I guess the answer to Dave's original thread title depends entirely on your perspective; from a British point of view, the Hercules gets tons of respect and is quite rightly regarded as one of the most successful wartime and post-war piston aero engines built. I can't offer facts and figures regarding reliability, but I know engineers who worked on them on aircraft like the Short Solent flying boats with our national airline in the 1960s and the Bristol Freighter, examples of which were flying here in New Zealand until the late 1980s. I also know of a chap who has carried out a ground up restoration on two to running condition to power one of the ex-Safe Air Bristols. None of these guys have ever commented on difficulty in comparison to other piston engines.
The Herc was - along with the other Bristol sleeve valve engines, something of a work of art. Their concept was quite different at the time and although tolerances of the sleeves to distorsion were small, in terms of maintenance complexity and reliability, certainly did not prove insurmountable. If they were that bad, then the Herc would not have been applied in the large number of different types it was used in.
Sure, the guys on the hangar floor would have moaned about the problems with sleeve valve engines when they first appeared, but over time, with maintenance frequency, engineers get used to a certain way of doing something and take things in their stride. The fact that Hercs were still in scheduled operations into the 1980s isn't just a testament to the fact that New Zealand is something of a home to old aircraft operating past their sell by date
)), but to the engineers and equipment they service.
A beautiful sectioned example in Scotland
Life is a pair of Bristols!
I've heard that the Lancaster was fitted with Merlins because an appropriate radial wasn't available early on.
Well, sort of; as early as April 1937 Roy Chadwick had raised the proposal of a four engined Manchester powered by Hercules', but many in the Air Ministry thought the Manchester had no further development potential; the only way the Lanc came about was through Avro pushing that Manchester production lines could be adapted relatively quickly.
Early discussions before the Manchester was built as early as 1937 stated that the prototype was to be powered by the Hercules, the HP.56, which was the twin engined forerunner to the Halifax to be powered, like the Manchester by the Vulture, was at one stage considered for the Hercules, although four Merlins were chosen because of lack of availability of the Hercules.
When exactly the four engined Manchester got its Merlins, I'm not sure, but it seemed the logical choice as the Halifax was being used as the benchmark for performance and capability, although the Halifax I was an utter dog. Ironically it wasn't until the Hali III that the Handley Page bomber got performance and capability near the Lancaster's!