Large bore diesels rule!

The contentious subject was, once again, large-bore diesel engines. The editorial reminded us that less than four years previously, the journal had “run into severe criticism” for suggesting that it would be necessary to consider larger-bore engines than currently employed. And a significant proportion of the pages in December 1960 were given over to various engines of around 850mm bore, with even larger cylinders in development. The editor reminded us that large engines had been tried before, with not particularly encouraging results. But current experience suggested that large-bore engines were here to stay this time round.

Our predecessors were proved right, of course. Then, an example of a successful ‘high power’ engine was a B&W 840mm bore design that had been tested to a remarkable output of just over 2,500 bhp per cylinder, which represented 120% of MCR. That of course looks tame by today’s standards, when we have engines normally rated at more than 100,000 bhp, albeit from some 14 cylinders (and neither should we forget that those engines have not been 100% trouble-free).

A further question concerned time between overhauls. Then, a few ultra-reliable engines were approaching 7,500 running hours (almost 330 days) before opening up. That is another area where real progress has been made with today’s engines, giving high specific power outputs along with high levels of durability.