NURSE YOUR DIESEL

Lake County Mail, Issue 11, 6 August 1947, Page 4

NURSE YOUR DIESEL

Care is Cheaper than Spares-

In the previous issue the w: of constant care in ensuring clei the tank and from the filter to 1

riter emphasised the importance in fuel in transit from drum to ;he injection pump.

We Avill leave the fuel system temporarily' and discuss the different types of Diesels, or'«tt least those that concern our readersSjinopt. Moat types fall into 'the four-stroke group, in which there is a crankshaft, connecting-rods, pistons, inlet and exhaust valves, and the : timing gear ■to ensure their opening and closing at the correct time; such timing gear consisting of a two-to-one .reduction 'gearing or sprocket and chain system, a camshaft, tappets, and sometimes‘ rockers, valve springs, washers apd .cotters.

and more power per 100 revolutions than its more common competitor. The injection system is common to both types, and if treated with respect will given long and satisfactory service. Word of Warning Do not tamper with the injection pump or injectors. They must be serviced by experts, equipped with ( expensive overhauling and testing equipment. More, however, on this subject later.

The four strokes occupy two complete revolutions of the crankshaft to complete -the - full cycle of operations, these being—1. Suction of air alone.

(To be Continued.)

2. Compression of same which heats the air to a temperature high enough to burn fuel, oil, sacking or anything of a combustible nature.

3. Injection of the fuel which ignites on contact with the hot air, burning of the ijuel '(not exploding, a point to be considered later). Expansion, which creates th'e power impulse to the pistoil;

4 i Exhausting of the burnt gases,

The above cycle of operations is similar to that used in your motor car and! most farm engines, excepting of course such as the Villiers two-stroke. There is, however, a limited number ofi two-stroke Diesels on the market.

These are mainly comparative newcomers to the farm-Diesel field, but •the principal is age-old, and they possess like all two-strokes certain definite advantages and originally but not necessarily in recent designs some slight disadvantages.

Advantages

The engines’ of this type have fewer working parts, generally a crankshaft, connecting rods, and pistons, no valves, springs, tappets, camshaft, gears, or chains, so that there is less to wear and reduce efficiency. The cycle of operations is:—

1, The piston is forced down on the power stroke by the burning gases, while descending, compresses air in the crankcase until near the bottom of the stroke it uncovers ports formed in the cylinder wall communicating with the exhaust system and then uncovers other ports communicating with a transfer passage from the crankcase, when the compressed air rushes into the cylinder and striking a deflector formed on the Jop of the piston, is diverted upwards and assists in pushing out the burnt gases into the exhaust system.

2. The piston then rises, closes the ports and compresses the air which, as in the four-stroke, heats it until at, or near the top of the stroke, the fuel is injected and igniting delivers the next power impulse and this cycle of operations is Repeated once each revolution of the crank-shaft. It is. obvious then that the two-stroke delivers twice as many power .impulses as the four-stroke for any given number of revolutions of the crankshaft. Disadvantages This cycle ysjjth.,apparently twice the' power, loses a little by virtue of some of the fuel and unburnt air passing out with the exhaust gases and some exhaust gas remaining and reducing the efficiency of bhG'jnpxt cycle of operations, but the net gain is, however, considQiabWj andxisbtne recent designs have eliminated these disadvantages.

It is apparent, therefore, that the two-stroke has very definite advantages in simplicity, fewer working parts,