It’s not just the 14.5m working width of the fully mounted GMD15030 that’s impressive. It’s more how the Kuhn engineers have managed to fold the mower into a neat road-going package. Now that takes some doing.

KEEPING IT BRIEF

  • The mower driveline uses new patented gearboxes.
  • There are several hydraulic rams working together to ensure good contour following.
  • Where possible, Kuhn has used existing components such as the headstock and mower beds.

Last summer, Kuhn launched the widest working mounted mower model, the GMD15030, that can clear a 14.5m path on every pass. We had a chance to drop several acres with it, and it didn’t take long.

Straightforward attachment

Already sitting on the shelf was the heavy-duty headstock, the same one that is used on the triple mower conditioners. This Cat III unit is spot-on for the near 3.8t four-gang mower. Welcome additions are the integrated parking stands, which mean the GMD15030 can be unhitched while it is still folded up. Previously, these slot-in park legs were only available separately. 

The boom bears the entire weight of the hefty 3.8t machine and features hydraulic suspension. Two pivot points cleverly allow it to breakback if it encounters an obstacle.

Kuhn completely redesigned the left and right mower arms so that they can support two cutterbars. Massive bearings form the inner pivot point for the ladder frame style arms, with a central hydraulic ram used for folding and also lifting at the headland.

The mowers butt up to each other at the pivot. The hydraulic ram relieves pressure on the outer unit.

Beast of a box 

But the pièce de resistance is the specially developed double gearbox, which is mounted horizontally on the end of the arm; it also acts as the pivot between the inner and outer mowers. This clever bit of engineering, manufactured in-house at the Saverne factory, is how Kuhn has been able to make the GMD15030 work.

This gearbox serves as both a way of transferring drive and as a hinge point. Together with the hydraulic Lift Control system, it also aids contour following while mowing.

The design allows the outer mower to fold through 180⁰ as it changes between modes, transport and work. But the main job is to transmit the tractor power and ensure that the two mowers on each side of the machine work in synch. The cutterbars are inline, rather than offset, so being synchronised is absolutely critical to preventing any missed strips.

A closer look at the bespoke gearbox that allows the mower to fold so neatly.

Power flows from the tractor into a central gearbox, which splits it to the left and right. On each side there is a friction clutch, another driveshaft, a right-angle gearbox with an overrun clutch and then one of the patented pivot gearboxes mentioned. Inside this gearbox runs a central shaft with two branches. The first drives the outer unit via a gear bevel, the second drives the inner mower. 

Familiar beds 

Everything that follows is identical to other Kuhn non-conditioner mowers: OptiDisc Elite gear driven beds, each with seven discs, the Protectadrive safety system with a shear point on the disc drive, a 3.0-6.5cm cutting height (up to 8.5 or 12cm with the firm’s optional high-cutting skids). 

On each side of the machine there is a left-hand and a right-hand driven cutterbar. This configuration means that Kuhn can also utliise its standard off-the-shelf drive system without any modifications. Conveyor drums between both mowers prevent material building up here. Flexible plastic guards protect the mower ends, resuming their original shape after hitting an obstacle. 

Contouring and suspension

Ground pressure control comes from Kuhn’s proven hydraulic LiftControl system: the arms carry the full load but are hydraulically suspended. However, because there is an extra pivot point now in play, the pressure control had to be extended to the outer unit as well. Kuhn solved this issue with a small cylinder on each side which is integrated into the LiftControl circuit.

The pre-pressurised cylinders press down against the outer mower from below, lifting it in coordination with the upper pivot point. This way, the GMD15030 can relieve the stress on its outer mowers. At the same time, there’s sufficient inward travel, which allows the outer mower to adapt to ground contours. 

According to Kuhn, each mower can oscillate between –4° and +6°, and in the uneven field we could see how well it was able to follow the ground contours. At the headlands, the cylinders press against the outer cutterbar, providing stability when turning.

If the inner mower encounters an obstacle, it pivots backwards around its central pivot point, while the outer unit swings forward.

Damage protection

To allow the combination to avoid obstacles, Kuhn fitted two pivot points on each side so the mowers can swing clear. When the outer unit hits an obstacle, the entire mower combination on that side swings back and up — just as you’d expect.

When the inner unit hits an obstacle, the inner unit swings back in its central pivot point whereas the outer mower swings forward. We simulated obstacles using an irrigation shaft and were impressed at how well the system worked. 

This simple control box is used for operating the 14.5m mower.

Easy operation

At the headland, you only need to use one single-acting spool, while all of the other functions are pre-selected on the KFA12 control box and then worked from a double-acting spool valve. There is an ISObus, load-sensing hydraulic option for an extra £5,000 or so, allowing the operation of the front linkage mounted 3.1m wide GMD3125F to be more integrated. It can also be used with the 3.5m wide front GMD3525F where you can travel on the road with it.

For the road, the GMD concertinas itself into a sub-3.0m package.

Impressive width

The mower unfolds in less than a minute. Operators who are used to wide four-rotor tedders won’t bat an eyelid at the massive working width. One important thing that you need to bear in mind with the linkage- mounted mower is that even small steering twitching will result in considerable lateral movement.

We used the GMD15030 on a John Deere 6250R. It didn’t have any issues handling the mower — we had hills to contend with but not a lot of grass due to the drought conditions. As the rear mower is mounted close to the tractor, weight distribution isn’t an issue. Start-up torque is surprisingly low and barely higher than, say, a set of triples with a conditioner.

Combined with a 3.10m front mower, there’s still a 46cm overlap according to Kuhn. 

The combination is remarkably nimble and lifts quickly. Body roll is limited, so headland turns are swift. 

The operator, who was on his second season with the machine, confirmed all our initial impressions. The big combination delivers serious mowing work rates: up to 18ha/hr at 12km/hr (without including headland turn times).

Summary

Kuhn claims to have the widest working, fully mounted mower model, the GMD15030, which spans a massive 14.50m. 

A key part of the design is the horizontal gearbox arrangement, which also forms a hinge between the inner and outer mowers. There’s genuine user demand out there as harvest windows get smaller and skilled labour is increasingly difficult to find. We reckon the mower stands a good chance of finding its place in the market, particularly with large-scale farmers who are happy to operate a plain mower set-up.

Christian Brüse

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