Griffon vs Merlin rotation.
Join Date: Jul 2004
Location: Sydney NSW
Posts: 513
Likes: 0
Received 0 Likes
on
0 Posts
Which way to turn?
The current and last few issues of the Rolls-Royce Heritage mag available on the web are instructive. Not only which way to turn but subtle mods to superchargers, turbochargers as a consequence of the handing. Its not just firing order.
Errors, myths, clangers etc would be avoided if only it dawned on folks that the FACTS are available through the Heritage society and even R-R itself rather than perpetuating some nonsense.
The Heritage soc is a separate body to R-R proper and includes Allison and Packard sections. The missives from the Derby and Hucknall branch are notable for their first-hand knowledge and technical authority.
Rather than recycle tired and wrong info why not sign up?
Errors, myths, clangers etc would be avoided if only it dawned on folks that the FACTS are available through the Heritage society and even R-R itself rather than perpetuating some nonsense.
The Heritage soc is a separate body to R-R proper and includes Allison and Packard sections. The missives from the Derby and Hucknall branch are notable for their first-hand knowledge and technical authority.
Rather than recycle tired and wrong info why not sign up?
Join Date: May 2008
Location: Japan
Age: 71
Posts: 204
Likes: 0
Received 0 Likes
on
0 Posts
Excellent. Thank you sycamore, DaveReidUK and enicalyth. Merlins aren't Etruscan vases. They still exist, still work, and the people who built them and maintained them are still alive. And yet, there is an amazing amount of total borrox spouted by those who should know better, and those who have nothing but an opinion.
Look at the F4U Corsair. 4000hp available and it had whacking great long legs to clear that windmill of a four blade prop.
To be pedantic, the F4U-5 got about 3200 horse out of a R2800. Even the F2G only got 3000 horse out of an early R4360.
Join Date: Aug 2003
Location: Sale, Australia
Age: 80
Posts: 3,832
Likes: 0
Received 0 Likes
on
0 Posts
Errors, myths, clangers etc would be avoided if only it dawned on folks that the FACTS are available through the Heritage society and even R-R itself rather than perpetuating some nonsense.
Packard Merlins were just the same as their U.K-built counterparts, except that they used U.S. sized nuts, bolts, threads etc
Lightning Mate, the Mossie props rotated in the same direction, irrespective of Mark. Your observation would be down to film frame rate as you say. You see the same effect in a film of a car wheel, at some point it will appear to be rotating in the reverse direction compared to its actual rotation. The clip you saw must have been on the very point where this effect takes effect, to coin a phrase. Slight difference in actual prop RPM would give the appearance of reverse rotation. Instructors used to use this strobe effect to determine if students had the RPM set correctly by flying astern and looking through their own prop disc at the students, and determining which direction the students prop appeared to be turning.
Join Date: May 2008
Location: Japan
Age: 71
Posts: 204
Likes: 0
Received 0 Likes
on
0 Posts
Thank you very much Brian Abraham. That is a nugget I have been looking for for a long time. I have been led to believe that within the development cycle, parts were essentially interchangeable between UK and US built merlins, but have found nothing authorititive. To have built different versions with either BSW/BSF or SAE threads would have been an incredible procurement SNAFU and led to a logistical and practical nightmare.
Join Date: Jun 2007
Location: deepest darkest recess of your mind
Posts: 1,017
Likes: 0
Received 0 Likes
on
0 Posts
Very little internally would interchange, due to the differing production methods described earlier. The hand fitting that took place in UK built engines put paid to that.
Join Date: May 2008
Location: Japan
Age: 71
Posts: 204
Likes: 0
Received 0 Likes
on
0 Posts
Are you sure, absolutely certain that UK Merlins were all individually hand built by skilled fitters?
"Ford's factory, which was completed in May 1941, was built in two distinct sections to limit potential bomb damage.[nb 10] At first, the factory had difficulty in attracting suitable labour, such that large numbers of women, youths and untrained men had to be taken on. Despite this the first Merlin engine came off the production line one month after the factory's completion, and the production rate was 200 Merlins per week by 1943.[27][67][nb 11] Ford's investment in machinery and the redesign resulted in the 10,000 man-hours needed to produce a Merlin dropping to 2,727 man-hours three years later, while unit cost fell from £6,540 in June 1941 to £1,180 by the war's end. In his autobiography Not much of an Engineer, Sir Stanley Hooker states: "... once the great Ford factory at Manchester started production, Merlins came out like shelling peas. The percentage of engines rejected by the Air Ministry was zero. Not one engine of the 30,400 produced was rejected ...""
