The Nipper

The fifth tractor is the famous Nipper, a Pulling tractor based on a MF265 with a Perkins diesel engine of 3800ccs with a power output of 60hp at 2000rpm. It should be noted that this project was put together by a small team of MF engineers as ‘an after work’ project. They were headed up by David Parnell, who was at the time, a Test Engineer. Others were Tim Turner, driver, Bill Randle, Paul Herbert, John Mills, Steve lveson, Dick Humphries and Ron Shirley. The base tractor was donated by Ron Gibbons, a tractor dealer. Other specialist parts donated:- cerametalic clutch by GKN Laycock, the three turbochargers by Garrett Ai Research, special cylinder head gaskets by Cooper Payen, a special aluminium front axle support bracket by DuPont Harper Castings but is now cast steel, Newbow Engineering snpplied the special shaping tool for the lugs of the rear 30.5 x 32 Firestone Pulling tyres, Gates Hydraulics supplied stainless hydraulic hose and spun aluminium rear wheels which, alas, are no longer fitted.

One of the normally three compression rings was removed and the internal expander ring and the oil control was removed to reduce friction and to create heavy oiling. The engine breather pipe was enlarged and leads to an oil catchment tank, hence heavy oil consumption of about 1 pint per 100 yards! The crankshaft was balanced, the connecting rods were shot peened to relieve internal stress and then matched for equal weight. The main and big end bearing shells were replaced by bronze but with slightly more clearance than standard, again to foster good lubrication under heavy loads. Twin CAV rotary injector pumps were installed, originally the intention was to provide sequential fuel injection. David told me they reverted to synchronising the injection of both pumps. Three Garrett Air Research turbo chargers have been fitted giving a boost pressure of 120psi, no waste gates are fitted. The first and smallest diameter unit, but highest pressure, is driven directly off the exhaust manifold. Its exhaust is fed into the second and slightly larger diameter turbo with its exhaust fed into the third, lowest pressure unit. All three are oil pressure fed. The starter and alternator are standard units.

As no official dynamometer figures are available I can only quote from the Autocar road test report which gives estimated values of 450/500hhp at 4500rpm, although the MF descriptive plate that came with Nipper claims 1000bhp at 5000rpm. With a standard MF265 in top gear and with Multi-Power in high ratio, this would give 13.9mph per 1000rpm.

In the Nipper’s ease, at 4500rpm this would equate to 59.35mph or, if you considered MF’s claim of a maximum engine speed of 5000rpm, would be 65.9mph. Autocar achieved a top speed of 65mph with their observer sitting on the rear transmission towing a fifth wheel speedometer!

There were a few other modifications:power steering was deleted, a second stop control for the engine was installed which was connected to the towing sledge by a light breakaway cable. This was to ensure that should the connection between the tractor and the sledge occur Nipper’s engine would shut down. Bonnet panels and some other parts were made from aluminium. An electric fan was fitted to a relatively small radiator. The fuel tank was hand made but with only a capacity for 18 litres. The fuel was diesel with 10% lanolin. Autocar reported a fuel consumption of 2mpg at 30 mph and just lmpg at 60mph. In its day the Nipper was a European Champion in the Super Stock Class in 1980 and British Super Stock in 1981.

When the Nipper anived at Coldridge, luckily for me the original rear wheels had been replaced by smaller 12.4/11 x 32 which reduced its width from 107″ (2718mm) to just under 96″ (2438mm) which made more manageable.

On one occasion we – David Parnell, Bill Randle, my friend Robin Haughton, myself and 2 or 3 other MF employees fired the Nipper up. I have a memory of one of the group with a can of Easy Start in each hand spraying into the air intake whilst the engine was being cranked over. After a bit it fired up but the black smoke from its 5″ (l25mm) stainless steel exhaust was disgusting! David would not allow them to bring it up to full revs because he had noticed a broken rear cylinder head bolt so we shut it down and man handled it back into the Hexagonal Shed.