By their nature forage wagons are simple beasts so buying a second-hand machine needn’t be a nightmare. British writer Nick Fone gets some expert advice.

Forage wagons have come on a long way in the last couple of decades. Modern versions can now achieve decent, consistent chop lengths and will now match or even exceed the outputs of trailed foragers.

In fact, as their capacity and reliability has improved, they’ve replaced many old-school tractor-pulled machines as well as self-propelled choppers in some places.

As such there’s a much bigger number on offer on the second-hand market. We took a visit to Devon to get some advice from James and Deborah Boundy who run Forage Wagons South West – specialising in servicing and selling used machines and parts.

The first thing to consider when looking at buying a forage wagon – new or used – is exactly what spec is required.

Like any equipment, standard spec will vary as will the optional extras. Most forage wagon manufacturers have two different spec bundles: Generally ‘Farmer spec’ models have a number of knives that’ll produce a chop length of about 45mm, chain-and-sprocket drive to the rotor and eight-stud axles with 500mm or 550mm wide tyres.

In contrast, with a greater number of closer spaced knives, ‘Contractor spec’ wagons will generally get chop lengths down to 35-38mm. Their rotor drive tends to come from a gearbox and they’ll tend to be running on 10-stud ag/commercial axles with 620mm wide rubber or bigger. Often they’ll have some form of rear-wheel steering and air-brakes. They might also have a twospeed floor for faster unloading as well as ISOBUS controls.

RING HITCH

Although all UK spec machines will have a lowlevel hitch they’ll generally have a selection of bolt holes to enable operators to set the drawbar to run level.

PTO SHAFT AND GUARDS

Almost all wagons of contemporary vintage should be running wide-angle PTO shafts which makes good sense but has an impact on running costs. While individual universal joint bearings and yokes can be replaced, more often than not if one is on its way out the whole lot will need doing in which case the sensible thing to do is replace the whole shaft end.

DRIVELINE

Many ‘farmer spec’ wagons will employ a chain and- sprocket drive to the rotor. While this is simple and straightforward it does require a scrupulous eye to keep it trouble-free. Generally chain tension needs to be tighter than normal – any slack can cause a whip effect which will eventually result in a chain break.

In contrast, most ‘contractor spec’ machines will use a gearbox to transfer drive to the rotor – a much more robust, reliable solution so long as oil levels are kept topped up. (Most Lely and Mengele wagons use gearboxes irrespective of spec.)

There’s a clear division between makers on how they approach the workings of pick-up tine drive. While Krone and Lely/Mengele have typically opted for cam-less arrangements, the remainder have stuck with rows of tines drawn in and out of work by a cam-track. The former is a much simpler approach that requires less maintenance and has many fewer moving parts.

As regards the tines themselves, there’s a broad discrepancy in the pricing of replacement parts.

ROTOR TINES

Depending on the brand the width of the rotor tine sections vary from 8mm to 25mm, giving varying degrees of clearance between them and the knives.

Logic would suggest the tighter the gap, the cleaner the shear of material as it passes through (much like a pair of scissors). The downside is that small foreign objects are less able to pass through so there’s less tolerance to damage.

Some makes and models start at 8mm-wide tines with big gaps either side of the knives while others have chunky 25mm tines. Put a sample of chopped grass from a wagon with narrow tines and alongside one with wider ones and you’ll see a noticeably cleaner, more precise cut.

Look out for bent rotor tines. With the machine coupled up to the tractor you’ll certainly hear if there’s metal-on-metal clashing. Generally caused by foreign objects passing through the knife bank, if there’s more than one or two it’s a good indicator that the machine in question hasn’t had the healthiest of diets.

Resolving the issue is a case of pulling the rotor out, cutting off the offending tines and welding or bolting on new ones. A good half-day job.

KNIVES

Assessing the wear of set of knives is pretty straightforward. As a rule of thumb if they’ve worn back to the point that the serrations are no longer visible they’ve probably done their time.

Genuine knives have less of a tendency to break but don’t wear any less quickly than non-branded replacements. So the answer is to fit genuine if you’re working in stony conditions but price up the alternatives if not. You’ll generally see a saving of 15-20% going non-genuine.

Be wary if you find blades of noticeably different sizes and vintages that would suggest replacements have been fitted when the majority are well worn. The potential problem here is that taller individual blades can score the rotor and it’s not unheard of for them to slice right through the drum.

KNIFE BANK

The weak point on all forage wagons, the knife bank takes a lot of battering. Throughout the season it’ll spend much of its time dripping in the corrosive juice from chopped grass and will rarely get washed off. Its condition is a good indicator of how well the machine has been looked after.

