Merlin engines

[Dr Jekyll]

Judging from the virtual production line of Mosquitos in New Zealand and various other projects. Supply of Merlin engines doesn't seem to be a constraint for the warbird movement as yet. Can they be rebuilt indefinitely using some new parts? Or are there still warehouses full of Merlins that can be refurbished and adapted where necessary?

[Jhieminga]

Have a look at: https://www.51-factory.com/inventory.htm and https://retrotrackandair.com/aero-engines/maintenance-department/. Places like this, and there are more, can deliver a lot of what the warbird movement needs. Some exotic engines and engine variants can be challenging... but so far a lot of issues have been sorted out and as you say, the Merlin engine situation does not appear to be a constraint here.

[ETOPS]

If you follow Kermit Weeks’s videos you will sometimes glimpse some 20 feet high racking with a large number of Merlin engines stored for future use.

Worth millions..

[Jhieminga]

I did the storage area tour at FoF many years ago. One of the places they took you into was the 'engine storage bay'. It can be seen (at least partially) in the second and third 'Tempest V' videos that were posted recently. Pretty sure that's the place you mean ETOPS .

[treadigraph]

I think Mike Nixon's Vintage V-12s at Tehachapi bought a lot of Merlin blocks and spares over the years, hydroplane Racers was one source as I recall.

I had a chat with Pete Rushen at Duxford once, he was dismantling a Merlin to get it running again; I think he said it was out of a Mossie and was heading to Australia - probably a swap for Beaufighter parts. TFC had probably already sold on their Mossie TV959 which is one of the ones now flying again.

[dixi188]

There are lots of different marks of Merlin, but do they all use the same basic 27 ltr. block?

[Jhieminga]

Essentially, yes, but I'm sure there's more to the topic than I know. Here's a quick breakdown of the main specs and the variants:

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/1172x650/screenshot_2024_03_20_at_13_51_47_e6acfef16c6e6622c3d4a870ee 4175306696bc54.png

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/1152x1100/screenshot_2024_03_20_at_13_49_11_6240c5d019a57d1029c6891e18 b1086bcae85d96.png
From: British Piston Aero-engines and their Aircraft, Alec Lumsden.

Edit: I understand that Calum Douglas wrote a pretty good book about, amongst others, the development of the Merlin, but I have not read it myself. See here: https://amzn.to/3VJ2Kpd

[DHfan]

There are lots of different marks of Merlin, but do they all use the same basic 27 ltr. block?

I don't believe so, although they may all use the same basic crankcase. I have definitely seen references to transport heads for the later civil versions and I'm fairly sure I've seen references to transport banks as well.

[megan]

I've read that the civil engines were more robust, but no details on what that actually means, mention was made that warbird operators find them a preferable fit.

[Jhieminga]

From a Key.aero thread (https://www.key.aero/forum/historic-aviation/44378-rr-merlin-what-are-transport-heads-banks):

Toward the latter end of the Merlin's military/civil life, some variants of the engine had been developed to a very high degree of longevity. Engine developed for the civil DC-4, the Tudor and the Argonaut for example - 600 & 700 series Merlins. Engines where longevity was of more importance than ultimate performance.When Transport Heads and banks are indicated it means that the cylinder blocks, cylinder heads, cams and operators are to this later specification and give an aspiration of longer life than normal over a stock Spitfire or Mustang engine.
Posted by Mark12
Transport heads were originally developed for the Avro York fitted with Merlin 24’s. These were the same engine as fitted to the Lancaster from about 1944 onwards. These were the most powerful of the engines fitted to the Lancaster 1 and were mirrored in the Lancaster III with 224’s from Packard. However the York had a greater life expectancy than the Lancaster and RR developed the 24T with improvement to the heads in particular to give a longer valve life. Up to this point development had concentrated on strengthening the pistons, improving the supercharger and better lubrication of the bottom end to improve performance.

Post war the Merlin 24T formed the basis of the 500 series that found its way into the Spanish built CASA CA2111. The 600 and 700 series engines were based on the 100 series that powered the latter Mosquito’s and Hornets, with vastly improved lubrication and were also 2 speed 2 stage engines. They were built exclusively for the civil market. It has been stated that the development effort expended on the Merlin post war was as large as that from 39 to 45, such was RR desire to gain a foothold in civil aviation with the Merlin.
Posted by TempestNut

[Geriaviator]

Another Merlin fate was to be used for tractor pulling. But my favourite memory is of the BOAC Argonauts opening up their four Merlins on the runway of RAF Khormaksar where my dad was stationed 1951-53. The original C54 used Twin Wasps which exhausted (I think) under the wing, making them much quieter than the Merlin stubs, but the Argonaut was 40mph faster. Passengers didn't like the noise but did like reduced time in the air -- not that it mattered much as long trips were broken up by night stops in those civilised times. Mind you, even then all eyes were on the graceful TWA Connies in their red and polished alloy livery atop a pressurised cabin.

Edited to add: just found another use for Merlins in Another Mossie Airborne thread below this one: After being sold to what proved to be an abortive project to use surplus Mosquito engines to blow air to protect fruit crops, the remains of NZ2308 ended up on a farm at Riwaka, This is the restored aircraft.

[DHfan]

There was a thread mentioning tractor pulling on Wix a few years ago. As I recall, although Merlins weren't unknown, generally the Allison was the preferred engine, performance at altitude not really being relevant.

[sycamore]

And a lot less parts than a Merlin...

[megan]

Post war the Merlin 24T formed the basis of the 500 series that found its way into the Spanish built CASA CA2111The 2111 was fitted with the Merlin 500-29. Also the HA-1112 Buchón (Merlin 500-45) and Fiat G.59 (Merlin 500-20) were powered with transport versions. One story I read was that RR had a stock of 500 series in preparation for airline production that never came to fruition, Spain and Italy thereby were able to obtain cheap deals to power their fighters and bombers.

[GeeRam]

And a lot less parts than a Merlin...

Less weight as well.

[tdracer]

For many years, Merlin's where the engine of choice for Unlimited Hydroplane racing - hence the term "Thunder Boats" due to the tremendous noise they generated. However they tuned those Merlin's to within an inch of their lives, so MTBF was pretty bad.
Eventually someone figured out how to make a small turbine work in that environment - which offered equal (or greater) power, high reliability, and much lower weight, and soon all the major Hydro teams switched over to turbine power (interestingly they still call them 'Thunder Boats' - even though they don't make that sound anymore). So, all those Hydro Merlin's were surplus'ed - and again became available for aviation.