing a crop, whether it's minimal till direct drilling or conventional ploughing and cultivation. If you do go down the cultivation road, then in my opinion the power harrow is the best finishing tool for the job, although not always the most economical option.
With that in mind, let me tell you about a power harrow I recently spent time testing, and which offers some very impressive features - the Alpego DK 400.
Trevor and Elly Lalich recently bought the Alpego from Piako Tractors in Morrinsville to replace their older 3m Amazone. The couple run a farming and contracting operation near Waitoa in the Waikato, so we headed there for our test. The test ground was a paddock with a loamy silt soil which was being prepared for maize in a couple of weeks' time. The land had been ploughed and spread with chicken manure prior to a finishing pass with the power harrow.
Alpego power harrows' range from 3m through the 7m. The Alpego DK 400 is a 4m, twin-bed folding model. For the test, the power harrow was attached to a 200hp Fendt 820 which had more than enough power for the job. However, the Lalich's plan to mainly use the Alpego behind a smaller John Deere 6930 which will still be more than suitable.
So far, Trevor and Elly have been more than happy with the Alpego's performance and as Trevor eloquently puts it, "You only need to look at it to realise it's built like a brick---------." Er, yes well, you know the rest.
The power harrow is mounted to the tractor's three-point linkage on a solid box section headstock, with CAT three pins. The two beds of rotors that make up the 4m width are also carried on a box section frame to take the stress off the bed of the power harrow. A single pin is used in the centre of this frame to attach the folding arms from the headstock, allowing the rotor bed to be fixed level or with the removal of a locking pin to float laterally and independently of each other. It's hard to say if this is of any benefit as most of the time you want a power harrow fixed solid to create a smooth level seed bed, but the idea might have some merit on hills or undulating ground. Two hydraulic rams take care of folding the beds up into the transport position and there is a lock to stop it opening, which is operated with a rope from the cab.
The skids plates on each side of the machine are held in place with solid rubber dampers that allow enough movement to prevent damage and have a greater lifespan than the steel springs that are common on most power harrows. All the steel used in the machine is high quality Swedish spring steel that will stand up to the demands and harsh conditions power harrows are generally used in.
The power from the tractor comes though a heavy duty driveshaft with a cam clutch to the main 300hp rated gearbox in the centre of the machine, where it's split and transferred through a driveshaft to a 90 degree gearbox on the bed on either side. It's great to see that the pivot in the universal joints on these drive shafts line up exactly with the pivot points where the machine folds, thus eliminating any damage-causing stress on the driveshaft and joint.
A handy feature in the main gearbox is the ability to change the gear cogs in the 'box relatively quickly. Adjusting the speed of the rotors to suit the conditions is pretty easy; you simply open a plate on the back of the gearbox and change the cogs, allowing the rotor speed to be varied from 150-450rpm.
A fast rotor speed will be more beneficial in heavy ground and tough conditions, whilst a slower rotor speed can be used in easier conditions, which will also lower power requirements and, as a result, your average fuel consumption.
Bed and rotors
As the DK 400 model is a folding machine, it uses two separate rotor beds that are constructed in the same way as all models in the Alpego range. The rotors in the bed are driven through bevel gear cogs to reduce the amount of friction, meaning the machine runs quieter and doesn't require an oil cooler. A shaft drops down from the rotor gear cog through two conical bearings to the rotor. Having these two bearings below the rotor ensures that they are always fully immersed in the semi-liquid grease that is used to lubricate the rotor bed. A double oil seal is used under the lower bearing to keep the grease in, and a double labyrinth seal is machined into the inside of the rotor to keep debris out. Alpego is confident that this set-up won't fail and they cover all the seals as part of their two year warranty on the machine.
So, more or less rotors on a power harrow? Opinions on this will be split, but Alpego runs with the theory that having more, smaller rotors is better. They have spaced the rotors at 250mm, unlike some other manufacturers that use larger rotors with 300mm spacing's. For Alpego, having the rotors at 250mm means there are 16 rotors across its width. This, coupled with the fact that the tines are timed at 98 degrees to the rotor rather than 90 degrees, means the tines break into a smaller amount of fresh ground in front of the machine one at a time, which lowers the overall power requirement needed.
Quick-fit tines are an option on all Alpego power harrows, although the owners of this particular machine feel they're unnecessary as tines can be changed easily with the machine folded. The Lalich's did however opt for tines that are double dipped in a tungsten coating for a longer lifespan.
Levelling bar and roller
The machine uses a well-built large diameter packer-roller on the back measuring 520mm in diameter. This helps avoid creating a wave in the soil like smaller rollers can do in some conditions. The roller uses adjustable tungsten-coated scrapers to keep it clean, which in turn leads to a longer lifespan and less regularly required maintenance.
But what I consider a stand-out feature of this machine is the levelling bar. The roller is connected to the back of the power harrow with a four-point parallel linkage. Here you can set both the height of the roller and depth of the power harrow. The levelling bar is then fixed to the roller linkage with screw adjusters, allowing it to move up and down with the roller.
At the end of a run it still held the soil in the rotor as it normally would, but when I lifted the power harrow up the roller (and therefore the levelling bar) stayed on the ground a little longer, levelling out that last bit of soil from the rotors. It also got rid of that lump of soil that most power harrows leave at the end of a run.
I really did struggle to find faults with this machine. Although the ground I worked it on wasn't the toughest, I could tell by the way the Alpego DK 400 is built that it'd do a great job on much rougher terrain. For the test though, it did a very satisfactory job and left a nice smooth seed bed.
The design and build of the machine is impressive with every part made from high quality steel. Features like the steel frame for carrying the beds, the rubber dampers on the side skid-plates and that unique levelling bar fixed to a parallel linkage which holds the roller, all combine to place this machine well apart from its competitors.
For those of you with a lot of acres of ground work ahead of you in the next few months, and who might own a power harrow that's looking past its best or not wide enough for the job, I would definitely recommend you check out an Alpego implement. If you're as impressed as I was, you might just end up taking one home.
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