View Full Version : RR Merlin life expectancy

Mr Proachpoint
31st Dec 2003, 15:55
I often read that most vintage V-12 piston aircraft will be grounded by either of two circumstances. The first is the consumption of all fossil fuels. Possibly a load of bollix……….. The other and more realistic cause is the consumption of all specialist and crucial spares. To get to nuts and bolts, I am talking about crankshafts, camshafts, impellers, prop shafts and all those components that are finite lifed and at the moment irreplaceable through manufacture. The books say that when the last crankshaft etc is used, the growl of the V-12 has gone because there is no capacity worldwide to manufacture suitable replacement.
Are we being naïve to think that in 2004, we blokes can’t produce an item mass produced by a bunch of (supremely worthy) chicks squinting into a wobbly old belt driven lathe or grinder.

I often see the product of the many Warbird restoration sheds that produce a fighter made to order by people who have the cash to produce an aeroplane worth its weight in gold. If the supply of crucial spares is due to dry up, what is the reality of the lack of these components grounding our WW Vee’s?

Some individuals go to ‘ridiculous’ lengths to rebuild a V-12 fighter. I find it hard to swallow the fact that the world in 2003/04 can’t produce the guts of the engine that has shaped history.

Any thoughts?


astir 8
31st Dec 2003, 16:06
There's nothing that can't be made (at a price).

But then there's the CAA/FAA paperwork and "product liablility" to deal with - which is why the "eternal warbird" will eventually be grounded.

Hence it's perfectly legal to fly with a 60 year old crankshaft made by relatively unskilled labour on a wobbly lathe (blessings be on both operator and lathe) because it was made in a Rolls Royce factory and has the 60 year old paperwork to prove it.

But highly skilled Fred Bloggs with his computer controlled lathe and modern steel just can't be trusted by the powers that be. :(

31st Dec 2003, 16:44
The Merlin may well be the exception to the rule. It must be the dominant engine among the A-list warbirds, when you consider the large number of active Spitfires and the flocks of Mustangs that are in regular use worldwide.

Mr Proachpoint
31st Dec 2003, 16:53
Astir and Brizzo,
Very good points there. Reno can't be helping...............

Hopefully we can do something about it.


Hats off to those young ladies.


Boss Raptor
31st Dec 2003, 18:06
A place I visit/work at builds the Yak-3 replicas, exactly to the original plans, although use of modern machining/techniques etc. reduces build time considerably and cost is not high either (until marked up by the dealer). They also build the Yak-52 including the engine. Ironically in Eastern Europe they have maintained the old fashioned metal bashing skills combined with the new equipment/technology/processes.

There is absolutely no reason a complete brand new full spec Merlin could be built (at this plant or elsewhere) and not at huge cost (with lower Eastern Europe labour rates). Getting plans from RR well that's a different matter :hmm:

Iron City
31st Dec 2003, 21:05
1. believe another major consumer of Merlins has been the offshore power boat racing community. I had heard that they consumed Merlin's at a rate far beyond the air racing community. What kind of demand do they place and how does that change the economies of scale, etc. They wouldn't need all the paperwork.

2. WRT the manufacture of parts and getting drawings from RR etc is it possible that the design passes into the public domain after a certain period of time ? I do not believe the Ford company gets a royalty every time a glass fiber copy of model T fenders is sold, so is it possible that the design of the Merlin has passed into the public domain? If that is so and the part is made by somebody (Joe's Machine Shop, for example) then whatever liability there is is Joe's. If the aircraft is operated in the Experimental category would that reduce/eliminate the paperwork requirements to a reasonable point.

1st Jan 2004, 19:07
Mr P,

Sadly we will eventually lose all the Merlins, whilst we may have lathes that can produce machined parts measured down to fractions of a micron, the problems are with the spec of steel that was used originally on those wobbly lathes, the steel industry just cannot produce such specification now despite all their equipment being run by Jap/Korean brains.

Even something as simple as the cross tie bolts that hold the bottom of the Merlin crankcase together were manufactured from steel no longer available to the spec design that Rolls Royce stipulated.

