The process of getting silage through the chopper and into the trailer is pretty universal, a curved spout and a lot of velocity does the trick – but what about getting the silage out of the trailer once it gets to its destination? Traditionally there were two choices, self-unloading or tipping trailers, but today compactor or ejector trailers are a more common sight running in and out of silage clamps.

 Silage trailer options

Whilst tipping trailers are seen as robust, versatile and simple, self-unloading trailers always had the impression of being a complex one trick pony. More common in mainland Europe, the self –unloading trailer has moved on and today offer huge capacity, low ground pressure and rapid reliable unloading, but they remain a very rare sight in the UK. And ejector trailers, well they offer some advantages of both, they are rugged, more versatile than self-unloading trailers but are a heavier construction, as they need to be, to withstand the compaction forces. That compaction is really the secret weapon – manufacturers claim up to 40% more silage in each load when compared to a simple box on wheels. 

Tipper vs Ejector head to head.

So let’s look in detail at two similar sized trailers, a monocoque 16t and an equivalent ejector. The figures are taken from a Richard Western SF16 and K-Two’s 1800 but other brands of equivalent sizes are similar. Both trailers offer a nominal silage volume of around 35m³ on a twin axle chassis with floatation tyres. Whilst the Richard Western provides 34.3m³ the K-Two claims 36m³ total volume with an equivalent silage volume of 54.5m³ when compacted, that figure is over 50% more than the box volume! The compact-ability of the silage will depend on lots of variables such as crop type, chop length and dry matter but you can clearly get quite a bit more into the compactor once you give it a squeeze.

Size matters

This extra volume isn’t at the expense of manoeuvrability either, the K-Two body is actually half a meter shorter than the Richard Western. This can be a real advantage in a tight yard or down narrow lanes. When it comes to height, the two are within a few millimetres of each other so the compact nature of the compactor is a clear advantage here. Looking over the compactor body construction, it’s easy to conclude that this is a heavy bit of kit but again, the spec sheets are very similar with both trailers coming in around 6.3t

Cycle times

Any cycle time will be dependant on oil flow and pressure from the tractor but in some field tests by Grassmen the time taken to empty and return a trailer was recorded on the same tractor. In a full cycle from fully loaded to fully retracted or body down, the tipping trailer was considerably quicker. However one advantage of the compactor is that it doesn’t have to wait until the pusher is returned before it can set off back to the field. Once you take this into account there was nothing in the cycle times. Brave boys might be leaving the yard with the third stage of the tipping ram still extended, but the ejector trailer will be right behind. And that brings us on to safety, and one clear difference - tipping trailers have the habit of tipping not just up, but over as well.

The ejector trailer (and the self-unloading option) is very much safer in this respect, sloping ground, uneven ground or sticky loads are not a problem. A tipping trailer is a whole lot more vulnerable. Available headroom is also an issue for ever bigger tipping trailers, be it low wires, branches or shed roofs, the tipping trailer is always more of a risk than an ejector.

Life in the old dog

That doesn’t mean to say tippers are on the way out; the versatility means they always have a place in the silage arsenal. An ejector might be half a metre shorter but reversing a tipper on a snaking route is a piece of cake once the body is raised enough to see the back of the chassis and that’s not an option for the ejector trailer. The tipper is also a cheaper item to produce. An equivalent ejector trailer might be in the region of 65% more expensive than a tipper, and it’s early days to predict re-sale values but it’s reasonable to assume they won’t have quite such an audience as a used tipper.

Some might be concerned about reliability of the compactor trailer and its ability to withstand the forces exerted on it, but the technology is not new, its been used by road side collection bin lorries day in, day out for decades. The operators need to be a bit more attentive in the field whilst loading to make the most of the compactor, but then their job at the clamp is much simpler.

Do the costs stack up?

Well perhaps they do, certainly for a large scale silage contractor. Below we consider a 4 trailer silage team running 600 hours a year for 10 years and a more conservative 25% compaction volume increase.

K-Two Compact & Push 1800 Richard Western SF16-HS

Capacity 36m³ 34.3m³

Equivalent silage volume (+25%) 45m³ 34.3m³

Total number 3 4

Overall volume 135m³ 137.2m³

Purchase cost £35,000 £21,000

Resale value £15,000 £12,000

Depreciation per hour £3.33 £1.50

Tractor costs per hour £40.00 £40.00

Cost per hr tractor & trailer £43.33 £41.50

Team cost per hour £129.99 £166.00

That’s a potential saving of £36 per hour, or over £21,000 per year. Obviously it only works if you are able to reduce the total team numbers but certainly don’t dismiss these specialist trailers just because the headline price tag is a bit scary. It could also be argued that you might need another 25hp on the front end of the ejector to give the same power to weight when fully loaded. There are definitely financial benefits to go along with the safety bonus of ejector trailer, and the neighbours might appreciate 25% less loads on the lanes too.

If you want to discuss the pros and cons of specialist silage trailers over universal tippers or any of the other aspects of silage making covered in this series – contact Jeremy Nash at Jeremy@silageconsultant.co.uk

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