RR Merlin Big End Lubrication.

That makes more sense!

CD, yes, the holes were positioned away from the outer rotational part to allow oil sludge to collect there, later, stand pipes were added internally to further avoid sludge blocking the feed holes, and yes, the engine is primed by a hand or electric pump if it has been standing for more than seven days, though nowadays, aircraft are often retro-fitted with pre-oiling systems.
Hercules engines have an oil centrifuge in the return circuit to separate some of the sludge.

P&P, no, they don’t leak, nice thought though!

Pete

It was the absence of these caps on my crank that had confused the issue. With the drawings above, all became clear.
Thank you gentlemen.

The other thing that occurs to me about these hollow crankshafts is how long they would take to fill with oil when the engine has been new-built (or rebuilt); is it necessary to pressure-fill them with oil before starting the engine?

Don’t forget that the caps that seal the hollow journals via a centre bolt are aluminium; that this aluminium component would absorb heat faster than the steel crankshaft and effectively allow oil to leak into and out of the journal; effectively a controlled valving system using differential expansion; four semi colons, a forum record! Happy New Year!

One interesting thing about the Merlin crankshaft is that the hollow centres of the journals seem to act as oil centrifuges; presumably this was not just accidental.

The other thing that occurs to me about these hollow crankshafts is how long they would take to fill with oil when the engine has been new-built (or rebuilt); is it necessary to pressure-fill them with oil before starting the engine?

That’s typical Wiki inaccuracy I’m afraid. I think what they meant to say was that the Griffon was the first engine to have an “end-fed” crankshaft, where oil is fed into each end rather than via a gallery into each main, and then into each big end, but in reality there is not a big difference in the crankshafts, and they have all been hollow since the very earliest types, for lightness. None were ever hollow right through the webs, just the journals.

I will check out that number, thanks for the info DAI.

Pete

I must admit that some time ago I was puzzled by the following entry in Wikipedia concerning the Griffon

“The Griffon was the first Rolls-Royce production aero engine to use a hollow crankshaft as the means of lubricating the main and big end bearings, providing a more even distribution of oil to each bearing.[7”

I had therefore been wondering how the Merlin bearings (main and big end) had been lubricated. The drawings supplied by Dairwin now explain it. Effectively the con rod big ends were each second in line to the adjacent main bearing for oil pressure. Not entirely ideal but the thought of manufacturing a “hollow” or at least fully drilled through V12 crankshaft is quite daunting.

Peter may well know, but in the meantime I do know that Merlin 324711 (39 engine numbers different) was built as a T24-2 by Derby within a batch of 168 engines produced between January and June 1946. That engine was later converted to a Merlin 500/29. Your crank might be from one of these.

324789 is the number I have Pete, can you tell me anything of its history?

Note that some of them don’t have diagonal drillings, some were drilled vertically through the web and plugged at the outer end, where the drill had to pass through, the plug being visible on the outer edge of the web / throw.
As a point of interest, the original engine number will be etched on the side one of the No5 throws, unless it’s a Packard.

Pete

I think the assumption that both he and I made was that it was fed from one end, all the way through, rather from each bearing journal.
I’m going to feed some lock wire into the big end journals to see the route more clearly, I think.

Pete, the crank was definitely used, from an airworthy engine.

Thank you all for your contribution.

C6

No, I agree. I just maybe thought that the crank-grinder had assumed that the crank was oil-fed from one end and not from each main journal and that ‘no feed holes’ meant no drillings between (some) journals rather than no oil lubrication holes in the big-end journals themselves…

…as you say, I can’t see how an engine could run without big-end lubrication (without destroying the bearings)!

Not every main and big-end journal will be connected so that the crankshaft is a single entity perhaps but is every big-end journal at least cross-drilled to one main bearing journal? In that way, in the version that all main journals are separately oil-fed, each big-end journal is also oil-fed (but they are not all interconnected within the crankshaft itself).

Those section drawings illustrate this better than I have described it..

…although the crankshaft has been ‘twisted flat’ to illustrate the oil-feed arrangement!

Quite true, but if a guy who does crank re grinds says there are no feed holes, then you have to assume there are none, otherwise he can’t be much good as a crank grinder!

Pete

…there doesn’t appear to be angled drillings in the crank to allow pressurised oil to travel to the big ends.

Not every main and big-end journal will be connected so that the crankshaft is a single entity perhaps but is every big-end journal at least cross-drilled to one main bearing journal? In that way, in the version that all main journals are separately oil-fed, each big-end journal is also oil-fed (but they are not all interconnected within the crankshaft itself).

Those section drawings illustrate this better than I have described it…

…although the crankshaft has been ‘twisted flat’ to illustrate the oil-feed arrangement!

[ATTACH=CONFIG]234150[/ATTACH][ATTACH=CONFIG]234151[/ATTACH] Close up of M100 on left, and MXX on right.

There are two basically different types of Merlin crankshaft, gallery fed and end fed, but both have drillings through from the mains to the big ends. I would seriously doubt that crank could have run like that, I assume it is unfinished. Is that possible?

Pete

Is this of any use to you?

http://aviationshoppe.com/manuals/v-1650_engine_packard/merlin.html

Forgive me if you already have a copy.

Rgds Cking