by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
TAS Country : September 16th 2010
Friday, September 17, 2010 Tasmanian Country 25 Tractor Tragic OPTIONS: A photo from the original sales brochure for the model L tractor which owed its existence to the prototype model Y and the low volume production model 62. The Hercules built engine would soon give way to a John Deere built vertical 2-cylinder unit and from 1941 a bigger version known as the model LA was added to the line up. POWER: John Deere Model 420 gasoline engine --- while the model 40 replaced the model M with minor improvements it was the model 420 of 1956 that boosted power of the vertical 2-cylinder with a new 113 cubic inch engine that was offered in a variety of fuels including LPG. vertical 2-cylinder John Deere 430 engine to diesel power so John Deere decided to pursue the only option they hadatthetime---tobuyan engine from an alternative supplier. For this engine John Deere turned to General Motors. None of the ''71'' series engines were small enough for powering a tractor the size of the model 430 but in 1957 General Motors had developed another range of smaller Detroit Diesel 2-stroke engines, the ''53'' series. Built in 2, 3, 4 and 6 cylinder variants it was the 2-cylinder 2-53 engine that suited John Deere's needs right down to the ground and provided an exhaust note like no 2-cylinder John Deere tractor had ever had before. The 2-stroke GM Detroit Diesel engines were unique power plants that had proven themselves through thousands of miles under truck bonnets and countless hours in earth moving machinery. What made a GM Detroit Diesel different was its design layout, like a normal 2-stroke it employed inlet ports uncovered by the piston to draw fresh air into the engine for combustion, but used conventional pushrod actuated valves for the exhaust and a ''Rootes'' type blower or supercharger to ''scavenge'' or clear the cylinder ready for the next new charge of fresh air. The distinctive sound of the exhaust coupled with the howl of the blower gave rise to the term ''screaming Jimmy'' as being a 2-stroke. With a cylinder bore of three and seven eighths inches and a piston stroke of four and a half inches, each cylinder of the little GM diesel displaced 53 cubic inches so with 2 cylinders this equated to 106.2 cubic inch swept volume making it a fairly close match to John Deere's own 113.5 cubic inch gasoline engine used in the model 430. While both engines operated at 1850rpm, the GM 2-53 packed a bit more punch through delivering twice as many power strokes as the John Deere built 4-stroke. The GM 2-53 ran a moderately high (for a diesel) compression ratio of 17 to 1 with an induction hardened counterbalanced crankshaft running on three main bearings. Full pressure lubrication was provided by a gear type oil pump with a bypass filtering element. The Rootes type blower was gear driven from the timing train, inside were two 3-lobe type rotors that compressed air to be delivered into the cylinders. While the blower was an essential piece of equipment for cylinder scavenging it had another great advantage to the engine. Most naturally aspirated engines suffer significant horsepower loss in higher altitudes due to lower air pressure, GM Detroit Diesel engines with their blower supplying pressurised air to the cylinders were hardly affected by this condition, a valuable selling point. .A pressurised cooling system was used with a centrifugal pump to aid circulation, 12 volt electric starting was featured which generally gave easy starting and at almost 33 horsepower the GM 2-53 pumped out quite a bit more power than the John Deere built gasoline vertical 2-cylinder engine used in the 430 range. John Deere mated the GM 2-53 diesel engine to the chassis of the model 430W to create the model 435 diesel which was introduced in March 1959 . Taking the power from the GM 2-53 was a foot operated clutch with a single 10 inch diameter plate which coupled the transmission that could be either a standard four-forward speed or an optional five-forward speed unit. Interestingly, top speed between both transmissions was thirteen and a half miles per hour but in the case of the 5-speed unit, fourth gear offered a handy seven miles per hour speed which was ideal for mowing. All gears in the transmission were alloy steel forged, cut and heat treated for long life. Two types of power take off units were available, one a transmission driven 560rpm item, the other required a two stage clutch and was a continuous running independent unit that offered both 560 and 1000rpm.
September 9th 2010
September 23rd 2010