& per T-C's recent interest in sleeve valve engine merits*, I found this Bristol TBO in a period 'Flight' article..
https://www.flightglobal.com/pdfarchive ... 01350.html
* The linked forum thread which included a Kiwi Bristol Hercules connection rang a personal bell..
( & where the splendid TBO's obtained by proper flight handling/maintenance in NZ, was duly noted)
..as a kid I recall the RNZAF Hercules-powered aircraft flying from the local military aerodrome,
& that they were markedly quieter than the US radial powered aircraft such as the Douglas machines..
The RNZAF used Bristol Hercules powered H-P Hastings' too, & ironically enough,they were replaced by
the Lockheed Hercules as transport aircraft - & yet even more ironically - the RNZAF sent their Hercules..
..powered Bristol Freighters to the ' Nam (to the incredulous amazement of US forces), rather than risk..
.. their expensive new C-130s in dicey supply runs, as the USAF were fairly profligately doing..
..meanwhile.. the USAF were flying Lockheed's next gen Starlifter to Antarctica, transiting via NZ..
We are standing on the toes of Hobbits. So wear safety boots.