Kivi-Pekka stone picker

By: Jaiden Drought, Photography by: Jaiden Drought

Date: 18.05.2011

The Kivi-Pekka stone picker is a pioneering machine that does two jobs at once, which technically halves the amount of time it takes to rid a farm of rocks, increasing land productivity

Kivi-Pekka stone picker

• One-man machine
• Solid construction
• Adjustable contour wheels
• High bin lift
• Extra soil sleeve to capture excess soil

In certain regions of the country, rock picking is a major job every time land is turned over, and something that can dramatically increase the productivity of farm land.

Rock pickers pick up rocks and throw them into a holding bin. When this is full the rocks are loaded into a waiting trailer. If the paddocks are very rocky the bin can need emptying every 20m – with speeds often not breaking 2km/h, it is painstaking work.

Usually a paddock is sprayed out and worked up with discs, and followed by a spring tine cultivator (rototiller), which brings most of the rocks to the surface. Rocks over 30cm in diameter will be removed with a tractor loader as these are too big for the picker to handle. Then a rock rake, which (depending on the size) will have one or two drums with fingers in a spiral shape (like a rotor in loader wagon), will move the rocks into a windrow for the picker to come along and follow the rows like a baler. The picker scoops up the rocks into the bin, filling chasing trailers. Then rocks are then dumped, usually used as fill.

This is very time consuming as you need to do two passes, either with separate tractors or by hitching and unhitching the rake and picker so the same driver can do both. There is a certain amount of care and accuracy needed, so you can appreciate that it is very hard on the gear.

The test

I tested the 5m Kivi-Pekka stone picker, designed and built in Finland, with Country Machinery Ltd in Sanson as the sole importer and distributor into New Zealand.

Why is this machine so much better than the rest? Because it does two jobs at once. One tractor, one operator, two jobs and technically halving the time it takes to do the job. The Kivi-Pekka is the only machine in New Zealand that rock rakes and picks at the same time, which is why it is a pioneering machine.

Soil sieve

Most rock pickers have a sieve where the stones are scooped off the ground to minimise the amount of soil in the bin, however the Kivi-Pekka has an additional soil sieve located on the back of the storage bin.

The sieving process happens in the tipping stage, when the bin is sitting 90 degrees to the ground, and the grated back wall of the bin allows the soil to fall into the soil container.

Drawbar attachment

The stone picker is attached to a tractor by the drawbar instead of a two-point hitch system, with the working depth adjusted via a hydraulic ram. This mounting system reduces wear on the PTO shaft and ensures that the working depth is constant or can be adjusted by the tractor’s hydraulic remote.

Drive system

Both the lifting drum and the rock rowers are all driven by separate strengthened belts.

According to the company, power is transmitted via drive belts, which absorb the shock from the stones when they come into contact with the machine. This is true, and they absorb the shock by slipping occasionally if they make contact with a large rock just under the soil’s surface that can’t be flicked out or if the machine is set too deep. Although it slips relatively often, if the operator is watching this would be causing minimal damage, plus belts are cheaper to replace than slip clutches.

The remainder of the drive-train is heavily built and very sturdy. Oversized SKF bearings are used with easily accessible grease nipples.

Lifting drum

The lifting drum on the test machine was 113mm wide and is where the rocks are pushed over the sieve to remove excess soil before being thrown up into the bin. The physical throwing of the drums is achieved with 12mm x 45mm tines, which have a maximum working capacity of one tonne per minute. The tines work very well but in extremely rocky conditions they will break, and at $70 a pop, your running costs can increase considerably if you are also replacing belts.

The flipside to that, of course, is that the heavier the rotor is the more power you need and the strain on other vital components is increased. To give you an idea, we broke one tine on the 4ha job during the test in what I would call only medium sized river stones – however there are 28 on the drum so you don’t have to replace broken tines immediately.

Rake wing lift

This is achieved by a single ram that is positioned vertically and lifts each individual wing on a pendulum type set-up. This works well and the machine can be folded for transport in 20 seconds without leaving the cab. The wings are dropped by pulling the a string that lifts the locking arm in a similar fashion to that found on a swather or folding power harrow. Once lowered, they have individual adjustable stoppers to allow floating over humps and hollows, with depth adjustment during operation done via the hydraulic drawbar.

Other features worth mentioning:

• High 1.7m bin tipping height
• Rake wing jockey wheels
• Toolbox and crowbar
• Large wheels
• Low power requirements
• In-cab monitor

See rock pickers/ rakes for sale.

Specifications

Keep up to date in the industry by signing up to Farm Trader's free newsletter or liking us on Facebook