Were surviving early Merlins rebuilt and upgraded? (1 Viewer)

[Admiral Beez]

When say, a Spitfire Mk.II with a year or more service is written off in a 1942 prang, but with a still operation Merlin XII, would that engine be sent back to RR to be rebuilt and upgraded to Mk. V spec?

 

[Geoffrey Sinclair]

The short answer is no, a working engine was normally returned to store until the version was classified as no longer required. Now for the exceptions, Ministry of Aircraft Production, Engine Conversions cumulative to 27 January 1945.

Engine	To	From	Quantity
Merlin	45​	III	90​
Merlin	46​	III	9​
Merlin	21​	XX	23​
Merlin	22​	XX	1​
Merlin	22A	XX	955​
Merlin	23​	22​	171​
Merlin	24​	22​	1​
Merlin	25​	24​	2​
Merlin	24​	27​	2​
Merlin	25​	27​	131​
Merlin	46​	45​	3​
Merlin	45​	46​	37​
Merlin	45​	50​	37​
Merlin	46​	50​	4​
Merlin	71SP	61​	1​
Merlin	72​	61​	20​
Merlin	85​	63​	3​
Merlin	63​	64​	36​
Merlin	63​	66​	4​
Merlin	65​	66​	4​
Merlin	85​	66​	6​
Merlin	66​	67​	34​
Merlin	266​	69​	417​
Merlin	77​	73​	1​
Merlin	266​	266P	296​
Griffon	VI	III	2​
Griffon	IV	III	8​
Hercules	XVI	VI	619​
Hercules	XVII	XVI	2​
Mercury	30​	XVI	658​
Mercury	30​	XX	24​
Mercury	30​	25​	16​
Taurus	XII	II, VI, XVI	17​
Centaurus	VI	IV	36​
Centaurus	VII	IV	49​
Sabre	IIa	II	910​
Sabre	IIIa	III	1​
Cheetah	XV	X	1​
Cheetah	X	XV	1​
Cheetah	IX	XII	32​
Gipsy Major I	Auster	Magister	30​
Gipsy Major I	Moth	Messenger	85​
Gipsy Major I	Moth	Civil	5​
Gipsy Major I	Messenger	Magister	9​
Gipsy Queen	II	I	23​

 

[glennasher]

I know that some of them were de-rated and converted to tank engines, but I don't know if they could go the other way. I'm doubtful about that. Then again, I not anything like an expert on engines in any case.

 

[Thumpalumpacus]

I'd be surprised if tired engines weren't used to train ground crews.

 

[Geoffrey Sinclair]

The derated version of the Merlin (600 HP) meant for tanks was called the Meteor, they were not second hand aviation engines,

Meteor tank engine deliveries September 1942 to September 1944, table 27, September 1944 Ministry of Aircraft Production Statistical Bulletin, figures to October 1944 only, after that they drop the reporting.

Sep to Dec 1942, 10, 35, 30, 66

1943 per month, 87, 88, 79, 77, 70, 49, 71, 87, 97, 142, 132, 107

1944 per month, 160, 112, 147, 190, 243, 257, 220, 173, 195, 111,

Originally meant for Centaur which were renamed Cromwell when the Meteor replaced the Liberty engine. Also used in Challenger, Avenger, Comet and Centurion.

Like written off airframes old engines could be sent to the training system.

 

[MIflyer]

Well, the Merlin was less somewhat amiable to that kind of thing than the V-1710, which had gearboxes and accessory sections that could be removed, unlike Merlin.

But there were the "Clipped, Cropped and Clapped" Spitfire Mk LFVb, designed to better handle the FW-190 below 10,000 ft, since they certainly could not handle it up higher. They clipped the wingtips to improve roll rate and cropped the supercharger impellers so they could run full bore at low altitude and not overboost the engine. The "Clapped" referred to their age and questionable history, not unlike ladies of the evening.

There were still some of those Spits flying combat in June 1944 (e.g. 234 Sqdrn) and the pilots mostly agreed that at low altitude they were the hottest thing around.

 

[Simon Thomas]

What is a Merlin 266P?

 

[Admiral Beez]

The derated version of the Merlin (600 HP) meant for tanks was called the Meteor, they were not second hand aviation engines,

Was it also used in MTGBs?

 

[EwenS]

Was it also used in MTGBs?

Cant think of any such use. The petrol engines that found their way into coastal craft were mainly

Isotta Fraschini V18 57ltr (eg in very early Vosper craft
Napier Sealion (eg BPB High Speed Launches)
Hall Scott V12 Defender (egFairmile B ML for example)
Packard 1A/4M 2500 V12 (eg later Vospers & Fairmile D)

 

[ThomasP]

There were a few marinized Merlins used in the early-war MGB(?). British Power Boat under Scott Paine helped develop it, and I think it was known as the Power-Merlin.

3 engines were fitted in several of the 1939 built RN boats, and at least 1 boat was sold to the US - I think it was operated as PT-9 (after being re-engined with Packard M-2500s?).