Rolls-Royce Merlin - Wikipedia, the free encyclopedia
"Ford's factory, which was completed in May 1941, was built in two distinct sections to limit potential bomb damage.[nb 10] At first, the factory had difficulty in attracting suitable labour, such that large numbers of women, youths and untrained men had to be taken on. Despite this the first Merlin engine came off the production line one month after the factory's completion, and the production rate was 200 Merlins per week by 1943.[27][67][nb 11] Ford's investment in machinery and the redesign resulted in the 10,000 man-hours needed to produce a Merlin dropping to 2,727 man-hours three years later, while unit cost fell from £6,540 in June 1941 to £1,180 by the war's end. In his autobiography Not much of an Engineer, Sir Stanley Hooker states: "... once the great Ford factory at Manchester started production, Merlins came out like shelling peas. The percentage of engines rejected by the Air Ministry was zero. Not one engine of the 30,400 produced was rejected ...""
Rolls-Royce Merlin - Wikipedia, the free encyclopedia
Join Date: Dec 2007
Location: Cyprus
Age: 91
Posts: 179
Likes: 0
Received 0 Likes
on
0 Posts
There was film made of flight refuelling trials with a Belfast attempting to fuel from a Victor; not very successfully. As the Belfast throttled back in order to make a fresh stab at the basket one very senior officer in the audience was heard to say that he hadn't realised that the engines could be reversed in flight in order to slow down.
Last edited by Lancman; 29th Sep 2012 at 13:38.
Join Date: Jun 2007
Location: deepest darkest recess of your mind
Posts: 1,017
Likes: 0
Received 0 Likes
on
0 Posts
Sorry Ken, my point was meant to be relevant to rolls production, not Ford. You are quite right about engines built by Ford. Very little actual fitting required. Pretty much just assembly necessary!
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
one very senior officer in the audience was heard to say that he hadn't realised that the engines could be reversed in flight in order to slow down.
by making me the ruler of the Queen's naveee!"
- Sir William Schwenck Gilbert
Join Date: Sep 2007
Location: On the Rump of Pendle Hill Lancashi
Posts: 614
Likes: 0
Received 0 Likes
on
0 Posts
No one has yet mentioned the Griffon with the Contra Prop fitted to Spits, these must have been a dream to fly, all that grunt and no descernable torque effect on t/o or landing, just a lot of willing horses trying to pull all the rivets out..!
Peter R-B
Peter R-B
Join Date: Jan 2009
Location: New Zealand
Age: 69
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
The Allison engines in the P38 were turbocharged, the Merlin and Griffon were supercharged
Of course supercharging can be mechanical or via a turbo (turbocharged)
Of course supercharging can be mechanical or via a turbo (turbocharged)
The Allison engines in the P38 were turbocharged, the Merlin and Griffon were supercharged
Join Date: Feb 2020
Location: Texas
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
The Allison engines in the P-38 Lightning were identical but were installed facing different directions to get the props to rotate in opposite directions. This was simpler than building the engines differently by using different valve camshafts and simplified the supply problem. Does anyone know if the Merlins and Griffons were capable of being installed "backwards"?
Allisons were built with left and right-rotating crankshaft versions. They could fairly be changed-over to the OTHER direction by replacing a few bits and bobs.
(All references to direction of rotation are as viewed from behind the engine)
Note...the Allisons with right-handed (Clock-Wise or "CW") props had crankshafts that were left-handed (Counter-Clock-Wise or "CCW" or Anti-Clock-Wise in the UK "ACW"), and the prop reduction gear assembly gave a prop that turned opposite in direction from the engine's crankshaft. The ones with left-handed/CW props, the reverse was true.
That said, ALLLLLL Merlins had left-handed crankshafts, and a prop reduction gear assembly similar to that of the Allison - two gears in the assy, so the prop turned to the RIGHT. The Merlins with left-handed props had a THREE gear assembly and therefore, their props turned to the LEFT. This setup was seen on the Merlin-powered P/F-82 Twin Mustangs and the Hornet/Sea Hornets. There were several Marks of Merlins where an engine with a right-handed prop had a "mirror-image mate" - with a different Mark.
Isn't this a LOT of fun!
Conversion of the Allison for different prop rotation as given by an overhaul shop..
