A frightening hill descent with no brakes provided the spur for the launch of a swappable compressor unit that lets farmers with hydraulically-braked tractors operate air-braked trailers.

Gwyn Jones, who farms with his son Stephen at Mainshill Farm, Winchendon, Buckinghamshire, was carting a load of 42 bales down a long, steep hill with his Case 5150 and ex-HGV trailer in 2007 when he felt the brake pedal going alarmingly soft. Looking behind him, he saw oil spurting from a fractured pipe on the trailer as the tractor and trailer gathered speed.

“It was bloody scary, and I was lucky there were no slow vehicles in front of me,” he says. “But I realised we had to do something about our trailer brakes.”

Buying a new John Deere tractor with a compressor, plus a new air-braked trailer, was the first move. However when the Deere had a puncture one day, they realised they now had no means of pulling the new trailer because all their other tractors could only run hydraulic brakes.

That set Chris Ecob, a family friend who was experienced at working on both agricultural and commercial vehicles, thinking about a solution. His answer was to design a compressor that fits on the back of any tractor (or telehandler) and provides the 100psi pressure needed to power trailer air brakes.

How does it work? Inside the steel casing is a pair of very heavy duty 12v compressors that take an electric feed direct from the tractor battery. Pipes connect to the tractor’s brake spool valve on one side and to the trailer’s air brakes on the other. Meanwhile, a small control box in the cab provides an emergency brake.

Braking is progressive – the harder you push the pedal the more air is let through – and a test at the local HGV test centre confirmed that it’s more than up to the job. It can power all air-braked ag trailers, says Mr Ecob, plus ex-HGV trailers with air brakes and air suspension.

The 40kg unit attaches to the tractor in two places – the bottom bolts to the top of the tractor pto guard while an adjustable-length mini top link fixes it directly to the existing top link bracket.

Shifting it from one tractor to another (assuming you’ve already installed a power lead from the battery to the back of the tractor) can be done by two people in about 2 minutes. The driver can still see the hitch too.

Mr Ecob took his prototype to hydraulic specialists Regent Hose and Hydraulic in Aylesbury, Buckinghamshire, who have tested it for several months. It’s about to go on sale for £2650, significantly cheaper than the typical £4500 cost of converting a tractor to air, says Mr Ecob.

• For more information phone 01296 717 200 or click here