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21 Aug 2018
Buyer's Guide: What to look for in a used maize drill
Offering chain-driven seeding units or electric drive and individual row control, Kverneland’s Optima maize drill has stood the test of time.
Geoff Ashcroft outlines things to check when evaluating a used six-row mechanical drive unit.
Kverneland’s Optima precision seeder first appeared in the UK in 1994. Since then its design has changed little and follows a basic format of individual seeding units mounted on a frame via a parallel linkage.
Early versions used aluminium seeding hearts, which were superseded with plastic versions.
In addition, a fertiliser hopper with its own metering system provides placement down the row, while seeding is managed via a vacuum system to hold seeds on a rotating metering disc.
Row count includes six-, seven- and eight-row units, with a 16-row TF Maxi also available. Some early models could be found as four-row units.
Coulters
Our featured model is a 2013 telescopic, tractor-mounted model equipped with Suffolk seeding and fertiliser coulters. Since 2009, optional HD twin disc coulters offering a pressure of 130kg or 229kg were also available.
Kverneland product manager Graham Owen says: “HD II seeding units on the latest models from 2016 offer double cutting discs, with seed slot closed by 25mm V-press wheels in place of the earlier single press wheel design. Additional coulter pressure is also a feature of the HD II.”
A high-speed SX seeding unit was introduced in 2017 for working speeds of up to 18kph.
“The telescopic model was replaced by the Optima V in 2015 and remains a current drill,” he says.
“Its hydraulically telescoping frame can include six or eight rows, giving the flexibility to set row spacings from 45-80cm on six row models, and from 33-55cm on eight row drills.
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“The trailed TF Profi model is an eight-row, six-metre seeder,” he adds.
The seeding heart can be fitted with a choice of seeding discs equipped with 12x5mm holes to 96x1.2mm holes, to suit a range of crop types from beans to oilseed rape.
As a alternative to chain drive, E-drive electrically driven seed metering has been available for 25 years.
SEEDING MECHANISM
THE heart of the Optima precision drill is its seeding mechanism. This uses a vacuum to hold seed against the holes on the cell wheel seeding disc. For maize, the most common cell wheel is a 40/50, which uses 40x5mm holes.
Some maize drills were fitted with 32/50 cell wheel offering 32x5mm holes and will result in a slightly slower forward speed.
Remove the cell wheel to check the vacuum interrupter behind it.
This can become clogged with dust, reducing its ability to block the vacuum and release seed at the correct moment.
Using a toothbrush is a good way to clean the interrupter, and also to clean the optical eye which counts seeds. The holes in a cell will barely wear but check the seed deflector plate is in place – it is needed to suit the use of small, medium or large seeds and is a critical adjustment for seed flow.
Consistent
Inspect the main singulator arm – its position is key to knocking excess seed off the cell wheel. Also, check the secondary singulator so it centres all seeds onto the hole. This will ensure consistent plant spacings down the row.
Finally, turn the metering units by hand with a spanner to check they have not seized.
FERTILISER DISTRIBUTION
FERTILISER distribution is via metering rollers. Remove the securing plates and inspect their condition. If these are damaged they will need to be replaced.
Also, if the fertiliser hopper has not been cleaned properly and allowed to thoroughly dry, fertiliser dust can solidify and seize the unit.
Left unchecked, this has the potential to damage the gearbox when started up in spring.
Inspect the fertiliser distribution pipes for cracks or splits, replacing any which have failed.
Check there is a generous selection of sprockets inside the gearbox cover, along with a chart, to allow seed and fertiliser rates to be varied.
Pressure
Tyre pressure on this mechanical drive version is critical so it is important tyres and bearings are in good condition. Pressures above or below the 1.4 bar inflation pressure will change the rolling radius, confusing the monitor and affecting the seed rate. Check and adjust if necessary.
CONSOLIDATION
STANDARD 370mm press wheels were fitted, with 500mm version available as options.
The larger wheels help create a more consistent sowing depth and better consolidation on lighter soils.
Inspect tyre condition and turn the wheel to assess bearings. Check scraper condition too.
Ahead of each wheel is a furrow closer. Some operators tweak their furrow closers, putting them closer together, but doing so can lead to excessive dragging of soil, which can impact on seed spacing.
Depth
This also creates a wave of soil ahead of the press wheel, which affects sowing depth and consolidation, so check there is a 125mm gap between closers.
Similarly, worn furrow openers behind the coulter can see their lower edges being folded inwards, giving somewhere for the seed to ride, instead of being accurately placed into the slot.
Replace them if there is any doubt about their condition.
CHAINS AND SPROCKETS
WITH a mechanically driven seeder, chains and sprockets can be subjected to harsh working conditions.
So pay particular attention to the condition of these elements.
Also inspect the tensioners too, and ensure idler rollers rotate freely. Replace any which offer resistance and excessively worn chains and sprockets will need to be replaced too.
Frame
Seeding units are suspended on a parallelogram frame, so check pivots and bushes for wear. They can be mistakenly over-tightened, restricting movement.
Finally, power up the control box to check for faults and functionality.
The control box also holds a total area counter, so you will know how much work the drill has really done.
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