POWER UNITS AND GARDEN MACHINERY ELEMENTS

This post refers to the use and care of garden tools, machines and appliances. Clearly, this is a very large topic and the kind of questions it raises might range from the selection of a spade, fork or hoe, to the use, care and maintenance of a small garden tractor.

The principal factor in the selection of any equipment must be:-

Does the tool do the job? and the following subsidiary considerations are:

safety, efficiency, speed, cost effectiveness, low maintenance, all-weather serviceability, easiness of cleaning, ease of use.

Virtually all the machines with power sources need maintenance. It is usual to be supplied with a maker’s handbook. This will set out a programme for its service, the operation of the machine and its maintenance schedules -daily, weekly, annually, plus its storage requirements. The manufacturers frequently use the number of hours of operation as the guide to the time for the changing of oil in air cleaners, engines and gearboxes, but for amateur machines, it may be that the specification is simpler with an annual oil change.

Generally speaking, when you receive a new machine from a dealer or other source it is wise to read the instruction book before putting the machine into service so that you are thoroughly familiar with the:-

1. Controls

2. Adjustments

3. Maintenance requirements

This may prevent you having to learn some of it the hard way.

Again in general terms, costly time when the machine is out of service can be saved by the generous use of oil on all moving parts. For reasons quite inexplicable to me, all too frequently some maintenance handbooks omit to mention the desirability of a light oiling of the control levers and cables with special attention to the points where they might wear. (Only the clutch and the electrical gear are best given a minimal lubrication.)

Generally, oil is cheaper than bearings, and when running in a new machine it may be wise to change the oil in the sump of

the engine after an hour or two’s operation, and again after 25 hours, if that is the instruction. The reasoning is sound enough – the oil’s function is to make two metal moving parts move easily against each other, (and in the engine it will also help to carry away heat). If there is grit in the oil, then this will behave like a grinding paste or scratchy polish, which will wear away the softer of the two metals in contact at an excessive rate, thus reducing the life of the working parts. The first few hours operation of an engine and the care given then may prolong or reduce the engine’s working life vastly more than care at other times when the engine is operating.

A manufacturer has to cater for a very wide range of users, and the advice in the handbook is generally very well worth taking. An important part of maintaining the machine’s serviceability is to keep the handbook in a safe, accessible place, together with a parts list and dealer’s address/phone number.

All machines have a working life and they do wear out. This wear may be fundamental wear or just wear to the working parts which may be replaceable or adjustable. One operator/user machines tend to last longer because the operator has generally rather more interest in the welfare of the equipment – to see that it is not overloaded in operation or used in an unsuitable way, is cleaned off adequately after use, and that care is taken in the essential lubrication and fuelling.

Fuel

Machines may use diesel, petrol, or petrol and oil mixture -it is essential to use the correct fuel and it is wise to fill the fuel tank through a FILTER funnel. A quite astonishing amount of debris does quickly collect in fuel tanks and most of this enters when the tank is filled.

Usually there are filters on the machine’s fuel line to the carburettor, but it is daft to expect these to cope forever, and when working in the field or.garden there is likely to be a good deal of dust about. Dust in the engine causes wear.

Fuel mixtures

The majority of two stroke engines need oil added to the petrol. The quantity required will be stated clearly in the handbook. Special two stroke oils are a good investment because they mix better and some warranty descriptions may require that a specific oil is used. It does pay to put in the right mixture.

When using machines, try not to exceed their normal working load. Do not try to rotovate too deeply or too fast. Do not try to get a lawn mower to cut off excessive grass in one swipe, when it might be wiser to re-set the height of cut and to cut over the lawn two or three times to gradually regain control of the grass. Bearing this in mind may double the machine’s life at least, since it is giving the extra load that tends to bend the parts or gradually weaken the castings so that something cracks and costly damage may ensue.

It is my view (0. N. Menhinick) that very few garden machine tools are made really well. Mostly there is a compromise between length of life of the equipment and cost of manufacture.

LAWN MOWER ADJUSTMENTS

Cylinder

Always switch the engine off before attempting to adjust the settings.

on

The height of cut is usually adjusted by raising or lowering the relative, position of the front roller. It may be checked with a straight edge as shown.

The correct cut between the cutting cylinder and the bottom plate or blade ‘ BP’ is a wiping scissor action. Usually the cylinder is adjusted on either side by heavily sprung adjusting screws. The good cutting action is best checked with paper which should be cleanly cut along the whole length without undue pressure. Care is always needed, as even a hand turned cylinder can injure.

