Oliver Mark opens up the workshop doors to reveal some ingenious ideas from Robin Humphries, a runner-up in Farmers Weekly Farm Inventions Competition
Mr Humphries’ 2013 Farm Inventions entry was a clever fence joiner with the back end of an everyday best cordless impact driver and a series of sprockets and bevel gears leading up to a spinning head at the front.
It was three years in the making. The original design involved a comparatively bulky two handed ratchet, which slowly evolved into the one handed, battery powered machine it now is. Bevel gears are sourced online and the entire joiner can be assembled for 50.
So, how does it work?
With the ends of two lengths of fence overlapping by 150 mm and ready to join, the two pieces of wire are bent through 90 deg (one pointing upwards, the other pointing downwards).
The machine has a sprag clutch which uses rollers on an inclined plane to let the disc head turn freely in one direction but not the other to allow the operator to turn the knob, and leading disc head, until the feed in channel lines up. At this point the two pieces of wire are fed into the machine.
Pulling the drill’s trigger turns the disc head until the two mini anvils mounted on it meet up with the two pieces of wire. Then it’s just a case of pulling the trigger until the wire has wrapped itself all the way round the opposing piece of metal. The faster it turns, the warmer the high tensile wire gets and the less draining it is on the 18V battery.
There’s no force required to operate it, either the machine finds its own centre and it’ll last several days on one battery.
Easily the most impressive piece of engineering on site is the two cylinder crankless Shane engine. It uses cams rather than a crankshaft to double the number of combustion strokes for every revolution.
Each piston in the patented motor hits top dead centre every 180 deg (or four strokes for each rotation), but there’s no conventional crankshaft for the piston’s big ends to connect to. That helps cut down on size and weight.
Instead, the stumpy con rods run on an internal cam assembly and only stray 5 deg either side of the centre line to improve efficiency.
The shape of the internal cams is designed to replicate the sinusoidal motion of an engine’s piston speed that means the piston stops at TDC and BDC and slowly increases/decreases in speed either side of this. But optimising the shape of the cam to replicate that crankshaft style motion proved difficult, says Mr Humphries, particularly making the profiles perfect during both induction and combustion (and compression and exhaustion) to keep the piston movements perfectly balanced all the time.
The wire cut cams are made of hardened tool steel because of its toughness and resistance to abrasion. They are connected to the pistons by rollers at the big end side of the con rod.
The cams run on rolled bronze bearings and, at the other end of a pivoting radius arm, push on bronze bearing pads to reduce friction and the wearing impact of both parts.
The radius arm is made of EN 36 steel the same material as you’d find in most motorcar components and joins the con rod’s cam rollers (the equivalent of big end bearings) to the rocker at the other end.
With four strokes occurring in each 360deg rotation, the engine produces double the torque of a conventional engine that fires once per crankshaft revolution. So a 600cc engine will produce 60hp and 125lb ft of torque.
Mr Humphries’s engine also has the advantage of a low shaft speed it means fewer gears are required to reduce the output speed down to a practical ground speed, for instance. It could also be extended to have more cylinders and more power, says Mr Humphries, so it’s potentially more efficient than a con rod and crank and is similar enough to conventional engines to share many of the advantages they have.
The last radical change in engine design was the Wankel engine. Its rotary design was simple, smooth and compact, but teething problems when it first hit the market put major manufacturers off experimenting with new designs.
Another novel idea from the Humphries stable was to attach a Bryce Suma post basher to a 6t dump truck, which Mr Humphries picked up for 4,500 with 900 hours on the clock.
The 400 Vulcan attaches to the Perkins powered Thwaites dumper through a new three point linkage bracket/headstock made by fabricator Martin Bushnell.
The original hydraulic rams are used to lift the knocker ready for road travel and a third was added to act as a top link to crowd the load.
Adding an extra spool with a detent for constant flow means everything can be controlled from the paddles on the post knocker.