If you jump on a little from the Merlin to such giants as the Griffon, the pylon racers mind set was for replacement engines and props between race's, with that sort of tumble weed thinking very shortly the Earths supply of used Griffs will be gone also:{

1st Jan 2004, 19:33
There would probably be many issues regarding manufacture of parts to a/c standards which would not be cheap.

Many changes with the different marks. The early ones were fundamentaly hand built although all the machining tolerances were changed by Ford (UK) ``1940 to enable mass production.

The materials eg a particular steel, may not be available now and almost certainly not with a/c QC. A single heat of a given steel may not be an economic proposition.

The materials may be illegal now eg asbestos gaskets.

The mountain of paper on materials, heat treatment, finishing etc etc is unlikely to exist even if the drawings still do. Minor changes in any of this could have major consequences. Would RR or whoever want the liability problems

How long will 100 octane be available, more changes

What this leads up to is it would have to be virtually a new engine with extensive development. Of course the offshore power boat racing community may be the answer for development in a relatively non critical enviroment - although they would probably prefer a Griffon

1st Jan 2004, 20:01
I forgot to put this on my earlier reply, but the last time I looked at the offshore racers docked pre race in Italy, the majority use V12 lamborghini/Merc/Volvo/Man Petrol and diesel mills, and other such exotica to propell them through the Azure liquide, these things make the consumption of Merlins /Griffons look like a Sunday school outing.

I once had a Marinised Griff attached to the marine G/box the whole unit was ready to be hoisted into any boat that could support it, that unit alone weighed 2.6 tonnes and was about two and a half time the normal length of the Aero Griff, an ex sailor who worked on boats powered like this normally had two such units and drank or should I say slurped 100Octane juice at he the rate of 5 galls per mile.

Another marine engine I had was the Issota Fraschini W18 (W config 18 cyls with trimated con rods)engine and box that came out of ex Norwegian Navy MTBs this of some 60litres reputable drank juice at about 12 Galls per mile, and was normally paired, to keep the weight down to 2.4 tonnes it was cast in Magnesium and other such exotic alloys :ok:

2nd Jan 2004, 01:46
See my post at end of "Lightning photo".........

Boss Raptor
2nd Jan 2004, 04:19
Good technical in-depth points Mr. Deaf and further detailed than my own knowledge.

If it were (as a hyperthetical question) possible then you would adapt current materials to the basic Merlin design. This happens now in all in-service aero engines where as materials technology moves forward components are made from other than the original design materials and certificated accordingly, I am thinking in terms of gas turbine blades, seals, bearings etc. and many others.

How far you would have to go and how far you would be able to go before having to completely re-certify the Merlin would be the issue. But again all 'modernised' components would have to go through individual test and certification as per my point above.

2nd Jan 2004, 11:46
Two possibilities if certification is required

A US type STC. For stuff like crankshafts or valves I suspect this would essentially involve a recertification test (the 150hr? one) for the new components.

A new! engine the Deaf V1670 with eg Packard crankcase and heads, RR gearcase with new pistons, crankshaft, valves, gears etc Modern fuel injection and ignition.

All it takes is money for development.

The engineering shouldn't be too difficult if the market is there, as an example look at VW's where you can build a complete motor from 3rd party parts which are often much improved from the original. We can assume that the materials have been improved considerably, even in cases where they are nominaly the same the nasties (eg P and S in steel) have been cut back and processes such as vacuum refining can help consistancy. Having said that there could still be surprise problems as shown recently with Lycoming crankshafts.

One point that should be noted is that with piston engines the development often has to be done with the whole engine while with turbines things like the compressor, combustion chambers and turbines can be developed separately in test rigs.

2nd Jan 2004, 15:43
These chaps should be able to answer all of your questions ref Merlin horoscope, I think we shall be able to hear RR V12 music for quite some time to come:ok:



Dr Illitout
3rd Jan 2004, 02:09
With all the advances in electon beam welding and flame spraying re-working most of the Merlins internal componants shouldn't be that much of a problem. Given enough money of course!!!. One big problem though might be the exhaust valves as they are filled with sodium, that is a whole new can of worms!.
But with enough money...................