Cornish farmer designs automatic fencing machine

An inventive farmer from Cornwall has come up with an inspired design that allows one man to erect fencing from the tractor seat.

David Carbis, the overall winner of this year’s Farmers Weekly farm inventions competition, has developed a unique fencing machine that loads the stakes, stands them up, holds them in position and then knocks them into the ground.

It also grips and unrolls the wire – all without the operator having to leave the tractor seat.

Mr Carbis, who farms with wife Pam at their 100ha (250-acre) Trenona Farm at Ruan High Lanes, Cornwall, usually works on his own. So when it comes to fencing he has, in the past, had to overcome the difficulties of accomplishing alone what is essentially a two-man task.

“I started by putting the posts in by hand with a sledgehammer, which was slow and exhausting work. Then I borrowed a manual post basher, which was even worse,” he explains. “After I got fed up with that I used a contractor who operated a post knocker on the tractor while I placed and held the stakes in position.”

He soon realised this wasn’t the answer either. He was not only paying for extra labour, but it remained a laborious job.

He thought there had to be an easier, safer and better way and set himself the task of designing something to do the job. The resulting design uses a combination of gravity, hydraulics and simple trip mechanisms to run the machine, which takes less than a minute to knock in a post.

The sequence is operated hydraulically – using the services for the front loader and with hoses transferring oil flow from the rear spools to the front. The main functions are operated by the loader’s joystick controller, while the rear spools run the post knocker, stake loading system and clamping device.

This is how it works.

See photo sequence below.

About 30 to 40 stakes (it works best with round posts) are loaded on to the tray at the front of the machine and are held back by a gate.

This is opened and closed by a small ram running off the same circuit as the knocker, allowing three or four posts through to lie horizontally in a rack.

A loading arm is then raised, hydraulically. Two small, pivoting latches on the arm catch the first post, and transfer it to rest on ex-baby buggy wheels.

These ensure it rolls off smoothly. As the arm is raised further the post’s point comes to rest on a trigger plate attached to a small, nylon roller.

This stays in position until the arm and post are nearly vertical, when the plate’s roller hits a stop, which releases the trigger. This allows the post to drop into a gripper at the base of the knocker’s beam.

When the loading arm is raised the same hydraulic circuit opens the gripper and when the post has dropped into position lowering the arm closes the gripper, which grasps the post.

The loader’s bucket crowd service is used to ensure the post is vertical. The rear spool valve runs the post knocker’s hammer.

After the post has been knocked in place the gripper is opened by raising the loading arm, which collects the next post on the way and holds it at an angle of about 45deg. The tractor drives forward to the next post position where the loading arm is raised to vertical, releasing the post and the process starts again.

But that’s not all this remarkable machine can do. It also uses another inspired design to unroll and tension galvanised sheep wire, rabbit fencing and even electric fences. Rolls of wire are held on a mandrel that fits into a special frame at the bottom of the knocker arm.

The base of the mandrel is an old car brake disc, which sits on brake pads on the frame. “This maintains the same tension as the wire unrolls, because as the weight reduces, so does the friction,” explains David.

The fence wire runs out between two vertical tubes that are secured by a catch at the top. When it’s time to stop unrolling and tension the wire, this catch is released, allowing the tubes to be turned through 270deg, trapping the wire between them in a figure of eight.

“This holds the wire very tightly – the machine will bend before it slips – but this doesn’t damage the galvanised coating in the process,” adds David. The fence is tensioned simply by driving the tractor forwards.

Key elements of the wire unroller, as well as other mechanisms on the machines, are all protected by patents. David is currently looking for a manufacturer to take the one-man fencer into production.

1: David Carbis took top spot in our inventions competition with this one-man fencing rig. The ingenious design loads and knocks in the posts as well as unrolling and tensioning the wire.

2: A small ram (top right) releases the posts, which fall into a holding rack. Pivoting latches on the loading arm catch a post, which rests on wheels.

3: As the loading arm rises the post’s point rests on a trigger plate. When the arm is near vertical this hits a stop, which releases the post.

 4: The post gripper is plumbed into the same circuit at the loading arm – opening when the arm is raised and clasping the post as it lowers.

 5: Tension on the wire is maintained by this simple, but effective brake on the base of the mandrel. Friction reduces as the roll unwinds and gets lighter.

6: Wire is fed out through two vertical tubes held by a catch at the top. These can be turned through 270degs, gripping the wire in a figure of eight for tensioning.


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