Somewhere, on the internet . . . there are images of the installation in one of the RN boats, and images of the engine installation on a test mount at BPB(?) or RR(?). The installation was similar to what was eventually used in the US ELCO boats powered by the Packard M-2500.

There was also a scanned purchase/production order posted somewhere.

I am not sure but I may have downloaded the images of the installed engines and the engine on the test mount - I will look for them.

 

[ThomasP]

Found this on the excellent "PT Boat Forum" website. It is not the purchase/production order I referred to above (that was for 97(?) engines and associated bits and pieces) but it proves the existence of the Power Merlin and its application to PT/MTB/MGB. The webpage is here: "The PT Boat Forum & Message Board - PT-9"

 

[Shortround6]

Cant think of any such use. The petrol engines that found their way into coastal craft were mainly

Isotta Fraschini V18 57ltr (eg in very early Vosper craft
Napier Sealion (eg BPB High Speed Launches)
Hall Scott V12 Defender (egFairmile B ML for example)
Packard 1A/4M 2500 V12 (eg later Vospers & Fairmile D)

There were some boats that used Merlins but they were early boats. Some boats used two Merlins instead of three Napiers. Some boats got three Merlins but the Air Ministry wanted most/all Merlins and that is what brought about the importation of the Isotta Fraschini engines and talks about license production. I don't know how far that got. I don't believe there was any British production.
Hall Scotts were good engines but they were heavy and most came without superchargers with about 600hp max power. With superchargers they were good for 700-900hp. The largest. most common version was 2281 cu in. Good engines in the Fairmile B ML but not so good in 72-80ft torpedo boats. Engine shortages saw them installed in some boats in 1940/41 but such boats were slow. The Big Packards took over in the fast boats.
The Packards powered the vast majority of MTB/MGB boats from 1941 on.

I don't know what happened post war for sure, any boats that got Merlins as replacements? Two boats (MTB 538 and MTB 539) used Packards and the Gay class of 1951-53 used a higher powered version of the Packard. These were substitute boats while they waited for the Deltic diesels to get sorted out for the Dark class. This would cast doubts about post war marine engine use of the Merlin as far as the RN goes. Private yachts/speed boats might have been possible.

Getting back to 1937-41, Merlins had been fitted to 1-2 prototype boats and some? boats of 1938 program although this is when the Isotta's were first used. Due to Italy entering the war in June 1940 only about 30% of Isottas' ordered had been delivered and this caused the scramble of using the un-supercharged Hall-Scotts. Due the BoB and the Blitz over the winter, no Merlins were released for maritime use?

Hope this helps.

 

[EwenS]

I've been doing a bit of digging in the deeper recesses of my library. The Haynes Manual "Rolls-Royce Merlin Owners Manual" has a brief paragraph on the marine Merlin that reads:-

"In 1938, a project was considered to provide marine Merlin engines for a new range of highly powerful, fast Motor Torpedo Boats for the British Navy. A large reduction gearbox was driven and coupled to the propellor shaft instead of the aero reduction gear. Initial trials were successful, but the Merlin project was cancelled in 1940 with very few boats completed."

Cancellation in 1940 would coincide with huge demand for Merlins for Hurricanes and Spitfires.

From there to "Warships of World War II" by Lenton & Colledge, the following are noted as having "Rolls Royce petrol engines":-

The following were all ordered from the British Power Boat Company by foreign navies but requisitioned. Originally inteded as Motor Anti-Submarine Boats (M.A/S.B) they were completed as MGB in 1940 and into 1941.

Nos 40-45 (6 boats) - 24 tons. 63 x 15 x 4.25ft. Two shaft RR petrol engines 2,200bhp giving 40/36 knots. Built 1940. (12 engines). These had originally been ordered by the Norwegian (4) & Swedish (2) navies and were requisitioned by the RN as intended M.A/S.B but completed as MGB.

No 46 (1 boat) - 32/37 tons. 70 x 20 x 4.25ft. Three shaft RR petrol engines 3,300/3,000bhp giving 42.5/39 knots. Built 1940. (3 engines). Originally ordered by the RNethN and requisitioned. Intended as an M.A/S.B but completed as an MGB
Nos 50-67 (18 boats) - 70 x 20 x 4ft. Three shaft RR petrol engines 3,300bhp giving 40/36 knots. Built 1940/41. (54 engines). Ordered by the French as M.A/S.B and requisitioned for completion as MGB.

So 25 boats with 69 "RR petrol engines". And all originally intended for foreign navies. BPB then switched to using the Packard engines for later MGB that had all been designed from the outset as such. All the other builders of coastal craft were using engines from other manufacturers.

Then we have the story of PT-9 / MTB258.

