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Advagiageo

27th January 1978
Page 54
Page 54, 27th January 1978 — Advagiageo
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Which of the following most accurately describes the problem?

*The article on engine cooling by "Preceptor" (CM, November 28) made very interesting reading.

I was disappointed, however, that the constraints of the article made it necessary to leave out certain benefits of direct air-cooling which, because they are not universally realised, will certainly interest your readers.

The principle at the heart of any cooling system is an important one, namely that all engines are air-cooled. Those engines described as liquid-cooled merely use the liquid as a means of transferring the heat of the engine to the air.

As Magirus Deutz are singled out as the only notable commercial vehicle manufacturers using air-cooling, I should like to point out certain advantages of our own engines, which received no acknowledgement in the article: 1 There is no possibility of crankcase or radiator corrosion.

2 There is no possibility of cavitation and, therefore, no localised overheating within the engine, of which no-one would be aware.

3 There is no water pump to leak, seize or fail.

4 The temperature indicated to the driver is the actual temperature of the cylinder head and not the cooling medium.

5 In the event of thermostat failure, five minutes work with a 10mm spanner allows the driver to by-pass the thermostat and be on his way.

6 It is far easier to carry out in-chassis repairs.

7 It is far easier to carry out engine removal and re-fitment. The article pointed out that there are certain drawbacks in putting air-cooling into practice. We agree. Magirus Deutz have been making air-cooled diesels since 1 944 and have invested huge sums in engine and cooling system design. The present range of diesel engines manufactured by Magirus Deutz is the result of many years of development work, in which problem areas have been systematically scrutinised and, we feel justified in saying, eradicated.

Allow me to list the disadvantages given in the article and explain how these have been overcome.

''A large fan and cowling must be provided . . so more power is required to drive it." As the fan is only driven at a speed proportional to engine temperature, the average power absorbed by the fan is very low. Moreover, the high speed of the fan allows the fitment of a centrifugal oil filter, which complements the normal filter, allows a degree of protection should the normal filter become blocked and also gives a guide to the most economical filter change periods.

"It is necessary to cast each cylinder separately." By manufacturing each cylinder and cylinder head separately, maintenance costs can be reduced, components standardised and hence spares holdings kept to a minimum. Engine overhauls are simplified with a consequent saving in downtime.

"Cylinders must be a fair distance apart." The distance between cylinders on the Magirus Deutz F8L413 engine is 165mm which, I think you will agree, is in keeping with conventional engines of similar power.

"It is more difficult to arrange a heating system for the cab" By using oil from the engine sump it is possible to design a more efficient heater than one which relies on hot water, simply because oil can be heated to far higher temperatures than the boiling point of water.

On the point of overheating in arduous conditions, I should like to point out that Magirus Deutz have earned a reputation second-to-none in tropical and semi-tropical countries, where not only is it difficult to prevent water-cooled engines overheating, but it is also difficult to obtain a ready supply of water.

In conditions of high ambient temperature, the temperature differential between the cooling medium (cooling fins — air-cooled, coolant — water-cooled) and the air governs the rate of heat transfer. Because this differential is greater in the case of the air-cooled engine, the rate of heat transfer is also greater and there is, therefore, less likelihood of overheating.

You can see, therefore, that the advantages of air-cooling are many and that the disadvantages are only there for a manufacturer contemplating air-cooling as a new venture.

At Magirus Deutz we are confident that the disadvantages have been overcome and that many have, indeed, been turned into benefits.

A. GRINDROD, Technical Manager, Magirus Deutz (Great Britain) Ltd, Wins ford, Cheshire.

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