To make a left hand engine from a right hand engine, you have to reverse the crankshaft, replace a regular gear with an "H" gear (this is a gear that skips over a gear that was used), and add a standard gear to reverse the prop rotation after you skip with the "H" gear. Every Allison engine has the ability to be reversed if you have an "H" gear and the added gear.The right hand bank as viewed from the distributor end (rear of the engine) must have several spark plug leads interchanged becasue the cam lobes are backwards. It works out the same for the left-hand bank, somehow ... no left bank changes to the firing order
Firing order RH rotation 1L-2R-5L-4R-3L-1R-6L-5R-2L-3R-4L-6R
Firing order LH rotation 1L-6R-5L-2R-3L-4R-6L-1R-2L-5R-4L-3R You can see the firing order of the left bank is unaltered
Basically, to make a left from a right, the engine must be almost disassembled becasue you must be able to get to the gearcase in front and must split the case and disconnect all the rods to reverse the crankshaft.
However, if you are BUILDING a left or right from parts, the difference in buildup is trivial, assuming you have an "H" gear, the new gear, and you know the plugs to interchange (this means rewiring the ignition harness on one side ... so it is MUCH easier to simply build a left or right wiring harness than it is to change one that is already wired).
The "H" gear:
A Standard gear is just a gear with a keyed center. An "H" gear looks like two standard gears joined by a small cylinder in the middle to skip over the gear that was formerly meshed by the standard gear. The new gear you add is to turn the skipped gear in the other direction. All gearcases have the ability to turn either way ... the gear bosses are in all of them, internally.
For both left and right engines, the cams turn the same direction and the crankshaft is reversed and turns backwards.
There is no other engine I know of from WWII that as so easy to make turn in either direction when being built up ... two gears, turn the crankshaft around, and change the right bank firing order ... that's it.
You need a starter that turns the other way, and you need an idler type gear to reverse the direction of the cam towers.
To make a left hand engine from a right hand engine, you have to reverse the crankshaft, replace a regular gear with an "H" gear (this is a gear that skips over a gear that was used), and add a standard gear to reverse the prop rotation after you skip with the "H" gear. Every Allison engine has the ability to be reversed if you have an "H" gear and the added gear.The right hand bank as viewed from the distributor end (rear of the engine) must have several spark plug leads interchanged becasue the cam lobes are backwards. It works out the same for the left-hand bank, somehow ... no left bank changes to the firing order
Firing order RH rotation 1L-2R-5L-4R-3L-1R-6L-5R-2L-3R-4L-6R
Firing order LH rotation 1L-6R-5L-2R-3L-4R-6L-1R-2L-5R-4L-3R You can see the firing order of the left bank is unaltered
Basically, to make a left from a right, the engine must be almost disassembled becasue you must be able to get to the gearcase in front and must split the case and disconnect all the rods to reverse the crankshaft.
However, if you are BUILDING a left or right from parts, the difference in buildup is trivial, assuming you have an "H" gear, the new gear, and you know the plugs to interchange (this means rewiring the ignition harness on one side ... so it is MUCH easier to simply build a left or right wiring harness than it is to change one that is already wired).
The "H" gear:
A Standard gear is just a gear with a keyed center. An "H" gear looks like two standard gears joined by a small cylinder in the middle to skip over the gear that was formerly meshed by the standard gear. The new gear you add is to turn the skipped gear in the other direction. All gearcases have the ability to turn either way ... the gear bosses are in all of them, internally.
For both left and right engines, the cams turn the same direction and the crankshaft is reversed and turns backwards.
There is no other engine I know of from WWII that as so easy to make turn in either direction when being built up ... two gears, turn the crankshaft around, and change the right bank firing order ... that's it.
You need a starter that turns the other way, and you need an idler type gear to reverse the direction of the cam towers.
stilton, because the Brits wanted the engines to be the same as fitted to the P-40. The Brits only received three examples, which were returned to the US after they realized it was not fit for purpose, and the order was canceled. Most of the order ended up being used in the US as trainers. The Brits were responsible for giving it the name "Lightning", Lockheed had wanted to call it the "Atalanta" after the Greek mythological virgin huntress, unwilling to marry, and loved by the hero Meleager.
While we're on the subject of correcting things.... AFAIK no Lancaster was re-engined with Griffons. This may relate to a batch of ex-Shackleton Griffon 57 engines that were converted to drive a single prop for use in Spitfires. That did involve a different gearbox, and the idle setup became a bit of a compromise between the rather high idle setting of the Griffon 57 and the much lower setting that the original Spitfire Griffons had. I know that the Rolls-Royce operated Spitfire XIX used one of these engines, don't know if that is still the case.