According to Lenton & Colledge this craft was built as a private venture in 1939. 30 tons; 70x20x4ft powered by three shaft RR petrol engines 3,300/3,000bhp giving 44.5/49 knots. Built 1939. The RN chose not to buy it. Instead it went to the USA as PT-9 arriving 5 Sept 1939 and per Navsource was acquired after trials by the USN on 24 July 1940. Navsource notes her as being engined with three 1,500shp Packard V12 M2500 gasoline engines on three shafts

Lend Leased to Britain on 11 April 1941 she was immediately passed to Canada along with US built experimental PT boat numbers 3, 4, 5, 6, & 7, where they spent the rest of the war in Canadian waters. This article notes that PT-9 was supplied to Canada without engines to be re-engined there with two Klermath 550bhp V12 petrol engines.

RCN Patrol Torpedo Boat: HMCS S-09

RCN Patrol Torpedo Boat HMCS S-09 (RCN Photo) HMCS S-09 (torpedo boat) This was one of six U.S. PT boats acquired by the RN under Lend Lease in 1941. Number PT-3, 4, 5, 6, 7, and 9, they were subsequently lent by the RN to the RCN. PT-9 was re-designated S-09, while her five sisters served ...

silverhawkauthor.com

So while the sources agree about the re-engining in Canada, it begs the question had she been re-engined while in the US? Looking at the Navsource histories of these early experimental PT boats, there is evidence of some re-engining having taken place.

Motor Torpedo Boat Photo Archive

 

[Engineman]

What is a Merlin 266P?

Hi,

That is an interesting question. The Merlin 266 was, of course, a Packard built version, very similar to a RR built 66. Due to the mass-production of Packard, many engines were built in batches that were to an earlier modification standard and by the time that they got to the UK it was decided that they must be upgraded before use. These changes were often for piston and/or conrod mods, so were very considerable work. I am guessing that somewhere in the paperwork trail it was decided to use the P for original Packard built standard of these early 266 engines. Of course, it may have been for Provisional or Pre-mod or similar and after upgrade they became the later 266 standard and the table shows a considerable 296 of them. Of note, the similar Merlin 69 was also a Packard built engine, but with a .42 reduction ratio. In the table we can see 417 of the Packard built Merlin 69 engines that were modified to 266 standard, presumably to the .479 ratio and with other updates required, for the Spitfire LF XVI production.

Eng

 

[Engineman]

When say, a Spitfire Mk.II with a year or more service is written off in a 1942 prang, but with a still operation Merlin XII, would that engine be sent back to RR to be rebuilt and upgraded to Mk. V spec?

Hi,

Knowing the way that the RAF MU and stores systems worked, I would say that engines generally remained within their allocated aircraft cohort during service. Salvaged, rejected and time-ex engines were repaired or modified to later standards after categorisation. However, in the table we can see the large 955 Merlin XX group that were modified to Merlin 22A standard and this was reflecting a drive to the improved standard with two-piece cylinderblocks. Similar upgrade programs existed with other engines but, they usually retained the original engine type, although the mod state would be listed on the engine data plates and in the engine log book.

Eng

 

[Shortround6]

Over 50,000 Merlins were repaired/rebuilt in 6 UK centers. This does not include repairs/rebuilds at overseas repair centers like Cario and India.

Repairing engines that had suffered prop-strikes was common and a way to brace a cracked and welded gear case was worked out that included a brace going from the rear of the gear case to the top of the crankcase on an angle. There were also ways to repair worn crankshafts and/or bearings.

Upgrading worn engines to higher power levels was probably not done. Rebuilt engines, on average, lasted less time than new engines of the same power level. Things (crankshafts and crankcases and cylinder blocks)) cracked with age/use.

A lot of old Merlins got used in training aircraft and target tugs. I don't know if they down rated them like the Americans did to the Allison. American training P-40s sometimes ran on 91 octane fuel with both lower rpm and boost ratings. But flying a 900hp P-40 was still a big step up from an A-6 trainer.

 

[ThomasP]

Found the picture of the Power Merlin installation in one of the 3-engine boats. If you expand the image to 200% you can just make out the Rolls Royce name on the side of the valve cover on the right-hand engine.

 

[Engineman]

A lot of old Merlins got used in training aircraft and target tugs. I don't know if they down rated them like the Americans did to the Allison.

The RAF WW2 training aircraft using Merlins were mostly OCU aircraft that were recently retired operational. It is as you say, conjecture if they were derated, but quite possible that some were operated to lower power ratings in their training use.
The UK dedicated training aircraft designed to use the Merlin seem to be the post-war AVRO Athena and Boulton-Paul Balliol trainers that used the post war Merlin T35. It is likely that all the RR engines for new-build aircraft were new build, and to a high standard.

Eng

 

[Simon Thomas]

I had never noticed this before, from 'The Merlin in Perspective" RRHT:
It's worth reading re this topic, as it includes the whole of life partnership RR had to keep the Merlin operational, such as defect investigation, modifications, repairs etc.

 

[ThomasP]

FWIW

In my notes (from sometime in the mid-1990s) I have the Merlin 266P and Merlin 69 carburetters being problematic, and the problem carburetters subsequently replaced with the same carburetter as used on the Merlin 266 and Merlin 66.