Packard vs Rolls-Royce Merlins

buffnut453 said:

Re post #56. That's good enough for me! Thanks SR. Appreciate the sourcing info.

I'm still struggling to understand how the RAF dealt with the supply/maintenance challenges of such variable tolerances. Manufacturing is one thing but maintaining engines at the squadron or MU level would be almost impossible if the units had to factor in, for example, engines with "all heavy" pistons and "all light" pistons (and, presumably, "all points in between" pistons!).

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I think the point that SR is making is that all production facilities making the Merlin - be they in the US or in the UK - worked to the same tolerances. That a piston from any one of these factories were to the same standard and would be interchangeable with one from another factory.

The proper comparison is between the Shadow (eg Ford) Merlins and Packard Merlins. The earlier Rolls Royce made ones were made for production order of few hundreds. The later vast factories were pushing them out by the thousands. Rolls Royce early production methods were appropriate to the investment for those low numbers. Had they invested at the beginning in the machinery that the huge factories used then Rolls Royce would have been bankrupt long before the war. The original Rolls Royce tolerances and the later shadow/Packard tolerances were both the right answers. But to different questions. Much as the Meteor was developed in a very different direction to the Merlin but was the right answer to the question of a powerful, reliable petrol tank engine at the time.