Push-off buckrake or silage fork flick?

When it comes to levelling silage on the clamp are you a fork flicker or a push over? If you are using a tractor mounted buck rake then the chances are that it will be a push off. Those of us old enough to remember trying to fill a clamp with a tipping buckrake on a 135 will remember the joy the first time we tried a push off. Until recently most shovels filling clamps were fitted with a relatively simple fork and there is much debate as the to best ram set up to give you the perfect flick. But here is the thing - in my opinion there is no such thing as the perfect flick!

How fast can you clear silage into the pit?

Keeping up with the harvester is becoming more and more of a challenge. Not too many years ago the number one harvester sold in the UK was a the Claas 860, today its the 970 (at the time of writing) The 860 was just short of 500 horsepower, the 970 is around the 800hp mark. That’s a 60% increase in grunt and at least a 60% jump in output. Sure some of this growth has been driven by the increase in maize harvested and the fact that lots of this stuff is being chopped really short for AD plants that demands more horsepower. But, as the contractors kit gets bigger, the pressure to get it into the clamp gets greater. Loading shovels have stepped up with more shove and more lift to clear the load before the next trailer arrives.

Pushing up silage with a pair of Volvo shovels

What hangs off the front of the shovel needed to get bigger too so folding forks have become the norm for may contractors and there are loads to choose from. A skilled operator can clear a load in a couple of swipes and hopefully keep the chopper pilot happy. So why am I so unhappy with a folding fork?

Whats wrong with a silage fork flick?

Getting the silage out of the way and into the pit is only part of the issue when it comes to filling the clamp. The stuff needs to be spread and compacted and this where we see the skill of the drivers flick. Now I’m not qualified to comment on relative benefits of single versus double rams and Z bars or parallel linkages, I will leave all that to others. What I am concerned over is the choice of fork on the front end and the effect this can have on the quality of silage. From all I have seen and from the operators I have spoken to, there is no doubt that a push off fork is much quicker than a fork and flick. To level the forage dump with a plain fork there needs to be lots of flicks forward to spread it over the clamp surface. Good operators can make this look pretty effortless and leave a lovely thin layer of silage which is what you need. My issue is not with the finish, it is what’s going on during the process that might be less than ideal.

MDE Warrior folding buckrake

Compaction is the key to good silage

This message seems to have hit home and almost everyone seems to get it - you need to compact silage to get the air out. But getting the air out is the trouble here because it’s easier to avoid getting the air in than it is to get the air out. In essence, it’s better if you don’t have any to get out in the first place. But what has this go to do with a fork flick?

Well that is the point here, the flicking action of the fork tines (in grass silage particularly) tends to produce cavitation behind the tine. In other words as the fork tine flicks forward it produces voids of air that get trapped in the silage. These need to be squeezed out by rolling but if they are too deep in the silage the air they contain doesn’t get squeezed out, it just gets dissipated into the silage mass. This air goes on to feed the undesirable aerobic organisms in the silage that delay fermentation and increase losses.

What’s wrong with the stop start motion

There are some more problems with this technique too and these centre around the wheels on the shovel. As the fork is flicked the resistance to forward movement changes enormously. If you watch this in slow motion it’s easy to see what’s going on. As the fork is flicked forward, the forces almost stop the machine as it is pushing against the load. The hydraulic power then starts to win and heap gets pushed forwards, so the shovel starts to creep forward. This accelerates until the fork is then returned back for the next flick, this then almost pulls the machine forwards. The whole cycle then starts again as the machine just about grinds to a halt as the fork travels forwards in the next flick. This process can be seen in all machines, even the greatest shovels with transmission lock-up.

JCB 419S in action on the clamp

Whilst this stop start rocking motion is just unpleasant for the driver, it’s not great for the silage quality underneath the wheels either. The massive variation in the torque and shear forces at the wheels start to introduce shear cavity in the silage that introduces air into the silage below and behind the wheels. This is really not good because the void was created during compaction loads so it is very, very difficult to close these voids with more compaction by driving over it again.

So are silage forks a disaster?

No not at all, these issues are not the biggest problems in making great silage; but they are solvable. This is where the push off fork starts to win because it is much easier to finely lay a 150mm thick layer of forage over the clamp with a push-off buckrake. There are now loads of manufacturers producing neat push off forks that fold just as quickly as a plain fork. So why wouldn’t you choose a push off fork - in other words.

Push-off Albutt folding buckrake

What’s the advantage of push off silage forks?

Inevitably a push off folding fork is more complex than a plain one but it is still probably the simplest piece of kit that is used to make silage. It's heavier than a plain one for sure, but lift capacity is not really the issue with a loading shovel working on the pit. Neither is oil supply going to be the issue even though a push off might need another hydraulic service.  Some manufacturers overcome this problem by incorporating an electrical switchover valve to enable the same service to be used to fold and push-off the fork. No the main issue is the price and that’s the same problem as all agricultural kit. I can’t quantify the potential saving from increased silage quality you will produce by using a push off over a plain fork, but I know there will be some. The contractor might never see these but there are savings they will see.

Push-off forks are quicker as MDE can demonstrate

The push off has a much reduced cycle time compared to a fork. The shovel’s progress over the “dump area” is much quicker with a push-off fork. This might just be enough to keep up with the new harvester because the same loader can shove more into a pit in the same time period with a push off silage fork. There is also sooooo much less wear and tear on the linkage pins on the loader when it is fitted with a push off fork. Flicks are brutal on the mechanical bits involved.

Alternatives to a silage fork?

Well for maize it's common to use a blade for pushing silage into the clamp in many parts of the world. I can’t really see any negatives for this, particularly when fitted to the front of a piste basher - but that’s a whole other story.

If you want to discuss how to place your silage into the clamp or would like to discuss any other aspects covered in this series, contact me at jeremy@silageconsultant.co.uk