Other adjustments

Throw plate – this is usually designed to work best at the middle setting. After a great deal of cutting cylinder grinding it may need to be brought forward.

Throttle – frequently the ‘slow running can be adjusted on

the throttle cable. The clutch cable may be similarly

adjusted.

When the clutch is adjusted it is important that the working position leaves the clutch springs free, not partially compressed, since as in riding the clutch with one’s foot in a car, the wear in the clutch is aggravated as some additional clutch slip occurs – this may be followed by heating and early failure of the clutch plate.

Chain care

Generally, chains work best well oiled. (There are exceptions where external chains work in dusty conditions and are designed to cope best largely dry – the presence of oil and grit may make for faster wear apparently.)

Over time, the chains stretch and the link becomes slack, also the sprockets wear, all of which make the chain slack. Usually there is a system for moving one or more of these sprockets to achieve a reasonably tight chain. There should always be some play, e.g 10 mm or so of slack, as a drum tight chain wears quickly. Some machines have a sprung roller sprocket or rider which reduces the need for frequent adjustment.

Chains are best kept clean by washing in paraffin annually, and then soaking in the correct grade of oil. The clip that retains the chain should go in the direction of the chain’s travel.

Engine oil changes

Engines with an oil sump need the oil changes following a recommended programme or maintenance schedule.

Oils come in many grades – with different viscosities, I.e. the SAE numbers. There are those with multigrade properties, oils which clean and oils which can tolerate very high pressures. It is important that the recommended lubricants are used because the bearings will have been designed to work best under those conditions. To give insufficient lubrication, to introduce contaminants or to provide the wrong sort of oil or grease will cause problems sooner or later.

Generally, the oil change is carried out at the end of a working period when the oil is hot. The sump plug is removed and the hot oil drained off into a handy container. When the oil is fully drained off, the sump plug is screwed back securely and fresh oil supplied sufficient to reach the correct level (when the engine is in the correct working position. Often there is a dipstick or other indication to gauge this level.

Air filters

Some air filters are made of paper as dust cartridges. These may be best replaced at specified intervals, e.g. annually, but in very dry and dusty working conditions they may need a daily inspection and dusting off or replacement. Oil bath type filters catch a noticeable quantity of debris and this has to be washed out with petrol or similar solvents; the wire gauze mesh should be rinsed and oiled before replacement. Sophisticated engines may have cartridge type filters (and for oil also) which would usually be replaced at every oil change or as specified.

Electrical

Spark ignition engines may have several weak points when the engine fails to fire or runs unevenly. The causes may be many, but frequently the troubles may include:-

1. The stop switch not being switched to on.

2. A poor connection between the ON switch and its wiring.

3. A dirty plug, or too wet from excess fuel – too much choke and a cold start.

4. The plug dwell gap (where the carbon thread is shown) may be unsuitable. Plugs do need adjustment to suit the engine requirements even when the plug is new. Sometimes the plug can be cleaned with a wire brush or sand blasting, but if the problem persists, it is better to change the plug and the fundamental cause ascertained. It may be due to dirt on the contact breaker points (if fitted) and re-set to the correct gap. It may be best if the contact breaker points are replaced.

Excessive engine wear, hopefully after long service, may cause problems and may need a de-coke. The latter is a major operation to remove the build-up of carbon from an engine’s combustion chamber.

Daily servicing

The pattern may include:-

checking/topping up the fuel

checking/topping up the oil

a light oil to the exposed control linkages and cables

checking and cleaning the air filter

check for loose nuts and satisfactory cutting condition.

Weekly or on the engine hour requirements:-

grease or oil all the oil/grease nipples as specified (frequently the lubrication to the bearings of the clutch races is given more sparingly to reduce the risk of excess oil reaching the clutch surfaces).

oil change, if required.

adjustments to the cutting mechanism, to take up the wear as required.

End of season:-

wash off and thoroughly clean.

change the oil and give a full service to all parts, filters, grease nipples, contact breaker cables.

check for wear – renew all cables, linkages and wearing parts which are unlikely to last the full season to come.

if the cutting cylinder and bottom plate need regrinding -book the machine in for this attention with the local grinding agent.

touch up lost paint patches.

store in the dry on blocks of wood.

some people advocate removing the spark plug and putting a few drops of oil on to the top of the cylinder head before replacing the plug. (I am not sure about this; I feel it is good for machines going into a long period of storage but hardly worth it for the winter only, since there is « always some risk of grit entering the cylinder every time the plug is removed.)

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