I`ve heard this many times, and I`m afraid I dont believe it, and I have never once seen any evidence for either figure (I`m sure the 7000 is true, but I dont think
any supercharged aero V12 will have a parts count varying by more than about 25% to any other, what on earth could they be ?, surely this is
something like one person counting each carburettor jet and magneto winding wire, and the other person ignoring all the ancillaries)
Even if each bolt had an extra lock pin and washer it would not amount to more than a few hundred bits.
Until someone takes both engines to bits and films it, and counts the bits - this one is firmly in the "myths" basket for me. I dont know, maybe if you
picked a fuel injected two-stage 1946 Merlin-100 and the very first V-1710 ever made in 1930... but like-for-like, no way.
As you will see in my book, generally speaking in terms of the basic engine architecture, I rate the V-1710 more modern than the Merlin.
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Maybe you haven't looked at the nut, bolt, and screw count when the engines are all apart in front of you. Understandable. Most of us haven't. I have been lucky in that regard. I worked at an Allison shop for more than 3 years and have volunteered at a museum where they sometimes take Merlins apart right in the restoration hangar where I work on restoration. Having seen both in pieces, I believe it.
Rolls-Royce seems to have the philosophy, "why use 40 screws when 100 works so well?"
Here's a center shot of a Merlin from the front:
Note the number of screws and bolts.
Here's a center shot of an Allison from the back:
BIG difference in parts count from the intake manifold system alone.
Not trying to be snarky here, Callum. Just observing and, in the case of Allisons, I spent most of my time disassembling them in the overhaul process. Some assembly. But mostly disassembly and cleaning the parts. It isn't straightforward to take an Allison or a Merlin apart to component pieces.
It takes 2 - 3 people about 13 weeks to overhaul an Allison V-1710. 12 weeks to disassemble, prep, replate, inspect and generally freshen up the parts and 2 - 3 days to assemble one, depending on interruptions. Takes another 3 - 4 days to put it on a test stand, pre-oil and run it in (seat the rings) until the inside of the exhaust manifolds turns light gray instead of dark wet black. Then you can ship it.
Cheers. Oh, and, I have your book. Magnificent work, Callum.
Sign me up for your book on radials when you write it.