It’s the bit that takes all the shock-loading from nasty unforeseen extras coming through in the swath. They all have some form of break-back protection and the associated moving parts. This is one weak point on Pottinger wagons which have a greater than average number of small components prone to wear. Assessing this is tricky without pulling the whole bank out but swinging it out from under the body will give an indication. Lots of slack in the blade carriers will suggest a revamp is necessary.

HEADBOARD

There are generally two different approaches to body design. The standard is a simple, regular rectangular box with the axles mid-mounted along the length of the chassis.

Lely (and others from time to time) offers the option of a body with a pivoting front headboard. When filling this is kept upright but as the body reaches capacity it is swung forward hydraulically to extend carrying capacity by up to 8-10 cu.m.

Although this doesn’t necessarily equate to extra cubic metres per load, it means the overall length of the wagon can be kept shorter than normal with less tail-swing making for a more manoeuvrable package. The downsides are that there are fewer options for mounting an additive applicator on the headboard and it’s likely to be a more costly bespoke build. Of course there are also more moving parts than usual.

It also appears to bring with it a weakness that sees the tinwork ripple and crimp after a few seasons’ work. This is thought to be because the minute the tailgate lifts, the headboard is automatically raised to its vertical position to ensure the entire load empties. The problem is that with grass up against the front at this point it puts strain on the body and it’s the tinwork that gives out first.

Many wagons will have a combination of ropes and bars running across and along the length of the body to keep things rigid and to stop grass spilling out over the top. Unfortunately these invariably end up getting bent either on overhanging trees or unseen steelwork.

TAILGATE

Different manufacturers tend to take a different approach to tail-board design. While Strautmann, Krone and Claas opt for gates that lock down in place, others go for  arrangements secured by the up-and-over rams.

The big plus point of the former is that it makes for a stronger more rigid structure when shut but problems surface if the tailboard gets pranged. Trying to straighten and realign bent locking versions is a tricky task that rarely makes for a satisfactory solution. In contrast free-swinging gates are a great deal more tolerant to knocks and scrapes.

WALKING FLOORS

Most wagon makers employ timber for the body floor but they will offer the option of a steel deck. Wooden floors tend to outlast metal as they’re less prone to corrosion – expect a good 20-30 years from timber.

As you might expect replacement is straightforward but the choice of board is critical – the upper surface must be planed smooth to ensure chopped grass is easily ejected without hang-ups.

As regards the chains and slats of the walking floor there’s rarely much issue but the joining links will get thin after four to five seasons’ work. Replacement is a simple job. Often carrying a significant weight in the field, most wagons tend to be shod on soil-friendly flotation rubber – anything between 500mm and 710mm wide.

Uneven wear – often the shoulders – is a sign that they’ve been run at lower than recommended pressures. Rather than wear it tends to be cuts and stone damage that spell the end for most tyres.

Capacity confusion

Anyone new to forage-wagons will quickly spot there’s something funny going on with how manufacturers quote body capacity.

Unlike trailers, the industry norm is to talk volume rather than weight which makes good sense. However there’s more to it than that – is the figure you’re looking at the actual cubic capacity of the wagon or a number referring to what you can actually cram in?

If you look at the makers’ spec sheets you’ll generally see a ‘DIN’ measurement which refers to a simple height x width x length figure. Then there’s usually a second number tagged as something along the lines of ‘medium compacted load’ or ‘maximum loaded volume’ – this is generally an idea of what a compressed load of grass ends up as.

For example a machine with a ‘DIN’ body capacity of 31 cubic metres will typically be able to squeeze in up to 50cu.m of grass once the rotor and walking floor have done their bit to cram it all in.

What are the extras worth?

• Certain key features that add value.
• Rear-axle steering
• Flotation tyres.
• Two-speed floor – bringing unloading time down below 30 seconds
• Additive applicator
• ISOBUS – plug’n’play controls don’t tend to add value.

What to pay?

The key thing to look at is the load count as an indicator of the work a machine has done. To do that you’ll need to hitch the control box up to a tractor. Be a bit wary of wagons with replacement boxes as that’ll often meant the clock has been reset.

As an average in Forage Wagons SW’s experience most farmer-owned wagons clock between 300-500 loads a year but it’s not unusual for contractor wagons to top 3000 loads. Lower-spec wagons may not have a load counter.

As a rule of thumb, with a 50 cu.m wagon it’s about an acre of grass per load (50 cu.m) as average across all cuts. So if you know the acreage of the farm it’s come from that’ll be a pretty good indicator.