saviour stivala wrote: ↑
Thu Feb 10, 2022 9:21 am
gruntguru wrote: ↑
Thu Feb 10, 2022 12:47 am
AFAIK the main reason for the odd cylinder count in each row of a 4T radial is even firing. Firing order simply follows the crankpin around - every second cylinder fires.
Yes. Exactly. Why design otherwise (an even number of cylinders in a row) when at design stage one can already achieve less vibration and provide for more even pressure pulses in the exhaust, that’s apart from having an engine that sounds smoother.
Evidently you haven't heard a large single-row radial (such as in a T-28, for example), they sound 'staccato' rough.
Indeed, training units would - on the report of 'rough running engine' from neophyte fliers - check each 'pot' was hot
(@ cyl-head), to ensure it was running on all of 'em, & if they were, then the classic - 'They all feel rough like that..'
rejoinder was trotted out - as a truism/stock-in-trade...
If you can be bothered to look - well Bill Pearce in his article site, gives the firing order which enabled the USAAC
NVH engineers to 'sign off' that Curtiss-Wright 'hexagonal' even numbered 'radialine' - as meeting airframe spec...