Prop rotation direction

Late model Mossies props rotated clockwise on both engines. the reason for different mark Nos was the auxiliaries that the engine drove. Power for the radar in the NF36 came from an alternator driven from the port engine.

“…..Alan, what restoration was this? I’m surprised it says the propeller was difficult to replace. There are plenty of options for hubs, new blades can be made & most parts can be manufactured if needed.

Jamie….”

Perhaps I should have said repair rather than restoration. It was SX336 following a wheels up landing in 2011

Yes, correct about the Hornet case, chaps. I’d forgotten about that. Was the late Mossie the same – Merlin 113/114? However, the main premise is the same; that the engine still rotated in the same direction, just the prop went the other way – or went the same way as the crank with the idler gear!

Anon.

I was reading about the restoration of the Seafire, and it was said that one of the most difficult things to replace, was the propeller.

Alan, what restoration was this? I’m surprised it says the propeller was difficult to replace. There are plenty of options for hubs, new blades can be made & most parts can be manufactured if needed.

Jamie.

From the Heritage trust book The Merlin 100 Series ( A very good read I might add as is The Merlin in perspective). The Merlin 131 reverse rotation reduction gears.

Miniman is correct. The Merlins installed in the DH Hornet had the propellers rotating in opposite directions, the Merlin 130 had standard spur gears and Merlin 131 had an added idler. Or so I have read

An engine’s rotation is defined by the direction the propeller rotates when viewed from behind.

As stated, the Merlin’s prop goes clockwise but the crankshaft goes anticlockwise due to the fact that the spur reduction gear reverses it.

Obvious, probably, but worth stating in case anyone is confused.

Not sure about the suggestion that some Merlins went the other way due to the idler gear. It would require major internal engineering changes if a Merlin were to be altered to rotate the opposite way.

If it was a contra-rotating propeller on the engine then, yes, each prop would have opposite rotation achieved for one of the propellers, as stated, by an idler gear off the aforementioned spur reduction gear to one of the propsets – but the crank would still rotate ACW when viewed from the rear.

hope that makes it clear as mud!

Anon.

Thanks for info.

As general rule yes, but there are some Merlin’s that were opposite rotation from normal, however this was achieved with an idler gear in the reduction gears, the engine itself still rotated in the “normal” direction.

Yes. The Merlin, for some reason, was “the wrong way round”. At some stage (late 1930s/early 1940s) the RAE called for consistency in these matters, which the Griffon matched.