With a choice of sizes to suit everything from a one-man silage-making operation on an upland farm to a professional contractor serving several customers, modern silage wagons have the capacity to a provide an efficient cut-and-haul grass harvesting system in almost any situation.

The concept has developed from the relatively flimsy, modest sized machines of the 1970s originally designed to gather hay in bulk, into the robust, fast-working, finer chopping and speedy hauling designs of today.

These big boxes on wheels pick up and slice grass destined for the silage clamp at remarkably fast working speeds. They also demand relatively little power and go about their business a lot more quietly than a roaring forage harvester.

Dutch manufacturers Schuitemaker and Veenhuis adopted the combi approach some years ago and have been joined by Pottinger and Strautmann with self-loading wagons that can also work as high volume silage trailers.

This involves building the load-carrying box tough enough do away with stabilising cross bars and other paraphernalia. When not required to pick up grass, they can be used to service a forage harvester in grass and maize crops, with hydraulic fold-down front panels giving the tractor driver a clearer view of the filling process.

The ES self-loading forage harvesting system from JF-Stoll is novel for combining a wagon and precision chop forager.

Thanks to its adjustable spout, this outfit can load trailers pulled alongside as well as its bunker. Also, precision chopping means being able to pack more grass into the trailer for haulage and into the silo for storage than with the longer chop produced by traditional forage wagons.

Comparing other features reveals there are more similarities than differences between the various machines.

Pick-up design

Apart from Pottinger’s flexible design, claimed to give more effective contour-hugging performance over undulating ground, the main novelties in swath pick-ups are the cam-less designs from Krone and Mengele and the trailing reel layout of the Schuitemaker Rapide.

The cam-less pick-up is simpler thanks to the lack of moving parts and can operate up to 30% faster, says Krone, which should mean faster working speeds are possible.

Schuitemaker’s pick-up is positioned further back than usual and lifts the crop into the star-shaped rotor that forces the material across the crop-slicing knives.

The installation is not only reckoned to be simpler and more compact, it also means the blades are more easily accessible. Instead of having to clamber beneath the machine, the small triangular blades can be lifted out for turning or replacement from above via a lift-up cover.

Crop slicing

While the Krone Titan and Pottinger Euroboss continue to use a series of cam-actuated rakes to feed crop over the slicing knives into the body, most have switched to the simpler and bigger capacity spiral rotor system as used on big balers.

Larger capacity models tend to have more rows of fingers to get the crop shifting quickly into the haulage compartments. Some are welded into place to create a single structure others are slotted into the rotor tube in segments for easier replacement should they become bent.

Drive to the intake rotor from the bevel gearbox and cross shaft at the front of the wagon is by chain transmission on medium-performance machines and by oil-bath spur gears on larger, high-performance models.

In most cases, the knife bank is retracted by hydraulic cylinders to give service and maintenance access or to temporarily clear the way for a plug of grass. On the larger Claas Quantum wagons, the complete intake throat can be opened up by 8cm to help clear a blockage.

Bed conveyor

An auto-load system makes the operator’s life easier by triggering the floor conveyor to move a few centimetres whenever the grass piling up inside reaches the top of the front panel.

While smaller wagons make do with two-chain conveyors and full-width slats, larger machines have a pair of two-chain conveyors or scrapers to cope with the added weight – Pottinger’s Jumbo Combiline dual-purpose wagon has a six-chain design to match its high capacity.

Fitting hydraulic drive to both ends of the drive roller is another feature of some bigger forage wagons, as is a two-speed arrangement that gives maximum speed for unloading or maximum torque to shift especially heavy loads.

Discharge rotors are mainly used to give a progressive flow of material when driving over the silage clamp in the continental style but can also be useful in conjunction with a cross conveyor for zero-grazing systems.

Running gear

With a lot of weight to carry, tandem axles carrying generous tyres are essential. Most include some form of leaf-spring suspension to help road behaviour and the biggest models from Pottinger and Strautmann can be had with triple axles to spread the load.

Fitting 26.5in tyres for added flotation is a more common option, although they have the disadvantage of pushing an already tall structure further away from the ground. Hydraulic levelling/stability cylinders help maintain stability across slopes and during turns when hauling at speed.

• You can see many of these machines at Grassland and Muck 2008 at Stoneleigh Park, Warwickshire on 21-22 May. For more details visit Grassland Event.