Bank on John Deere ProDrive’s pulling power

July 16, 2010 | By James Lane

John Deere’s ProDrive hydrostatic drive system for its foragers promises infinitely adjustable speeds and excellent traction, but does it deliver? SIMON HENLEY tracked down the first machine in the UK with the system fitted to find out.

THE UK’s first 7950 ProDrive, John Deere’s latest and most impressive self-propelled forage harvester to date, has been working in Carmarthenshire since the 2010 silage season started.

So far it has proved to be an impressive machine, but with whole crop and maize to come, there is a lot more hard work to do for the Deere range-topper.

The Davies brothers, from St Clears, own one of the largest grassland contracting operations in west Wales, and effectively keeping down costs to customers is vital. So their demand for efficient, productive equipment is, naturally, very high.

Lyn and Huw Davies have been impressed by John Deere’s self-propelled forage harvesters since they purchased a second hand 6810 in the mid-nineties. Since then, Deere foragers have handled all of their silage duties, starting with the first cut of grass in early May, working right through to late October in maize.

The firm currently runs two John Deere 7050-series foragers, a 2009 7850 ProDrive, and their new 7950 ProDrive – purchased in April from Deere dealer LAS Agric, Narberth, Pembrokeshire.

“This particular 7950 ProDrive is the first one to be sold in the UK,” reveals LAS Agric service manager Stephen Lawton.

“It is fitted with a 40-blade drum and the redesigned three-metre 630C header – featuring many improvements, plus an ability to pitch laterally, or oscillate.”

Significant feature

One significant new feature of the 7950 is its huge 19-litre Cummins engine. Producing an impressive 812hp, this engine gives the forager the potential for harvesting 300 tonnes/hour.

Like all John Deere foragers, the 7950 can be purchased as an ‘i’ model, fitted with HarvestLab dry matter monitoring system and JDLink – John Deere’s remote GPS-based performance management system.

Fundamentally, the 7950 is very similar to its predecessor, the 7850. The ProDrive transmission still handles both power application and braking functions seamlessly, offering infinitely variable speed control in both field (0-20kph) and road (40 kph) modes.

However, the addition of engine speed management on the 7950 means the power reserve of the Cummins engine can be used more efficiently.

In short, by automatically compensating for lighter loads, the engine rpm is reduced without losing forward speed, thus saving valuable fuel in the process.

“One of the features we particularly liked when we bought our 7850 was the Cummins engine.” explains Lyn Davies. “These engines have tremendous staying power and handle big crops without losing momentum.”

“We would have bought another 7850 if they were available, as we initially didn’t feel the extra power of the 7950 was necessary.

“We wanted another machine with a Cummins engine and the 7950 was the obvious choice.”

According to Lyn’s brother Huw, when the new forager arrived they were initially unimpressed. On flat land the Cummins 15-litre powered 7850 could almost keep up with the new model, but once they started working on gradients, the extra power of the 7950 soon became clearly evident.

Working on hills

“When you are working on hills and banks, she pulls ahead comfortably,” admits Huw.

“The extra power is also noticeable in heavier crops. In fields where there is 10-14 tonne/acre of grass, we have found where we used to run just one loader on the clamp, now we often need to run two just to handle the volume.”

Fuel consumption for the 7950 is comparable to the 7850, the big Cummins burning 1,000-1,200 litres/day – equating to around 12-17 litres/ha (5-7 litres/acre), depending on crop density. Working speeds of 12-15 kph are easily maintained in all but the heaviest crops, with an adjusted output of 200-250 tonnes/hour, chopping grass at 18-20mm in length.

“The big Deere certainly has a healthy appetite to feed too,” as Lyn Davies explains: “We normally row up with a 12.5-metre rake, but we tried the 7950 in an 18-metre (59ft) windrow. This pulled the harvesting speed down to a brisk walking pace of 7kph, but the machine handled it well.”

The Deere 7950 ProDrive has had a lot of attention this season around Carmarthenshire and its outstanding performance so far raises an interesting point. Are two engines in a forage harvester really necessary? No doubt that question will be answered when the Davies brothers start harvesting later in the year.